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Responses to flooding intensity in Leontodon taraxacoides
Abstract
Natural flooding is one of the major factors affecting vegetation dynamics in many regions of the world. The Flooding Pampa Grasslands (Argentina) are frequently exposed to flooding events of diverse intensity and duration, some of which Leontodon taraxacoides, an exotic dicot. frequent in these grasslands, seems to survive. Its responses to four different water depths (0, 1, 7 and 13 cm) were studied. The results indicate that plants in conditions of total submergence (depth of 13 cm) did not survive. In less severe flood conditions, increases in the leaf insertion angle resulted in the maintenance of a large proportion of the total leaf area above the water. Differences in leaf length and a decrease in the width and the proportion of lobes per leaf were also found under partial submergence conditions (depth of 7 cm). Root and leaf aerenchyma, present in unflooded plants, showed a significant increase in flood conditions. In spite of the anatomical and morphological responses, total biomass and leaf area were severely affected by water depth. Control plants allocated more biomass to reproductive organs, while partly submerged plants allocated more to leaves and less to reproductive organs. Mature L. taraxacoides plants presented a wide range of plastic adjustment as a survival strategy in soil anaerobiosis, and appear to be able to survive short spring floods in a vegetative state; in contrast, they might not tolerate total submergence conditions imposed by more intense and long-lasting floods.
... En los últimos años se ha generado conocimiento sobre las respuestas y los mecanismos vinculados a la tolerancia a excesos hídricos que poseen especies presentes en los pastizales naturales Grimoldi et al., 1999;Insausti et al., 2001;Grimoldi et al., 2005;Striker et al., 2006;2010), leguminosas forrajeras del género Lotus Manzur et al., 2009;Striker et al., 2011; 2011b; Striker y Colmer, 2016) y gramíneas megatérmicas (Imaz et al., 2012;Striker et al., 2017). Sin embargo, son escasos los estudios realizados en las gramíneas templadas más utilizadas en la implantación de pasturas de la Pampa Deprimida como son Schedonorus arundinaceus y Thinopyrum ponticum (INDEC, 2002;Ploschuk et al., 2017). ...
... A nivel morfológico, las plantas incrementan su altura a través de la elongación de distintos órganos aéreos (láminas foliares, pseudotallos, pecíolos, etc., dependiendo de la especie). En consecuencia aumentan la cantidad de área foliar por encima del nivel de agua (Insausti et al., 2001;Grimoldi et al., 1999;Striker et al., 2012b). Esta respuesta permite a las plantas mantener el nivel de fotosíntesis aérea y facilitar la captura de oxígeno por las hojas, favoreciendo de este modo la oxigenación de tejidos sumergidos (Laan et al., 1990;Striker et al., 2005;Colmer y Voesenek, 2009). ...
... Se ha demostrado que el disparador de la mayor elongación de dichos órganos es la acumulación de etileno en el interior de los órganos sumergidos, lo que promueve la extensión de los tejidos activando la síntesis de giberelinas e inhibiendo a su antagonista el ácido abscísico (Voesenek et al., 1990(Voesenek et al., , 2006Fukao y Bailey-Serres, 2008;Jackson, 2008). El incremento en la longitud de los órganos aéreos provoca un aumento en la proporción de área foliar ubicada por encima del nivel del agua, lo que mejora la captación de oxígeno (Laan et al., 1990;Grimoldi et al., 1999;Striker et al., 2005). También se ha reportado que las especies tolerantes a la sumersión parcial son capaces de mantener, durante el período de inundación, una altura de planta similar a la que presentan sus respectivos controles (Striker et al. 2011;Imaz et al., 2012b). ...
Submergence is a major factor affecting seedling recruitment and growth of forage grasses in the grasslands of the Flooding Pampas (Argentina). Information on the effects of flooding on plants of the same species at different developmental stages is scarce. This work aimed at evaluating the responses of Thinopyrum ponticum (Podp.) Barkw. & Dewey, cv. Hulk, the most important forage species sown in the region, to partial and complete submergence in early stages of development. The experiments were carried out in a greenhouse at the Unidad Integrada Balcarce. Plants were grown in plastic containers until reaching three expanded leaves for the Experiment 1, and five expanded leaves for the Experiment 2. At these developmental stages three treatments were applied: field capacity (CC), partial submergence (SP), and complete submergence (SC). In both experiments, the submergence lasted 14 days, followed by a subsequent recovery period of 14 days at CC. Three harvests were carried out: before submergence (C1, 3 or 5 expanded leaves), at the end of the submergence (C2) and at the end of the recovery period (C3). At each harvest, the percentage of surviving plants, plant height, lamina and pseudostem length, live leaves and tiller number, total dry biomass, leaf surface area and specific leaf area, root length, soluble carbohydrates (CHS) in pseudostem were determined. In addition, the quantum yield of photosystem II and the percentage of aerenchyma in root cross sections were also determined in C2, and greenness (SPAD units) was measured in C2 and C3. The relative growth rates (RGR) corresponding to the submergence and recovery periods were calculated for shoots and roots. Data were analyzed by ANOVA plusTukey test (P < 0.05). The results of both experiments indicate that under SP plants increased the length pseudostem and lamina length, and the proportion of root aerenchyma. In Experiment 1, biomass production, and lengths of leaves, tillers and root were negatively affected by SP, both in C2 and C3. In Experiment 2, these variables presented similar or even higher values in SP than in CC when assessed at the end of the stress period. Under SC conditions the plants were severely affected, 70% of the plants died during the recovery period of Experiment 1. In both experiments, negative RGR values were found during the application of SC. In C2 root length, leaves and tillers number, and CHS content values were similar or lower than those recorded in C1. During the recovery period, surviving plants from complete submergence in both experiments showed positive RGRs. In general and for both intensities of
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... leaf blades, pseudostems and petioles depending on the species). Consequently, the amount of leaf surface area above the water level would increase (Grimoldi et al. 1999;Insausti et al. 2001;Striker et al. 2012). This response allows partially submerged plants to maintain (or even increase) the level of aerial photosynthesis and to facilitate the capture of oxygen by the leaves, which will favour the aeration of submerged tissues (Laan et al. 1990;Striker et al. 2005;Colmer and Voesenek 2009). ...
... In recent years, knowledge has been generated about the responses and mechanisms linked to the water excesses tolerance of several forage species (Grimoldi et al. 1999;Insausti et al. 2001;Grimoldi et al. 2005;Striker et al. 2005Striker et al. , 2007Manzur et al. 2009;Imaz et al. 2012Imaz et al. , 2015Striker and Colmer 2017). Nevertheless, there are few reports in the literature about the mechanisms of tolerance of Thinopyrum ponticum (Podp.) ...
... The better performance in growth of the larger plants (five expanded leaves stage) compared with the smaller ones (three expanded leaves stage) is in line with their higher potential for oxygen capture (Fig. 3) and subsequent root aeration (Fig. 4). In this respect, the increased height of plants (86% taller than C) and pseudostem along with an enhanced leaf blade lengthening (61 and 31% longer than C respectively) under PS allow inferring that an increased proportion of leaves would be above water level to improve oxygen capture (Laan et al. 1990;Grimoldi et al. 1999;Striker et al. 2005). In addition, taller plants with increased leaf area in contact with the atmospheric oxygen under PS increased the proportion of root aerenchyma (from 6 to 17%) whereas plants with three expanded leaves did not, which strongly suggests a high potential for root aeration in plants with five expanded leaves (Colmer 2003). ...
Seedling recruitment and growth of forage grasses in flood-prone grasslands is often impaired by submergence. We evaluate the responses of Thinopyrum ponticum (Podp.) Barkw. & Dewey to partial and complete submergence at two early stages of development. Two greenhouse experiments were carried out with plants at three expanded leaves (Experiment 1) or five expanded leaves stage (Experiment 2). In each case, three treatments were applied for 14 days: control (C), partial submergence (PS; water level to half plant height), and complete submergence (CS; water level to 1.5 times plant height). Submergence was followed by a recovery period of 14 days at well drained conditions. Assessments included plant survival, height, leaf blade and pseudostem length, soluble carbohydrates in pseudostem, and shoot and root dry mass accumulation at the beginning and end of the submergence, and at the end of the recovery period. Root aerenchyma formation was determined on day 14 in both experiments. Under PS all plants survived, and the impact of the stress was related to the plants' developmental stage. However, plants with five expanded leaves increased total plant biomass with respect to control by 48%, plants with three expanded leaves reduced it by the same percentage. This response could be related to a higher ability to form root aerenchyma (17 vs 10%), and an enhanced leaf de-submergence capacity due to promoted leaf blade and pseudostem lengthening. Complete submergence treatment compromised the survival of 70% of the individuals with three expanded leaves but did not affect the survival at the five expanded leaves stage. In any developmental stage (three or five expanded leaves) plants fail to promote enough elongation of leaf blades or pseudostems to emerge from the water, so that always remained below the water surface. Root aerenchyma was not increased by CS at either of these two plant developmental stages. The high amount and concentration of pseudostem total soluble carbohydrates of the larger (five expanded leaves) plants facilitated their recovery growth after submergence. Our results predict the successful introduction of this species in areas where water excesses can cause soil waterlogging or shallow-partial plant submergence, but suggest avoidance of areas prone to suffer high-intensity flooding that lead to full plant submergence as this would highly constrain plant recruitment.
... All these negative effects are predicted to inhibit plant growth, reduce dry matter accumulation, and consequently decrease reproduction output (Voesenek and Bailey-Serres, 2015), which means not only the reduction of seed number but also the decrease of seed size. Additionally, to cope with waterlogging stress, plants are preferential to allocate more biomass to vegetative organs (e.g., leaf) than to reproductive organs (e.g., seed) (Grimoldi et al., 1999). Therefore, we hypothesize that seed morphological traits differ between seeds from inundated and non-inundated individuals, with smaller and lighter seeds at inundated habitats. ...
... Nutrient availability is a determining factor for plant growth and reproduction output. Additionally, as mentioned above, plants tend to allocate more nutrients to growth rather than to reproduction (Grimoldi et al., 1999). Therefore, a potential limitation of nutrient availability under waterlogging stress is reduced concentrations of nucleic acid-protein elements (e.g., N, P, and K) and structural elements (e.g., C and Ca). ...
... We took advantage of the extreme precipitation in July 2016 to understand the plastic responses of the seed traits (e.g., morphological traits and element concentration) of the endemic tree species to the extreme climate events. It is clear that serious waterlogging at this period will jeopardize its leaf and seed production (Grimoldi et al., 1999;Xu et al., 2015). For terrestrial plants, two-weeks waterlogging probably caused unrecoverable damage to seeds. ...
Understanding how plant species respond to extreme climate events is crucial for planning management and conservation actions. As extreme precipitation accelerates, the waterlogging related to it is predicted to be more severe and frequent. To date, however, empirical studies addressing the effects of extreme precipitation-induced waterlogging on the seeds of wild plants are still scarce. In this study, we compared the size, mass and element concentration of seeds produced by non-inundated and inundated individuals of Sinojackia huangmeiensis, a critically endangered tree species with only one extant wild population. Compared to the seeds from non-inundated individuals, the seed length, seed width, and seed mass were all smaller for seeds from inundated individuals. However, the concentrations of four chemical elements in the seed displayed an opposite trend, except those elements (e.g., C, K, Ca, Mg, Al, Fe, Ni, B, Mo, and Cu) with no significant difference. Some toxic elements (e.g., Mn) accumulated in the seeds from inundated individuals, as well as some nucleic acid-protein elements (e.g., N and P) and enzymatic (e.g., Zn) elements. Our study provides rare empirical evidence that wild plants could respond to extreme precipitation-induced waterlogging by changing both seed morphological traits and element concentrations.
... No effective mechanisms to protect the plants from the consequence of oxygen deficiency, such as formation of adventitious roots Dias-Filho, 2002) or change in morphology of leaves (Rubio & Lavado, 1999), were observed in the taxa studied. On the contrary, different extents of aerenchyma formation (Rubio et al., 1995;Loreti & Oesterheld, 1996;Grimoldi et al., 1999) might have been responsible for the survival of the plants for such a long time under the flooded conditions. It should be noted that some species, in spite of their tolerance to partial or temporary submergence through the presence of effective mechanisms, can still be susceptible to total submergence imposed both by intense and long-term floods and can subsequently die (Grimoldi et al., 1999). ...
... On the contrary, different extents of aerenchyma formation (Rubio et al., 1995;Loreti & Oesterheld, 1996;Grimoldi et al., 1999) might have been responsible for the survival of the plants for such a long time under the flooded conditions. It should be noted that some species, in spite of their tolerance to partial or temporary submergence through the presence of effective mechanisms, can still be susceptible to total submergence imposed both by intense and long-term floods and can subsequently die (Grimoldi et al., 1999). Plant roots are particularly prone to tissue injury induced by insufficient oxygen supply and initial effect of Table 3 Log-linear analysis of the effects of taxon (T) and flooding intensity (F) on the presence of above-ground dead tissue (G) flooding is thus apparent in the root system (Blom & Voesenek, 1996). ...
... Plant roots are particularly prone to tissue injury induced by insufficient oxygen supply and initial effect of Table 3 Log-linear analysis of the effects of taxon (T) and flooding intensity (F) on the presence of above-ground dead tissue (G) flooding is thus apparent in the root system (Blom & Voesenek, 1996). Therefore, the reaction of floodingtolerant species is to shift at least to some degree allocation of biomass from below-to above-ground parts when flooded and thus to reduce root:shoot ratio Neill, 1993;Rubio et al., 1995;Grimoldi et al., 1999). This is related to the effort of plants to increase mass of above-ground aerial shoots, which would provide oxygen to the flooded parts via gas-transport. ...
Response to flooding intensity in three closely related taxa, Elytrigia repens, E. intermedia and their hybrid was studied. Plants were exposed to three intensities of flooding for a 30-day period. Response to flooding intensity was estimated by measuring dry mass of the following: total biomass, above-ground living biomass, above-ground dead biomass, below-ground biomass, rhizome and root mass and by the allocation of dry mass into rhizomes and root:shoot ratio. Reduction of nearly all the biomass compartments with increasing flooding intensity was observed in the three taxa. All three taxa can thus be regarded as flood-intolerant. Based on the parameters measured, E. repens is regarded as the relatively most flooding-tolerant, E. intermedia as the least tolerant, while the hybrid displayed intermediate flooding tolerance. The higher flooding tolerance in E. repens was likely related to its ability to accumulate a sufficient mass of rhizomes before flooding, due to higher regeneration ability. E. repens also displayed the highest phenotypic plasticity, as deduced from the reaction norms constructed for total biomass and rhizome mass of particular clones of the three taxa studied. This indicates that, on the species level, E. repens is better adapted to changing environmental conditions and it can be expected to colonize flooded soils. Both Elytrigia species also occur as weeds: E. intermedia grows in agricultural environments in warm regions, while E. repens infests many different types of habitats. Where they co-occur, hybridization between them may lead to the enrichment of their gene pools with genes responsible for survival of the parental species under extreme conditions; their weedy potential may thus be enhanced.
... Merat.). Tajos konstatēja, ka ilgstošas applūšanas gadījumā izdzīvoja tie augi, kuru lapu plātnes gali atradās virs ūdens virsmas, uzturot lapu kontaktu ar gaisa vidi (Grimoldi et al. 1999). Salīdzinoši lielas starpšūnu telpas daudzu mitru augteņu augu lapās bieži saista ar šo augu nepieciešamību pēc drošām skābekļa pieejamības rezervēm, to saknēm augot anaerobos apstākļos (Cronk, Fennesy 2001;Keddy 2010). ...
... Merat. have showed that only plants whose leaf tips emerged above the water surface survived completely, showing the vital importance of recovering air-shoot contact to flood-survival ability (Grimoldi et al. 1999). Proportionally large air space is a characteristic of leaves of many wetland species and it's often associated with their need for secure oxygen availability for roots growing under anaerobic conditions (Cronk, Fennesy 2001;Keddy 2010). ...
... Herbaceous plants are known to be more sensitive to overflow than trees and shrubs, because seeds of many herbs can germinate after even a single overflow event, whereas those of trees and shrubs require many such events for germination (Xu et al., 2009). Other studies (Capon and Brock, 2006;Grimoldi et al., 1999;Simpson et al., 2013) have shown that the duration and frequency of overflows constrain the degree to which the vegetation responds to restoration efforts. However, lack of long-term data and insufficient quantification of the duration and frequency of overflows have been major impediments to elucidating the lasting impacts of overflows on succession in plant communities. ...
... However, seedlings of perennial herbs (such as K. caspica) were more resistant to drought and had greater tolerance to salt than the seedlings of P. euphratica (Jia and An, 2004;Xu et al., 2009). Some earlier studies (Bornette and Amoros, 1996;Capon and Brock, 2006;Garssen et al., 2015;Grimoldi et al., 1999;Simpson et al., 2013) have shown that the duration and the intensity (frequency) of floods determine the composition of plant communities and the distribution of species. Our experiment on overflow disturbance (Figs. ...
Intermediate water disturbance (in the form of overflow of surface water and changes in the depth of groundwater) may help to accelerate restoration of degraded riparian forest ecosystems in extremely arid areas and enhance the resistance of those ecosystems to drought. To test this possibility, we selected the lower reaches of the Tarim River in China to analyse monitoring data on vegetation and hydrology spanning a 16-year period, and a 100-year data record of tree rings in Populus euphratica. The results suggested that ecological water conveyance can restore degraded desert riparian forest ecosystems. In the early stages of restoration, the interval between two overflows should not be longer than 3 years. Intermediate disturbance (1–2 overflows a year, each lasting 21–30 days) proved conducive to the formation of a plant community that is both diverse and stable, thereby supporting the intermediate disturbance hypothesis. Both P. euphratica and Tamarix chinensis adopt suitable strategies for using groundwater from different depths to adapt to drought. Based on these results, appropriate disturbance modes related to both surface water and groundwater are proposed for the restoration and conservation of desert riparian forest ecosystems under varying intensities of drought. These modes offer scientific guidance on more efficient use of water and on ecosystem management in similar areas around the world.
... Although hl formation exists in long-term morphological responses that involve genetic activation, protein synthesis, catalysis reactions and cellular death (Eldhuset et al. 2013;Voesenek et al. 2016), flooding causes plastic responses involving movement and changes in the leaves angle (Grimoldi et al. 1999;Cox et al. 2003) as observed to O. arborea plants. ...
... The leaf movements (nastic movements) can be induced by light or others stimulus factors, this event, widely observed in Fabaceae (Baudet 1974) is caused by reversible turgor changes in the pulvinus cells, and mechanisms that involve hormones (ethylene), potassium flux, H + -ATPases and water potential of vacuoles cells (Sasidharan and Voesenek 2015; Takahashi and Kinoshita 2016). Although the adaptive value of leaves inclined down in O. arborea under flooding is not clear, other authors emphasise that changes in the leaf insertion angle and hyponastic growth can contribute to leaves emergence above water surface avoiding the unfavourable condition (Grimoldi et al. 1999;Cox et al. 2003). The phenotypic changes induced by flooding are considered favourable, and may facilitate gaseous exchanges in the leaf enabling the plant able to maintain a higher assimilation rate during water logging (Kozlowski 1997;Tatin-Froux et al. 2014) to O. arborea plants, but the morphological plasticity was not enough to halt the decline of the majority of physiological variables. ...
The success of restoration practices in areas subject to seasonal flooding is associated with the selection of plant species tolerant to both flooding and post-flooding conditions. Morphophysiological changes of Ormosia arborea (Vell) Harms (Fabaceae) seedlings were studied to evaluate the plasticity related to the water regime. O. arborea seedlings were flooded for 0, 15, 30, 45 and 60 days. At the end of each flooding period, the seedlings were removed from the pools to assess seedling survival at 75 days after completion of the flooding regime. The seedlings survived under the flooding and post-flooding regime and expressed lenticel hypertrophy. During longer periods of flooding, the seedlings exhibited a reduction in the quantum efficiency of PSII and gas exchanges (except for the internal concentration of CO2, which increased during this period). During the reestablishment, the metabolism was resumed, however, when plants was submitted to more prolonged flooding (60 days), the photosynthetic rates and carboxylation efficiency were not completely recovered. Stomatal conductance and water use efficiency was not recovered at the level of the control independent of the flooding period. These morphophysiological adjustments indicate phenotypic plasticity and potential for survival in temporarily flooded areas.
... A common response underlying the tolerance to flooding of some species is the development of aerenchyma, which facilitates oxygen diffusion from the atmosphere to the roots and towards the rhizosphere and the outward diffusion of potentially toxic compounds such as ethanol, acetaldehyde and CO 2 (Calvo-Polanco et al., 2012;Le Provost et al., 2012). I Evaluating the presence of aerenchyma from histological sections (Vartapetian and Jackson, 1997;Parent et al., 2008) is common practice; however, it is important to test the role that aerenchyma plays in the transport of air because the intercellular spaces in the aerenchyma could contain water (Sojka, 1988;Grimoldi et al., 1999). Thus, it would be appropriate to assess the content of air in root tissues (porosity) if related to flood tolerance (Sojka, 1988;Grimoldi et al., 1999). ...
... I Evaluating the presence of aerenchyma from histological sections (Vartapetian and Jackson, 1997;Parent et al., 2008) is common practice; however, it is important to test the role that aerenchyma plays in the transport of air because the intercellular spaces in the aerenchyma could contain water (Sojka, 1988;Grimoldi et al., 1999). Thus, it would be appropriate to assess the content of air in root tissues (porosity) if related to flood tolerance (Sojka, 1988;Grimoldi et al., 1999). There are two types of aerenchyma: one is inducible aerenchyma, which forms in low-oxygen environments; the other is constitutive aerenchyma, which fundamentally forms in the absence of external environmental stress as an integral part of ordinary root development (Jackson et al., 1985). ...
In fruit trees, flooding stress can affect plant survival and growth, and tolerance to root anoxia is determined by rootstock characteristics. Similarly to almond, peach trees are also among the Prunus species proving most susceptible to root anoxia in flooded soils. The aim of our study was to investigate the short-term responses to flooding of different Prunus rootstocks, in terms of growth and development and physiological variables. Flood treatments were continuously applied for 6 days to myrobalan plum Sansavini 2/5 (Mr. S. 2/5), Monegro and Nemared peach rootstocks. Trees that were not exposed to flooding served as controls. Physiological and growth variables were evaluated. Flooding negatively affected net photosynthesis (Pn), leaf conductance (gs) and water potential (Ѱw) in Monegro and Nemared but not in Mr. S. 2/5 rootstock. However, flooding treatments did not affect the intercellular concentration of CO2 (Ci) in any of the rootstocks. We propose that the lack of alterations in Ci indicates that the processes related to photosynthetic metabolism are affected simultaneously with stomatal closure. Flooding only reduced the leaf growth of Monegro and Nemared rootstocks. The Mr. S. 2/5 rootstock had the highest constitutive root porosity, which increased its tolerance to flooding compared to the other rootstocks. The differences in the responses to flooding of various rootstocks should be considered in production settings where it is not possible to properly control irrigation to prevent short periods of flooding or in soils that do not drain irrigation or rain water quickly.
... At 3 MAT, 6C and 10C had the most leaves and the control had the least (Table 2). When grown in saturated conditions, seedlings produced more leaves than plants grown in the nonsaturated control treatment; a similar observation was made by Grimoldi et al. (1999). Increased leaf numbers, another survival mechanism, increases the surface area making contact with oxygen, light, and carbon dioxide (Grimoldi et al., 1999). ...
... When grown in saturated conditions, seedlings produced more leaves than plants grown in the nonsaturated control treatment; a similar observation was made by Grimoldi et al. (1999). Increased leaf numbers, another survival mechanism, increases the surface area making contact with oxygen, light, and carbon dioxide (Grimoldi et al., 1999). ...
Sea oats (Uniola paniculata) is an aesthetically pleasing native plant used for beach restoration along the northern Gulf of Mexico coast. Many beaches in this region have shallow, saturated dune profiles, which reduces sea oats survival. The objective of this study was to develop methods to identify saturation-tolerant sea oats breeding lines. Sea oats seedlings were evaluated for saturation tolerance in greenhouse, beach, and field environments from 2010 to 2012. In 2010, sea oats grown under eight treatments (seven greenhouse treatments and a natural beach site) were examined. In 2010, sea oats seedling survival 2 and 3 months after transplanting (MAT) was greatest for four greenhouse treatments (nonflooded control, 6 cm cyclic flood, 6 cm static flood, and 10 cm cyclic flood) and least at the beach environment (Holly Beach, LA). In 2011 and 2012, sea oats grown under six treatments (four greenhouse treatments, a natural beach site, and a saturated field site) were examined. In 2011, sea oats seedling survival 3 MAT ranged from 0.3% to 98%. The nonflooded greenhouse control had the greatest survival, whereas plants grown on dry bench regularly watered with 35 parts per thousand (ppt) saline solution had the least survival. Sea oats constantly flooded with 14 cm of saline water in the greenhouse had the least survival 2 and 3 MAT, 70% and 41%, respectively. Sea oats survival when flooded with 14 cm of fresh water 3 MAT correlated with a saturated beach environment, Holly Beach, LA, 6 MAT (r=0.970, P=0.030) and a saturated field environment, Baton Rouge, 6 MAT (r=0.994, P 0.006). These findings suggest that survival of sea oats grown in a greenhouse in 14 cm fresh water for 3 months correlates to sea oats survival at saturated beaches after 6 months, in the absence of significant storm events. Identifying protocols for selection of saturation-tolerant sea oats lines is essential to increase the efficiency and effectiveness of northern Gulf of Mexico sea oats breeding programs.
... The aerenchymatic tissue gives plants a lower resistance pathway for oxygen transport through diffusive mechanisms from air-exposed shoots towards the submerged tissues (Colmer 2003;Colmer and Voesenek 2009). At the morphological level, flooded plants increase their height, usually through petiole/leaf elongation, and as a result, they increase the leaf area exposed above the water level (Grimoldi et al. 1999;Insausti et al. 2001;Striker et al. 2011b). This allows plants to maintain aerial photosynthesis and facilitates the capture of oxygen by leaves for the oxygenation of submerged tissues through the aerenchyma system (Laan et al. 1990;Striker et al. 2005;Colmer and Voesenek 2009). ...
... In both cases, the relatively solid plant performance in this scenario was associated with two main responses, oxygen capture and transport, which facilitated the aeration of submerged tissue (Colmer 2003;Colmer and Voesenek 2009). First, both species were able to reach the same seedling height as C during the experiment (Fig. 2); the proportion of leaves above water level progressively increased, which promotes oxygen capture (Laan et al. 1990;Grimoldi et al. 1999;Striker et al. 2005). Second, oxygen transport to the roots through diffusive mechanisms appears to be facilitated by high initial constitutive aerenchyma, which was further increased by PS as a result of increases in root diameter and cell lysigeny in the root cortex (Fig. 1, see also Visser et al. 2000;Striker et al. 2007). ...
Submergence is a major factor affecting seedling recruitment in lowland grassland ecosystems. Our aim was to
evaluate the tolerance to increasingflooding intensity of the seedlings of tropical grassesChloris gayanaK. andPanicum
coloratumL., whose use as a forage species is increasing in humid grasslands. For this purpose, 2-week-old seedlings of
C. gayanaandP. coloratumwere subjected to control, partial submergence (PS) and complete submergence (CS) in clear
water for 14 days and allowed to grow for a subsequent 12-day period to assess their recovery. The following responses were
assessed: generation of root aerenchyma, morphological changes and emergence from water, biomass allocation in relation
to plant size, and biomass accumulation. Results showed that constitutive root aerenchyma was high in both species. Under
PS and CS, root aerenchyma increased by up to 50–55% inC. gayanaand up to 40–48% inP. coloratum.Under PS, the
increase in seedling height for both species was the same as for controls. Under CS,C. gayanafurther increased its height and
emerged more quickly from water;P. coloratumwas not able to increase its height, and therefore the seedlings always
remained underwater. The escape-from-water response ofC. gayanawas associated with preferential biomass allocation
towards shoots and with a marked lengthening of leaf blades. By contrast, there was no change in allocation inP. coloratum,
and its leaves were shorter under CS. Thefinal biomass ofC. gayanaunder CS was similar to that under PS, and equivalent to
54% of its controls. InP. coloratum, biomass under PS and CS were 64 and 21% of its controls (respectively), which indicates
that injury caused by CS persisted during the post-submergence period. In conclusion, both species are tolerant to PS at the
seedling stage. However, whenflood depth increases by submerging the seedlings,C. gayanais able to escape from water
whileP. coloratumis not, thus strongly affecting its recovery. Therefore,C. gayanaappears to be a more promising species
for cultivation in lowland grasslands prone toflooding of unpredictable intensity.
... Conversely, N. lutea and Nymphaea alba L., with their low growth rates and large storage systems, may survive long inundation. More generally, herbaceous plants tend to be intolerant of prolonged inundation (Grimoldi et al., 1999). Species that survive can be described as plastic, with morphological and ⁄ or metabolic adaptations to deal with inundation and anoxia, such as aerenchyma formation, adventitious root formation, increasing specific leaf area and leaf and stem elongation (Vartapetian & Jackson, 1997;Jackson & Colmer, 2005;Voesenek et al., 2006). ...
... Species that survive can be described as plastic, with morphological and ⁄ or metabolic adaptations to deal with inundation and anoxia, such as aerenchyma formation, adventitious root formation, increasing specific leaf area and leaf and stem elongation (Vartapetian & Jackson, 1997;Jackson & Colmer, 2005;Voesenek et al., 2006). Aerenchyme formation, and leaf and stem elongation should increase the plant capacity to reach the water surface, and thus to survive anoxia (Grimoldi et al., 1999;Lenssen et al., 2000). ...
The effects of connectivity cannot be reduced to a simple gradient. River overflows disturb the vegetation of connected wetlands but, reducing competition, promote plant diversity. Overflows also bring nutrients, silt and plant propagules. Nutrients increase eutrophication and promote phytoplankton development, which reduces water transparency and impedes the growth of rooted plants. Silt inputs accelerate terrestrialization but provide regeneration niches that favour the recruitment of allochthonous propagules. These multiple effects are combined into a model that predicts diversity and life-history traits of aquatic plants (growth form, potential size, phenology and frequency of flowering, vegetative reproduction and defence against herbivores) in relation to the connectivity of the riverine wetlands.
... Both leaf sheath and leaf blade length along with an unaltered stomatal conductance under flooding of subsp. dilatatum Lowland reveals its high capability to emerge from water and to capture atmospheric oxygen (Grimoldi et al., 1999;Laan et al., 1990;Voesenek et al., 2006). In contrast, the lack of (or a limited) leaf length along with the stomatal closing in flooded plants of dilatatum Upland and subsp. ...
... flavescens suggest a less plastic responce to flooding compared to dilatatum lowland plants. Consequently, if flooding is intensified (e.g., in duration, water depth) such morphophysiological limitations of the upland populations could constrain their performance to a greater extent due to the difficulty of recovering adequate contact with air (Grimoldi et al., 1999). ...
The grass Paspalum dilatatum Poir. subsp. dilatatum inhabits periodically flooded lowlands as well as non-flooded uplands of the flooding Pampa grasslands (Argentina), while P. dilatatum Poir. subsp. flavescens Roseng., B.R. Arrill. & Izag. inhabits only the upland sites. An experiment was designed to determine if there is local adaptation to flooding in physiological, anatomical and leaf morphological traits. To this end, plants of these populations were subjected to flooding (6 cm water depth) and control conditions (watered daily) for 60 days in an experimental garden. Flooded plants of the subsp. dilatatum from the lowland had 35% higher photosynthesis compared to controls without affecting their stomatal conductance, transpiration rate and leaf water potential. By contrast, both subsp. dilatatum and subsp. flavescens from the upland did not increase their photosynthesis, and had reduced their stomatal conductance and leaf transpiration rate by 35% and 45% when growing in flooded conditions. Upland populations had higher leaf water potential with respect to controls. All populations had high constitutive root aerenchyma (28–42%), and leaf sheath porosity increased by 75% in flooded conditions (from 22–28% to 35–48%). Leaf lengthening differed among populations according to their habitat: subsp. dilatatum from the lowland was the only one that had longer leaf sheaths and blade lengths when flooded. In contrast, flooded plants of subsp. dilatatum from the upland only increased leaf sheath length while subsp. flavescens neither increased leaf blade nor leaf sheath. In conclusion, both the physiological performance and the leaf length plasticity differed among populations. The results agree with those expected based on the species’ habitat, and indicate the better adaptation to the flood-prone habitat of P. dilatatum subsp. dilatatum taken from a lowland area.
... We conducted an outdoor microcosm experiment using plants of P. dilatatum naturally established in soil monoliths extracted from a lowland grassland site (near Pila, Buenos Aires Province, Argentina). The use of microcosms helped overcome most problems concerned with manipulating soil waterlogging in the field, while it also allowed us to monitor individual plant responses in the presence of natural neighbours (Grimoldi et al. , 1999) . Twenty plants of P. dilatatum of similar size and prostrate architecture were obtained during spring from a lowland grassland site grazed year-round by cattle. ...
... Flooding changed the shoot architecture of P. dilatatum, increasing the amount of leaf and tiller area deployed above the water surface (Figs 4, 5). Similar morphological changes have been reported for other herbaceous species growing in periodically flooded habitats (Bleecker et al., 1986; Van der Sman et al., 1991; Naidoo & Naidoo, 1992; Grimoldi et al., 1999). Several studies suggest that shoot elongation in submerged plants may be controlled by phytohormones, and in particular by ethylene production, as in flood-tolerant Rumex species (Van der Sman et al., 1991; Banga et al., 1996). ...
Summary • We studied individual responses to flooding in the perennial grass Paspalum dilatatum, a widespread species in the Flooding Pampa of Argentina, using plants established in species-diverse grassland microcosms. • Flooding effects were evaluated on root and leaf sheath anatomy and shoot morphological traits. Leaf water status and CO2 exchange rates were monitored in flooded and unflooded plants under changing, natural and controlled atmospheric conditions. • Root porosity and leaf sheath aerenchyma increased with flooding. Leaf extension rates and tiller height were also higher in flooded plants, which resulted in a large fraction of the shoot architecture emerging above the water surface. Flooding enhanced stomatal conductance, leaf water potential and net photosynthesis, especially under conditions leading to high air-vapour pressure deficits. Therefore, flooded plants experienced fewer water deficits during periods of high atmospheric evaporative demand. • P. dilatatum showed tight regulation of water and carbon relations under severe soil-oxygen deficiency, even in the presence of natural competitors. The suite of adaptive responses documented here might help to explain the observed increase in abundance of this species during extensive floods.
... Conversely, N. lutea and Nymphaea alba L., with their low growth rates and large storage systems, may survive long inundation. More generally, herbaceous plants tend to be intolerant of prolonged inundation ( Grimoldi et al., 1999). Species that survive can be described as plastic, with morphological and ⁄ or metabolic adaptations to deal with inundation and anoxia, such as aerenchyma formation, adventitious root formation, increasing specific leaf area and leaf and stem elongation (Vartapetian & Jackson, 1997;Jackson & Colmer, 2005;Voesenek et al., 2006). ...
... Species that survive can be described as plastic, with morphological and ⁄ or metabolic adaptations to deal with inundation and anoxia, such as aerenchyma formation, adventitious root formation, increasing specific leaf area and leaf and stem elongation (Vartapetian & Jackson, 1997;Jackson & Colmer, 2005;Voesenek et al., 2006). Aerenchyme formation, and leaf and stem elongation should increase the plant capacity to reach the water surface, and thus to survive anoxia ( Grimoldi et al., 1999;Lenssen et al., 2000). ...
1. We propose a model of plant strategies in temperate fluvial hydrosystems that considers the hydraulic and geomorphic features that control plant recruitment, establishment and growth in river floodplains.
2. The model describes first how the disturbance gradient and the grain-size of the river bed load affect the relative proportion of erosion and deposition processes, and how the frequency of flood disturbance affects the intensity of such processes.
3. Secondly, the model predicts plant strategies according to direct and indirect effects of floods (disturbances through erosion versus deposition processes, and associated nutrient excess or limitation).
4. The relevance of the model as a prediction tool is discussed. Some proposals are made to validate the model, and traits are proposed that should be considered in future research for improving the predicting value of the model.
... This facilitates internal oxygen transport through an interconnected system of gas-filled intercellular spaces (Armstrong, 1979). In addition, common responses to flooding also include an increase in plant height and consequently, in the proportion of biomass above water level (Grimoldi et al., 1999;Naidoo and Mundree, 1993). This also helps to facilitate the oxygenation of submerged tissues through the aerenchyma tissue (Laan et al., 1990). ...
... During the experiment, containers were periodically rotated and provided with holes that allowed water to drain freely. The use of mesocosms helped overcome the problems of flooding simulation in field conditions and of keeping control during natural flooding (Fraser and Keddy, 1997;Grimoldi et al., 1999;Insausti et al., 1999). In addition, the use of mesocosms allowed us to register the responses of the target species in presence of their usual neighbors . ...
Lotus corniculatus L. and Lotus glaber Mill. are warm-season legume species adapted to many kinds of environmental stress, including flooding conditions, whereas
other popular forage legumes, like alfalfa or white clover, cannot thrive. This study evaluates the relationship between root
aerenchyma, water relations and leaf gas exchange and the differential tolerance to soil flooding of L. corniculatus and L. glaber. Adult plants of these species, established independently in grasslands mesocosms, were subjected to 40days of early spring
flooding at a water depth of 6cm. Both species presented constitutive aerenchyma tissue in the roots. Under flooding conditions,
this parameter was 26.2% in L. glaber and 15.3% in L. corniculatus. In addition, flooded plants of L. glaber presented a leaf biomass 47.5% higher above water while L. corniculatus showed a leaf biomass 59.6% lower in the same layer, in comparison to control plants. Flooded plants of L. glaber maintained the stomatal conductance (g
s) and transpiration rate (E) for 25days, although these parameters reduce slightly to 40–60% in comparison to controls after 40days of flooding. In
this species, a reduction in photosynthesis (A) in flooding conditions was detected only on the last day of measurement. In L. corniculatus, the same parameters (g
s, E and A) were affected by flooding since day 18 of treatment, and values reached 25–40% in comparison to control plants after 40days
of flooding. Flooding did not affect above-ground biomass in L. glaber; while in L. corniculatus, above-ground biomass was 35% lower than in control plants. Our results confirmed that L. glaber is more able to cope with flooding stress than L. corniculatus, even in the presence of natural competitors. On the whole, this experiment provides information that can aid in the identification
of anatomical and physiological parameters associated with flood-tolerance in this forage legume species, with economic potential
for the agricultural areas subject to periodic flooding.
... The responses of plants to stress are reflected in morphological variations and show insufficient adaptation to changing environmental conditions. Generally, these responses can be caused by natural processes: volcanic eruptions, floods, salt dispersion (Oosting, 1945;Collins, 1969;Grimoldi et al., 1998;Hotes et al., 2004;Pardos, 2004;Dale et al., 2005;Jiménez et al., 2013;Sakagami et al., 2020;Shao et al., 2020) or by anthropogenic activities (Bacci and Gaggi, 1987;Sandermann, 1992;García et al., 2006;Collins et al., 2011;Burden et al., 2020). ...
Until not so long ago, Antarctica was considered to be a polar region practically pristine. The Antarctic Peninsula has the highest concentration of scientific stations from different countries. Anthropogenic activity has caused alterations in the Antarctic ecosystems directly affecting terrestrial vegetation. This fact requires the finding of biomarkers in native plants to estimate the effects of human impact. Deschampsia antarctica Desv. (Poaceae) is the unique native grass described so far for Antarctica and was used for multiple investigations. In this study, plants were collected on Carlini scientific station, 25 de Mayo (King George) Island, Potter Peninsula, South Shetland Islands. Thus, the main objective planned consists of the evaluation of leaf stomata-related parameters as pollution biomarkers. The results of the stomatic index (SI), density (SD), and area (SA) were shown at sites with different levels of human impact (close and far away from the scientific station). It was found that the correlation between SD and SI, on the adaxial side of the leaves, resulted in a good biomarker for estimating the degree of anthropogenic impact in each studied area.
Graphical abstract
... The responses of plants to stress are re ected in morphological variations and show insu cient adaptation to changing environmental conditions. Generally, these responses can be caused by natural processes: volcanic eruptions, oods, salt dispersion (Oosting 1945;Collins 1969;Grimoldi et al. 1998 Taken into account all the information stated in the previous paragraphs, the present work aimed to determine and evaluate the stomatic´s index (SI), density (SD), and area (SA) in leaves of D. antarctica, as biomarkers of exposition to pollution. ...
Deschampsia antarctica Desv. (Poaceae) is the only native grass described so far for Antarctica, with a distribution mainly centered on the Antarctic Peninsula.
The plants were collected at Argentinian Scientific Station Carlini, 25 de Mayo (King George) Island, to determine and evaluate in their leaves: the stomatic index (SI), density (SD), and area (SA) as pollution biomarkers. Samples were taken within the Station's influence area: (A) Supply Area (loading and unloading of fuel and supplies), (B) the area adjacent to the Electric Power Station, and (C) area of Fuel Tanks. Besides, other samples were taken from a pristine area called Peñon 7 (D). The results of SD showed significant differences only on the leaf abaxial face from the plants of the 4 studied sites: Peñón 7 (57.36 ± 2.03), Supply Area (61.30 ± 2.32), Electric Power Station adjacent area (69.56 ± 2.23) and Fuel Tanks area (80.11 ± 2.42). The SI as well as the SA did not have significant differences (p > 0.05) for all the analyzed sites. However, correlation analyses between SD and SI showed a positive and significant association only for the leaf adaxial face from all sites.
From the obtained results, we could suggest that the correlation (SD-SI) on the adaxial side of the leaves was a good biomarker to estimate the degree of anthropogenic impact in each studied area.
... This may allow plants to be partially exposed to the air, likely resulting in significant increases in survival capacity (e.g. Grimoldi et al. 1999;Vivian et al. 2014). However, the tolerance of riparian species typical of lower bank elevations in the region, such as Alternanthera denticulata and Persicaria decipiens, to summer submergence also remains largely unknown and requires further investigation, including any longterm impacts of pulsed submergence. ...
River regulation has altered the seasonal timing of flows in many rivers worldwide, impacting the survival and growth of riparian plants. In south-eastern Australia, demand for irrigation water in summer often results in high river flows during a season that would naturally experience low flows. Although unseasonal high summer flows are thought to significantly impact waterways, their effects on vegetation are poorly quantified. We investigated the responses of five grass species commonly occurring in riparian zones to different durations of submergence in summer. We experimentally tested the response of three exotic and two native grasses to four submergence treatments (4 weeks, 8 weeks, 2-week pulses and no submergence), and two levels of shading (no shading and 80% light reduction), over 8 weeks in summer and early autumn. All submergence treatments, including the 2-week pulse, resulted in the death of all plants of three species (Bromus catharticus, Dactylis glomerata and Rytidosperma caespitosum). Lolium perenne exhibited moderate survival rates in the shorter-duration unshaded submergence treatments, while Poa labillardierei largely survived all treatments. Similar responses across species were observed for plant height and biomass, although height generally increased while biomass growth was reduced by shading. These results show that even 2-week periods of summer submergence can reduce growth and cause the death of some riparian grasses. Although some species may survive longer submergence durations, impacts on other aspects of fitness, and ongoing effects of repeated unseasonal submergence, remain uncertain. Our study highlights that the impacts of unseasonal flows require further investigation and careful management.
... Furthermore, compared with the former 2 yr, LAI greatly increased in the latter 2 yr under both heavy rainfall treatments in this study, although total AGB was not changed (Fig. 6a,c). Increasing leaf area has been reported for various herbaceous species growing in periodically flooded habitats as a result of more and longer parenchymatous cells and ethylene production ( Van der Sman et al., 1991;Grimoldi et al., 1999;Insausti et al., 2001). Large leaf area would enhance stomatal conductance at the community level, increase oxygen diffusion (de Oliveira & Joly, 2009), facilitate transpiration (Lai, 2015) and thus improve nutrition transportation and oxygen supply, which would benefit plant photosynthesis and respiration simultaneously. ...
Heavy rainfall events are expected to increase in frequency and severity in the future. However, their effects on natural ecosystems are largely unknown, in particular with different seasonal timing of the events and recurrence over multiple years. We conducted a four‐year manipulative experiment to explore grassland response to heavy rainfall imposed in either mid‐ or late‐growing season in Inner Mongolia, China. We measured hierarchical responses at individual, community, and ecosystem levels. Surprisingly, aboveground biomass remained stable in the face of heavy rainfalls regardless of seasonal timing, while late‐growing season heavy rainfall had consistent negative impacts on belowground and total biomass. However, such negative biomass effects were not significant for mid‐growing season heavy rainfall. By contrast, mid‐growing season heavy rainfall had greater positive effects on ecosystem CO2 exchanges, mainly reflected in the latter two years of the four‐year experiment. This two‐stage response of CO2 fluxes was regulated by increased community‐level leaf area and leaf‐level photosynthesis and inter‐annual variability of natural precipitation. Overall, our study demonstrates that ecosystem impacts of heavy rainfall events crucially depend on the seasonal timing and multi‐annual recurrence. Plant physiological and morphological adjustment appeared to improve the capacity of the ecosystem to respond positively to heavy rainfall. This article is protected by copyright. All rights reserved.
... When coupled with subsequent shoot elongation, it directs underwater leaf growth along the shortest route to the water surface. Flooding-induced leaf hyponasty is observed in several species including Arabidopsis thaliana (Polko et al., 2012(Polko et al., , 2013Rauf et al., 2013), Paspalum dilatatum (Insausti et al., 2001), Leontodon taraxacoides (Grimoldi et al., 1999), and Rumex palustris (Cox et al., 2003). The molecular processes mediating hyponasty have been extensively investigated in the dicot semi-aquatic Rumex palustris, a flood tolerant species found in frequently flooded riparian areas (Peeters et al., 2002) (Figure 2). ...
Flooding is a frequently encountered abiotic stress that is extremely detrimental to plant growth and development, metabolism, function, and yield. Water severely restricts gas exchange impeding photosynthesis and respiration, and ultimately leads to an energy crisis that can prove fatal. Most land plants are extremely sensitive to prolonged waterlogging and submergence. owever, some plant species are at home in frequently flooded environments. This is linked to a set of adaptive traits and metabolic adjustments that confer the ability to either avoid or cope with flooding-induced oxygen deprivation. Here, we outline the current knowledge on these morphological, anatomical, and metabolic tolerance traits, and how they facilitate flooding survival. Furthermore, we elaborate on the molecular processes and signalling mechanisms that regulate some of these traits. A better understanding of these tolerance attributes is essential in the quest towards the generation of climate resilient crops in an era of global warming and increased food demand.
... Studies show that plants develop a suite of anatomical and morphological mechanisms to adapt to a submerged environment (Armstrong, 1979;Kozlowski, 1984;Vartapetian and Jackson, 1997;Seago et al., 2005;Striker et al., 2005;Colmer and Voesenek, 2009). Methods of plant adaptation and evolution under flooding stress include the generation of aerenchyma in tissues, adventitious root formation, fast petiole extension, stem hypertrophy, hyponastic growth, stomata closing, reduction of transpiration and inhibition of photosynthesis (Justin and Armstrong, 1987;Laan et al., 1990;Naidoo and Mundree, 1993;Armstrong et al., 1994;Grimoldi et al., 1999;Cox et al., 2003;Striker et al., 2005). Bacanamwo and Purcell (1999b) indicated that adaptation and acclimation of soybean to flooding stress involved preferential allocation of photosynthates, development of porous adventitious roots and formation of aerenchyma. ...
... In response to flooding stress, the plants developed a suite of anatomical, morphological and physiological mechanisms to adapt to the submergence environment (Armstrong, 1979;Colmer & Voesenek, 2009;Kozlowski, 1984;Striker, Insausti, Grimoldi, Ploschuk, & Vasellati, 2005;Vartapetian & Jackson, 1997). Plant responses under flooding stress included the generation of aerenchyma in tissues, adventitious root formation, fast petiole extension, stem hypertrophy, hyponastic growth, increase in plant height, stomata closing, reduction in transpiration and inhibition of photosynthesis (Armstrong, Strange, Cringle, & Beckett, 1994;Cox, Millenaar, van Berkel, Peeters, & Voesenek, 2003;Grimoldi, Insausti, Roitman, & Soriano, 1999;Justin & Armstrong, 1987;Laan, Tosserams, Blom, & Veen, 1990;Naidoo & Mundree, 1993;Striker et al., 2005). All these main plant responses facilitate the transport of oxygen from shoots to roots, allow root growth and soil exploration under anaerobic conditions, continue nutrient uptake under flooding conditions, regulate the water balance of plants to prevent leaf dehydration, and improve plant flooding tolerance (Armstrong, 1979;Ashraf, 2003;Bradford & Hsiao, 1982;Colmer & Greenway, 2005;Kozlowski & Pallardy, 1984;Striker et al., 2005). ...
Soybean (Glycine max [L.] Merr.) cultivars are generally sensitive to flooding stress. The plant growth is severely affected and grain yield is largely reduced in the flooded field. It is important to develop flood-tolerant soybean cultivars for grain production in regions of heavy rainfalls worldwide. In this study, a total of 722 soybean genotypes were evaluated for flooding tolerance at R1 stages (first flower at any node) in the 5-year flooding screening tests. Differential soybean genotypes exhibited diverse responses to flooding stress with that plant foliar damage score (FDS) and plant survival rate (PSR) ranged from 1.9 to 8.8 and 3.4% to 81.7%, respectively (p < .0001). Based on our standard of flooding evaluation, most genotypes were sensitive to flooding with 6.0 of average FDS and 38.7% of PSR. Fifty-two soybean genotypes showed flooding tolerance and 11 genotypes were with consistent flooding tolerance during 4- to 5-year continual evaluations. In the meantime, six genotypes were identified with consistent high sensitivity to flooding. The group analysis showed that genotypes from different sources had distinguishable responses to flooding stress (p < .0001). The interacting analysis of year and flooding tolerance indicated that FDS and PSR means were significantly different among 5 years due to weather temperature and flooding treatment time influences of each year (p < .0001). Furthermore, five breeding lines with high-yielding and flood-tolerant traits were developed using selected consistent flood-tolerant and high-yielding genotypes through conventional breeding approach.
... The most common anatomical response is the generation of aerenchyma in tissues, which facilitates the transport of oxygen from shoots to roots (Justin and Armstrong, 1987;Seago et al., 2005;Colmer, 2003). At the morphological level, usual responses to flooding include adventitious rooting and increases in plant height and consequently, in the proportion of biomass above water level (Naidoo and Mundree, 1993;Grimoldi et al., 1999). This also helps to facilitate the oxygenation of submerged tissues through the aerenchyma tissue (Laan et al., 1990;Colmer, 2003). ...
Global climate change is predicted to lead to extreme temperatures, severe drought as well as heavy storms, and periodic flooding. The discussion on the consequences is spreading across the world. Global climate change is likely to increase the problems of food insecurity, hunger, and malnutrition for millions of people, particularly in South Asia, sub-Saharan Africa, and small islands. Plant breeding is necessary to create cultivars adapted to these new climate demands, which keep up with pest and disease evolution and can meet new environmental demands, while also meeting demands for quality and high yield.
... In the same way, Nabben et al. (1999) found that the responses to an increase of flood frequency and duration of Rumex species in riparian habitats varied according to their age. Our results suggest that in addition to the survival of L. girardianum, flood duration has a strong negative effect on leaf production and leaf area (Hellings and Gallagher, 1992;Lenssen et al., 1998;Blanch, 1999;Grimoldi et al., 1999;Mommer et al., 2007). Blom and Voesenek (1996) showed that plant species subjected to flooding can respond to anoxia by developing structures to reach the water surface. ...
j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / a q u a b o t Effects of experimental submersion on survival, growth, and dry biomass allocation of the rare salt marsh plant Limonium girardianum a b s t r a c t In order to define the flooding tolerance capacity of Limonium girardianum according to growth development stage, we submerged 200 seedlings and 200 four-month-old juveniles in fresh water. During the eleven weeks of the experiment, we recorded the survival, growth and dry biomass of both seedlings and juveniles. Every week, we removed a group of ten seedlings and ten juveniles from submerged conditions and put them in drained conditions. We measured the leaf production rate and variation in total leaf area of both seedlings and juveniles. We measured the final above and below-ground dry biomass for both seedlings and juveniles. The seedlings started to die from week-2, while juveniles started to die from week-7. Fifty percent of seedlings died over a six weeks period, while fifty percent of juveniles died over a ten-week period. Beyond seven weeks and nine weeks for seedlings and juveniles respectively, total submersion stopped growth, and delayed leaf production and the increase of the total leaf area. Above-ground dry biomass significantly decreased from 30 g to 10 g for seedlings and from 30 g to 25 g for juveniles, according to flood duration. Below-ground dry biomass percentage increased from 60% to 80% between week-4 and week-7 for seedlings. Below-ground dry biomass of juveniles decreased from 80% to 50% between week-4 and week-9. Our study showed that flood-prone plant species have a different response to flood conditions according to the developmental stage. The higher sensitivity to submersion of seedlings is due to its lower survivorship, lower leaf production, lower growth and more important dry biomass decrease than juveniles. This statement can be seen as a threat for population viability in the long term since human activities, such as construction of heavy industrial infrastructures and roads, induces too long flood duration that would compromise the persistence of L. girardianum populations.
... The responses of plants to excess soil water are determined by time, duration and intensity (depending on water depth) of the stress and the plant genotype (Caetano & Dias-Filho, 2008, Dias-Filho, 2002de Oliveira & Joly, 2010, Grimoldi et al. 1999Mahelka et al. 2006;Manzur et al. 2009;Mollard et al. 2008). Moreover, the stage of plant development at the time of imposition of stress also determines the pattern of response to excess water in the soil (reviewed by Bailey-Serres & Voesenek, 2008;Colmer & Voesenek, 2009). ...
... Flooding and grazing are disturbances particularly important in shaping the structure and function of many grasslands of the world (McNaughton 1983;Soriano 1992;Oesterheld et al. 1999). There is much information on adult plant responses that involve anatomical, morphological and physiological changes to tolerate or avoid stress (Blom & Voesenek 1996;Grimoldi et al. 1999;Insausti et al. 2001), yet only a few studies have addressed the interactive effects of flooding and grazing on individual growth (Oesterheld & McNaughton 1991;Gough & Grace 1998;Merrill & Colberg 2003). None of these papers have considered these interactive effects upon population recruitment. ...
Abstract Seed germination and seedling emergence are key processes for population recruitment. Flooding and grazing are disturbances forming gaps that may strongly influence recruitment patterns in space and time, but their combined effects and action mechanisms have rarely been addressed. In this study we analysed the effects of microhabitat conditions associated with winter flooding and spring-summer defoliation on seed germination and seedling establishment of Paspalum dilatatum, a dominant perennial C4 grass in native grasslands of the Flooding Pampa, Argentina. The dynamics of seedling emergence from natural seed banks and buried seeds was studied in a factorial experiment with flooding and defoliation treatments applied to soil monoliths (mesocosms) collected from natural grassland. Additional laboratory experiments were applied to investigate seed germination under different combinations of temperature, light quality and imulated flooding. Seed germination and seedling emergence of P. dilatatum were promoted by flooding and high intensity defoliation. Gaps generated by flooding were maintained by high intensity defoliation exercising a synergistic effect on survival seedlings. Flooding resulted in the breaking of seed dormancy and higher germination rates associated with alternating temperature and the activation of the phytochrome system. Our results indicate that microhabitat conditions associated with the disturbances forming gaps, such as flooding and heavy grazing, synergistically promote the recruitment process of this dominant grass species.
... La disminución de las dicotiledóneas con la inundación fue muy notable en el estrato inferior del canopeo. Sin embargo, algunas especies como Leontodón taraxacoides, Phyla canescens y Eryngium ebracteatum, modificaron la posición de sus hojas, mostrando una marcada plasticidad morfológica, localizando una fracción mayor del área foliar en estratos altos, por encima del nivel del agua de inundación(Grimoldi et al., 1999;Jackson, 2008).En otro experimento en mesocosmos se evaluó la interacción entre el pisoteo vacuno simulado y la inundación(Striker et ai., 2011). Aquí, se demostró que el pisoteo del pastizal inundado potencia la acción de las inundaciones sobre la dominancia de las graminoides y el retroceso de las dicotiledóneas. ...
... Aerobic respiration is affected through the slowdown of glycolysis in waterlogged plants leading to decreased adenosine triphosphate (ATP) production and switch to less energy yielding anaerobic fermentation (Bramley et al., 2007;Zabalza et al., 2009). Consequently, oxygen deficiency due to waterlogging is predicted to lead to reduced plant growth, development and survival (Grimoldi et al., 1999;Ashraf et al., 2011;Krishnamurthy et al., 2011). In addition to reduced growth, plants that are subject to waterlogging often develop symptoms of leaf yellowing, wilting, root rotting, and root blackening (Jackson, 2002;Dodd et al., 2013;Shaw et al., 2013). ...
Using field collected asexual Epichloë endophyte infected (E+) and endophyte free (E−) Hordeum brevisubulatum plants in a greenhouse experiment, we demonstrate that endophyte infection increases host plant resistance to waterlogging. All plants assigned to waterlogging treatment started to wither and lose their root vitality, and consequently lost considerable photosynthesizing and root tissues. However, E+ plants showed significantly less symptoms of damage, and they produced significantly greater content of chlorophyll, more tillers, higher shoots and higher under-ground biomass compared to E− plants. Waterlogging induced osmoprotective proline production particularly in E+ plants and had lower malondialdehyde content and electrolyte leakage, suggesting that endophyte infection positively affects osmotic potential and oxidative balance of the host plant. We propose that higher resistance of E+ plants of H. brevisubulatum to waterlogging should be acknowledged in breeding programmes and the scenarios of changes in grassland ecosystems as a result of climate change.
... The responses of plants to excess soil water are determined by time, duration and intensity (depending on water depth) of the stress and the plant genotype (Caetano & Dias-Filho, 2008, Dias-Filho, 2002de Oliveira & Joly, 2010, Grimoldi et al. 1999Mahelka et al. 2006;Manzur et al. 2009;Mollard et al. 2008). Moreover, the stage of plant development at the time of imposition of stress also determines the pattern of response to excess water in the soil (reviewed by Bailey-Serres & Voesenek, 2008;Colmer & Voesenek, 2009). ...
... In the same way, Nabben et al. (1999) found that the responses to an increase of flood frequency and duration of Rumex species in riparian habitats varied according to their age. Our results suggest that in addition to the survival of L. girardianum, flood duration has a strong negative effect on leaf production and leaf area (Hellings and Gallagher, 1992;Lenssen et al., 1998;Blanch, 1999;Grimoldi et al., 1999;Mommer et al., 2007). Blom and Voesenek (1996) showed that plant species subjected to flooding can respond to anoxia by developing structures to reach the water surface. ...
In order to define the flooding tolerance capacity of Limonium girardianum according to growth development stage, we submerged 200 seedlings and 200 four-month-old juveniles in fresh water. During the eleven weeks of the experiment, we recorded the survival, growth and dry biomass of both seedlings and juveniles. Every week, we removed a group of ten seedlings and ten juveniles from submerged conditions and put them in drained conditions. We measured the leaf production rate and variation in total leaf area of both seedlings and juveniles. We measured the final above and below-ground dry biomass for both seedlings and juveniles. The seedlings started to die from week-2, while juveniles started to die from week-7. Fifty percent of seedlings died over a six weeks period, while fifty percent of juveniles died over a ten-week period. Beyond seven weeks and nine weeks for seedlings and juveniles respectively, total submersion stopped growth, and delayed leaf production and the increase of the total leaf area. Above-ground dry biomass significantly decreased from 30 g to 10 g for seedlings and from 30 g to 25 g for juveniles, according to flood duration. Below-ground dry biomass percentage increased from 60% to 80% between week-4 and week-7 for seedlings. Below-ground dry biomass of juveniles decreased from 80% to 50% between week-4 and week-9. Our study showed that flood-prone plant species have a different response to flood conditions according to the developmental stage. The higher sensitivity to submersion of seedlings is due to its lower survivorship, lower leaf production, lower growth and more important dry biomass decrease than juveniles. This statement can be seen as a threat for population viability in the long term since human activities, such as construction of heavy industrial infrastructures and roads, induces too long flood duration that would compromise the persistence of L. girardianum populations.
... Dias-Filho & Carvalho (2000) and Dias-Filho (2002) also found a decrease in RMR and an increase in LMR in flooded Brachiaria spp. Also, a higher proportion of biomass allocated to leaves was observed in flooded Leontodon taraxacoides (Asteraceae) by Grimoldi et al. (1999). In contrast, Mattos et al. (2005) reported that flooding caused a lower LMR in Brachiaria spp. ...
Some morphophysiological responses of Brachiaria brizantha cv. Marandu, cv. Piatã, cv. Arapoty, B163, B166 and B. ruziziensis R124 were compared in plants grown in pots, under flooded and well-drained conditions. Flooding reduced leaf elongation rate in all accessions. Leaf dry mass production was lower under flooding than in the control plants in all the studied accessions, except in cv. Piatã. Root dry mass production was reduced by flooding in cv. Marandu and in R124, while the proportion of biomass allocated to roots was reduced by flooding only in R124. It was not possible to detect significant differences between water regimes in the percentage of biomass allocated to culms and leaves for all accessions. Flooding decreased the number of tillers in cv. Marandu, in B163, B166 and in R124. Relative growth rate was decreased by flooding in cv. Marandu, in B163 and in R124. Flooding reduced gas exchange parameters in all accessions, but cv. Arapoty. The accessions tested differ in their relative tolerance to flooding. B. brizantha cv. Arapoty is considered the most tolerant. B. ruziziensis R124 is the most sensitive, followed by B. brizantha cv. Marandu. B. brizantha cv. Piatã, B163 and B166 are intermediate in flooding tolerance.
... Flooding and grazing are disturbances particularly important in shaping the structure and function of many grasslands of the world (McNaughton 1983; Soriano 1992; Oesterheld et al. 1999). There is much information on adult plant responses that involve anatomical, morphological and physiological changes to tolerate or avoid stress (Blom & Voesenek 1996; Grimoldi et al. 1999; Insausti et al. 2001 ), yet only a few studies have addressed the interactive effects of flooding and grazing on individual growth (Oesterheld & McNaughton 1991; Gough & Grace 1998; Merrill & Colberg 2003). None of these papers have considered these interactive effects upon population recruitment. ...
Seed germination and seedling emergence are key processes for population recruitment. Flooding and grazing are disturbances forming gaps that may strongly influence recruitment patterns in space and time, but their combined effects and action mechanisms have rarely been addressed. In this study we analysed the effects of microhabitat conditions associated with winter flooding and spring-summer defoliation on seed germination and seedling establishment of Paspalum dilatatum, a dominant perennial C4 grass in native grasslands of the Flooding Pampa, Argentina. The dynamics of seedling emergence from natural seed banks and buried seeds was studied in a factorial experiment with flooding and defoliation treatments applied to soil monoliths (mesocosms) collected from natural grassland. Additional laboratory experiments were applied to investigate seed germination under different combinations of temperature, light quality and simulated flooding. Seed germination and seedling emergence of P. dilatatum were promoted by flooding and high intensity defoliation. Gaps generated by flooding were maintained by high intensity defoliation exercising a synergistic effect on survival seedlings. Flooding resulted in the breaking of seed dormancy and higher germination rates associated with alternating temperature and the activation of the phytochrome system. Our results indicate that microhabitat conditions associated with the disturbances forming gaps, such as flooding and heavy grazing, synergistically promote the recruitment process of this dominant grass species.
... The major graminoids in our mesocosms have highly constitutive root aerenchyma and great plasticity, allowing them to increase the proportion of aerenchyma without losing root strength (for P. dilatatum and P. geminatum see Striker et al. 2006Striker et al. , 2007. By contrast, most forb species have roots with low constitutive aerenchyma (for L. taraxacoides and M. pulegium see Grimoldi et al. 1999Grimoldi et al. , 2005, which presents a disadvantage. In these species, the increase in root aerenchyma induced by flooding favours the structural weakness of the root system (Striker et al. 2007). ...
Questions: What are the interactive effects of flooding and cattle trampling upon the structural attributes and the floristic composition of a plant community? Do the effects on the plant community persist over an extended recovery period?
Location: Flooding Pampa grasslands, Argentina (36°30′ S, 58°30′ W).
Methods: We assessed the effects of 40-d of flooding, trampling and the combination thereof on plant cover and biomass, vertical distribution of foliage and floristic composition in lowland grassland mesocosms. We considered a 120-d recovery period to evaluate the persistence of flooding and trampling effects on the plant community.
Results: Flooding, with or without trampling, increased cover and biomass of the graminoid species, especially marsh grasses, which developed a taller canopy, whereas most of the forb species were negatively affected. This was enhanced by trampling, as the aerial biomass of the dominant legume Lotus tenuis decreased by 90%, while three major forb species disappeared. Trampling under flooding conditions did not reduce the total above-ground biomass production, as the growth enhancement of graminoids was enough to compensate for the breakdown of the forbs. Below-ground biomass was lower when both perturbations occurred simultaneously. After 120-d of recovery, graminoids continued to be dominant while the remaining forbs (including L. tenuis) recovered only partially. Below-ground biomass recovered fully at the end of the growing season.
Conclusions: The combination of flooding and trampling shifts the community co-dominance of graminoids and forbs towards a persistent dominance of graminoid species. When both perturbations are combined, the above-ground production of the grassland is unaffected and root biomass is rapidly recovered. However, the loss of the legume L. tenuis deserves attention because this is the unique nitrogen-fixing species of the ecosystem, which improves the forage quality for livestock production.
... -textured soils. The degree of submergence is an important determinant of plant responses to flooding; water logging of the root zone and complete submergence of aboveground portions of plants may obstruct gas exchange for non-aquatic plants. Complete inundation is shown to be more harmful to plants than mere soil inundation or partial submergence (Grimoldi et al . 1999;Mauchamp, Blanch & Grillas 2001). The effect of anoxia on plants is species-specific, and the individualistic responses of species affect community composition in somewhat predictable ways. Some riparian species have effective anaerobic respiration, while others can endure only very short periods of inundation, as reflected in the typica ...
Summary • Flooding governs riparian plant diversity along boreal rivers but the ecological role of extreme floods is only partly understood. We studied the dynamics of riparian plant composition and richness in the free-flowing Vindel River in northern Sweden, and the importance of reach type in sustaining high species richness. • We conducted three surveys of riparian plant species richness over a period of two decades. The first and last of these surveys were conducted 1–3 years after significant flooding and the second was carried out after a period of more moderate flooding. • Our results suggest that extreme floods reduce riparian plant species richness in tranquil (slow-flowing) reaches but that a subsequent period of less extreme flood events facilitates recovery. Tranquil river reaches were also more prone to invasion by ruderal species following major floods. Species richness in turbulent reaches (rapids and runs) remained constant during all surveys. One possible explanation for this pattern is that tranquil reaches become more anoxic during floods because they have more fine-grade soils with lower hydraulic conductivity than turbulent reaches. Anoxic conditions may cause stress and plant death, opening up space for colonization. Turbulent reaches maintain a better oxygenation in the root zone of plants through high groundwater turnover, reducing negative effects of prolonged floods. • The fact that turbulent reaches preserved species richness regardless of flood magnitude suggests that they are important for the resistance of riparian ecosystems to prolonged inundation. In contrast, tranquil reaches, with a higher water-holding capacity, might instead maintain their species richness during drought periods. • Synthesis and applications. Our findings highlight the importance of spatial and temporal variation in riverine plant species richness and composition. To conserve these habitats at a landscape scale, a full range of reach types is necessary to allow for recovery in reaches where species richness has declined. To maintain healthy riparian zones, river managers should focus restoration efforts on interactions between hydrology, geomorphology and biota. Journal of Applied Ecology (2007) 44, 147–157 doi: 10.1111/j.1365-2664.2006.01223.x
... Increases in leaf lengths under flooding conditions is a common response of flooding-tolerant plants as it helps their leaves to emerge from water to recover contact with the air (Laan et al. 1990;Grimoldi et al. 1999;Voesenek et al. 2006). On the other hand, floodsensitive plants do not increase and even diminished leaf length and plant heights in flooding or waterlogged conditions (Oesterheld & McNaughton 1991;Dixon 1996;Malik et al. 2001). ...
It was hypothesised that subtle topographical differences might cause the existence of ecotypes along a floodplain. The apomict grass Paspalum dilatatum subspecies dilatatum inhabits flood-prone lowlands as well as nearby uplands in the floodplains of Argentina, while the sexual P. dilatatum subspecies flavescens almost exclusively inhabits the uplands. The aim of the present study was to identify the different traits that allow these P. dilatatum populations to inhabit different habitats. Plants of P. dilatatum were reciprocally transplanted between uplands and lowlands. Morphophysiological traits related to flooding tolerance were measured during a flood. Subspecies dilatatum from the uplands and subspecies flavescens showed a high physiological performance in the uplands but a considerable decrease in stomatal conductance, net photosynthesis rates and tiller number in the flooded lowlands. In contrast, the subspecies dilatatum from the lowlands showed relatively lower and stable stomatal conductance, photosynthesis rates and leaf water potential at both sites. Subspecies dilatatum from the lowlands outperformed upland populations at the lowland site with respect to tillering. Leaves of subspecies dilatatum from the lowlands that had grown at the lowland habitat had a lower blade/sheath proportion than leaves of plants transplanted to the uplands. This behavior did not occur in both upland populations. Results suggest that dilatatum Lowland plants have the typical strategy of stress-tolerant genotypes and that the upland populations are adapted to habitats where competitive species are selected. In conclusion, habitats with subtle differences in topographic level can favour both ecotypic differentiations within an apomict subspecies but also the maintenance of morphophysiological similitudes between coexisting upland populations belonging to different subspecies.
... This idea was previously stated only for grass species, which regrow mainly from current assimilation (see Hayball and Pearce 2004 for Bolboschoenus caldwellii; Merril and Colberg 2003 for Deschampsia caespitose; Oesterheld and McNaughton 1991 for Cenchrus ciliaris and Panicum coloratum; and Striker et al. 2008 for Paspalum dilatatum). At all defoliation treatments, the continuous emergence of shoots from water in flooded soil allows plants to restore contact of leaves with atmospheric oxygen (Bailey-Serres and Voesenek 2008; Colmer and Voesenek 2009; Grimoldi et al. 1999; Striker et al. 2005), allowing the capture and transport of oxygen from shoots to roots of increased porosity (i.e. higher aerenchyma tissue) through passive diffusion (Colmer 2003). This de-submergence shoot response, which is relevant in determining the flooding tolerance of once defoliated plants (see also Striker et al. 2008), negatively determined the outcome of plants subjected to a higher defoliation frequency. ...
Repeated defoliation and flooding trigger opposite plant morphologies, prostrated and erect ones, respectively; while both
induce the consumption of carbohydrate reserves to sustain plant recovery. This study is aimed at evaluating the effects of
the combination of defoliation frequency and flooding on plant regrowth and levels of crown reserves of Lotus tenuis Waldst. & Kit., a forage legume of increasing importance in grazing areas prone to soil flooding. Adult plants of L. tenuis were subjected to 40days of flooding at a water depth of 4cm in combination with increasing defoliation frequencies by
clipping shoot mass above water level. The following plant responses were assessed: tissue porosity, plant height, biomass
of the different organs, and utilization of water-soluble carbohydrates (WSCs) and starch in the crown. Flooding consistently
increased plant height independently of the defoliation frequency. This response was associated with a preferential location
of shoot biomass above water level and a reduction in root biomass accumulation. As a result, a second defoliation in the
middle of the flooding period was more intense among plants that are taller due to flooding. These plants lost ca. 90% of their leaf biomass vs. ca. 50% among non-flooded plants. The continuous de-submergence shoot response of frequently defoliated plants was attained in
accordance to a decrease of their crown reserves. Consequently, these plants registered only 27.8% of WSCs and 9.1% of starch
concentrations with respect to controls. Under such stressful conditions, plants showed a marked reduction in their regrowth
as evidenced by the lowest biomass in all plant compartments: shoot, crowns and roots. Increasing defoliation frequency negatively
affects the tolerance of the forage legume L. tenuis to flooding stress. Our results reveal a trade-off between the common increase in plant height to emerge from water and the
amount of shoot removed to tolerate defoliation. When both factors are combined and defoliation persists, plant regrowth would
be constrained by the reduction of crown reserves.
KeywordsCrown reserves–Defoliation frequency–Flooding–Leaf removal–
Lotus tenuis
–Plant height
... The development of sclerenchyma in the collapsed phloem is probably simultaneous to dilatation growth, and the cells that become sclerified may experience a considerable enlargement before they develop secondary walls (Esau 1969). Diverse studies have suggested that sclerenchyma serve as mechanical support and may play a role protecting the aerenchyma from collapse in roots cortex (Ashford and Allaway 1995;Grimoldi et al. 1999;Purnobasuki and Suzuki 2004) and possibly this is true for the collapsed phloem region. The gelatinous fibres observed in the immersed portion of the stem of P. aquatica (Angeles 1992a) were not observed in the studied species A. glabra and L. racemosa which presented fibres in the phloem. ...
Growth and physiological response of woody plants to flooding have been analyzed in detail; however, relatively few studies
have been oriented towards the effects of water immersion on cambial activity and wood and bark anatomy of trees that are
growing in prolonged flooding conditions. These studies are important to understand the possible effects of predicted sea
level rising in mangroves as a consequence of global warming. We studied five species growing in a mangrove forest, sampling
three to six trees of each species, in sites that have the longest flooding period. Differences in bark appearance and phloem
structure between the submerged stem portion and the portion of the stem above the water surface exist in all species. Although
aerenchyma formation and stem hypertrophy are the most common events related to flooding, each type of tissue responded differently.
Annona glabra L., Laguncularia racemosa (L.) Gaertn f. and Hibiscus
tiliaceus L. developed rythidome. Avicennia germinans (L.) Stearn developed rythidome only in the submerged stem portion. Phyllanthus
elsiae Urb., developed one periderm in both stem portions. Species that developed rythidome also developed aerenchyma between periderms
and in the phellem. H. tiliaceus and P.
elsiae, showed the highest values for anatomical phloem and periderm characters below water surface, while an inverse tendency was
observed in A. glabra and L. racemosa, suggesting that prolonged flooding modifies vascular cambium and phellogen differently. Results indicate that sea level
rising would affect distribution of the species according to their specific flooding tolerance.
... However, in the frequently flooded zones, because of its characteristic mode of growth, C. palustre had a high proportion of its total leaf area (photosynthetically active biomass) above the water surface even in deep water. A similar response has also been noted for Leontodon taraxacoides (Vill) Merat, a tolerant herb that grows on flooded grasslands (Grimoldi et al. 1999). The structural response to flooding was apparently reflected in the stand's gross photosynthesis during extended flooding, because it was higher than could be predicted on the basis of the model with only water level as a variable. ...
Littoral wetlands comprise a terrestrial to aquatic continuum along which carbon dioxide is exchanged with the atmosphere and organic carbon is transferred to lakes. Net ecosystem productivity-the difference between atmospheric CO2 uptake and total ecosystem respiration-in these shore areas depends partly on the extent and duration of spring flooding. Ecosystem-atmosphere CO2 fluxes were studied at a boreal lake in Finland to analyze how flooding affects the dynamics of littoral net ecosystem productivity. Two shore transects with different hydrological conditions and vegetation distributions were studied during consecutive ice-free periods with contrasting flooding patterns. Net ecosystem productivity in different vegetation zones did not respond consistently to extended flooding; the response depended on the phenology of plant emergence during the flood and on the decrease in the water level after flooding. The decrease in the water level was steeper in silt-mud sediment than in fen peat, With an exceptionally high water level relative to the height of the vegetation, net ecosystem productivity decreased by 50-100% (net loss, 0.4-7.4 mol m(-2) of CO2 during the wetter open-water period). However, the wetter season could also have a 60-140% higher net ecosystem productivity (net CO2 gain of 0.7 Mol m(-2) to net loss of 6.8 Mol m(-2)) because of the decreased decomposition rate. An extended flooding period greatly reduces the amount of litter produced in a specific year. In both flooding patterns, the littoral zone was an overall net CO2 emitter, but the large variation in the decomposition rate suggests that there are differences in the load of organic matter from the littoral to the pelagic zone.
Plant growth hormones are synthesized throughout the plant, but apical meristems and young, developing tissues are rich sources of these compounds. The phytohormone ethylene effectively controls the growth and senescence of plants. However, depending on its concentration, timing of application, and the plant species, it promotes or inhibits growth and executes senescence processes. Ethylene also mediates the adaptive response to a variety of stress factors such as drought, salinity, flooding, and pathogen attacks. Although ethylene is recognized as the ripening hormone, it has comprehensive effects on a number of other biological processes, including, but not limited to, seed germination, flowering, abscission, senescence, and stress responses. Likewise, it is evident that ROS (reactive oxygen species) trigger biological activities in response to stress. On the other hand, evidence from several decades of research indicates that ROS are involved in plant growth and developmental processes as well. ROS regulate the cell cycle, seed dormancy and germination, root growth, pollen tube, leaf development, and more. In this chapter, we discuss the crosstalk between ethylene and ROS in plant developmental processes.
Riparian habitats are associated with diverse hydrological conditions that may enhance population differentiation in species inhabiting areas close to water. Cardamine scutata Thunb. is a widespread riparian herb that is typically characterized by compound leaves. On the Nohbi Plain in central Honshu, Japan, it has, however, been reported that plants of C. scutata occurring in tidal wetlands along the lower reaches of large rivers have simpler leaves than those inhabiting areas further upstream. In this study, we quantitatively describe environmental conditions, leaf shape and other phenotypic traits of populations in tidal and non‐tidal habitats. Measurements of the electrical conductivity of interstitial water and fluctuations in water levels indicated that tidal populations of C. scutata occurred in typical tidal freshwater wetlands. We found that tidal and non‐tidal populations are characterized by distinct leaf shapes, simple and compound, respectively, under both field and common growth conditions. These observations indicate that differences in leaf shape reflect a genetic differentiation between populations of the same species inhabiting distinct habitats. In addition to leaf shape, we found several phenotypic differences relating to growth form, with plants in tidal populations having elongated hollowed stems and elongated inflorescences. We conclude that tidal populations of C. scutata are a discrete ecotype inhabiting freshwater tidal wetlands, presumably derived either through adaptation or genetic drift. Cardamine scutata Thunb. is a widespread riparian herb and we found that tidal and non‐tidal populations of the species are characterized by distinct leaf shapes, simple and compound, respectively, under both field and common growth conditions. These observations indicate that differences in leaf shape reflect a genetic differentiation between populations of the same species inhabiting distinct habitats.
Submergence is a major constraint that delimits rice productivity in Assam of Northeast India where rice is widely cultivated. Most of the agricultural field of Assam are flood prone that leads to a huge decrease in rice production and therefore, it is necessary to identify the submergence tolerant rice to be exploited for future rice breeding program. Six traditional rice cultivars selected from flood prone area of Assam, India were subjected to submerge stress for 7 and 14 days and their morpho-physiological, biochemical and antioxidant properties were analysed. Based on the overall analyses, Maguri, Nania and Kola Joha have been recorded as tolerant while Bora and Prasadbhog showed susceptible traits as compared to controls. However, in biochemical analysis, shoot and root showed significant differences in antioxidant activity. In case of shoots, Swarnasub1, Nania and Maguri exhibited the tolerance characteristics while Lachit along with Bora, Prasadbhog and Kola Joha were susceptible. On the other hand, root antioxidant analyses showed that Kola Joha was sharing tolerance trait with Swarnasub1 whereas, Prasadbhog and Bora appeared to be susceptible. From this investigation, we also evaluated the enzymatic and non enzymatic analyses under submergence stress with an aim to screen out the best cultivars that could be further utilized for developing submerged tolerant rice cultivar.
Waterlogging Stress influences crop productivity, especially high commercial crop like tobacco, which is very sensitive to an excess of water. This type of environmental stress might happen because of unpredictable season occurred in tropical region, including Indonesia. Global climate change as a consequence of rapid growing industries all over the world might responsible for this. This study aims to investigate the response of some Nicotiana tabacum varieties which are treated with periodic waterlogging stress. Some morphological aspects including plant height, stem diameter, leaves width and the emergence of adventitious roots were investigated. In addition, total chlorophyll content was also measured as physiological parameter. Three different varieties are used such as var. Jepon Pelakean, Jinten, Manilo and Morakot. Data were analyzed using One-Way Annova followed by Tukey post-hoc analysis. In all morphological aspects var. Jepon Pelakean demonstrated best responses compared to other varieties. Meanwhile, we observed a sharp decline of total chlorophyll content in var. Manilo under this periodic waterlogging stress. The overall results suggest that each variety of tobacco possess a specific mechanism against periodic waterlogging stress.
A greenhouse study to evaluate adaptation of 4 herbaceous summer legumes to temporary waterlogging was conducted. Species evaluated were Desmanthus virgatus and Aeschynomene americana in their vegetative stage, and Macroptilium lathyroides and M. atropurpureum in both vegetative and reproductive stages. The experimental design was randomized blocks with 5 replications and treatments were: T0, control; T1, saturation by capillary movement placing pots in buckets of 5 L with 10 cm of permanent water; and T2, flooding, placing pots in buckets of 10 L and a layer of water 5 cm above the soil. The duration of the water treatments was 7 days. Waterlogging did not affect shoot or root biomass production nor nodulation in A. americana, whereas D. virgatus had its highest dry matter production in saturated soil (T1). In M. lathyroides flooding tolerance was more evident in the reproductive than in the vegetative stage, probably due to more production of adventitious roots and formation of aerenchymatic tissue. Macroptilium atropurpureum showed adaptation to temporary flooding. Survival and quick recovery of these species would confirm their potential as forages for temporarily waterlogged soils.Keywords: Forage legumes, flooding, Aeschynomene americana, Desmanthus virgatus, Macroptilium lathyroides, Northeast Argentina.DOI: 10.17138/TGFT(2)278-286
To characterize flooding-affected anatomical morphology changes in soybean, flooding-tolerant cv Pung-sannamulkong (PSNK) and flooding-sensitive cv. Sobaek-namulkong (SBNK) at 5 trifoliate leaf stage were exposed to flooding by maintaining tap water 2 cm above soil surface for 9 days and resultant microscopic anatomical changes in leaf and hypocotyl cross-sections along with chlorophyll content and photosynthetic rate changes were compared. Flooding-sensitive SBNK exhibited more significant decrement in chlorophyll content, photosynthetic rate, number of palisade parenchyma, and leaf dry matter compared to cv. PSNK. Flooding decreased fineness of palisade parenchyma, while inducing wider xylem vessel, especially in PSNK. The aerenchyma formation in hypocotyls under flooding could be observed only in flooding-resistant PSNK. All these anatomical changes seems to be related with higher physiolocial activity and resultant resistance against flooding in PSNK compared to flood-sensitive PSNK.
We compared the growth responses of the floating-leaved species Nymphoides peltata to gradual and rapid rising water levels under two nutrient concentrations (1g and 12g of slow released fertilizer (N–P–K: 16–8–12) per container filled with 8kg washed sand), and predicted the population expansion after these floods. The results showed that the capacity for petiole elongation was dependent on leaf age, and only leaves that were no more than five days old had the capability to reach the water surface when the water level increased rapidly from 50cm to 300cm. Plants subjected to a gradual rising water level tracked the increase in water depth whose petioles elongated at 3.96±1.70cm per day and 4.80±0.16cm per day under low and high nutrient concentrations respectively throughout the experiment period. When water levels were rapidly raised, leaf petioles elongated rapidly at 25.48±1.51cm per day and 26.64±2.24cm per day under low and high nutrient concentrations respectively during the first ten days. Plants under a constant water level maintained highest mean leaf recruitment (mean 3.0±0.33 leaves and 24.4±5.87 leaves every ten days under low and high nutrient concentrations, respectively). Therefore, more young leaves existed in the canopy ensuring that when the water level increases, young leaves can rapidly emerge after submergence. Gradual water level rise did not significantly affect biomass and ramet production (4.75±1.41g and 5.50±1.22 ramets in low nutrient; 48.49±21.45g and 35.67±11.78 ramets in high nutrient), but rapid water level rise negatively affected ramet production in both nutrient concentrations (3.00±1.26 ramets and 11.25±4.19 ramets in low and high nutrients, respectively). The results indicated that continual leaf recruitment and rapid petiole elongation were both important ways in which N. peltata adapted to increasing water levels. Extreme flooding may be a disturbance factor that affects plant growth and the population expansion of N. peltata, while small gradual water level rise should not harm this species.
Abstract The effect of the duration of waterlogging on the pre-dawn water potential, gas exchange, biomass accumulation and survival was investigated on four species, Leptospermum scoparium (Forst et Forst.f.), Acacia melanoxylon (R. Br.), Eucalyptus obliqua (L’Herit) and Nothofagus cunninghamii (Hook.). These species co-occur, but are restricted to particular microsites. The three waterlogging treatments applied to potted seedlings were: four cycles of 15 days, two cycles of 30 days or one 60-day cycle, followed by an equal period in freely drained conditions. Water potential, gas exchange, biomass accumulation and survival were not significantly affected by the duration of waterlogging in L. scoparium or A. melanoxylon. With increased waterlogging duration, N. cunninghamii had progressively decreased survival, had less biomass accumulation in all waterlogging treatments and more negative water potential after the 60-day waterlogging cycle. In contrast, E. obliqua had low survival under the 15-day waterlogging cycle treatment, although survival, biomass accumulation and maximum net photosynthesis were decreased by all waterlogging cycle treatments. Water potential was significantly lower (more negative) in E. obliqua than other species after the 30- and 60-day waterlogging cycle treatments only. When exposed to oxygen deficit in hypoxic nutrient culture for 5 days, L. scoparium had 100% survival and maximum net photosynthesis was not affected. Acacia melanoxylon had 80% survival and decreased photosynthesis from 2 days of exposure onwards. Nothofagus cunninghamii and E. obliqua had 70% and 30% survival, respectively, and their photosynthesis was significantly depressed after 1 day of exposure to hypoxic conditions. Relative tolerance of the species examined to waterlogging and hypoxia was consistent with adaptation to conditions of seasonal variation in water table height and soil oxygenation concentration observed at the microsites occupied by the respective species. The results indicate that duration of waterlogging may be a major determinant in the microsite distribution of the co-occurring species investigated.
Natural flooding is a major component of the disturbance regime in many grassland ecosystems. The objective of this study was to analyze the relationship among constitutive and plastic root traits and tolerance to flooding in coexisting perennial species of the flooding pampa grasslands (Argentina). A mesocosm experiment was designed for five native species (Paspalidium paludivagum, Paspalum dilatatum, Bothriochloa laguroides, Eryngium ebracteatum, and Eclipta bellidioides) and two exotic ones (Mentha pulegium and Plantago lanceolata). Across species, constitutive root porosity was positively correlated with the tolerance to soil flooding. Moreover, the generation of additional aerenchyma was larger in species with intermediate values of constitutive root porosity and lower in species with low or high constitutive root porosity. This differential increase in the root porosity of each species, combined with the values of constitutive root porosity, resulted in a stronger correlation between final root porosity and tolerance under flooding conditions. Native grasses increased the proportion of root aerenchyma, showing a small change in the number of lysed cells but a significant increase in the cortex proportion and diameter of roots. Exotic dicots generated lysigenous aerenchyma throughout their cortex; in contrast, native dicot species maintained the cell layers adjacent to the stele. A lag in the development of secondary growth during flooding was detected in both groups of dicots, a response that was particularly evident in the exotic species, contrasting with their prominent growth under nonflooded conditions. In general, our results indicate that constitutive and plastic root traits are very significant in terms of the effects of periodic flooding on the abundance of coexisting species of the flooding pampa grasslands.
Cuttings of black willow (Salix nigra), a naturally occurring wetland species, are used for restoration and streambank stabilization. As an adaptation to their wetland habitat, this species develops aerenchyma tissue to avoid root anoxia. To determine the effects of combined copper and ultraviolet-B radiation exposure on aerenchyma tissue (measured as root porosity), black willow cuttings were grown hydroponically and exposed to three ultraviolet-B (UV-B) intensities and three Cu concentrations in a completely randomized 3 × 3 factorial design. While both UV-B (F
2,42 = 11.45; p = 0.0001) and Cu (F
2,42 = 6.14; p = 0.0046) exposure increased root porosity, total biomass decreased in response to both UV-B (F
2,43 = 3.36; p = 0.0441) and to Cu (F
2,43 = 4.03; p = 0.0249). Root biomass decreased only in response to Cu (F
2,41 = 3.41; p = 0.0427) resulting in a decrease in the root/shoot ratio (F
2,42 = 3.5; p = 0.0393). Copper exposure also resulted in a decrease in the number of leaves/shoot (F
2,42 = 7.03; P = 0.0023). No UV-B and Cu interaction was found. While the present research indicates the negative effects of Cu contamination and elevated UV-B intensities on S. nigra, it also points out potential mechanisms that S. nigra uses to alleviate these stresses.
Most herbaceous species in the examined southern Wisconsin floodplain forests had definite elevation optima and could be categorized as either light specialists for high or low light, or light generalists. Higher elevation areas were dominated by tall competitive perennial forbs. As flooding frequency increased, smaller perennial forbs (stress-tolerant competitors) and tall annuals (competitive ruderals) increased in importance. In areas of greatest flooding frequency, the dichotomy in plant strategies was most extreme; slow-growing, flood-tolerant sedges and grasses (stress tolerators) shared the ground with small, fast-maturing, annual forbs (ruderals). Tolerance to flooding in sedges and grasses may be related to the position of their shoot apex, which affords protection from mechanical damage caused by turbulent flooding. Light was important in differentiating guilds (high light specialists, light generalists, small spring-flowering forbs) only when flooding was infrequent. One environmental event, such as flood, fire, or drought, may be seen as a disturbance by short- lived ruderal species and as a stress by tolerant, long-lived perennials.-from Authors
The C-4 African grass, Pennisetum setaceum (fountaingrass), has a greater altitudinal distribution than any other grass on the island of Hawaii. Clones of P. setaceum were reciprocally transplanted among coastal dry grassland, montane dry shrubland, and subalpine dry forest sites on the leeward side of Hawaii to evaluate the contribution of local adaptation and individual tolerance to the broad ecological amplitude of this grass. Physiological, growth, and reproductive responses differed among sites without evidence of local adaptation. Greatest tiller production and the highest photosynthetic rates were observed at the mid-altitude site, but plants at the coastal site attained greater basal areas, aboveground biomass, and number of inflorescences. Correlation among the responses of different plant characters was environmentally dependent, suggesting that the integrated expression of these characters is also plastic. Few differences in plant responses, however, were attributable to a population's origin or the site-by-population interaction; resident populations and introduced populations responded similarly at each site. Furthermore, few characters exhibited variation among clones, indicating that these populations likely possess little genetic variation. Limited clonal variation was, however, detected for net photosynthesis, the ratio of internal to ambient CO2 concentration (c(i)/c(a)), and specific leaf area, but only on two of five dates over a 1-yr period. Phenotypic plasticity for both individual characters and the integration of physiological and morphological characters have apparently been most important in allowing P. setaceum to become dominant across diverse habitats on Hawaii.
The distribution on shorelines of four helophyte species (two gramineous species, viz. Phalaris arundinacea L. and Phragmites australis (Cav.) Trin. ex Steudel and two cyperacean species, viz. Scirpus maritimus L. and S. lacustris L.) was studied in relation to growth responses in the water-depth gradient. Stands of S. lacustris were found at lower depths relative to the mean water level (average fringe depth 69 __ 19 cm) than stands of Phragmites australis (av. 45 + 20 cm), S. maritimus (av. 36 + 8 cm) and Phalaris arundinacea (av. 25 _+ 8 cm). The growth responses to a gradient of water depth were studied by planting the four species at five distinct water depths in outdoor basins, and determining morphological parameters and biomass distributions of the species grown for two consecutive years. The biomass of Phalaris arundinacea was reduced below 30 cm water depth, while Phragmites australis and S. maritimus showed reduced biomass at 80 cm water depth. S. lacustris showed no biomass reduction even at 80 cm water depth. An increased above-ground: below-ground biomass ratio in deeper water was demonstrated for each of the species under study; however, the modification of biomass distribution in the gramineous species occurred abruptly in very shallow water contrary to the cyperacean species. Mean basal stem diameter increased with water depth in all four species. Mean stem length increased with water depth in three of the four species. Stem elongation with increasing water depth was strongest in the cyperacean species. The gramineous species showed enhanced formation of adventitious roots at submerged nodes. The similarity of responses to water depth was greatest within each of the groups of gramineous and cyperacean species. The responses reflect the zonation of the species along the water-depth gradient: S. lacustris in relatively deep water, Phragmites australis and S. maritimus in shallower water, and Phalaris arundinacea in very shallow water.
The impact of cattle trampling on the porosity of a representative soil (Typic Natraquoll) of the flooding Pampa of Argentina was studied from 1984 to 1987. Water content, total porosity (TP), macroporosity (> 30 μm) and mean weight diameter of water-stable aggregates (MWD) were determined in undisturbed topsoil samples taken from adjacent continuously grazed (1.0 animal unit/ha/yr) and ungrazed (since 1976) areas. It was expected that trampling would decrease macroporosity when the soil was ponded, and that the damaged macropores would regenerate during the subsequent soil drying. This was only partly verified. The soil varied in TP from 58 to 64% in the ungrazed area, and from 53 to 78% in the grazed area. This variation resulted mainly from shrink-swell processes. Trampling decreased soil macroporosity (mainly >60 μm) from 8 to 5% and decreased MWD from 5.35 to 4.58 mm under dry soil conditions. The damaged soil pores regenerated and aggregate stability recovered during the subsequent period of surface water ponding, when soil swelling increased macropores in the grazed area but not in the ungrazed area. There was no evidence of poaching damage in this soil.
Polygonum aviculare subsp. aviculare is an annual selfing weed common in abandoned arable fields where it occurs as a widespread hexaploid cytotype (6x=60) and a rarer tetraploid cytotype (4x=40). The basis of phenological differentiation between the two cytotypes observed in a natural population where they coexist was examined in a greenhouse experiment comprising six soil conditions consisting of factorial combinations of two levels of fertility and three pot sizes. The environmental and genetic component of variation in 11 life history and morphological traits was quantified. Even though all traits except life span were plastic the two cytotypes appear to have evolved contrasting life history strategies and it is inferred that this can account for the temporal niche differentiation observed in the abandoned field during the first year of dereliction. Tetraploids are short-lived plants allocating a high proportion of their biomass to reproduction and completing their life cycle before July when the plant cover is sparse. Hexaploids are larger, later flowering, longer lived, plants with a lower reproductive effort and a higher final seed yield; it is inferred that these traits enable the hexaploids to compete successfully with the dense herbaceous layer of summer annuals that develops in the course of the first year of secondary succession. Differentiation in phenotypic plasticity between the two cytotypes was interpreted as indicative of higher opportunism and lower tolerance of poor soils and restricted rooting space in the hexaploid compared to the tetraploid cytotype.
Phenotypic plasticity is an environmentally based change in the phenotype. Understanding the evolution of adaptive phenotypic plasticity has been hampered by dissenting opinions on the merits of different methods of description, on the underlying genetic mechanisms, and on the way that plasticity is affected by natural selection in a heterogeneous environment. During much of this debate, the authors of this article have held opposing views. Here, we attempt to lay out current issues and summarize the areas of consensus and controversy surrounding the evolution of plasticity and the reaction norm (the set of phenotypes produced by a genotype over a range of environments).
1. Mikania scandens plants of three stem-length classes: small ( 10 cm), were transplanted into flooded or drained soil. After six weeks the relative growth rates (RGR), based on both dry weight and stem elongation, of the small plants under flooded conditions were 50% greater than those in drained soil. For the medium and large classes, the RGR values of the drained and flooded plants were similar. 2. Stem and root cross-sections revealed that flooded plants had two- and threefold respectively more aerenchyma tissue, with the amount in the stem decreasing in an acropetal direction. The stem surface contained stomata, not lenticels. The mean number of stem stomata was 267 and 57 for flooded and drained plants respectively on the 21 cm stem section above the water or soil line. 3. In root tissue ethanol and malic acid were below detectable concentrations, suggesting that anaerobic respiration was not an important component of metabolism under flooding. 4. Rather, M. scandens acclimatized anatomically with an increase in aerenchyma tissue and stem stomata, which would facilitate oxygen diffusion to the roots. Unlike other herbaceous, wetland species that use leaf stomata, the oxygen appeared to be derived from stem stomata. In this vine, insufficient oxygen diffusion down the long internodes probably necessitates use of stem stomata near the water-line. 5. These results indicate that M. scandens is flood-resistant, and may partially explain why it becomes a weed problem in flooded areas of Florida.
The leaf primordia of R. flabellaris have the genetic competence to develop in either an expanded or a dissected form, depending upon the environment. In both forms, branching of the leaf primordium early in the second plastochron produces the three major segments of the tripartite blade. Subsidiary lobes arise in acropetal sequence on these segments with the initiation of cell division at alternate sites along each segment and its inhibition in the putative sinus regions. Production of lobes at a greater rate in the submerged shoot, continued division in these elevating lobes, and inhibition along their margins accounts for the characteristic dissected form. Form is regulated primarily through control of cell division in the leaf primordium, and the environmental influence is apparently exerted here. That the environmental stimulus is effective during development of the leaf is apparent in the production of intermediate leaf forms from primordia present in the bud when shoots are transferred to an opposite environment. A comparison of shoot apices of terrestrial and submerged plants reveals no difference in size or organization during the development of diverse leaf forms. In addition to the terrestrial or submerged environments, temperature and photoperiod affect leaf form. Limited experiments failed to reveal translocation of a form determining factor from older leaves. It is our interpretation that the shape of the leaf in this heterophyllic aquatic may be affected by any of several environmental stimuli acting directly upon the distribution and frequency of cell division in the primordium so that the inherent zones of growth initiated on the primorduim are modified in their development. The seasonal variation in leaf form in R. flabellaris may be explained in terms of interplay of these environmental factors.
The roots and stem base of intact, 10 day old maize (Zea mays L. cv. LG11) plants, grown in nutrient solution, were continuously aerated either with ethylene (5 μl l-1) in air or with air alone. Ethylene treatment hastened the emergence of adventitious (nodal) roots from the base of the shoot, but slowed their subsequent extension. Ethylene also promoted the collapse of cells in the cortex of these roots, with lysigenous development of prominent air spaces (aerenchyma). Non-aeration of the nutrient solution caused endogenously produced ethylene to accumulate in the roots, and stimulated both the emergence of adventitious roots and the formation of cortical air spaces in them. With non-aeration the concentration of oxygen did not fall below 1% in the equilibrium gas phase (air=20.8%). Complete deoxygenation of the nutrient solution, produced by passing oxygen-free nitrogen gas, prevented both air space formation and the evolution of ethylene by root segments.
These results suggest that adventitious rooting and cortical air space formation in nodal roots in Zea mays may be stimulated by enhanced concentrations of endogenous ethylene arising either from entrapment of the gas by unstirred water layers around the roots and/or by increased biosynthesis. These responses are considered conducive to survival in waterlogged soil.
SUMMARY The effects of a combined regime of flooding and trampling on survival, growth and reproduction of some species from river forelands, were studied in a large-scale, outdoor experiment. In additional pot experiments, trampling effects were separated into effects of shoot damage and of soil compaction. Resistance of individual leaves to a tearing force and recovery from damage were measured. Species were selected according to their occurrence in the field in relation to trampling and flooding: Rumex acetosa from seldom flooded, extensively trampled sites; R. crispus from frequently flooded, non-trampled sites; Plantago major ssp. pleiosperma from regularly flooded, non- to heavily-trampled sites and P. major ssp. major from seldom flooded, very heavily trampled sites. Only R. crispus showed obvious morphological adaptations to flooding but their significance was vastly reduced when flooding was combined with trampling. Although they did not possess any important morphological adaptations, both Plantago subspecies survived flooding. Of both Plantago subspecies, P. major ssp. pleiosperma performed better than P. major ssp. major when soil compaction resulted in hypoxia. P. major ssp. major, responded better when the major effect was an increase in penetrometer value. R. acetosa was negatively affected by trampling, flooding and the combination of both. Flooding inhibited flowering during the experiment and trampling reduced seed production. In the pot experiment no interaction was found between shoot damaging and soil compaction due to trampling. Responses to shoot trampling could largely be explained by the tearing resistance in combination with the recovery characteristics of the species. Species occurring on more trampled sites in the field had a higher resistance to tearing stress and a better recovery after shoot damage.
Cohorts of Chenopodium rubrum, Rumex maritimus and R. palustris were raised in accordance with a flooding regime which was based on the average flooding conditions of their natural habitats in river forelands. Survival of submergence in the pre-reproductive phase was high in both species of Rumex, but relatively low in C. rubrum. Biomass reduction following flooding depended on plant size before flooding and on mean temperature of the flood-water. Both Rumex spp. were less reduced in size during flooding, and better capable of regeneration afterwards, than C. rubrum. Later-raised cohorts of the short-day species C. rubrum started to flower after a shorter time and at an earlier developmental stage than earlier cohorts. Flooding had little effect on probability of flowering and caused only a slight delay in flowering in this species. In both long-day species of Rumex, flowering stems were not initiated until a minimal leaf number was formed. As a result later cohorts remained vegetative, while flooding delayed flowering until later in the season or even until the following year. All flooded plants of C. rubrum and most flooded plants in early cohorts of R. maritimus attempted to reproduce in the first growing season. Seed number was severely reduced in C. rubrum due to both reduction of plant biomass and destruction of flowers during flooding. In flooded plants of R. maritimus, seed output was correlated with plant size at the time of bolting. Seed number was maximized at the expense of seed size in R. maritimus. -from Authors
Upon submergence this species exhibited rapid elongation of shoots. In the rosette stage, petioles showed a fast and large response; during early stem elongation the response of petioles was less, but the extension of the lower internodes considerable; during flowering stem development, high internodes extended and the contribution to final stem length diminished. Ethylene accumulated in the submerged plant due to increased synthesis as well as a reduced diffusion from the plant to the water (instead of air). Directly after submergence a further increase of ethylene synthesis was observed, which may be of vital importance in causing shoots to continue their rapid elongation even after the water surface is reached. Survival of submerged plants depended on the ability to emerge above the water surface, while seed production was positively correlated with shoot height above the water. -from Authors
Plants grown from seeds of Sagittaria falcata, S. lancifolia, S. platyphylla, S. rigida, S. isoetiformis and S. papillosa were grown in water-saturated soil or soil submerged to 4.5, 12, 19.5 or 27 cm. Length and width of leaves and petiole lengths were measured at anthesis of the first flower on the first inflorescence produced by each plant. In general, leaf width and length were decreased by submergence, and petiole length increased. The species × water depth interaction was significant for emersed leaf width, leaf length and petiole length except for S. lancifolia leaf length and S. papillosa leaf length and width. These trends indicate genetic differences among, and variability within, taxa. Leaf width, leaf length and petiole length of plants growing in seed source populations were measured. The means from these measurements, when compared to those from experimental plants, indicate that both groups of plants respond similarly to variations in water depth.
Ninety-one plant species from wetland (WL), intermediate (INT) and non-wetland (NWL) habitats were grown in flooded and drained soils and responses to flooding were assessed in relation to root anatomy and fractional root porosity (FRP).
Flooding response and tolerance were related to FRP. Rooting depth increased with FRP in accordance with diffusion model predictions and emphasized the ventilating efficiency of aerenchyma. Major determinants of FRP were cortical cell configurations, closeness of cell packing, the relative proportions of configuration types, porous: non-porous tissue ratios, aerenchyma development and the type and degree of secondary growth. A classification of cortical types based on cell and aerenchyma patterns is presented.
Aerenchyma, both schizogenous and lysigenous, developed preferentially where pre-aerenchymatous cortical cell configurations (in TS) were radial and particularly, cubic and radial typical of WL and INT species. Aerenchyma rarely formed from hexagonal non-radial arrays which occur chiefly in NWL and in the outer cortical zones of WL and INT plants. The ventilating potential in non-aerenchymatous tissue was shown to be greater for cubic (fractional porosity, FP, max. 0–2146) than for hexagonal arrays (FP max. 0˙0931); closer packing greatly accentuated the differences. It is suggested that cubic: hexagonal zonal ratios in roots may reflect a balance between respiratory and mechanical needs.
In a majority of WL and INT species, shoot weights were unaffected by or increased with flooding and maximum rooting depths usually much exceeded 50 mm. Cubic packing raised the FRPs, as did aerenchyma which was often much greater under flooding. In the dicotyledonous species, a suppression of secondary growth in some, and a highly porous phelloderm in others, helped maintain high FRP. A minority of species were anatomically and responsively similar to NWL plants; survival under flooding was attributed to shallow rooting.
Under flooding, the FRP of almost all NWL species was < 0˙055 due to hexagonal packing, a lack of aerenchyma and, in dicotyledonous plants, secondary growth with scanty phelloderm. Shoot weights were reduced in 50% of cases, rooting depths were <50 mm, and some species died. Some species were exceptional in having cubic and radial packings; a lack of aerenchyma was associated with continuing meristematic activity in the primary cortex.
. The first objective of this paper was to assess the effects of grazing on seedling establishment of two species whose relative abundance at the adult stage is affected by grazing in a contrasting fashion. Second, we evaluated the relative importance of seed versus safe-site availability in explaining the effect of grazing on seedling establishment. We monitored seedling establishment on a grazed area, on two areas which had not been grazed for two and seven years, and on plots which had been experimentally defoliated. The species compared were Dan-thonia montevidensis, a native perennial grass which dominates both grazed and ungrazed communities, and Leontodón taraxacoides, an invading exotic rosette species from the Compositae family. Continuous grazing enhanced seedling establishment of both species through its effect on the availability of safe sites. Seed availability accounted for only one, but very important, grazing effect: the lack of response by L. taraxacoides to the defoliation in the seven-year old exclosure. Its seed supply was depleted by exclusion of grazing and, consequently, its short-term regeneration capacity after disturbance was lost.
Root research can benefit under many circumstances from determination of the % fraction of root volume occupied by air (root porosity). Root porosity provides an indication of root reaction or adaptability to environments with insufficient oxygen availability. Three primary approaches have been used for root porosity determinations: cross-sectional ratios, pycnometry, and dynamic gas displacement. These three methods are explained and their relative advantages and disadvantages discussed.
Plants of Rumex thyrsiflorus Fingerh., R. crispus L. and R. maritimus L., which are zoned along a gradient of elevation in a river foreland ecosystem, and differ in their flood-tolerance, were
subjected to different flooding levels. Under conditions of soil flooding, the growth rates of the flood-tolerant R. crispus and R. maritimus were as high as under drained conditions, but that of the flood-intolerant R. thyrsiflorus was halved. Upon submergence, the low elevation species R. maritimus showed rapid shoot elongation; when elongation resulted in a protrusion of leaves above the water surface, the plants survived.
Alternatively, underwater photosynthesis also led to a 100% survival of submerged R. maritimus plants, provided that enough inorganic carbon was made available in the water. This could be attributed in part to the use
of photosynthetically-derived oxygen for root respiration; in a hydroculture experiment, with 5.0 mM CO2 in the water in the shoot environment, photosynthetically-derived oxygen contributed more than 50% to root oxygen consumption
at low oxygen concentrations in the root environment.
The intermediately elevated species R. crispus appeared to be much more tolerant towards conditions of prolonged total submergence: older plants survived eight weeks submergence
in the dark. This response was explicable in terms of a dormancy-strategy, which is characterized by a slow consumption of
carbohydrates stored in the tap-root. The differential responses of R. maritimus and R. crispus to total submergence reveal the limitations of flood-tolerance and reflect the different life-histories of the species.
Changes in community composition of 2 grassland sites exposed to a flood of unusual intensity and duration were investigated in the Flooding Pampa. These grasslands are subject almost annually to floodings of lesser magnitude. The study sites were adjacent to each other, and differed in vegetation structure and composition. One had been grazed continuously by cattle and was showing signs of intense deterioration. The other had remained ungrazed during 15 years. Basal cover by species was measured in summer, before and after the flooding event. Compositional difference between sites decreased with flooding from 68.9 to 39.1%. In the grazed site the cover of alien forbs was reduced by 48%. After the flooding native graminoids represented 99.7 and 86.7% of the cover, inside and outside the exclosure respectively. Total basal cover was not affected but was redistributed among species already present before the flood. Floristic changes would have led to an improvement of the forage source. We conclude that plant community response to the event was influenced by the previous grazing history of the site. The large flood acted as an overriding environmental factor which partially reverted the effects of grazing upon grassland composition.
We analysed the response of two grass species, Danthonia montevidensis and Paspalum dilatatum to waterlogging, soil-nutrient enrichment and the combination of both factors. Waterlogging did not affect total biomass of D. montevidensis, but it slightly promoted growth of P. dilatatum. Most analysed variables showed no significant interaction between fertilization and waterlogging. Therefore, waterlogging does not produce a detrimental effect either in the growth of these species or in their response capacity to stimulating growth factors, such as fertilization.
Many studies have analysed plant responses to flooding or drought separately, without addressing the relations between plant resistance to each of these factors. In this paper, we compare the responses to drought and flooding under glasshouse conditions of three populations of Paspalum dilatatum, a perennial C4 grass dominant at different positions along a topographic gradient in the flooding pampa of Argentina. Our results showed that flooding effects on yield were negative on an upland, null on an intermediate, and positive on a lowland population, whereas drought reduced yield equally across populations, showing that resistance to flooding was not related to resistance to drought at a population level. Drought decreased height and aerenchyma, and increased the proportion of roots, while flooding had opposite effects on these traits. The responses of the single clones that made up each population showed a positive relation between the resistances to both factors: along the ecocline formed by 58 clones, those more resistant to drought were also more resistant to flooding. In addition, the combined resistance of each clone to both factors was negatively related to yield at field capacity, (i.e. the most resistant clones were less productive) and unrelated to the proportion of roots and aerenchyma. This result agrees with predictions of Grime's plant strategy theory and differs from a few previous studies, which showed negative relations between the resistances to flooding and drought among genera and species.
Both distribution of terrestrial plants and species composition in flood plain communities are strongly influenced by flooding
(waterlogging, partial submergence, or submergence). The interaction between a plant's flooding resistance and the seasonal
timing, duration, depth, or frequency of flooding often determines plant distribution in flood plains. Flooding may be accompanied
by marked physical changes in light, carbon availability, diffusion rate of gases, and density of the environment. Various
physiological processes may be affected by these flooding-induced physical changes, including aerobic respiration, photosynthesis,
and processes in which light acts as a source of information (e.g., phytochrome photoequilibrium). Certain plant species acclimatize
and adapt to these physical changes to relieve the constraints imposed by the flooded environment. Underwater photosynthesis,
enhanced shoot elongation, adventitious roots, and aerenchyma formation are typical adaptive responses which are believed
to improve the oxygen status of submerged plants. Ethylene and other plant hormones play a central role in the initiation
and regulation of most of these adaptive responses, which permit “escape” from anaerobiosis. Mechanisms of direct tolerance
of anaerobic conditions, such as a vigorous fermentative respiratory pathway, are of particular importance when the plant
is very deeply submerged, or during the night and when the water is sufficiently turbid to exclude light.
Studies on the cosmopolitan genus Rumex, distributed in a flooding gradient on river flood plains, have integrated plant hormone physiology with plant ecology. Rumex species showed a high degree of interspecific variation in ethylene production rates, endogenous ethylene concentrations,
ethylene sensitivity, and ethylene-mediated growth responses. The field distribution of Rumex species in flooding gradients is explained in terms of a balance between endogenous ethylene concentrations and sensitivity
towards this growth regulator (“ethylene economy”). Much data has been gathered using a recently developed laser-driven photoacoustic
detection technique capable of detecting six parts of ethylene in 1012 parts air flowing continuously over the plant.
Rumex thyrsiflorus, Rumex crispus andRumex maritimus show a differential flood-tolerance in the river ecosystem in the Netherlands.R. thyrsiflorus occurs at high-elevated habitats and is flood-intolerant, the other two species occur at lower-elevated habitats and are flood-tolerant. We compared their respiratory activity under aerobic and anaerobic conditions in the root environment and quantified the internal gas transport. The results indicate that aerial oxygen can be used for root respiration in both aerobically and anaerobically grown plants. The amount of oxygen used via internal aeration increased with decreasing oxygen concentration in the root environment. Aerobically grown plants ofR. maritimus andR. crispus already showed a high internal aeration, but there was a significant increase in internal oxygen transport in anaerobic plants, where new, aerenchymatous roots had formed. This indicates the functional significance of new root formation for respiration in these species upon hypoxia. After two weeks of anaerobiosis, more than 50% of the total respiration of the roots of young plants ofR. maritumus and 40% of roots of young plants ofR. crispus was due to internal aeration at low oxygen concentrations in the root environment.
InR. maritimus both young and old plants performed in this way, inR. crispus only young plants, whileR. thyrsiflorus showed some internal aeration, but this was hardly detectable. These differences can be explained on the basis of a different morphology and concomitant diffusive resistance of both root and shoot system.
In experiments with different submergence levels of the shoot, the amount of internal aeration was positively correlated to the total leaf area protruding above the water surface inR. maritimus. This indicates a functional significance of the petiole and leaf elongation response upon total submergence of this species.
Publisher Summary This chapter focuses on evolutionary significance of phenotypic plasticity in plants. The expression of an individual genotype is modified by its environment. The amount by which it can be modified is termed its plasticity. This plasticity can be either morphological or physiological; these are interrelated. The plasticity of a character is related to the general pattern of its development, and apart from this, that plasticity is a general property of the whole genotype. Plasticity of a character appears to be specific for that character, specific in relation to particular environmental influences, specific in direction, under genetic control not necessarily related to heterozygosity, and able to be radically altered by selection. Because plants are static organisms, plasticity is of marked adaptive value in a great number of situations. Examples of all these situations in plant species are discussed. They indicate that adaptation by plasticity is a widespread and important phenomenon in plants and has evolved differently in different species. The mechanisms involved in plasticity are varied. At one extreme, the character shows a continuous range of modification dependent on the intensity of the environmental stimulus. At the other, the character shows only two discrete modifications. The stimulus causing these modifications may be direct or indirect. The mechanisms found can be related to the particular environmental situation involved.
Floodplains and wetlands are highly suitable for plant ecological studies, whether for agricultural interests, nature conservation or basic science. Traditional work has entailed a descriptive approach at the community or individual plant level. Nowadays these studies are evolving into physiological research on relationships between flooding stress and vegetation zonation. Current experiments aim to unravel the adaptive mechanisms whereby terrestrial plants cope with the peculiar conditions of the floodplain, from the whole plant down to the cell.
The structure and response to flooding of root cortical aerenchyma (air space tissue) in a variety of wetland (flood-tolerant) species was investigated and compared with some flood-intolerant species. In some species aerenchyma consisted of enlarged schizogenous intercellular spaces and in others aerenchyma formation involved lysigeny. Two types of lysigenous aerenchyma were distinguished. In the first the diaphragms between lacunae were arranged radially and consisted of both collapsed and intact cells. In the second type, which was confined to the Cyperaceae, the radial diaphragms contained intact cells, and stretched between them were tangentially-arranged diaphragms of collapsed cells.
Flooding in sand culture generally increased root porosity (air space content) although there were exceptions. The flood-intolerant species Senecio jacobaea produced aerenchyma but did not survive long-term flooding. Among the flood-tolerant species, Filipendula ulmaria did not produce extensive aerenchyma even when flooded. Eriophorum angustifolium and E. vaginatum produced extensive aerenchyma under drained conditions which was not increased by flooding. In Nardus stricta root porosity was increased by low nutrient levels as well as by flooding.
Rio de La Plata grasslands Temperate subhumid grasslands. Ecosystems of the world
- A Soriano
Soriano A. 1991. Rio de La Plata grasslands. In : Coupland RT, ed. Temperate subhumid grasslands. Ecosystems of the world. Natural Grasslands, vol 8A. Amsterdam, The Netherlands : Elsevier, 379–382.
Caracterı! sticas del re! gimen acuico de un Natracuol de la Pampa Deprimida
- Taboada Me
- Lavado
Taboada ME, Lavado RS. 1986. Caracterı! sticas del re! gimen acuico de un Natracuol de la Pampa Deprimida. Ciencia del Suelo 4 : 66–71.