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Effects of drought on needle anatomy of Pinus canariensis
Abstract
Summary The needles of Pinus canariensisexhibit morphological drought adaptations, such as special stomata morphology or rigid scle- renchymatic hypodermis. In the present paper the hypothesis that drought exposure during needle elongation triggers formation of xeromorphic traits was tested. With onset of the elongation growth of the new flush, 5-year old P. canariensis seedlings were exposed to 53 days of reduced water supply under controlled climate chamber conditions. The treatment resulted in a decrease of needle water potentials from - 1.5 MPa to - 4 MPa in drought stressed plants, whereas no change was observed in water poten- tials of control needles. Needles of drought exposed trees remained shorter and thinner. Cross-sections of elongating needles taken at 1 cm distance from the needle base were taken repeatedly during the experiment. Cross-section areas of different needl e tissues were measured in an image analysis system. In needles of drought stressed trees sclerenchymatic tissues in the hypo- dermis and adjacent to the vascular bundles increased due to large increases in the number - not the size - of sclerenchymatic cells. The ratio of assimilation parenchyma to the vascular bundle (supplied versus supplying tissue) decreased. We conclude that these changes, which adapt needles to drought conditions, are triggered by drought stress experienced while needles are gr owing.
... Morphological traits, such as needle length, leaf mass per area (LMA), and root-to-shoot ratio, are known to be related to water availability and drought coping mechanisms [6][7][8][9][10]. Trees that grow under high water availability have longer needles [6,7], a larger needle cross section area [7], a larger crown, and a higher foliage density [6]. ...
... Morphological traits, such as needle length, leaf mass per area (LMA), and root-to-shoot ratio, are known to be related to water availability and drought coping mechanisms [6][7][8][9][10]. Trees that grow under high water availability have longer needles [6,7], a larger needle cross section area [7], a larger crown, and a higher foliage density [6]. Changes in LMA occur in response to drought stress [8,9]. ...
... Morphological traits, such as needle length, leaf mass per area (LMA), and root-to-shoot ratio, are known to be related to water availability and drought coping mechanisms [6][7][8][9][10]. Trees that grow under high water availability have longer needles [6,7], a larger needle cross section area [7], a larger crown, and a higher foliage density [6]. Changes in LMA occur in response to drought stress [8,9]. ...
Hybrids between Pinus brutia Ten. and Pinus halepensis Mill. have mainly been investigated with respect to their growth rate. Less attention has been paid to factors that contribute to their resistance to drought, although the hybrids have been shown to thrive over P. brutia in semi-arid regions. To understand the superior hybrid phenotype, we investigated morphological traits, growth parameters, and physiological response to drought stress in P. brutia, P. halepensis, and their vigorous hybrids. Rooted cuttings were propagated from mature trees and were examined in a high-throughput gravimetric system to evaluate their response to drought. Higher root-to-shoot ratio, needle length, and leaf mass per area (LMA) were observed in the hybrids compared to the two parental species. P. halepensis demonstrated higher transpiration rates (E) and stomatal conductance (gsc) than P. brutia, and an earlier reduction in E and gsc in response to drought stress. Similar to P. brutia, the hybrids showed low E and gsc, and an early stomatal closure in response to drought similar to P. halepensis. Our study suggests that the hybrids exhibit a unique combination of traits that may contribute to forest resilience in semi-arid regions undergoing climate change.
... URL: www.rjbn.uh.cu ISSN 2410-5546 RNPS 2372 (DIGITAL) -ISSN 0253-5696 RNPS 0060 (IMPRESA) largo plazo afectará la supervivencia y el crecimiento de la planta (Grill & al. 2004, Huang & al. 2016). Variaciones en la morfología y la estructura anatómica de la acícula entre individuos y poblaciones obedece a diferencias en las condiciones de edátopo y los regímenes de humedad del hábitat donde crecen , Tiwari & al. 2013, Ghimire & al. 2014, Meng & al. 2018) y pueden ser usados como un método rápido para explorar la variación genética entre poblaciones (Boratyńska & al. 2015a, 2015b, Zhang & al. 2017. ...
... En la primera localidad, Marbajita, mayor cantidad de células de la hipodermis y entre los mayores valores de grosor del tejido de transfusión (Tabla II), todo ello relacionado con características vinculadas a los procesos de regulación hídrica. Grill & al. (2004) y Dörken & Stützel (2012) describen que las especies de Pinus que crecen en ambientes muy secos, generalmente desarrollan una cutícula prominente, gruesa y una hipodermis conformada por varias capas de células gruesas de forma circular. Por otra parte, el comportamiento detectado es similar al reportado para P. canariensis C. Sm. ex DC. (López & al. 2007), P. heldreichii Christ (Nikolić & al. 2019) y P. sylvestris L. (Galdina & Khazova 2019), y donde los tejidos protectores, en especial la epidermis y sus modificaciones, juegan un rol importante en la adaptabilidad a las condiciones áridas. ...
... El aumento del grosor de la hipodermis no siempre está acompañado con un mayor número de capas de células de la hipodermis, aunque ambas características regulan las pérdidas de agua, en especial si se acompaña de esclereidas como elemento del tejido de sostén (Grill & al. 2004). Nikolić & al. (2014Nikolić & al. ( , 2019 en estudios de las poblaciones naturales de Pinus heldreichii en los Balcanes reportaron que hacia sitios más secos, debido a la pendiente y el sustrato, el grosor de la hipodermis y cutícula eran mayores, pero con un menor número de capas de la hipodermis. ...
Variation of anatomical characters is crucial in the recognition of ecological adaptability, especially in Pinus. Pinus caribaea var. caribaea is an endemic taxon of Western Cuba that grows in pure populations or sympatry with Pinus tropicalis and occupies a great variety of ecotopes that are also distinguished by the characteristics of the edatope. The objective of this research is to determine the anatomical variation of the needles as an adaptive differential response to the environmental conditions determined by lithology, altitude and slope. From 20 to 30 individuals from all the ecotopes where the taxon grows naturally were sampled. Cross sections were made of 10 needles from each tree and 12 anatomical variables, related to water regulation, transport and storage of metabolites, were assessed. The results of the statistical analysis revealed significant differences between ecotopes. The principal component analysis showed a relationship between anatomical variables that follow a functional pattern of water regulation and assimilation. The cluster and discriminant analysis made possible to distinguish the formation of groups by the relationship of the anatomical variables, mainly due to the effect of lithology, and those that contributed the most to differentiate them were those of water regulation, primary metabolism together with cuticle thickness. The results are a contribution to the local conservation of the taxon since the structure of the anatomical variation is a consequence of the genetic evolution of the populations and are very important in ecological and for silvicultural management.
Citation: Geada-López, G., Sotolongo-Sospedra, R., Pérez-del Valle, L. & Ramírez-Hernández, R. 2021. Diferenciación anatómica foliar en poblaciones naturales de Pinus caribaea var. caribaea (Pinaceae) en Pinar del Río y Artemisa, Cuba. Revista Jard. Bot. Nac. Univ. Habana 42: 175-188.
Received: 23 March 2021. Accepted: 13 May 2020. Online: 21 July 2021. Editor: José Angel García-Beltrán.
... Pero estos reportes para especies insulares (P. taiwanensis Hayata [Sheue & al. 2014] y P. canariensis C. Sm. ex DC. [Grill & al. 2004, López & al. 2016) sean o no coníferas, son insuficientes. ...
... El estudio muestra claramente las diferencias anatómicas entre las dos especies bajo un mismo ambiente (Tablas II y III), es decir cada una ha desarrollado sus propios mecanismos anatómicos y funcionales para contrarrestar las condiciones de estrés. Dörken & Stützel (2012) y Grill & al. (2004) describen que las especies de Pinus que se desarrollan en ambientes extremos, generalmente desarrollan una cutícula prominente, gruesa y una hipodermis conformada por varias capas de células gruesas de forma circular. Sin embargo, P. caribaea desarrolla mayor número de capas y grosor de la hipodermis (tipo multiforme) como adaptación a iguales condiciones. ...
... (Ghimere & al. 2014), P. taiwanensis (Sheue & al. 2003), P. roxburghii Sarg. (Tiwari & al. 2013), o especies de su sección que habitan ambientes muy secos: P. canariensis (Grill & al. 2004), P. heldreichii Christ (Nicholić & al. 2016). A diferencia de estos resultados, en Cuba no existen gradientes de temperatura, precipitación, humedad, altitud o exposición, a excepción de los sustratos en que se desarrolla, que expliquen esta adaptación en la especie cubana. ...
Las variaciones en la anatomía foliar pueden ser respuestas adaptativas o de aclimatación interpoblacional al estrés edafoclimático, sobre todo de especies que se desarrollan en ambientes extremos. Pinus caribaea var. caribaea y P. tropicalis se distribuyen en el occidente de Cuba, principalmente en la provincia de Pinar del Río donde forman poblaciones puras o en simpatría. Es objetivo de este trabajo comparar las características anatómicas distintivas de las acículas de ambos taxones en diferentes localidades donde se asocian simpátricamente. Para ello se realizaron cortes transversales de las acículas y se evaluaron 14 variables anatómicas. Los análisis estadísticos empleados permitieron diferenciar claramente los dos taxones y ambos presentan variaciones propias para adaptarse a un mismo ambiente. El análisis de componentes principales mostró que dentro de cada taxón las poblaciones se segregan en relación al edátopo donde se desarrollan. Para P. caribaea var. caribaea las variables anatómicas que más contribuyeron a la variación y ordenación fueron el número de estomas, grosor y número de capas de células de la hipodermis; en P. tropicalis el grosor de la cutícula y el parénquima clorofílico, y para ambos taxones el tipo de canal fue inequívocamente endonales y marginal.
... In conifers, the needles are the key organs for both carbon assimilation and transpiration. Structural plasticity has been observed in response to environment (Grill et al. 2004;Gebauer et al. 2015) and can result in a greater proportion of mesophyll and a higher photosynthetic capacity in several species (Niinemets et al. 1999(Niinemets et al. , 2007. In maritime pine, the cuticular wax content of the needles of maritime pine seedlings was modified by water stress. ...
... The area of the cross-section used for assimilation (A a ) was calculated as the area of the needle below the epidermis minus the area of the central cylinder (CCa). V/A is the relationship between supply and assimilation tissues (Grill et al. 2004). ...
... One of the classic effects of drought in pines is a decrease in total needle length, as shown in cohorts of Pinus canariensis (Grill et al. 2004). This quantitative plasticity has also been detected in mature Pinus laricio, with needle lengths 30, 19 and 29% shorter in trees subjected to drought than in control trees over a period of three years (Cinnirella et al. 2002). ...
Key Message
Needle anatomic plasticity enables fast-growing maritime pine trees to cope with water limitations by enhancing both water-use efficiency and embolism resistance.
Abstract
Maritime pine is a major forest tree grown for wood production in Southern Europe. A breeding program for the selection of fast-growing varieties was established in the 1960s, in France. In the context of climate change, the magnitude of phenotypic plasticity is a key issue for the prediction of putative decreases in productivity in the improved genetic material. We characterized the phenotypic plasticity of anatomical and physiological traits in two families with contrasting growth rates, under different water regimes, at the juvenile stage. An analysis of 38 traits showed that the fastest growing family had the greatest phenotypic plasticity for morphological, anatomic, chemical and physiological traits, enabling it to increase its water use efficiency and embolism resistance in response to water deficit. The observed modifications to the extravascular (proportion of spongy parenchyma in needles) and vascular (xylem in the needles and stem) compartments in response to water constraints were consistent with a higher water use efficiency and greater embolism resistance. The ability to optimize meresis and auxesis according to environmental conditions during needle development could be related to growth performance over time in different environmental conditions. These results suggest that selection for growth in maritime pine leads to the selection of individuals with greater phenotypic plasticity related to higher performances in non-limited conditions.
... If high-elevation sites are becoming more suitable for P. patula within its altitudinal range, this should be evident in their leaf anatomical traits, which in several taxa tend to display a coordinated variation along with elevation gradients (e.g., Grill et al. 2004, Jiménez-Noriega et al. 2017. However, the detected trends along resource gradients documented for several taxa in worldwide or regional-level studies, may not be the same to those at local conditions and infraspecific level (Niinemets 2015). ...
... We expect that the photosynthetic leaf tissue (mesophyll) increases towards conditions of higher moisture availability. This increase should be proportionally more elevated than that of conductive tissues, as has been observed in P. canariensis (Grill et al. 2004). If this correct, leaf thickness should also increase in conditions of high moisture, as the mesophyll layer is a substantial component of the leaves (see below). ...
... Therefore, any change in mesophyll width should have direct implications on plant growth. We also analyzed the root square of xylem area-to-mesophyll length ratio as an estimate of the ratio of supplied versus supplying tissues (Grill et al. 2004) with elevation to explore the possibility of coordinated changes at leaf level between tissues involved in water and mineral transport (xylem) and tissues involved in carbon fixation (mesophyll). We used the root square of the xylem area to have a dimensionless (and more straightforward) ratio since our mesophyll estimation is linear (width). ...
Background:
Indicators of productivity could be useful to identify vulnerable species to climate change, stress and safeguarding sites, and early detection of climate change effects, but require to be developed and tested.
Species study:
Pinus patula is a tropical Mexican mountain pine on which divergent opinions are available regarding its sensitivity to global warming. Local anecdotes indicate upslope shifts.
Methods:
We use a space-for-time substitution to infer climate change sensitivity in Pinus patula, testing putative productivity indicators at different elevations: the normalized difference vegetation index (NDVI) and leaf anatomical traits, after following standardization protocols.
Results:
As elevation increases, the NDVI, leaf thickness, and the mesophyll width increased, while the xylem-to-mesophyll ratio decreased, probably as different plant manifestations to higher productivity towards the mountain tops. These results concur with other studies showing evidence of more productivity toward higher elevations on the leeward side of the southern Mexico mountains based on NDVI, small mammal abundance, soil macrofungi carpophore cover, and tree basal area. Under global warming, high elevations in south Mexico appear to become more favorable because of their less extreme cold temperatures and higher rainfall.
Conclusions:
Our results provide an explanation of previous findings suggesting that global warming could reduce the population size and the habitable area of Pinus patula, and the observed upslope shifts. After following standardization protocols, the NDVI, mesophyll width, and xylem-to-mesophyll ratio could be promising tools to assess climate change sensitivity in terrestrial plants and deserve further studies to test their validity in other situations and species.
... The anatomic preparations were performed freehand at the central portion of each needle, and the transversal sections were treated with 5% NaOH for 4 h at 70°C, according to the methods of Arnott and Brady cited by Ruzin [33]. The majority of the adaptive characters found in C. atlantica [34] and in Pinus canariensis [35] were measured. The length of the needle (Nl) was determined manually with an accuracy of 0.25 mm. ...
... It is important to clarify the factors that cause variation in these characters. Grill et al. [35] showed that AS, AMp, and ACc of P. canariensis in seedling needles decreased under controlled conditions of drought, while Maurice and Crang [46] showed that AS of P. strobus needles increased in response to acid misting. In further studies, Bleweiss et al. [47] found that high levels of sulfur in the needles of C. libani caused needles to develop xeromorphic characteristics, with very thick cuticle, thick cutinized walls of the epidermis and hypodermal cells, sunken stomata, and plicate mesophyll cells. ...
... This could be attributed to fewer individuals (10 individuals) analyzed from the Middle Atlas in contrast to 30 from the Rif [21]. The similarity of NSc between the three populations is not in agreement with the results of Böcher [49] and Grill et al. [35], who found an increase in NSc in response to drought and/or high temperature in the year of growth of needles, to avoid the collapse of the vascular package under conditions of turgor loss. In contrast, the high CV of Kha trees, compared to Tam, may be confirmed by the trend of C. atlantica to adapt its photosynthetic apparatus to water deficits and by its low thermotolerance [16,17] in response to the elevation in temperature and the subsequent drought during the summer season caused by the steep slope of 37% inclination (Fig. 2, Tab. 1). ...
The variation in some adaptive characters of cedar needles was studied in two different regions of the Moroccan Middle Atlas that have different local environmental conditions and levels of genetic diversity. The two populations are localized in the Azrou and Ifrane regions. Tukey’s tests showed that the needle/brachyblast number (Nn/R), length (Nl), and needle width (Nw) showed the greatest variation. In addition, all anatomical characters studied showed a significant correlation with Nw, whereas only the area of the vascular bundles (AVb) was related to Nl. Discriminant analysis revealed that Nn/R, Nl, and the area of the central cylinder (ACc) are high-discriminating characters among populations of Azrou and Ifrane and confirms their isolation. These adaptations of the morphological and anatomical traits of the Atlas cedar needles of the Azrou and Ifrane regions are discussed in relation to the local environmental conditions and have been found to be in harmony with their genetic distinctiveness revealed previously.
Key words: Anatomy; Cedrus atlantica; Leaf; Morphology; Population
... This feature would hint that this P. canariensis was the most flammable. Although, P. canariensis needles are known to be more drought-tolerant than the other pines [29], which is usually a characteristic of fire resistance according to White and Zipperer [3], by dint of its drought-coping mechanisms especially the structure and positioning of stomata [30,31]. Nevertheless, generally, pine needles are substantially flammable once their H drops below 100% [32]. ...
... SVR mean values of P. canariensis needles showed an upward trend over the seasons, although the needles H remained substantially unchanged. Pinus canariensis needles have different anatomical and physiological specificity than other pine needles [29][30][31]. Besides being classified into a leaf shrinkage category different from other pine needles [40], P. canariensis needles also have a different response to water stress [29][30][31]40]. ...
... Pinus canariensis needles have different anatomical and physiological specificity than other pine needles [29][30][31]. Besides being classified into a leaf shrinkage category different from other pine needles [40], P. canariensis needles also have a different response to water stress [29][30][31]40]. ...
Surface area-to-volume ratio (SVR) strongly influences plant flammability and it is widely used in most fire behaviour prediction systems all over the world. In these prediction systems, SVR was regarded only as an average of the whole species present at the site. However, SVR is species-specific and fluctuates strikingly according to leaf and needle moisture content (H) depending on environmental conditions. This situation results in inaccuracies in predicting fire behaviour and lack of reliability of the systems used. Hence the need to model the relation SVR vs H for each plant species, taking into account the possible effects of the site and season. This modelling would yield the SVR values corresponding to the immediate H of leaves and needles, leading to a more efficient and accurate fuel hazard assessment meeting a wide range of H. Several leaf and needle samples were collected from thirteen tree and shrub species over the four seasons of the year, at six sites in western Rif Mountains, Morocco. Every season, SVR and H were measured regularly during the drying of the samples. SVR values were significantly affected by both site and season for all species. Correlation between SVR and H was significant for all species except Cistus crispus. The modelling of the relation SVR vs H highlighted two separate groups of species regarding the response to water stress. SVR changed significantly under the effect of H and the environmental conditions relating the season and site. However, SVR response showed two distinct behaviours according to species. Further research would extend the SVR database to other plant species, in order to cover more ecosystems and therefore be able to integrate it into the fire behaviour prediction systems.
... The three sites where P. canariensis needles were sampled indicated all statistical differences. This is due to anatomical differences in P. canariensis needles, owing to the environmental conditions variability (Grill et al. 2004). Regarding the leaves of P. lentiscus, only one site (Dardara) was significantly different from the other sites (Ahl Srif and Souk L'Qolla), considered similar. ...
... Sclerophylly is enhanced by building parenchymatous tissues and the upper cuticular layer (Bacelar et al. 2004;Bussotti et al. 2002), increasing thereby the leaf tissue density (Aranda et al. 2014;Bussotti et al. 2002) and avoiding desiccation (Aranda et al. 2014;Pardos et al. 2009;Bacelar et al. 2004;Bussotti et al. 2002). The increased tissue density and water conservation both help to limit leaf shrinkage, since the parenchymatous tissues act as reinforcement support for the leaf internal components (Grill et al. 2004) and the water retention maintains the leaf turgor (Bacelar et al. 2004). Indeed, the sclerophyllous character of the leaves of oak species made them least shrinkable as shown in the shrinkage classification table (Table 4). ...
... The high shrinkage potential of P. pinaster and P. pinea can be explained by the prominence of two main parameters. Pine needles have, first, thin cuticle, allowing increased cuticular transpiration (Aranda et al. 2014;Pardos et al. 2009) and, secondly, pine needles are less sclerophyllous, depriving thereby the leaf of a mechanism limiting uncontrolled transpiration (Grill et al. 2004). This results in high desiccation susceptibility of the needles (Grill et al. 2004), which increases therefore the shrinkage potential (Bacelar et al. 2004). ...
Leaf shrinkage provides insights into the potential variation of foliar SVR, within the same species, when leaf moisture content is changing in response to water deficit. Since SVR is among the most significant plant flammability features, leaf shrinkage would be a relevant component of fuel hazard assessment through its influence on SVR, enhancing—if it is taken into account—thereby the wildfire prediction accuracy. The purpose of this work is, first, to consider the leaf shrinkage by characterizing the plant species towards the shrinkability of their leaves, taking account the possible site effect, to characterize the behavior of shrinkage as a function of moisture content and finally to perform a classification for some dominant Mediterranean species based on the shrinkage levels. The assessment of the hierarchical relationships between the dimensional shrinkages is also aimed. Leaves and needles of thirteen tree and shrub species were harvested from six different sites in western Rif Mountains. Leaves dimensions and moisture content were measured regularly during a gradual drying at the laboratory. Dimensional shrinkages were calculated at each moisture content level. Dimensional shrinkages behaved similarly whether in leaf or timber and kept the same reporting relationships between each other. Among the species sampled in different sites, site effect is significant only in Pinus canariensis and Pistacia lentiscus. A classification of the plant species was carried out in three separate classes. Generally, shrinkage class of the plant species studied gave an idea on its flammability ranking reported in the literature, implying thus a cause-and-effect relationship between both parameters.
... Interestingly, P. canariensis is able to control transpiration tightly (Rozas et al., 2013, and citations therein), and this appears to be inconsistent with the presumed role of stomatal wax plugs as an anti-transpiration adaptation (Jeffree et al., 1971;Yoshie and Sara, 1985;Brodribb and Hill, 1997). It was found that xeromorphic traits develop in needles of P. canariensis trees growing in drier areas (Grill et al., 2004). Possible changes in stomatal wax plugs were, however, not considered in the study of Grill et al. (2004). ...
... It was found that xeromorphic traits develop in needles of P. canariensis trees growing in drier areas (Grill et al., 2004). Possible changes in stomatal wax plugs were, however, not considered in the study of Grill et al. (2004). Note that P. canariensis was the only species in this study which was cultivated in a glasshouse. ...
Background and aims:
Foliar water uptake (FWU) has been documented in many species and is increasingly recognized as a non-trivial factor in plant-water relations. However, it remains unknown whether FWU is a wide-spread phenomenon in Pinus species, and how it may relate to needle traits such as the form and structure of stomatal wax plugs. In this contribution, these questions were addressed by studying FWU in current-year and one-year old needles of seven Pinus species.
Methods:
We monitored FWU gravimetrically and analyzed the needle surface with cryo-scanning electron microscopy. Additionally, we considered the effect of artificial wax erosion by application of the surfactant Triton TM X-100, which is able to alter wax crystals.
Key results:
The results show for all species that 1) FWU occurred, 2) FWU is higher in old needles compared to young needles, and 3) there is substantial erosion of stomatal wax plugs in old needles. FWU was highest in P. canariensis which shows a thin stomatal wax plug. Surfactant treatment enhanced FWU.
Conclusions:
The results of this study provide evidence for 1) widespread FWU in Pinus, 2) the influence of stomatal wax plugs on FWU, and 3) age-related needle surface erosion.
... Some studies argue that low stomatal density may possibly improve drought tolerance (Hepworth et al., 2015), while others (i.e., Larcher, 1994;Fahn, 1994) are of the opinion that drought stress increases stomatal density, indicating a better control of water loss (Larcher, 2003). These two views seem contradictory; however, it should be kept in mind that differing stomatal morphology among different species, and within the same species or between species with comparable stomata morphology, may have differences in stomatal control of water loss (Grill et al., 2004). The decrease in stomatal size and increase in stomatal density resulting from mistletoe-induced water stress with increasing severity of infection observed in this study provide evidence that needles might undergo anatomical adaptations that could increase its capacity to uptake carbon dioxide and better regulate water loss. ...
... Cinnirella et al., 2002;Grill et al., 2004;Irvine et al., 1998). ...
White mistletoe (Viscum album ssp. abietis, Santalaceae) is a hemi-parasitic plant and is regarded as one of the most significant biotic factors affecting fir forests. Mistletoe affects its host in many ways, including changes in leaf development. This paper studies and quantifies the effect of white mistletoe on morphological, anatomical traits and photosynthetic pigment content of cilicican fir (Abies cilicica (Antoine & Kotschy) Carrière, Pinaceae) needles growing on uninfected branches of infected and uninfected trees in relation to varying mistletoe infection severity. Morphological (needle length and width, area and weight, and specific leaf area), anatomical (needle width and thickness, epidermis and central vein thickness, needle cross sectional and mesophyll area, epidermis plus hypodermis and central vein area, xylem and phloem area, transfusion and resin duct area), stomatal (number of stomata rows, stomatal band width, stomata length and density) traits and photosynthetic pigment content (chlorophyll a and b, total chlorophyll (a+b), total carotenoid) were measured in one-year-old needles growing on uninfected branches from a total of 48 cilicican fir trees. Of the trees, 10 were uninfected, 13 lightly infected, 14 moderately infected and 11 severely infected. The results indicated that morphological dimension of needles decreased steadily with increasing infection severity. Stomatal size of needles decreased gradually while stomatal density increased gradually with increasing infection severity. Reduced anatomical dimension were only evident in needles from moderate and severe infection classes, while chlorophyll content decreased in only severely infected trees.
... Sclerenchymatic tissues along the vascular bundle contributed to avoiding collapse of vascular bundle elements under turgor loss conditions (Grill et al., 2004). Such criteria could be used according to Luković et al. (2009) in the selection of drought tolerant genotypes. ...
... In severe salt stress, 'Meski' cultivar appeared stressed, by maintaining similar vascular tissue to the control and the development of fibers tissue. The fiber tissue contains sclerenchyma which decreases the cellular flexibility under turgor loss conditions (Grill et al., 2004). ...
The table olive cultivar 'Meski' was subjected to two stresses related to water, scarcity and salinity. Anatomical adaptations of leaves, stems and roots were studied and compared, to value the water use efficiency of the tree. Two stress levels were adopted corresponding to moderate and severe levels. Thus, the trees behaviour was influenced by the stress type and intensity. The aerial part of the trees showed more adaptation modes than the underground part. Under both stresses, plants have fortified the protection of the leaf tissues by developing upper envelope and multiplying the trichomes. Plants reinforced the support tissues by multiplying the collenchyma and sclereids, and have amplified the transport tissues by enhancing vascularity through multiplying the number of conductive vessels. However, different behaviours seemed to be specific to each stress such an enlargement of liber and reduction of wood in the drought stress and a restriction of liber and wood tissues in salt stress. Additionally, a retraction of the palisade parenchyma and an extension of the spongy parenchyma in drought stress inversely to salt stress were noted. In the treated stems and roots, development of stomata, suber, pericyclic fiber and liber, and a restriction of wood especially in severe stress were observed. The plants developed important changes in moderate stresses; however in the severe, the plants seemed to be stressed, by presenting no significant changes relatively to the control.
... A study by Aboal et al. (2000) in northern Tenerife demonstrated that throughfall under a canopy of Pinus canariensis represented up to 2.2 times the incident rainfall captured by a pluviometer in an open field at the same site. This capability, combined with its long and very deep roots and special physiological adaptations of the needles to resist drought, contributes to the ample distribution range of Pinus canariensis (Grill et al., 2004). For instance, in the study area, we find natural pines occurring from 350 to 1500 m asl and many more above 2000 m asl as a result of the reforestation efforts cited above. ...
... Furthermore, we believe that the lack of competition in the lava flow is allowing Pinus canariensis to exploit its tolerance range to adverse abiotic conditions as many of its competitors at lower and higher altitudes do not have the characteristics needed to survive in this kind of environment, but which are present in Pinus canariensis. For example, very deep roots to search for water and a very effective stomatal regulation system, adaptable leaf morphology depending on location and regulation of secondary metabolites concentration to resist the intense drought periods (Grill et al., 2004;Jiménez et al., 2005), which are probably even more severe due to the lack of a humidity accumulating soil in the lava flows. This point is further supported by observational evidence made at different altitudes on the vegetation surrounding the lava flow across the lava fields. ...
Vegetation research on the lava flows of the historic volcanic eruption of 1705 in Arafo, Tenerife, Canary Islands, is presented. The study area located in the 830000-year-old valley of Güímar was created after a massive landslide 47 km3 in volume. The research is divided into three parts, which cover an altitudinal range from around 35 to 1583 m a.s.l. from the Lower-semiarid Inframediterranean up to the Lower-dry lower-Mesomediterranean bioclimatic belts. First, a phytosociological study of the vegetation present in the area was made and concluded that richness in pioneer communities form a vegetation complex with a high degree of endemicity. Two new associations and four pioneer communities are proposed. Especially notable are the communities of Stereocauletum vesuviani and the pioneer communities of Pinus canariensis. The second part of the research was a field sampling study of 450 individuals of Pinus canariensis, which were measured at different altitudes to obtain data about the colonization dynamics of this species on this 300 years old substrate. We found that stem diameter seems to be a good indicator for healthy tree development at a range between 700 to 1300 m asl, which corresponds to the pine forest as potential vegetation and that many individuals show signs of nutrient deficiency. The third part consists of the publication of two new populations of the Canarian endemism Himantoglossum metlesicsianum, a highly endangered orchid. The monitoring of these two populations has recently begun, and further research will be conducted on all three aspects of this publication, which will be presented and expanded upon in the future.
... As a consequence, the tree growth of both long-term and short-term re-irrigated Scots pine increased and the trees' total leaf area per shoot was significantly larger than that of the trees growing under naturally dry conditions ( Figure 5), mainly due to the irrigated trees having longer shoots and needles (Figure 4). An increase in leaf area depends on water availability via the trade-off between additional carbon gains and water loss through evapotranspiration (Girard et al. 2011), as has also been found for pine species in other drought manipulation experiments (Lebourgeois et al. 1998, Cinnirella et al. 2002, Grill et al. 2004). Moreover, the higher nutrient availability for irrigated trees at the sites Varen and Planige (Figure 2) may have led to an increase in the photosynthetic capacity, as indicated by the higher needle N content of the re-irrigated trees in Lens ( Figure 6). ...
... see Figure S2 available as Supplementary Data at Tree Physiology Online) led to trait-specific responses in Scots pine, with the control trees having shorter and narrower needles than in 2010 (Table 3). This finding is in agreement with that of other studies, showing that water availability during the current year's spring has a high impact on the needle area of pine species (Grill et al. 2004, Dobbertin et al. 2010. In contrast to these direct responses, we found no significant reductions in the number of needles and the shoot length in control trees in 2011 (Table 3). ...
In xeric environments, an increase in drought is related to reduced forest productivity and to enhanced mortality. However, predictions of future forest development remain difficult as the mechanisms underlying the responses of mature trees to long-term variations in water availability are not well understood. Here, we aimed to compare the adjustments in radial growth and morphological needle and shoot traits of mature Scots pine (Pinus sylvestris L.) growing along open water channels with those of control trees growing under naturally dry conditions at three sites in Valais, an inner-Alpine dry valley of Switzerland. The trees growing along two channels had been irrigated since germination (>70 years), whereas those along another previously drained channel had been irrigated only from 2010 to 2012, when the channel was re-established, and could thus be used to quantify the short-term effects of re-irrigation. Linear mixed models revealed that needle and shoot lengths as well as early- and late-wood basal area increments (BAIs) were most responsive to short-term and long-term irrigation. However, the magnitude of the response to the short-term irrigation exceeded that of the long-term irrigation. An extreme drought during the first half of 2011 led to an immediate decrease in the needle length, needle width, and early- and late-wood BAIs of the control trees, whereas the shoot length and needle numbers of control trees reacted with a 1-year delay to the extreme drought, as the shoots were responding to water availability of previous year's summer. Such negative responses to dry climatic conditions were even found in irrigated trees at one of our sites, which might be linked to tree growth becoming more sensitive to drought with increasing tree height and leaf area. In order to improve predictions of future forest development, long-term studies are necessary that consider lagged responses and adjustment processes of trees to changes in water availability.
... As a consequence, the tree growth of both long-term and short-term re-irrigated Scots pine increased and the trees' total leaf area per shoot was significantly larger than that of the trees growing under naturally dry conditions ( Figure 5), mainly due to the irrigated trees having longer shoots and needles (Figure 4). An increase in leaf area depends on water availability via the trade-off between additional carbon gains and water loss through evapotranspiration ( Girard et al. 2011), as has also been found for pine species in other drought manipulation experiments ( Lebourgeois et al. 1998, Cinnirella et al. 2002, Grill et al. 2004). Moreover, the higher nutrient availability for irrigated trees at the sites Varen and Planige (Figure 2) may have led to an increase in the photosynthetic capacity, as indicated by the higher needle N content of the re-irrigated trees in Lens ( Figure 6). ...
... see Figure S2 available as Supplementary Data at Tree Physiology Online) led to trait-specific responses in Scots pine, with the control trees having shorter and narrower needles than in 2010 (Table 3). This finding is in agreement with that of other studies, showing that water availability during the current year's spring has a high impact on the needle area of pine species ( Grill et al. 2004, Dobbertin et al. 2010). In contrast to these direct responses, we found no significant reductions in the number of needles and the shoot length in control trees in 2011 (Table 3). ...
Our knowledge on tree responses to drought is mainly based on short-term manipulation experiments which do not capture any possible long-term adjustments in this response. Therefore, historical water channels in inner-Alpine dry valleys were used as century-long irrigation experiments to investigate adjustments in tree growth to contrasting water supply. This involved quantifying the tree-ring growth of irrigated and non-irrigated (control) Scots pine (Pinus sylvestris L.) in Valais (Switzerland), as well as European larch (Larix decidua Mill.) and black pine (Pinus nigra Arnold) in Vinschgau (Italy). Furthermore, the adjustments in radial growth of Scots pine and European larch to an abrupt stop in irrigation were analyzed.
Irrigation promoted the radial growth of all tree species investigated compared to the control: (1) directly through increased soil water availability, and (2) indirectly through increased soil nutrients and humus contents in the irrigated plots. Irrigation led to a full elimination of growth responses to climate for European larch and black pine, but not for Scots pine, which might become more sensitive to drought with increasing tree size in Valais. For the control trees, the response of the latewood increment to water availability in July/August has decreased in recent decades for all species, but increased in May for Scots pine only. The sudden irrigation stop caused a drop in radial growth to a lower level for Scots pine or similar level for larch compared to the control for up to ten years. However, both tree species were then able to adjust to the new conditions and subsequently grew with similar (Scots pine) or even higher growth rates (larch) than the control.
To estimate the impact of climate change on future forest development, the duration of manipulation experiments should be on longer time scales in order to capture adjustment processes and feedback mechanisms of forest ecosystems.
... Potential reasons for a post-drought legacy effect leading to a stem growth reduction, are often attributed to morphological changes such as a reduced needle or shoot length (Grill et al., 2004;Zweifel and Sterck, 2018;Zweifel et al., 2020) or a shift in carbon allocation below ground to the roots (Kannenberg et al., 2019b). However, how such legacy effects affect the timing and rates of tree growth processes during post-drought years is still unclear. ...
Severe drought events negatively affect tree growth and often cause legacy effects, expressed by smaller tree rings in the post-drought recovery years. While the pattern of reduced tree-ring widths is frequently described the processes underlying such legacy effects, i.e., whether it is due to shorter growth periods or lower growth rates, remains unclear and is investigated in this study. To elucidate these post-drought effects, we examined radial stem growth dynamics monitored with precision band-dendrometers on 144 Douglas fir, Norway spruce and silver fir sample trees distributed along four elevational gradients in the Black Forest (Southwest Germany) during the post-drought years 2019 and 2020. Growth onset of all investigated species occurred between 11 and 24 days significantly earlier in 2020 compared to 2019. Modelling growth onset based on chilling and forcing units and taking the study year into account explained 88–98 % of the variance in the growth onset data. The highly significant effect of the study year (p < 0.001) led to the conclusion, that other factors than the prevailing site conditions (chilling and forcing units) must have triggered the earlier growth onset in 2020. On the other hand, for Douglas fir growth rates were significantly higher in 2020 compared to 2019 (2.9 μm d⁻¹) and marginally significantly higher for silver fir (1.3 μm d⁻¹), underlining the explanatory power of growth rate on recovery processes in general and suggesting that Douglas fir copes better with droughts, as it recovered faster. Growth dynamics at the beginning of the year showed limited growth for earlier growth onsets, which, however, could not explain the difference between the investigated years. Our results provide evidence that legacy effects of drought events are expressed by a delayed growth onset and a reduced growth rate in the post-drought year and that Douglas fir has a superior recovery potential.
... First, individual trees of a given species might be less vulnerable to a similar drought event when growing under dry compared to humid climatic conditions due to long-term adaptation mechanisms (Martín-Benito et al., 2010; Martínez-Vilalta et al., 2012; Trouvé et al., 2017;Stojnić et al., 2018). Intra-specific traits variations associated with adaptation to dry environments include differences in rooting depth, root to shoot ratio, leaf/sapwood area ratio, wood anatomy (thickness of xylem walls, tracheid diameters…) or changes in leaf morphological features such as leaf area (Linton et al., 1998;Lloret et al., 1999;Grill et al., 2004;Martínez-Vilalta et al., 2009;Pritzkow et al., 2020). Under similar drought intensities, the constraint experienced by the trees would thus differ depending on climate. ...
Increasing species diversity is considered a promising strategy to mitigate the negative impacts of global change on forests. However, the interactions between regional climate conditions and species-mixing effects on climate-growth relationships and drought resistance remain poorly documented.
In this study, we investigated the patterns of species-mixing effects over a large gradient of environmental conditions throughout Europe for European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.), two species with contrasted ecological traits. We hypothesized that across large geographical scales, the difference of climate-growth relationships and drought resistance between pure and mixed stands would be dependent on regional climate. We used tree ring chronologies derived from 1143 beech and 1164 pine trees sampled in 30 study sites, each composed of one mixed stand of beech and pine and of the two corresponding pure stands located in similar site conditions. For each site and stand, we used Bootstrapped Correlation Coefficients (BCCs) on standardized chronologies and growth reduction during drought years on raw chronologies to analyze the difference in climate-tree growth relationships and resistance to drought between pure and mixed stands.
We found consistent large-scale spatial patterns of climate-growth relationships. Those patterns were similar for both species. With the exception of the driest climates where pure and mixed beech stands tended to display differences in growth correlation with the main climatic drivers, the mixing effects on the BCCs were highly variable, resulting in the lack of a coherent response to mixing. No consistent species-mixing effect on drought resistance was found within and across climate zones. On average, mixing had no significant effect on drought resistance for neither species, yet it increased pine resistance in sites with higher climatic water balance in autumn. Also, beech and pine most often differed in the timing of their drought response within similar sites, irrespective of the regional climate, which might increase the temporal stability of growth in mixed compared to pure stands.
Our results showed that the impact of species mixing on tree response to climate did not strongly differ between groups of sites with distinct climate characteristics and climate-growth relationships, indicating the interacting influences of species identity, stand characteristics, drought events characteristics as well as local site conditions.
... Notably, stomatal conductance related with water stress is an important trait because it controls the internal CO 2 concentration and photosynthesis dark reaction. Plants also acclimatize to water availability by adjustment of the root to shoot ratio [88,89], of stomatal regulation sensitivity [90] and of leaf features, such as trichomes, epicuticular wax, cuticle, hypoderm, and stomata density [91][92][93][94][95][96][97]. Thus, in our computed and site trait simulations, we assume that the increased variations of NPP may be balanced by variations of other traits. ...
Improving the model-based predictions of plant species under a projected climate is essential to better conserve our biodiversity. However, the mechanistic link between climatic variation and plant response at the species level remains relatively poorly understood and not accurately developed in Dynamic Vegetation Models (DVMs). We investigated the acclimation to climate of Cedrus atlantica (Atlas cedar), an endemic endangered species from northwestern African mountains, in order to improve the ability of a DVM to simulate tree growth under climatic gradients. Our results showed that the specific leaf area, leaf C:N and sapwood C:N vary across the range of the species in relation to climate. Using the model parameterized with the three traits varying with climate could improve the simulated local net primary productivity (NPP) when compared to the model parameterized with fixed traits. Quantifying the influence of climate on traits and including these variations in DVMs could help to better anticipate the consequences of climate change on species dynamics and distributions. Additionally, the simulation with computed traits showed dramatic drops in NPP over the course of the 21st century. This finding is in line with other studies suggesting the decline in the species in the Rif Mountains, owing to increasing water stress.
... Furthermore, timing of drought can affect needle anatomical plasticity. Particularly, spring drought can induce considerable changes in needle foliar anatomy (Grill et al. 2004). In our study tissue differentiation in needles had been largely completed by the start of the summer drought treatment (June), with lignified tissues (i.e. ...
Despite worldwide reports of high tree mortality, growing evidence indicates that many tree species are well adapted to survive repeated dry spells. The drought resilience of trees is related to their phenotypic plasticity and ecotypic differentiation. Whether these two mechanisms act at the same organisational level of a tree and involve similar plant traits is still unknown. We assessed phenotypic plasticity and ecotypic differentiation across four populations of Pinus sylvestris and Pinus nigra seedlings grown for three years under a recurrent summer drought treatment or well‐watered control conditions in a common garden. We measured the response to the summer drought treatment of a total of 26 traits including shoot and needle morphology, needle anatomy, and foliar macronutrients, and related the traits to the growing season water deficit (GSWD) at the location of the seed origin. Foliar phenotypic plasticity in response to recurrent summer drought was surprisingly low, with the needle length and the fraction of mesophyll and phloem tissue adjusting to some extent. In comparison, shoot morphological traits were much more plastic in both species with predominant responses to the summer drought stress including shorter and less numerous apical and lateral shoots. These three traits were also correlated with GSWD at the seed origin, indicating local adaptation. In contrast, between‐population variation of foliar morphological and anatomical traits, and macronutrients were mostly unrelated to the GSWD at the seed origin. Consequently, phenotypic plasticity and ecotypic differentiation occurred at the same level of organisation and in the same plant traits, i.e. shoot morphology. This combination of plasticity and ecotypic differentiation allowed P. sylvestris and P. nigra seedlings to rapidly acclimate to recurrent and long‐lasting dry‐spells. Synthesis: P. sylvestris and P. nigra seedlings showed considerable ecotypic differentiation and phenotypic plasticity of shoot morphological traits, and not foliar traits. Acclimation to recurrent severe summer drought was achieved by reducing shoot growth.
... In addition, scanning electron microscopy (SEM) studies have revealed, in secondary needles, deeply sunken stomata of an unusual type with an enlarged pre-stomatal cavity, which are very likely related to a strong resistance to water loss [18,26]. When developing under water stress, the secondary needles are additionally able to adapt their internal anatomy by rising the number of schlerenchymatic cells adjacent to the vascular bundles and by diminishing the ratio of assimilation parenchyma to vascular bundle [27]. The surface of primary needles, on the other hand, is completely covered by tubular wax crystals resulting in a glaucous appearance that increase protection against UV-radiation and also against high photon flux densities [28]. ...
Great variation in shape and size between primary (juvenile) and secondary (adult) needles, so-called leaf-heteroblasty, occurs in several Pinus species. Most of them loss primary needles during the juvenile-to-adult transition of the tree. An exception to this is Pinus canariensis (a Canary Islands endemism) in which basal resprouting twigs of adult trees frequently wear both primary and secondary needles. Taking advantage of this extraordinary study-case-species, we conducted an exhaustive comparison of both needle types through quantitative analyses of needle anatomy, photochemical performance, gas exchange, and resistance to extreme dehydration and to extreme needle temperature. We hypothesized that primary needles would show lower investment to leaf structure but higher photosynthetical efficiency. Primary needles had less stomatal density and thicker and less wettable cuticles. In cross section, primary needles showed smaller structural fraction (e.g., percent of hypodermis, endodermis and vascular tissue) and higher fraction of photosynthetic parenchyma. Significant differences between primary and secondary needles were not found in net carbon assimilation not in their leaf mass area values. Interestingly, secondary needles showed higher electron transport rate, and they were additionally much more efficient in retaining water under severe and controlled desiccant conditions. When subjected to extreme temperatures (−10° to +50 °C), primary needles recovered better their photochemical efficiency than secondary needles, after +46° and +48 °C heat-shock treatments. Our results indicate that both needle types broaden the diversity of physiological responses against environmental constrains in basal twigs of adult P. canariensis trees. Considering that this is a fire-resistant and resprouting species, this advantage could be particularly useful after a drastic environmental change such a fire or a gap opening in the forest.
... Il distinguait les populations, même si elles ne sont pas géographiquement éloignées les unes des autres (Fig. 5, Tab. 1), et il confirmait même l'étude de De Lillo et Fusaro (1990) (Cinnirella et al., 2002 ;Grill et al., 2004). ...
L’objectif de cette thèse vise l’identification des caractères morphologiques et
anatomiques adaptatifs permettant de discriminer entre les populations du cèdre Marocaines distantes géographiquement.
... It is known that needle length is related to water availability . The effect of drought on needle size has been documented in many studies in pine species Grill et al., 2004;Irvine et al., 1998). The reduction in needle length observed in this study may therefore be ascribed to water stress on trees due to mistletoe infection. ...
Leaf area-sapwood area relationship in Scots pine (Pinus sylvestris L.) under mistletoe (Viscum album ssp. austriacum) infection Abstract: Leaf area is linearly correlated with sapwood area in trees. The linearity of this relationship can be affected by some biotic and abiotic factors. Mistletoes are hemi parasitic plants that take up water and mineral nutrients from their hosts and affect host physiological responses. There is no conclusive evidence to show the effect of pine mistletoe (Viscum album ssp. austriacum) on leaf area and sapwood area relationship in Scots pine trees (Pinus sylvestris L.) at tree level. The aim of this study is to determine and quantify the effect of pine mistletoe on the structural variation of leaf area and sapwood area relationship at tree level in Scots pine. A total of 18 mistletoe infected and 12 uninfected Scots pine trees were destructively sampled. All needles and mistletoes were completely removed from sampled trees to determine needle and mistletoe characteristics, biomass and leaf area. Sapwood areas at breast height (BH) and at crown base height (CBH) were determined from wood discs taken from BH (1.3m) and CBH. Sapwood area was delin-eated by benzidine staining method. Pearson correlation, t-test and regression analyses were conducted to determine the relationship between sapwood area and needle-mistletoe leaf area relationships. The results indicated that both the relationships between sapwood area and leaf area in uninfected, and sapwood area and total leaf area (needle plus mistletoe leaf only) in infected trees were linear. However, the slope of regression equation for mistletoe infected trees was considerably lower when compared to the uninfected trees. As for the variation of the sapwood area along the stem below live crown, there was a slight difference between sapwood area at BH and CBH. The study showed also that mistletoe infection led to a significant reduction in needle size (length, width, area and weight) in Scots pine trees. Significant relationships were found between the sapwood area and leaf area in this study. The results of this study may help fill the gap in the knowledge concerning the impacts of pine mistletoe on the dynamics of Scots pine trees.
... These studies have reported drought-induced reduction in mesophyll cell size (Granier and Tardieu, 1999), epidermal cell size (Cutler et al., 1977;Jones et al., 1980), guard cell size (Xu and Zhou, 2008;Fu et al., 2013;Galmés et al., 2013) and, usually, an increase in whole lamina and mesophyll thickness (Zhang et al., 2012;Galmés et al., 2013;Binks et al., 2016). In pine needles, drought led to a decreased thickness while increasing the abundance of sclerenchyma (Grill et al., 2004). Drought usually affects the differentiation of stomata, however the response of stomatal density seems to be species specific, varying from reduction (Quarrie and Jones, 1977;Hamanishi et al., 2012) to increase (Xu and Zhou, 2008;Fu et al., 2013). ...
Xeromorphism is a set of structural traits facilitating plant functioning under the conditions of water deficit. While leaf xeromorphic traits have been widely described in a variety of species, much less is known about the ability of plants to acclimate to drought by plastically modifying their leaf structure. We hypothesized that such modification would recapitulate the xeromophic syndrome.
We conducted a greenhouse experiment in which a genetically and phenotypically diverse population of barley (Hordeum vulgare L.) cultivars and hybrid lines were subjected to controlled drought followed by re-watering. Leaves produced after the onset of drought were sampled for determination of lamina length and 18 anatomical traits of adaxial epidermis and central transverse lamina sections.
Across all studied genotypes, mean leaf length, width, and dimensions of all internal structures were reduced by drought, whereas the density of veins, stomata, and trichomes increased. However, since anatomical traits were commonly correlated with leaf length and following drought the leaves became shorter, we statistically controlled for the leaf size-related variation. Although leaf shortening explained much anatomical response to drought, several traits exhibited additional, leaf-length independent modification. For example, vein and stomatal density increased and xylem area and vessel diameter decreased to a greater extent than expected from leaf size reduction.
These results confirm the occurrence of modest facultative xeromorphism in barley but also emphasize the need to use allometric analysis to uncouple the true plasticity of traits from changes attributable to altered plant and organ size.
... The ability of pine to develop in extreme forest conditions, conditions of fierce competition and excessive moisture, determines their potential for survival (Egorova, Kulagin 2007). Adaptation to different environmental conditions occurs through changes in the proportions of needles (Apple et al. 2002;Grill et al. 2004;Luomala et al. 2005). Due to the fact that pine exhibits xeromorphic features (Farjon, Styles 1997), adaptation to changes in conditions will be manifested through the water supply tissue (Larcher 2003). ...
The aim of the study was to determine the adaptive characteristics of pine needles associated with age and different growing conditions. The length of the needles decreases and its variability reduces with increasing dryness and poverty of the soil. In oppressed trees, the coefficient of variability of the length of the needles on the tree is 8%. The coefficient of variation in the length of needles approaching 20% will indicate the best conditions for the growth of a particular tree. Trends of the dependence of width and thickness of needles on growing conditions were not identified. The area of needles in pine forests with optimal water regime of soils (blueberry, cowberry type) varies in the range of 112–124 mm<sup>2</sup>. In extreme growing conditions pine needles area is reduced by 27–33% and equals 76–86 mm<sup>2</sup>. These ranges of values of the areas of needles are typical for plantings of the third and fourth classes of age. Changing the width and thickness of the needles is aimed at compensating for changes in the length of the needles in the direction of maintaining the optimal area for these conditions needles. In extreme conditions, the area of the assimilating tissue increases, and the area of the conducting tissue (stele) decreases. Correlation dependences of the area of the stele of needles with the cross-sectional area, with the area of conducting beams, with the number of resin canals and with the cover fabric are revealed.
... Needle traits have evolved in a way that is consistent with adaptation under drier conditions. Regulation of water loss may be influenced by the density of stomata, particularly as plants exposed consistently to drought in sunlit conditions have evolved lower densities of stomata to reduce potential water loss (Grill, Tausz, Pollinger, Jimenez, & Morales, 2004). Reduced density of stomata among the island trees suggests that density of stomata may have been reduced in response to increased evapotranspiration. ...
Rare species present a challenge under changing environmental conditions as the genetic consequences of rarity may limit species ability to adapt to environmental change. To evaluate the evolutionary potential of a rare species, we assessed variation in traits important to plant fitness using multigenerational common garden experiments. Torrey pine, Pinus torreyana Parry, is one of the rarest pines in the world, restricted to one mainland and one island population. Morphological differentiation between island and mainland populations suggests adaptation to local environments may have contributed to trait variation. The distribution of phenotypic variances within the common garden suggests distinct population-specific growth trajectories underlay genetic differences, with the island population exhibiting substantially reduced genetic variance for growth relative to the mainland population. Furthermore, F1 hybrids, representing a cross between mainland and island trees, exhibit increased height accumulation and fecundity relative to mainland and island parents. This may indicate genetic rescue via intraspecific hybridization could provide the necessary genetic variation to persist in environments modified as a result of climate change. Long-term common garden experiments, such as these, provide invaluable resources to assess the distribution of genetic variance that may inform conservation strategies to preserve evolutionary potential of rare species, including genetic rescue.
... In the leaves of Pinus monophylla, the chloroplasts change their shape from ellipsoid to irregular and possess dark stained plastoglobuli when exposed to the stressing conditions such as acid rain (Back and Huttunen, 1992). Although ultrastructure of the coniferous plants has not been studied in detail, a few reports (Back and Huttunen, 1992;Boddi et al., 2002;Grill et al., 2004;Stabentheiner et al., 2004) provide some information on the gymnosperm chloroplast structure. It has been observed that some Pinus chloroplasts, probably at the stage of senescence, are full of small vesicles (Whatley, 1975). ...
... Given that polyphenols are derived from shikimic acid, and as the shikimic acid content did not change significantly until leaf water potential was less than −1.8 MPa, there is still a possibility that an increase in total needle polyphenol content could occur at more negative water potential values than the ones reached in this study. Alternatively, enhanced shikimic acid contents might reflect increased transformation of shikimic acid into lignin (Becerra-Moreno et al. 2015) as observed in Pinus canariensis (Grill et al. 2004). This could serve as a mechanical barrier against pathogens (Monties and Fukushima 2001). ...
Key messageA multiphasic response to water deficit was found in Scots pine primary and secondary metabolism. First, an increase of terpenoids coincided with the stomatal closure. Second, an accumulation of proline, ABA, and shikimic acid was detected when photosynthesis was negligible. ContextDrought-induced mortality is characterized by a major needle yellowing followed by severe defoliation and whole branch death. Before these external visual symptoms of drought stress take place, different alterations occur in plant metabolism. AimsThis study aims to detect changes in primary and secondary metabolism of Pinus sylvestris L. in response to a decrease in soil water availability. Methods
We analyzed needle water potential, photosynthetic characteristics, and concentrations of proline, terpenoids, shikimic acid, total polyphenols, and abscisic acid (ABA) in P. sylvestris through a 55-day soil water deficit period. ResultsConcentrations of most metabolites varied with the decrease in soil water availability, but changes in different compounds were triggered at different times, highlighting a multiphasic response. Increases in monoterpene and sesquiterpenoid content at moderate water deficit coincided with stomatal closure which preceded the accumulation of proline, ABA, and shikimic acid under severe water deficit when net photosynthesis was negligible. Conclusion
This work confirms that most of the secondary metabolites under investigation in Pinus sylvestris did not increase until a moderate to severe water deficit was experienced, when photosynthesis was limited by stomatal closure.
... Pinus canariensis is well adapted to the dry treeline environment ) exemplified by xeromorphic needles (Grill et al. 2004), deeply inserted stomata with an elongated epistomatal chamber (Jimenez et al. 2000), and tap roots extending down to 15 m (Luis et al. 2005;Climent et al. 2007), allowing trees to use soil water reserves in deep soil layers when the upper soil profiles are exhausted (Brito et al. 2015). These ground water reserves originate from cold and wet season rainfall (from previous-year October into current-year March), which typically provides more than 90% of the annual precipitation. ...
Tree growth of Pinus canariensis at treeline in Tenerife, Canary Islands, is thought to be primarily controlled by wet season precipitation (P) prior to the current year´s growth. Therefore, we investigated the inter-annual variations in stem water deficit (ΔW) and radial growth (RG) during two consecutive years differing in wet season P. ΔW was extracted from stem circumference variations, and the influence of environmental variables was evaluated by Pearson correlation statistics. Wet season P was considerably lower in 2008 than in 2009; despite this difference in P between both years, shallow soil water availability was almost exhausted during both summers. However, the effect of shallow soil drought showing a clear seasonality of ΔW and RG was only detected in 2008. In summer 2009, RG rates were highest during the summer indicating that P. canariensis was able to tap water from deep soil layers originating from P prior to the current year´s growth. The ability to use deep soil water during extended periods of shallow soil water deficit was also reflected in a close positive correlation between RG and whole-tree water use. In our study, the effect of only one hydrological dry year resulted in a severe reduction in annual RG. Thus, when wet season P is low for a number of years, chronic drought may have negative implications for tree growth at treeline in Tenerife.
... In the present study, we used tree ring width and stable C isotope analysis to evaluate the effects of rising C a and drought on growth and iWUE of Pinus canariensis (Sweet ex Spreng.) at the semi-arid treeline in Tenerife, Canary Islands, Spain. At present, no other tree species can compete with P. canariensis an endemic conifer of the Canary Archipelago, which is well adapted to xeric conditions exemplified by xenomorphic needles (Grill et al. 2004) and tap roots extending down to 15 m belowground (Luis et al. 2005;Climent et al. 2007). Our specific objective were (1) to determine the main limiting climatic factor for radial growth of P. canariensis at its upper distribution limit and (2) to test if rising atmospheric CO 2 concentrations and changing environmental conditions (temperature and precipitation) at the semiarid treeline of Tenerife have caused changes in tree growth and iWUE during the past 37 years (1975-2011). ...
Key message:
Intrinsic water-use efficiency of Pinus canariensis (Sweet ex Spreng.) growing at a semi-arid treeline has increased during the past 37 years. Tree-ring width by contrast has declined, likely caused by reduced stomatal conductance due to increasing aridity.
Context:
Rising atmospheric CO2 concentration (Ca ) has been related to tree growth enhancement accompanied by increasing intrinsic water-use-efficiency (iWUE). Nevertheless, the extent of rising Ca on long-term changes in iWUE and growth has remained poorly understood to date in Mediterranean treeline ecosystems.
Aims:
This study aimed to examine radial growth and physiological responses of P. canariensis in relation to rising Ca and increasing aridity at treeline in Tenerife, Canary Islands, Spain.
Methods:
We evaluated temporal changes in secondary growth (tree-ring width; TRW) and tree ring stable C isotope signature for assessing iWUE from 1975 through 2011.
Results:
Precipitation was the main factor controlling secondary growth. Over the last 36 years P. canariensis showed a decline in TRW at enhanced iWUE, likely caused by reduced stomatal conductance due to increasing aridity.
Conclusion:
Our results indicate that increasing aridity has overridden the potential CO2 fertilization on tree growth of P. canariensis at its upper distribution limit.
... The negative effect of drought over such a long integrated period can have multiple implications for growth reduction: Drought during the previous fall and current spring, and heat during the growing season can reduce tree growth (Rigling et al. 2002;Fritts 1976). Spring drought also affects the elongation and development of young needles (Grill et al. 2004), whereas storage reduction due to late summer drought reduces shoot length in the following year (Löf and Welander 2000). Another indirect negative effect on growth is the reduction of photosynthetic capacity due to needle loss following drought stress (Pouttu and Dobbertin 2000;Solberg 2004). ...
The temporal variability of the forest sink is associated with high uncertainties in both its magnitude and the driving ecological and climatic processes. In this study, we assess the inter-annual variability (IAV) of carbon uptake using annually resolved aboveground biomass increment (ABI) estimates from 272 pseudorandomly sampled trees at a long-term monitoring plot in the dry valley of the Valais in Switzerland. Over the 1950–2011 period, the mean ABI is 86.8 g C m−2 year−1 with an IAV of ±31 %. The IAV is largely driven by hydrological conditions throughout the water year from previous August to current August (r SPEI = 0.56; 1st differenced r = 0.75, p < 0.001). During extremely dry years (such as 1972, 1976, 1998, and 2011), the carbon accumulation was reduced up to 63 % from the long-term mean. Furthermore, our analysis explores possible biases of annual ABI derived from manual band dendrometers in permanent plot inventories caused by water status related changes in tree size. During the
... In the case of drought stress, the structural responses, thus, vary as a function of the drought severity, chronicity and ontological tissue development. Leaves affected by water stress during their ontological development show fewer and smaller organelles in mesophyll or increased lignification within veinlet or hypodermis cells (Grill et al. 2004;Pitman et al. 1983). In differentiated leaves, acute water stress causes the development of gradients of injury with stress symptoms within most cell organelles and characteristic terminal stages including the disruption of compartments, plasmolysis and cytorrhisis (Olmos et al. 2007;Ristic and Cass 1991;Vassileva et al. 2012). ...
Key message
In droughted oak foliage, water shortage and carbon starvation caused structural injury varying in severity between cell types and indicative of adaptive reversible and degenerative irreversible processes.
Abstract
Warmer temperatures as a consequence of climate change have already started to affect forest ecosystems, enhancing drought frequency and severity. Also depending on drought chronicity and ontological tissue development, tree foliage can respond to drought by enhancing structural acclimation and thus delay injury. More comprehensive characterization of micromorphological responses in foliage is needed for evaluating the tolerance of forest trees in the future. In the present study, structural reactions in foliage of three oak species exposed to acute summer drought were analyzed using transmitted light, fluorescence and electron microscopy. Oak leaves withstood drought stress for a considerable length of time before injury in the form of necrotic leaf margins appeared. In the leaf parts still asymptomatic, structural changes indicative of water stress and carbon starvation were observed. In the epidermis, autophagic processes—with exocytosis of degraded material—contributed to cell wall thickening. However, they also accelerated the degeneration of cell content whereas stomatal guard cells often remained unscathed. In mesophyll, the material in autolytic vesicles was internalized in vacuoles, which contributed to maintaining the cell turgescence. Plugging of xylem and phloem cells with polysaccharidic and proteinic material was mechanistically related to necrosis of leaf margins. These structural changes were indicative of reversible adaptive and irreversible degenerative processes. The functionality of upper mesophyll and stomata was prioritized, allowing foliage to resume gas exchange within hours of rewatering. Hence, extensive structural changes within still asymptomatic parts of the foliage were accountable in increasing the drought tolerance of the oaks.
... Si tratta di un albero endemico delle Isole Canarie, dove si riscontra -talora con ruolo di specie legnosa dominante -in contesti ecologici differenti, partecipando a formazioni forestali sia pure sia miste lungo un range altitudinale e climatico molto ampio da 500 sino a 2.100 m s.l.m., in contesti caratterizzati da precipitazioni medie annue comprese tra 200 e 2.000 mm (FERNÁNDEZ-PALACIOS & DE NICOLÁS, 1995;CLIMENT et al., 2004;GRILL et al., 2004). Nei secoli passati l'eccessivo sfruttamento delle risorse forestali delle isole Canarie ha comportato la notevole frammentazione dell'areale originario di questa conifera (DEL ARCO AGUILAR et al., 1992), che pertanto figura tra le specie minacciate nelle liste della IUCN (FARJON, 2006). ...
First case of naturalization of Pinus canariensis in Sicily and first population of Acacia cyclops on the main island. Both cases of naturalization have been recorded within the Nature Reserve “Foce
del Fiume Platani” (S Sicily). Additional information on the demography and distribution of both species within the afforestations of the protected area are provided, as well as a forecast of their invasive attitudes according to scientific literature.
... leucodermis (Table III). An increase in the number of hypodermis layers within the same species may be the plant's response to droughtrelated stress (Grill et al. 2004 and the quoted authors). The fact that Bosnian pines growing on higher terrains (Montenegro) have a slightly lower average number of hypodermis layers (3.1 -3.4) than Bosnian pines from Serbia (3.7; present results, Table III) corroborates this claim. ...
Variability of eight morpho-anatomical characters of 2-year-old needles of the Bosnian pine (Pinus heldreichii Christ.), collected from natural populations in Montenegro (Lovćen, Zeletin and Bjelasica) and Serbia (Zlatibor-Pešter) were investigated. The needles have 0-13 resin ducts, predominantly of the medial type (settled in mesophyll tissue). The average values were as follows: 7.86 cm (needle length), 1.44 mm (needle width), 0.85 mm (needle thickness), 20.82 μm (cuticle+epidermis thickness), 21.08 μm (height of hypodermal cells), 3.31 (number of hypodermis layers), 4 (number of resin ducts) 57.05 μm (resin duct diameter). Needle width and thickness were the most variable characters. Principal component analysis separation of the geographically most distant populations Lovćen and Zlatibor-Pešter from themselves and from other populations. Cluster analysis suggests biggest similarities between populations Lovćen and Bjelasica and biggest differences between Lovćen and Zlatibor-Pešter.
... (Gieger and Leuschner, 2004). In addition to anatomical adaptations of the needles to the harsh environmental conditions at the semi arid treeline (Grill et al., 2004 and further references therein) this physiological drought adaptation mechanism of P. canariensis fits to a typical water-saving strategy (sensu Levitt, 1980). Our measurements show that P. canariensis is able to tap water from deep soil layers whenever it is possible and this contribution to year round E c depends on previous wet period (October-April) precipitation. ...
Given its importance, transpiration of forest canopies has been measured in a wide range of environments. However, measurements in treeline ecosystems with Mediterranean climate are rare more so in semi arid climates. Therefore in the present study we investigate inter-annual variation in canopy transpiration (Ec) of a Pinus canariensis forest located on a treeline ecotone in Tenerife, Canary Islands, Spain, where the climate is typically semi arid Mediterranean. Meteorological conditions and sap flow were continuously monitored during two consecutive years. In both years, atmospheric conditions were typical for the study site. Nevertheless large differences were detected in precipitation (P) with a high inter-annual variability. Calendar year (January–December) P was higher in 2008 than in 2009, while in the corresponding hydrological year (October–September), P was considerably lower in 2008 than in 2009. Despite this difference in P between both years top soil water availability was almost exhausted during both summers. However, the effect of top soil drought, showing a visible seasonality on Ec was only clearly detected in 2008 with values down to 0.02 mm day−1 during summer. During the summer 2009, in contrast, Ec rates were up to 1.12 mm day−1 showing that P. canariensis is able to tap water from deep soil layers when P of the previous wet period (October–April) recharged these reserves. This points out the importance of evaluating sap flow studies in semi arid treelines with respect to hydrological year P. Climate change models predict a reduction of more than 30% in precipitation. In our study the effect of only one hydrological dry year resulted in severe water stress. Thus, when winter rainfall is low for a number of years, chronic drought may have negative implications for tree and stand transpiration in semi arid treelines.
... The Canary Islands pine is a generalist tree that can occur from near sea level up to about 2300 m (Jiménez et al., 2005) and is well adapted to fire (Climent et al., 2004b). Its needles exhibit morphological drought adaptations (Grill et al., 2004), and its cones and seeds vary in size with altitude (Gil et al., 2002). However, P. canariensis is one of the few pines that are able to resprout as adult trees, from root collar and stems, immediately after a fire (Climent et al., 2004b). ...
... The aboveground parts of the trees are also modified, as drought leads to crown decline via the reduction of needle length, needle area, and needle fresh and dry weight (Cinnirella et al. 2002;Dobbertin et al. 2010;Grill et al. 2004). Furthermore, the crown transparency of conifers often increases in the year following a drought event (Solberg 2004). ...
• Context
One short-term adjustment of trees to drought is the reduction of photosynthetic tissues via leaf shedding. But in conifers, it usually takes several years to fully restore needle mass and assimilation capacity.
• Aims
This study aims to evaluate whether leaf shedding sustainably damages conifers or if these trees still have the ability to recover from drought with respect to their foliage and wood formation.
• Methods
An irrigation experiment was established in a mature dry forest to test the growth reactions of Scots pine (Pinus sylvestris L.) differing in crown transparency (low, medium, high) to a drought release by irrigation in comparison with equivalent control trees growing under naturally dry conditions on the same site.
• Results
Drought and high crown transparency had a combined negative effect on radial tree growth: Control trees with medium to high crown transparencies showed a substantially shorter growth period and a long-lasting growth depression in response to the severe summer drought in 2003. However, all trees benefited from irrigation, irrespective of their crown status, and immediately increased growth in response to irrigation.
• Conclusion
The progressed drought-induced defoliation seemed to be a weakening factor for trees suffering from drought, but this can be reversed if the water supply is improved.
... The typical pine needles, the secondary needles, are up to 30 cm in length and are grouped in fascicles of three on short shoots. Recently some structural investigations showing a high degree of xeromorphosis were published (Jiménez et al. 2000; Grill et al. 2004). In the development of the seedling the secondary needles are preceded by short glaucous primary needles growing on long shoots. ...
Surface characteristics of primary and secondary needles of Pinus canariensis were investigated using scanning electron micro-scopy and gas chromatography to study structure and composition of epicuticular wax, cuticle micromorphology and the structure of stomata.
Tubular waxes could be observed on the whole needle surface of the glaucous primary needles whereas on secondary needles they were restricted to the lower surface of young needles. Recrystallization resulted in comparable wax tubes and, addition-ally, plate like structures recrystallized from primary needle wax. Isolated cuticles of primary needles were tender and showed a simple stomata complex with six subsidiary cells whereas the cuticles of secondary needles were massive and revealed 9–12 subsidiary cells. In contrast to the cuplike epistomatal chamber of the primary needles that of the secondary needles was larger and often irregularly formed. Main constituents of the cuticular wax were ω-hydroxy-n-alkanoic acids, 10-nonacosanol and n-alkanoic acids with no differences in the qualitative composition between primary and secondary needles but with some differences in the quantitative pattern.
The possible role of the investigated cuticular features in adaptive strategies of the needles to avoid light and water stress is discussed.
... This change in carbon allocation for the benefit of root growth leads to a reduction in the shoot/root ratio under drought conditions (Linder and Axelsson 1982; Waring 1987). The aboveground parts of the trees are also modified, as drought leads to crown decline via the reduction of needle length, needle area, and needle fresh and dry weight (Cinnirella et al. 2002; Dobbertin et al. 2010; Grill et al. 2004). Furthermore, the crown transparency of conifers often increases in the year following a drought event (Solberg 2004). ...
... This tree is adapted to live near sea level up to 2400 m (Jimenez et al., 2005), but today is restricted to 500-2400 m in the south and 1000-2000 in the north. This pine tree is well adapted to volcanism (Climent et al., 2004), its needles exhibit morphological drought adaptations (Grill et al., 2004) and its cones and seeds vary in size with altitude (Gil et al., 2002). A Canary pine tree can grow 40-50 m in height and live for more than 700 years (Ceballos and Ortuñ o, 1951). ...
The Canary Islands great spotted woodpecker Dendrocopos major canariensis is an endemic bird restricted to the Pinus canariensis forests of Tenerife and Gran Canaria. Classification tree models were applied to explore the relationship of the occurrence of this picid and habitat variables between two contrasting periods (breeding vs. non-breeding seasons) and for the entire annual cycle. During the reproductive period the availability of mature trees (DBH > 60 cm), and snags (dead trees), for nesting and roosting, characterize the breeding territory. Outside the breeding season the choice of locations was driven by a tree cover larger than 28.5% and the presence of trees taller than 8.5 m on average, a pattern explained by the availability of pine seeds in the cones of well-developed canopies, and less so by predation risk. Overall, during the annual cycle, well-developed canopy sites influenced the presence of this picidae (tree cover > 38%) and on more open sites (<38%) the presence of mature trees (DBH> 60 cm) became the second most important predictor of occurrence. We suggest that food abundance and availability could be the ultimate factor explaining the intra-annual variation observed, with the availability of snags being an important factor during nesting. In the range of this endemic, we recommend selective cuts in pine plantations, to allow the trees to set seed and improve their crops, minimizing the elimination of snags, and killing some large pine trees if the priority is to expand the distributional range of the woodpecker.
... A short-term morphological/physiological adaptation of the needle characters to the water supply in the past and recent growing seasons could be another explanation for the observed pattern. Such drought effects have been observed for a range of other species as well, for example in Picea abies (Palá tová , 2004), Pinus canariensis (Grill et al., 2004), or Pinus cembroides (Poulos and Berlyn, 2007). Larcher (1994) explained this adaptation by lesser photosynthetic production and a reduced cell elongation Table 6 Measurements of 11 morphometric traits: (1) length of apical needle (mm), (2) length of lateral needle (mm), (3) width of apical needle (mm), (4) width of lateral needles (mm), (5) thickness of ultimate apical branchlet (mm), (6) thickness of ultimate lateral branchlets (mm), (7) number of apical scales, (8) number of lateral scales, (9) cone length (mm), (10) cone diameter (average of 2 independent measures in an angle of 901) (mm), (11) seed number per cone. ...
Intra- and among-population variations of Juniperus seravschanica were morphologically examined in eight populations originating from elevations of 1300–2200m a.s.l. in Kyrgyzstan. Eleven traits of needles and cones were studied on 70 vouchers. In addition, height, diameter, stem form, and sex of 172 trees were recorded in the field in order to test whether male trees invest more in vegetative growth than females and if sex ratio is shaped by (limited) environmental resources. Morphological differences among populations were small, but needle length, width and thickness were statistically different. However, differences based on needle traits were independent from geographical, altitudinal and environmental distances. In sharp contrast to studies in other Juniperus species, sex ratio in J. seravschanica was strongly female biased (3.5 females : 1 male). Moreover, no correlation between the habitat conditions and the sex ratio was detected, suggesting that within the altitudinal range of this species, females occur more frequently. This has implications for sustainable use and the conservation of J. seravschanica populations. It is likely, that due to the higher investment of male individuals in vegetative growth males are more exploited than females. An average effective population size of 70% of the respective census suggests that conservation measures and non-selective logging regimes are required to allow reproduction and a natural regeneration of this species.
... However, we observed significant interspecific differences in needle density and dry to fresh mass ratio at higher irradiance ( Figures 4C and 4D), and in the total volume fraction of mechanical tissues over most of the light range ( Figure 7G). Enhanced support investments and higher foliage density are typical features of species from dry habitats (Grill et al. 2004, Wright et al. 2004. Thus, these needle features may partly explain the greater drought tolerance of P. patula. ...
Acclimation potential of needle photosynthetic capacity varies greatly among pine species, but the underlying chemical, anatomical
and morphological controls are not entirely understood. We investigated the light-dependent variation in needle characteristics
in individuals of Pinus patula Schlect. & Cham., which has 19–31-cm long pendulous needles, and individuals of P. radiata D. Don., which has shorter (8–17-cm-long) stiffer needles. Needle nitrogen and carbon contents, mesophyll and structural
tissue volume fractions, needle dry mass per unit total area (MA) and its components, volume to total area ratio (V/AT) and needle density (D = MA/(V/AT)), and maximum carboxylase activity of Rubisco (Vcmax) and capacity of photosynthetic electron transport (Jmax) were investigated in relation to seasonal mean integrated irradiance (Qint). Increases in Qint from canopy bottom to top resulted in proportional increases in both needle thickness and width such that needle total to
projected surface area ratio, characterizing the efficiency of light interception, was independent of Qint. Increased light availability also led to larger MA and nitrogen content per unit area (NA). Light-dependent modifications in MA resulted from increases in bothV/AT and D, whereas NA changed because of increases in both MA and mass-based nitrogen content (NM) (NA = NMMA). Overall, the volume fraction of mesophyll cells increased with increasing irradiance and V/AT as the fraction of hypodermis and epidermis decreased with increasing needle thickness. Increases in MA and NA resulted in enhancedJmax and Vcmax per unit area in both species, but mass-based photosynthetic capacity increased only in P. patula. In addition,Jmax and Vcmax showed greater plasticity in response to light in P. patula. Species differences in mesophyll volume fraction explained most of the variation in mass-based needle photosynthetic capacity
between species, demonstrating that differences in plastic adjustments in mass-based photosynthetic activities among these
representative individuals were mainly associated with contrasting investments in mesophyll cells. Greater area-based photosynthetic
plasticity in P. patula relative to P. radiata was associated with larger increases in MA and mesophyll volume fraction with increasing irradiance. These data collectively demonstrate that light-dependent increases
in mass-based nitrogen contents and photosynthetic activities were associated with an increased mesophyll volume fraction
in needles at higher irradiances. They also emphasize the importance of light-dependent anatomical modifications in determining
needle photosynthetic capacity.
... This generalist tree occurs from 1200 to 1500 m up to 2000 m in the north and from 500–700 m to 2300 m in the south (Jiménez et al. 2005) and is well adapted to volcanism (Climent et al. 2004) and its consequences (Arévalo et al. 2001). Its needles exhibit morphological drought adaptations (Grill et al. 2004) and its cones and seeds vary in size with altitude (Gil et al. 2002). The effect of fire on the pine forest bird community is poorly understood and non-natural forest fires and their increased frequency are being considered by Canarian authorities as a major threat to this ecosystem because between 1986 and 2006 a total of 11 751 ha were burnt on the island of Tenerife alone. ...
Capsule Tree cover and seeds on the ground influence the occurrence of Blue Chaffinches during the non‐breeding period.
Aims To study the feeding habitat selection of the common Tenerife Blue Chaffinch race during the non‐breeding period as a desperate measure to conserve the endangered Gran Canaria race, whose critical area was burnt in the summer of 2007.
Methods Basic statistics were used to test for differences between occupied sites (n = 35) and available representative sites (n = 35). Univariate classification tree models were applied to explore the relationship between a single response variable (presence–absence) and multiple explanatory variables and the relative importance of these. Pine seed availability was quantified on the trees (n = 70) and on the ground (n = 140; 1 × 1 m plots).
Results We found a non‐random feeding habitat selection by Blue Chaffinches on Tenerife. During the non‐breeding period Blue Chaffinches selected those areas for feeding on pine seeds where the tree cover was higher than 38% (mature areas with tall and thick trees with good crops). When the tree cover was lower than 38%, the mean number of seeds on the ground influenced the presence of this finch (> 0.05 seeds per m2).
Conclusions This study highlights that Blue Chaffinches primarily select sheltered sites for feeding during the non‐breeding period. The selection of less sheltered sites seems to be mediated by pine seed availability. Therefore, in this endemic forest system, perceived predation risk, food abundance and availability, and overall availability of safe foraging options are all possibly determining the winter feeding habitat selection. We recommend selective cuts in high‐density pine stands to recreate those conditions that allow the pine trees to set seed and management aimed at creating a structure of dispersed small‐area compartments with mature trees that provide food and shelter. The installation of artificial feeders seems to be a post‐fire priority action for the conservation of the Gran Canaria race.
... The Canary Islands pine is a generalist tree that can occur from near sea level up to about 2300 m (Jiménez et al., 2005) and is well adapted to fire (Climent et al., 2004b). Its needles exhibit morphological drought adaptations (Grill et al., 2004), and its cones and seeds vary in size with altitude (Gil et al., 2002). However, P. canariensis is one of the few pines that are able to resprout as adult trees, from root collar and stems, immediately after a fire (Climent et al., 2004b). ...
Fire is a key ecological force in pine forests worldwide, and faunal responses to this disturbance have been a major topic of ecology, yet little is known for oceanic island environments. Using line transects we surveyed the bird community of a natural Pinus canariensis forest burned in the summer of 2007 on Tenerife, Canary Islands, Spain. Our goal was to identify important environmental variables and the thresholds that influenced the pattern of bird abundance at the community, foraging guild, and species-specific level. Models were constructed by means of regression trees and cross validation applying the 1-SE rule. Mixed results were observed and only 2 species were clearly affected by fire severity. Overall, total bird abundance, total species richness, and total bird diversity were positively influenced by low, very low, and moderate canopy fire severity, respectively, and the presence of either Erica or Myrica shrubs. Consequently, high canopy fire severity had an overall negative effect on bird community characteristics. Abundance of Myrica shrubs affected positively general ground foragers such as common blackbird (Turdus merula cabrerae) and Canary Islands chiffchaff (Phylloscopus canariensis), a canopy forager. The number of thin trees was important for canopy foragers such as goldcrest (Regulus regulus teneriffae) and African blue tit (Cyanistes teneriffae teneriffae), but also for a bark forager, the great spotted woodpecker (Dendrocopos major canariensis). European robin (Erithacus rubecula superbus) and the ubiquitous endemic blue chaffinch (Friugilla teydea teydea) were influenced by low and moderate canopy fire severity, respectively. We recommend that land managers incorporate these results into future post-fire management plans. Priority post-fire actions should be directed toward the protection and conservation of the endemic blue chaffinch, a species of conservation concern on the nearby island of Gran Canaria.
... While well-watered plants increased substantially their LAR under low irradiance (a typical response in shaded plants) drought-stressed shaded plants tended to reduce their investment in needle area and to increase allocation to roots. The expected reduction in SLA responding to water stress is congruent with the increase in protection tissues at the expenses of photosynthetic tissue reported for this species (Grill et al., 2004). Nevertheless, in our experiment, this morphological shift occurred only in the low light treatment. ...
Aiming to test the existence of constraints in the ability of Pinus canariensis seedlings to withstand water stress under low irradiance, we carried out a greenhouse trial combining two highly contrasted light environments (90 and 5% of full sunlight) and two levels of water availability (42 and 10% in volume). Shaded seedlings displayed an extremely low dry weight, 2% of well-illuminated seedlings biomass at the end of the experiment (158 days). Light × water interactions were significant for most traits considered. However, the complementary allometric analysis showed that the effect of water availability under high irradiance could be explained through ontogenetic differences related to plant size. Shaded plants exhibited higher root biomass and reduced leaf area ratio in response to low water availability, and this was confirmed by allometric analysis. By contrast, plants under full sunlight showed only apparent plasticity; i.e. ratios for both watering treatments belonged to common allometric trajectories. Moreover, only the seedlings under low irradiance underwent a significant decrease in specific needle area due to a shortage in water availability. We, therefore, conclude that the effect of the imposed drought was more dramatic in the shaded environment.
... This may mean that habitat specialization provides a fitness payoff in females (Dudley 2006; Hultine et al. 2007) and in wetter conditions females T. baccata can win competition with males, in spite of their higher reproductive effort. The more xeromorphic , shorter needles of male individuals of T. baccata found in our investigation can be treated as indirect support for their ''preference'' for drier sites, because coniferous trees form shorter needles under conditions of water deficit (Grill et al. 2004). It was also found that male individuals of wind-pollinated dioecious plant species dominate in populations on higher and drier microsites (Freeman et al. 1976; Ortiz et al. 1998; Hultine et al. 2007). ...
Sex ratio and sexual dimorphism were studied in the dioecious tree Taxus baccata. We examined five populations of T. baccata in Poland and Ukraine to identify the differences between male and female individuals. The sex of all individuals, height
and diameter, needle length and area, specific leaf area (SLA), the number of stomata rows, stomatal density, and content
of carbon and nitrogen were measured to identify the differences between male and female individuals. The relationship between
sex ratio and climatic conditions, age and population size were analysed using data collected from the field and the literature.
Female trees were shorter than males, but needles of females were longer and had larger area. Although there were no differences
among sexes in SLA, nitrogen and carbon concentration, we found a positive correlation between nitrogen concentration and
SLA among females. The sex ratio changed with tree height within populations, and taller height classes were biased in favour
of males. Regardless of population age, the percentage of females within populations was positively correlated with precipitation.
Probably high reproductive effort caused female trees to lose in competition with males, and this loss may also be enhanced
by lower drought tolerance in females and could contribute to risk of extinction for T. baccata. The continental geographic range of T. baccata may be restricted by limited occurrence of females, which demand higher water resources than males.
Los artículos de acceso abierto publicados en la Revista del Jardín Botánico Nacional se distribuyen según regulaciones de Creative Commons Attribution 4.0 International licence (CC BY 4.0-Variación anatómica foliar en poblaciones naturales de Pinus tropicalis en Pinar del Río, Cuba RESUMEN La variación de los caracteres anatómicos es crucial para evaluar la adaptabilidad ecológica, la cual reviste gran importancia para el manejo forestal y la conservación de especies endémicas. Pinus tropicalis es un árbol endémico distribuido por la provincia Pinar del Río y la Isla de la Juventud, Cuba. Ocupa gran variedad de ecótopos en poblaciones puras o en simpatría con P. caribaea var. caribaea. El objetivo de este estudio fue evaluar la variación anatómica de las acículas de P. tropicalis como respuesta diferencial adaptativa a las condiciones ambientales determinadas por la litología, la altitud y la pendiente. Se muestrearon de 20 a 30 individuos de todos los ecótopos donde crece la especie naturalmente. Se realizaron cortes transversales a 10 acículas de cada árbol y se evaluaron 12 variables anatómicas. Los resultados de los análisis estadísticos revelaron diferencias significativas entre individuos de los ecótopos, fundamentalmente en las arenas cuarcíticas con alto contenido de sílice. El análisis de componentes principales mostró una relación entre variables anatómicas relacionadas con la economía hídrica y la asimilación. El discriminante distinguió grupos definidos a partir de la relación de las variables anatómicas con la litología. Las variables que más contribuyeron a discriminar entre ecótopos fueron las relacionadas con la regulación hídrica, el número y diámetro de los canales de resina y el grosor de la cutícula. La disponibilidad de agua y la oligotrofia de los sustratos son los factores que más influyeron en la variación anatómica. Los resultados son una contribución a la ecología y la silvicultura de la especie. Palabras clave: adaptación, análisis multivariado, diferenciación anatómica ABSTRACT The variation of anatomical traits is crucial to assess ecological adaptability, which is of great importance for forest management and the conservation of endemic species. Pinus tropicalis is an endemic tree distributed in the province of Pinar del Río and Isla de la Juventud, Cuba. It occupies a great variety of ecotopes in continuous pure adaptability populations or in sympatry with Pinus caribaea var. caribaea. The objective of this study was to evaluate the anatomical variation of Pinus tropicalis needles as an adaptive differential response to environmental conditions determined by lithology, altitude and slope. Twenty to thirty individuals were sampled from all the ecotopes where the species grows naturally. Cross sections were made from 10 needles of each tree and 12 anatomical variables were evaluated. The results of the statistical analysis revealed significant differences between ecotopes, mainly in quartzite sands with high silica content. The principal component analysis showed a relationship between anatomical variables related to water economy and assimilation. The discriminant distinguished groups defined from the relationship of the anatomical variables with the lithology. The variables that contributed the most to discriminate between ecotopes were those related to water regulation, the number and diameter of the resin channels, and the thickness of the cuticle. The availability of water and the oligotrophic substrates are the factors that influence anatomical variation. The results are a contribution to ecology and silvicultural management of the species.
Begonia is one of the largest plant genera that widely distributed in the tropics and subtropics. This genus has important value and has been cultivated intensively as ornamental plants. Hence, this purpose of this research is to investigate the leaf anatomical characteristic of five Begonia species; B. maculata , B. cucullata , B. masoniana , B. acetosa and B. listada ; which are important in horticulture. The mini-microtome with a liquid preservation method has been used to obtain the transverse section. The result showed that the epidermis, hypodermis, and trichome characters are varied, and each species could have a different character’s combination. The qualitative and quantitative parameters of five Begonia were also described and compared in this study.
Fast growing tree species can generate high wood production in a short time frame. However, maximum productivity is dependent on environmental and management conditions as well as intrinsic plant traits. Within this framework, our research was into tree species with the highest Mean Annual Increments (MAIs) in southern Italy, particularly in Sicily. Eucalyptus spp., Acacia saligna Labill. H. L. Wendl., Ailanthus altissima Mill. (Swingle), Pinus halepensis Mill. (including Pinus brutia Ten.), Pinus canariensis C.Sm. and Pinus radiata D. Don. were identified. In particularly suitable conditions, the MAI of eucalypt coppices ranged from 8 to 12 m 3 ha-1 , and from 13 to 19 m 3 ha-1 , in Eucaliptus camaldulensis Dehnh. and Eucaliptus globules Labill., respectively. The MAI of E. camaldulensis high forests was slightly over 6 m 3 ha-1 , while that of E. globulus high forests was very similar to its coppice value. Considering the preliminary data, Acacia saligna Labill. H. L. Wendl. can achieve good wood production. Pinus halepensis Mill. and Pinus brutia (Ten.) Holmboe achieved MAIs of 5-7 m 3 ha-1. Other species may be promising but either data is very limited or their invasive potential requires careful consideration. This historical review has shown that with optimal tree species-planting site-cultivation technique combinations, tree species can achieve wood yields typical of fast-growing species in Mediterranean Italy, too.
Canary Island pine (Pinus canariensis) is an endemic conifer of the Canary Archipelago where it forms the treeline in Tenerife and La Palma at 2,000–2,100 m a.s.l. Due to climatic and edaphic drought and immature soils, the treeline in the Canary Islands is 1,000–1,900 m lower than in continental mountains at similar latitude. This review summarizes the present knowledge on the ecophysiology of P. canariensis growing at treeline where the climate is typically semiarid with high winter precipitation and summer drought. Studies on needle anatomy together with specific root patterns, allowing to search for water, suggest that P. canariensis is able to withstand climatic and edaphic drought. At the treeline in Tenerife, drought relates to the quantity of winter precipitation. Treeline trees are able to tap water from deep soil water reserves originating from ample winter precipitation prior to a dry summer. Winter precipitation also influences growth and determines whether forests at treeline are carbon sinks or carbon sources. Topsoil desiccation, however, impedes seedling establishment, a prerequisite for regeneration and potential treeline migration.
In this review we summarize work carried out over the last 10 years on Pinus canariensis, an endemic tree species of the Canary Archipelago, in order to find out: how it is able to adapt to living from near sea level up to about 2.200 m; the response to different environmental conditions; the causes which prevent the natural regeneration in reforested areas and the methods needed to achieve nursery quality plants for reforestation. P. canariensis is able to modulate its physiology, the pigment and antioxidants content, the needle temperature resistance and the structure of its needles depending of the site where it grows, and it has a good stomatal control. The low light in reforested areas influences seedling growth and vigour. Also it has been shown that good quality planting stock obtained with fertilized artificial substrates is important for reforestation success.
Tree-ring growth of Pinus canariensis at high elevation on Tenerife, Canary Islands, has been suggested to be mainly controlled by drought-induced stress. Aspect of mountain slopes on this oceanic island strongly influences local water input, with trade winds maintaining humid weather conditions on windward, while leeward slopes remain much more arid. We tested whether P. canariensis tree-ring growth is controlled by local water availability and the large-scale climatic pattern North Atlantic Oscillation (NAO) along its elevation range on windward and leeward slopes on Tenerife. Wood cores were taken from six stands on windward and six on leeward at elevations of 1120–1930 m. We found outstanding differences between windward and leeward as regards tree growth responses to local climate and NAO. Responsiveness to winter temperature was greater on windward, while tree growth on leeward was mainly controlled by total annual rainfall, which was strongly linked to NAO variation. Tree-ring growth was dependent on water input throughout the whole leeward slope, but elevation gradients did not show to be relevant for tree growth dynamics. The unique exception was the lowest stand on windward, placed within the most humid environment on Tenerife, with a detrimental effect both of rainfall in late winter-spring and heat in summer. We conclude that slope aspect and exposure to trade winds are mostly driving P. canariensis growth. Prospects of growth of this species should consider that NAO-driven drought stress can affect populations on leeward slopes, where drier conditions can become limiting in the future.
Abstract
The effects of air pollutants on the epicuticular wax structure of conifer needles and the ecophysiological consequences of the injuries are reviewed on the basis of published literature and the authors' recent investigations. Degradation of the epicuticular waxes, which appears as a fusion of wax tubes in the epistomatal chambers and finally results in an amorphous appearance of the waxes, is the most common micromorphological injury type observed in studies on the genera Abies, Larix, Picea, and Pinus. The rate of erosion correlates well with the level of air pollution, but clear evidence for the specificity of the symptoms for different air pollutants has not been observed. It is concluded that the erosion of the epicuticular waxes, a phenomenon with a large geographic distribution, is a relevant factor of the multiple forest decline syndrome. Erosion of the waxes can change needle wettability and rain retention. Increased needle wettability and permeability of the cuticles can result in enhanced leaching of nutrients and uptake of pollutants. Increased or decreased stomatal and cuticular diffusion resistance of the needles leads to altered transpiration rates. Due to the changed chemical microenvironment of the needles, the conifers are predisposed to various biotic and abiotic stresses. Because the epicuticular waxes are one of the first targets of a variety of air pollutants, they can widely be used as an early indicator of air pollution effects.
This work was supported by the Academy of Finland. Contribution from the Dep. of Botany, Univ. of Oulu.
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The aim of this study was to examine the influence of long-term soil water deficit on growth and physiological processes of two black pine varieties (Pinus nigra ssp. laricio var. Corsicana and Pinus nigra ssp. laricio var. Calabrica). Three-year-old seedlings grown in larges boxes (volume: 1.62 m3) were subjected to a prolonged summer drought (99 days from the end of June until the end of September) and photosynthesis (A), stomatal conductance (gw), water status and growth were measured. No marked differences arose between Corsican and Calabrican pines feature to drought. At least in their juvenile stage, both varieties exhibited a 'drought-avoidance strategy' characterized by an efficient stomatal control of transpirational water loss. This result is consistent with previous studies on Pinus nigra and confirm the water stress adaptation of this collective Mediterranean species. Because a significant decrease of gw (about 30 %) was observed with no obvious variation in Ψ wp, the data suggested that predawn water potential was not the best indicator to precociously detect water stress. However, both A and gw reduced to nearly zero as soon as the threshold value of Ψ wp = -1.6 MPa was reached (respective values 0.5 μmol m-2 s-1 and 11 mmol m-2 s-1). Because most fine roots were within the upper 40 cm of the soil, a superficial soil desiccation has probably induced rapid stomatal closure, triggered by a biophysical and/or biochemical signal from the desiccated roots to the leaves. Embolism seems not to be responsible for the effect of drought on physiological processes, because the minimum value of Ψwp observed at the end of the drying cycle (-2.5 MPa) remained higher than the threshold inducing a significant xylem cavitation for these varieties (-4 MPa). Summer drought significantly reduced annual stem diameter (-20 %) and needle length (-25 %), but not stem elongation. Total elaborated dry weight was reduced about 45 %. Seedlings grown in the dry regime reduced belowground growth proportionally more than aboveground growth, causing a significant decrease in the R/S ratio. Such a result, which diverges with classical models of whole plant biomass partitioning, might be partially explained by seasonal pattern in the root growth which typically has its most important peak in mid-summer, period of maximum drought in our study. With the parameters studied here, the expression of the genetic characteristics between varieties in drought tolerance appeared to be limited. Thus, further investigations could be undertaken to learn about drought feature at cell and molecular levels. (© Inra/Elsevier, Paris.)
The response of mature forest stands to a reduction in water availability has received little attention. In particular, the extent to which a short-term reduction in gas exchange can be alleviated in the long-term by acclimation processes is not well understood. We studied the impact of a severe reduction in water availability on the water relations and growth of 35-year-old Pinus laricio Poiret. trees in a replicated experiment. Sapwood and needle increments, soil and tree water status, stand transpiration, xylem embolism and plant hydraulic architecture were monitored over a 3-year period in control and drought-treated plots. Needle length was reduced in drought-treated trees by 30, 19 and 29%, and sapwood increments by 50, 27 and 24% over the 3 years. Drought did not result in tree mortality or in extensive xylem embolism or foliage dieback. On the contrary, a conservative water-use strategy was observed, because minimum leaf water potentials did not differ between treatments or over the season. Plant hydraulic resistance was also unaffected by restricted water availability. Stand transpiration was strongly reduced by drought treatment over the summer, but not during the winter, despite significant differences in leaf area between control and drought-treated trees, implying higher transpiration rates per unit leaf area in the droughted plants. This suggests that water transport capacity, rather than the amount of leaf area, controlled stand transpiration, which is at variance with expectations based on experiments with seedlings and short-term experiments with mature trees.
In the present paper, we investigate antioxidants, chloroplast pigments, ultrastructure, and chlorophyll fluorescence in needles of Pinus canariensis Chr. Sm. ex DC. collected at four natural stands covering an altitude range from 200 to 2000 m a. s. 1. in the South-East of Tenerife. The contents of chloroplast pigments were lower at the most elevated sites showing chlorophyll concentrations of about 1 mg g(-1) needle dry weight (DW) versus 2 mg g(-1) DW at the lowest sites. Mean antioxidant concentrations in one year old needles were 260 to 200 mu g g(-1) DW for alpha-tocopherol, 3 to 4.5 mg (-1) DW for ascorbic acid and 340 to 180 nmol g(-1) DW for glutathione. A strict altitude dependence of these parameters was not found. Chlorophyll fluorescence measurements revealed Fv/Fm above 0.75 for all sites indicating healthy photosynthetic apparatus, but revealed initial states of oxidative stress at one particular site. Depressions in Fv/Fm went together with decreased alpha-carotene/beta-carotene ratios and a decrease in the ratio of violaxanthin to total xanthophyll cycle carotenoids. Ultrastructural investigations of the chloroplasts indicated no severe damage to the thylakoid systems.
The present study using light, transmission and scanning electron microscopy contains information about the structure of the needles of Pinus canariensis, an endemic pine of the Canary Islands. As a three-needled species, they have a triangular shape in transverse section being the abaxial side hemispherical. The deeply sunken stomata and the waxes covering the epidermal cells as well as the epistomatal chamber, constitute a good adaptation to the loss of water. The mechanical tissue below the epidermis contributes to a higher drought resistance and to maintain the shape of the long needles as a skeletic tissue. The ultrastructure of mesophyll cells, transfusion tissues as well as endodermis and resin ducts is also described. The results of this study should be used as reference data for further investigations of physiological, biochemical and ultrastructural responses of this species to environmental variations due to pollutants and different altitudinal and exposure situations.
Negative hydrostatic pressure can be measured in plants.
Diurnal courses of sap flow density, changes in stem radius, needle level transpiration, and needle water potential were measured in 50-year old Pinus canariensis trees at a forest stand in 1650 m a.s.1. in Tenerife, Canary islands, Spain. A direct comparison of sap flow density estimated at the stem base and canopy transpiration measured at the needle level showed only small deviations in their diurnal courses. Needle water potential and stem radius decreased from the onset of canopy transpiration, reached minimum values at noon, when sapflow was highest, and then continuously increased. Within the canopy however, gas exchange was highly variable among differently orientated twigs. Depending on the inclination of the sun a steep microclimatic gradient across the canopy affected apparent transpiration, leaf conductance and needle water potential. However, there were no significant differences in the amount of water transpired during a day between differently orientated twigs. Thus, our results suggest that sap flow sensors are a suitable tool for estimating canopy transpiration of pine trees in an environment where the crowns are often enveloped by mist or fog, which is typically for pine forests at higher elevations in the western Canary islands.
The distribution of wax tubes on the leaf surfaces is described, especially the presence of wax tubes in the antechambers of the stomata. The extra resistances which the wax-filled antechambers add to the other resistances in the pathway for diffusion of water vapour and of carbon dioxide are calculated. We conclude that the wax-filled stomatal antechambers reduce the rate of transpiration by about two thirds but reduce the rate of photosynthesis by only about one third. Thus wax-filled stomatal antechambers are excellent antitranspirants.
The plant cuticle is frequently referred to when the direct effects of air pollutants on the above-ground parts of higher plants are discussed. It covers all primary parts of higher plants and makes up the largest portion of the plant surface area directly exposed to the atmosphere. Thus, gaseous, wet and particulate air pollutants are primarily intercepted at this plant-atmosphere interphase. The cuticle determines the rates of uptake of all substances reaching the leaf surface which are not able to enter the stornata by diffusion in the gas phase. It also limits the transport of material (e.g., inorganic ions, metabolites) from the interior of the plant to its surface.
Needle surfaces of Pinus sylvestris L. were examined at three sites, two in clean air (SO2 < 10 μg m−3) at Saltoun, (altitude 200 m) and Cairngorm (400 m) and one in polluted air (SO2 c 40 μg m−3) at Gorple (300 m). Needles one, two and (where available) three years old were sampled during the period July 1981 to March 1982. Needle longevity was greater at the two clean air sites where 50 % of two year old needles were present compared with only 10% at the polluted site.
The physical structure of epicuticular wax was assessed using scanning electron microscopy. The wax tubes shortened, thickened and fused into an amorphous surface ‘crust’ with time. The rate of this‘weathering’ declined logarithmically. A constant (k) was denned as the weathering constant for this process. Values of/? (months−1) differed significantly between sites (Saltoun 0.061 ±0.01, Cairngorm 0.084 + 0.012 and Gorple 0.154±0.013).
In addition to faster weathering, needles at the polluted site were heavily contaminated with particulate debris, much of which had the physical characteristics of pulverized fuel ash that is produced by large coal combustion sources. During‘weathering'the surface layer of tubular wax crystals show a marked increase in thickness from ∼ 130 nm for newly exposed needles to 220 nm after 30 months old. No significant inter-site differences in the rate of change in tube width were noted.
This book analyses various processes interacting within forest ecosystems. It covers transport and deposition of air pollutants, the direct effects of pollutants on above-ground plant parts, the responses of soil to acid rain, and the changing nutrient availability, and the accompanying effects on plant metabolism and growth. The role of fungi, microorganisms and soil animals in the decline of these stands is also assessed.
The three-dimensional (3D) morphology of the stomata in leaves of Pinus canariensis is described with respect to the spatial arrangement of guard cells, subsidiary cells, polar and lateral cells. Serial semi-thin sections of the stomatal apparatus were digitally reconstructed and analysed with regard to the position, shape and size of the cell types involved. The stomatal complex consists of 16 cells with uniquely shaped polar and lateral cells. The polar cells form a kind of roof above the epistomatal chamber thereby reducing the surface aperture. The structural features of the stomatal complex differ from other Pinus species and are presumed to be an adaptation to extreme environmental conditions.
Gas exchange characteristics and chlorophyll fluorescence of the Canarian endemic pine (Pinus canariensis) were measured during the day for a year in a field stand on Tenerife, Canary Islands, Spain. Diurnal tendencies of gas exchange were variable depending on ambient conditions. In general they paralleled photosynthetic photon flux density with only one peak at midday, except on summer days with high air vapour pressure deficit (VPD), when needles exhibited a severe midday depression of CO2 assimilation rate (A), in parallel with a reduction of stomatal conductance (g
s). The internal CO2 concentration tendencies during the day suggest that stomatal closure was the main cause of the midday depression of photosynthesis. Chlorophyll fluorescence data corroborate this assertion, with the parameter F
v/F
m reaching high values throughout day and year. P. canariensis living in the sub-tropic exhibited high values of A (maximal A value of 17 µmol m−2 s−1) and high optimal needle temperature for photosynthesis (25°C) which were at the upper limit of the values given for conifers and similar only to data obtained for some pine species adapted to habitats at similar latitudes. g
s was reduced to half when VPD attained 40 mbar, allowing this pine to have high A/g
s values during high evaporative demand conditions.
Contents of Ca, Mg, K, Na, S, Cl, P, N, pigments, ascorbic acid, glutathione, and tocopherol together with chlorophyll fluorescence were measured in needles of Pinus canariensis trees growing at four field stands at 4 different altitudes at the south-eastern slope of the Teide in Tenerife. S contents reflected impacts of SO2 at lower altitudes. Via Na and Cl contents the influence from the sea was assessed up to 1000 m. Above 1000 m we found higher levels of ascorbic acid, less chlorophyll, higher carotenoid/chlorophyll-ratios, and lower α/β-carotene ratios. This pattern suits in a picture of elevated oxidative stress these trees are responding to. Decreases in Fv/Fm-ratios of chlorophyll fluorescence below 0.80 reflecting damages in the photosynthetic apparatus were only found at one site at 1500 m, where altitude stress was probably amplified by drought stress.
A method is described which permits measurement of sap pressure in the xylem of vascular plants. As long predicted, sap pressures
during transpiration are normally negative, ranging from -4 or -5 atmospheres in a damp forest to -80 atmospheres in the desert.
Mangroves and other halophytes maintain at all times a sap pressure of -35 to -60 atmospheres. Mistletoes have greater suction
than their hosts, usually by 10 to 20 atmospheres. Diurnal cycles of 10 to 20 atmospheres are common. In tall conifers there
is a hydrostatic pressure gradient that closely corresponds to the height and seems surprisingly little influenced by the
intensity of transpiration. Sap extruded from the xylem by gas pressure on the leaves is practically pure water. At zero turgor
this procedure gives a linear relation between the intracellular concentration and the tension of the xylem.
Moral Structure and ultra-structure of Pinus canariensis needles
- Jim Énez
- M S Zel
- G Nig
- E Stabentheiner
- J Peters
Jim énez, M. S.; Zel l nig, G.; Stabentheiner, E.; Peters, J.; Moral es, D. & Gril l , D. (2000): Structure and ultra-structure of Pinus canariensis needles. – Flora 195: 228–235
The cuticles of conifers: Structure, composition and transport properties Forest decline and air pollution
- M Riederer
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- O L Lange
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Xeromorphic leaf types. Evolutionary strategies and tentative semophyletic sequences
- A Blanco
- M Castroviejo
- J L Fraile
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- O Sanchez Palomares
Blanco, A.; Castroviejo, M.; Fraile, J. L.; Gandullo, J. M.; Munoz, L. A. & Sanchez Palomares, O. (1989): Estudio ecologico del pino canario. ICONA. Serie Teenica, num 6. Madrid. 199pp. Böcher, T. W. (1979): Xeromorphic leaf types. Evolutionary strategies and tentative semophyletic sequences. – Bio-logiske Skrifter 22: 8.
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Estudio ecologico del pino canario
- A Blanco
- M Castroviejo
- J L Fraile
- J M Gandullo
- L A Munoz
- O Sanchez Palomares
Blanco, A.; Castroviejo, M.; Fraile, J. L.; Gandullo,
J. M.; Munoz, L. A. & Sanchez Palomares, O. (1989):
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Teenica, num 6. Madrid. 199pp.
- J Peters
- D Morales
- M S Jiménez
Peters, J.; Morales, D. & Jiménez, M. S. (2003): Gas
exchange characteristics of Pinus canariensis needles in a
forest stand on Tenerife, Canary Islands. -Trees (in press).
Forest decline and air pollution
- M Riederer
Riederer, M. (1989): The cuticles of conifers: Structure,
composition and transport properties. In: Schulze, E. D.;
Lange, O. L. & Oren, R. (eds.), Forest decline and air
pollution. Ecol. Stud. 77: 157-192. -Springer, Berlin
Heidelberg.
- G Wieser
- J Peters
- V C Luis
- D Morales
- M S Jiménez
Wieser, G.; Peters, J.; Luis, V. C.; Morales, D. & Jiménez,
M.S. (2002): Ecophysiological studies on the water relations in a Pinus canariensis stand, Tenerife, Canary
Islands. -Phyton 42: 291-304.
Estudio ecologico del pino canario
- Blanco
Xeromorphic leaf types
- Böcher