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Does climate-related in situ variability of Scots pine (Pinus sylvestris L.) needles have a genetic basis? Evidence from common garden experiments
Abstract
The correlations of phenotypic traits with environmental drivers suggest that variability of these traits is a result of natural selection, especially if such trait correlations are based on genetic variability. We hypothesized that in situ correlations of structural needle traits of Scots pine (Pinus sylvestris L) with minimal winter temperature (Tmin) reported previously from a temperate/boreal transect would be conserved when plants are cultivated under common conditions. We tested this hypothesis by analyzing needles from two common gardens located in the temperate zone, one including adult trees and the other juvenile seedlings. The majority of adult needle traits for which correlations with Tmin were found in the field turned out to be under environmental influence. In contrast, the majority of traits studied in juvenile needles were correlated with the original Tmin suggesting the role of past natural selection in shaping their variability. Juvenile needles thus appeared to be inherently less plastic than adult needles, perhaps reflecting the stronger selective pressure acting during juvenile, as compared with adult, ontogenetic stage. Genetically based cold-climate adaptation in either juvenile or adult needles, or both, involved an increase in leaf mass per area and leaf density, decrease in needle length, reduction in the amount of xylem and phloem, increase in thickness of epidermis, decrease in tracheid diameter and increase in tracheid density, and increase in diameter and volume fraction of resin ducts. We also show that at least some traits, such as transverse xylem and phloem areas and number of fibers, scale with needle length, suggesting that climate-related trait variation may also be mediated by changes in needle length. Moreover, slopes of these allometric relationships may themselves be plastically modified. The phenotypic syndrome typical of needles from cold environments may thus be under environmental, genetic and allometric control.
... Such forestry-centered provenance trials have, however, focused mostly on productivity traits and genotypes, whereas e.g. drought-resistance traits may be more prominent in populations from less productive locations (Jankowski et al. 2019). As a consequence, information on the genotypic variability of traits conferring drought tolerance is still limited. ...
... In addition, foliar morphological traits, such as leaf size and area (Poorter et al. 2009), as well as foliar anatomical traits (He et al. 2018) have been linked to differences in climatic conditions between species and populations. For instance, P. sylvestris populations from Central and Northern Europe show strong correlations of needle traits with the minimal winter temperature at the seed origin when grown in a common garden (Jankowski et al. 2019). Hence, both phenotypic plasticity and ecotypic differentiation of various functional traits have been observed frequently, and may occur simultaneously. ...
... The study was conducted as part of a common garden experiment located at the bottom of the northern Rhone valley (Switzerland; 46°18'33''N, 07°41'10''E; 610 m a.s.l.; 19.2 ºC average temperature in July; 602 mm annual precipitation). Common garden experiments are powerful for identifying genetic variation among populations (Jankowski et al. 2019), and if combined with experimental treatments allow to compare adaptive with plastic responses of functional traits. The overall experiment included manipulations of precipitation, light and CO 2 availability as described in detail in Moser et al. (2016) and Bachofen et al. (2019). ...
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.
... El número de canales varía muy poco entre los ecótopos, aunque hacia los lugares más secos aumentó ligeramente. Esta respuesta se ha observado en algunas especies asociado a un gradiente de precipitación y humedad, tales como Pinus sylvestris (Donnelly & al. 2016, Köbölkuti & al. 2017, Galdina & Khazova 2019, Jankowski & al. 2019, P. tabuliformis Carrière (Zhang & al. 2017, Meng & al. 2018, P. thunbergii Parl. (Ghimire & al. 2014), P. yunnanensis Franch. ...
... Hasta el momento no se comprende totalmente el rol de los canales de resina en la regulación del agua, pero se conoce su papel defensivo ante el ataque de plagas (Krokene & Nagy 2012, Krokene 2015. Se ha detectado que la mayor densidad de canales se asocia a áreas de menor disponibilidad de humedad (Jankowski & al. 2017(Jankowski & al. , 2019 y su incremento en número y tamaño está correlacionado en Pinus yunnanensis con disminuciones de la precipitación y aumento de la temperatura, que contribuyen a reducir la influencia de la extrema sequía y el calor (Huang & al. 2016). Además, variaciones en este carácter inclusive han sido usados para demostrar la adaptación local en poblaciones de P. heldreichii (Nikolić & al. 2019, Hodžić & al. 2020, P. tabuliformis (Meng & al. 2018) y P. yunnanensis (Zhang & al. 2017). ...
... Los resultados de las pruebas de procedencias de Pinus caribaea en Cuba (Álvarez-Brito & al. 1991a, 1991b, Mercadet-Portillo & al. 2001, García-Quintana & al. 2007, entre algunas procedencias en China (Wang & al. 1999), las respuestas diferenciales de la procedencia Cajálbana en diferentes condiciones edáficas en Vietnam (Dieters & al. 2006) y en Australia (Dieters & Nikles 1997), así como las diferencias detectadas en este estudio apuntan a la existencia de ecotipos en la especie, los que además pueden distinguirse por las características anatómicas foliares. Por tanto, el manejo de los recursos genéticos de P. caribaea debe realizarse a la luz de estos resultados y refuerza la necesidad de la conservación local, pues la estructura de la variación se considera consecuencia de la evolución genética de las poblaciones y son muy importantes en estudios ecológicos y de mejoramiento genético (Jankowski & al. 2019). También es necesario llegar a un consenso relativo a su estado de conservación, dadas las diferentes categorías asignadas al taxón (Farjon 2013, González-Torres & al. 2016. ...
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.
... For example, petiole vessel radius and other hydraulic traits scale positively with leaf area (Coomes et al., 2008;Sack et al., 2012;Gleason et al., 2018;Wyka et al., 2019;Zhong et al., 2019). In needles of Pinus sylvestris, the central transverse areas of vascular bundles and xylem and phloem tissues scale with the length of the needle across diverse geographical provenances and needle lengths (Jankowski et al., 2019). In the same study, vascular sclerenchyma fibers also scaled with needle length, showing that size-related biomechanical demands in addition to transport requirements regulate anatomical variation. ...
... In fact, and contrary to our hypothesis, both measures produced equivalent and rather robust relationships with xylem and phloem size, indicating a close coordination of both vascular tissues and stomata development with needle expansion. This result recapitulates at within-leaf scale the allometric relationships of vascular tissue vs. leaf size based on central sections previously reported for interspecific samples (Coomes et al., 2008;Sack et al., 2012;Gleason et al., 2018) and for intraspecific whole-needle comparisons (Jankowski et al., 2019). Stomatal distribution was non-uniform, with an increase in the number of stomatal files contributing to the acropetal increase in stomatal density. ...
... Over most of the length, the Polish needles thus had lower number of fibers than would be found in Scandinavian needles, were they to reach a comparable volume of supported tissue. This refines the previous finding that the number of vascular sclerenchyma fibers is overall positively related to needle length, based on median needle section analysis (Jankowski et al., 2019), showing the utility of the present approach. The relatively low investment in fibers in the Polish needles, seen especially in basal parts, may be related to the lower cumulative intensity of mechanical stress (such as, for instance, ice load) to which they are exposed during their expected lifetime (<3 years, contrasting with >7 years in north Scandinavian needles; Jankowski et al., 2017). ...
Intraspecific variability of anatomical leaf traits is usually determined on the basis of median sections and interpreted as adaptive. We hypothesized that anatomical traits may relate to the position within the leaf, reflecting functional coordination e.g., between transport and gas exchange capacities and between supporting tissue and the supported leaf weight. Anatomical variation may thus be partly controlled by leaf size. We examined variability of transverse anatomical traits and stomata at different positions along the leaf axis using Scots pine (Pinus sylvestris L.) needles collected from three geographical locations with contrasting climate (Poland, Southern and Northern Sweden) and differing in length.
Transverse xylem and phloem area, and the number of tracheids at a given cross-section scaled positively with length of the distal needle part and the number of distal stomata. Similarly, the number of vascular sclerenchyma fibers in a cross-section scaled with the length and volume of the distal needle part. Allometric slopes were less steep in the longer, southern-sites needles. Additionally, our study revealed an increased sclerification of epidermis towards the needle apex, the occurrence of widest tracheids in central or subapical regions, a reduced number of resin ducts in basal and apical parts, as well as overall basipetal decreases in duct diameter, the number of stomatal files and stomatal density.
These results show that allometry accounts for significant amount of intraspecific variability in xylem, phloem and fibers, and that environmental adaptation involves also modification of the within-needle allometric relationships. The allometric component of variability, together with the nonlinear distribution of certain traits along needle length, should be considered when designing comparative studies of foliar phenotypes and scaling up from transverse sections to entire needles.
... The subspecies in our experiment were all grown in same environment under non-stressed conditions for the comparison of functional traits. Hence our study minimized the influence of environmental variation and can provide information about the influence of genotype on morpho-physiological traits (McLean et al. 2014, Jankowski et al. 2019. We observed large significant differences in some morphological traits: leaf size differed threefold among the subspecies and we observed significant differences in SLA. ...
... For example, leaf size was both related (Pritzkow et al. 2020) and unrelated to climate (Warren et al. 2005, Drake et al. 2017. Positive and negative relationships between SLA and temperature have been reported among different populations of three boreal plant species (Pensa et al. 2010) and for Pinus sylvestris (Jankowski et al. 2019), whereas SLA was correlated with MAP but not with MAT in populations of Eucalyptus sideroxylon (Warren et al. 2005). The absence of relationships among functional traits and climate of origin among D. viscosa subspecies may be because mean or median climate parameters do not represent the range of climatic conditions experienced by the plant; i.e., habitats can have large interannual or seasonal variation in rainfall or aridity. ...
Climate has a significant influence on species distribution and the expression of functional traits in different plant species. However, it is unknown if subspecies with different climate envelopes also show differences in their expression of plant functional traits or if they respond differently to drought stress. We measured functional traits and drought responses of five subspecies of a widely distributed, cosmopolitan polymorphic shrub, Dodonaea viscosa Jacq. in an experiment with one-year old plants. Functional traits, such as leaf size, specific leaf area, turgor loss point (ΨTLP), maximum stomatal conductance and maximum plant hydraulic conductance differed among the five subspecies. However, while the were some differences among traits, these were not related to their climate of origin, as measured by mean annual temperature, mean annual precipitation and mean annual aridity index. Drought response was also not related to climate of origin, and all subspecies showed a combination of drought avoiding and drought tolerance responses. All subspecies closed their stomata at very high water potentials (between −1.0 to −1.3 MPa) and had large hydraulic safety margins (drought avoidance). All subspecies adjusted their ΨTLP via osmotic adjustment, and subspecies with inherently lower ΨTLP showed greater osmotic adjustment (drought tolerance). All subspecies adjusted their midday water potentials in response to drought but subspecies from more arid environments did not show greater adjustments. The results indicated that climate niche was not related to plant trait expression or response to drought. The combination of drought avoidance and drought tolerance behavior seems to be a successful strategy for this widely distributed species that occupies many different climate zones and ecosystems. Hence, the wide distribution of D. viscosa seems to be related to plasticity of trait expression and drought response rather than long-term genetic adaptations to different environmental conditions.
... Thus, the variability in needle length may in turn drive the difference in anatomical traits. In conifer needles, the thick-walled epidermis and the underlying Fig. 4 Scatter diagram of the first two principal coordinates (PC1 and PC2) from PCA for the 17 Picea species based on growth traits, needle gas exchange and needle morphology and anatomy hypodermis are the principal mechanical tissues (Jankowski et al. 2019). Needles must be rigid and flexible enough to support their own weight as well as bend or twist without breaking when subjected to external forces (Raupach and Thom 1981;Vogel 1989). ...
... Even if our common garden experiment is efficient in revealing genetic variation among species of different origins, it is inevitably that away from native sites artefactual phenotypic modifications may be induced (Jankowski et al. 2019). Therefore, current variation in needle traits among species might be a combination of genetic difference and the adaptive nature in response to both historical and current environmental conditions. ...
The genus Picea has wide geographical range and includes species with great economic and ecological value in the northern hemisphere. Growth traits, gas exchange parameters and needle morphology and anatomy vary greatly among Picea species, but the instrinsic relationship among these traits has not been well studied for the genus Picea. We thus conducted a common garden experiment to study the relationship for these traits in 13 native and 4 exotic Picea species growing at an experimental site in Tianshui, Gansu, China. Nearly all of these traits were significantly different among the 17 species and most traits were under relatively strong genetic control. The four species introduced from abroad (P. abies, P. pungens, P. glauca and P. mariana) exhibited good growth performance in the experimental site. We found that the growth traits showed significantly positive correlation with branching characteristics. Moreover, the species with good growth performance had a relatively high photosynthetic rate. The correlation analysis based on needle morphological and anatomical traits revealed that needle traits were interrelated and needle anatomical traits might be impacted by needle size due to the increase of mesophyll area and central cylinder area with needle length. Furthermore, the relationship between needle structures and gas exchange parameters may indicate that a higher photosynthetic rate can be attributed to variations in needle structures. In addition, both the cluster analysis and principal component analysis based on needle morphology, anatomy, gas exchanges and growth traits might partially reflect the evolutionary history of the 17 Picea species. Our study represents a comprehensive survey of variation within the genus Picea to date and opens new avenues for exploring the instrinsic relationship among growth traits, needle gas exchange and needle morphology and anatomy.
... These observations indicated that the frost resistance of P. densiflora needles was not achieved by increasing cell sap concentration. Needles from cold sites have wider resin ducts that account for a larger proportion of needle volume than the needles from warmer sites [41,42]. Lipid synthesis in needles of Sitka spruce was significantly promoted during cold acclimation [43]. ...
Overwintering and spring recovery of pine needles have important ecological significance. The natural changes in physiological state, photosynthetic function, and material metabolism in needles of Pinus densiflora Siebold & Zucc. from the autumn of 2020 to the spring of 2021 were assessed. The photosynthetic rate (Pn) of P. densiflora needles decreased first and then increased, with the maximum Pn observed in the autumn. After experiencing sub-zero temperatures in the winter, needles of P. densiflora still performed weak photosynthesis at a temperature above zero. In the spring, the Pn gradually recovered but could not recover to the maximum. Under sub-zero temperatures in the winter of 2020, the plasma membrane permeability and MDA content of needles increased, whereas the chlorophyll content and Fv/Fm decreased significantly. The needles showed obvious characteristics of freezing injury. During the whole process, the water content of needles remained at a low level (about 60%), which gradually decreased with the increase of leaf age. The cell sap concentration and soluble sugar content of needles decreased with the decrease in air temperature and recovered in spring. Therefore, P. densiflora needles do not improve frost resistance through osmotic adjustment. However, the increasing carotenoid content is helpful for needles to tide over the winter. The soluble sugar and protein contents increased, implying they are important for the recovery of needles in spring. This study expands our understanding of the mechanism and ecological contribution of overwintering and spring recovery of pine needles.
... (Huang & al. 2016 Arenas cuarcíticas-llanuras bajas-terrenos llanos, AcS-LLB-Tll: Arenas cuarcíticas con sílice-llanuras bajas-terrenos llanos, AP-SM-Tli: Areniscas polimícticas-submontaña-ligeramente inclinados, AG-ALM-Tfi: Areniscas grises-alturas medias-terrenos fuertemente inclinados, AG-ALM-LI: Areniscas grises-alturas medias-ligeramente inclinados, AG-LLM-Tfi: Areniscas grises-llanuras medias-terrenos fuertemente inclinados, AG-SM-Tfi: Areniscas grises-submontañas-terrenos fuertemente inclinados, RV-LLB-TIl: Sedimentos vegetales-llanuras bajas-terreno llano. Se ha detectado que la mayor densidad de canales de resina se asocia a áreas menos húmedas (Jankowski & al. 2017(Jankowski & al. , 2019 y su incremento en número y tamaño en P. yunnanensis está correlacionado con la disminución de la precipitación y el aumento de la temperatura; lo que contribuye a reducir la influencia de la extrema sequía y el calor (Huang & al. 2016), similar a lo encontrado en esta especie. Por otro lado, se ha documentado en P. pinaster una relación estrecha entre sitios muy pobres en nutrientes, en especial con bajos contenidos de fósforo, con incrementos en número y diámetro del canal y la producción de resina (Sampedro & al. 2011, Moreira & al. 2015. ...
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.
... As a final note, we wish to point out that, our study was carried out in a common garden, so current variation in the measured traits among species might be a combination of genetic differences and the adaptive nature in response to both historical and current environmental conditions at the experimental site [77]. Additionally, photosynthetic parameters were estimated at the leaflevel, while the actual consequences of various structural designs on carbon gain and water use must ultimately be evaluated from shoots (the functional unit) to crowns and canopies [9], which requires further work. ...
Background
Picea species are distributed and planted world-wide due to their great ecological and economic values. It has been reported that Picea species vary widely in growth traits in a given environment, which reflects genetic and phenotypic differences among species. However, key physiological processes underlying tree growth and the influencing factors on them are still unknown.
Results
Here, we examined needle structures, needle chemical components, physiological characteristics and growth traits across five Picea species in a common garden in Tianshui, Gansu province in China: Picea glauca , P. mariana , P. likiangensis , P. koraiensis , and P. crassifolia , among which P. glauca and P. mariana were introduced from North America, P. likiangensis was from Lijiang, Yunan province in China, P. koraiensis was from Yichun, Heilongjiang province in China, and P. crassifolia was native to the experimental site. It was found that nearly all traits varied significantly among species. Tissue-level anatomical characteristics and leaf mass per area (LMA) were affected by needle size, but the variations of them were not associated with the variations in photosynthetic and biochemical capacity among species. Variations in area-based maximum photosynthesis (P nmax ) were affected by stomatal conductance (g s ), mesophyll conductance (g m ) and biochemical parameters including maximum carboxylation rate (V cmax ), and maximum electron transport rate (J max ). The fraction of N allocated to different photosynthetic apparatus displayed contrasting values among species, which contributed to the species variations in photosynthetic nitrogen use efficiency (PNUE) and P nmax . Additionally, all growth traits were positively correlated with P nmax and PNUE.
Conclusion
Needle structures are less important than needle biochemical parameters in determining the variations in photosynthetic capacity across the five Picea species. P nmax and PNUE are closedly associated with the fraction of N allocated to photosynthetic apparatus (P photo ) compared with leaf N content per area (N area ). The tremendous growth differences among the five Picea species were substantially related to the interspecies variation in P nmax and PNUE.
... This suggests that LMA changes may be more responsive to temperature than to moisture limitation in PIST. In agreement with this conclusion, Pardos et al. (2014) found higher tolerance to cold temperatures and higher LMA in Pinus pinea L. Similarly, Jankowski et al. (2019) found increased LMA in both juvenile and adult needles of Pinus sylvestris L. grown in common gardens, a plastic response exhibited in colder growing temperatures. ...
Pinus strobiformis (P. strobiformis) faces dual threats of climate change shifting its environmental niche and mortality due to a non-native, invasive fungal pathogen. To inform efforts to sustain this species, we established three field experimental common garden trials along an elevational gradient with drought treatments to assess trait responses in P. strobiformis. We measured predawn and midday water potential on 44 maternal families from 10 populations at each garden. We used regression between predawn and midday water potentials to estimate hydroscape area, an index of stomatal regulation of transpiration. We measured leaf carbon isotope ratio and estimated carbon isotope discrimination and leaf mass per area to understand effects of gardens and treatments on stomatal aperture and leaf structure. Water stress caused by experimental drought and temperature decreased leaf carbon isotope discrimination and leaf mass per area, indicating formation of thin leaves with low stomatal conductance in response to heat and drought. P. strobiformis’ hydroscape area suggests tight control of transpiration via stomatal closure, similar to other isohydric pines. Families with greater stomatal closure (inferred from carbon isotope ratio) at the warm, dry garden had higher survival than other families, suggesting an important role of isohydry in acclimation of P. strobiformis to expected habitat drying and warming.
... For example, including in the analysis gymnosperms with relatively light, delicate leaves, such as Larix sibirica, Taxodium distichum or Metasequoia glyptostroboides could strongly impact our results. The explanation of such high values may result from the lack of frost resistance of the mentioned species (Jankowski et al., 2019(Jankowski et al., , 2017. Evergreen species are biologically adapted to freezing climates. ...
Specific leaf area (SLA, leaf area to dry mass ratio) is a widely used functional trait in functional ecology. In most studies, SLA is collected by compiling large databases. However, standardized protocols of data collection include only measurements from the sunny side of the crown. We investigated interspecific SLA variability among 179 woody species in common garden conditions of Kórnik Arboretum (W Poland). Then, we quantified the differences in SLA measurements between sunny and shaded parts of the crowns of those species. On average, shade leaves had 43.3% higher SLA than sun leaves. Including differentiation between sun and shade measurements explained an additional 12.2% of SLA variability (in total 95.2% explained by species, family and canopy position). In conclusion, intra-canopy SLA variation can result in providing lower SLA values in databases while following the standardized data collection protocols. Here, we contribute to improved understanding of the importance of SLA variability in the context of its wide use in mechanistic and physiological modelling of ecosystem functioning.
... Allometric analysis has been widely used for studies of biomass distribution in plants (Weiner, 2004;Poorter et al., 2012) and in macroscopic morphology (e.g., Castorena et al., 2015). It is now becoming a useful, although still underused, tool for analysis of organ size-anatomy relationships (Olson et al., 2014;Osunkoya et al., 2014;Jankowski et al., 2019). ...
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.
Continuous light (CL) is available throughout the polar day for plants in the Arctic during the growing season, whereas provenances of the same species experience a very different environment with non-continuous light (NCL) just a few latitudes to the south. Both provenances need to acclimate to climate warming, yet we lack comprehensive understanding of how their growth, photosynthesis and leaf traits differ. Further, the provenances presumably have morphological and physiological adaptations to their native environments and therefore differ in response to photoperiod. We tested the height growth, leaf longevity, biomass accumulation, biomass allocation and rates of gas exchange of northern (67°N) and southern (61°N) Finnish silver birch (Betula pendula Roth) origins in CL- and NCL-treatments in a 4-month chamber experiment. Irrespective of photoperiod, 67°N had higher area-based photosynthetic rate (Anet), stomatal conductance (gs) and RGR, but lower stomatal density and fewer branches and leaves than 61°N. Photoperiod affected height growth cessation, biomass and photosynthetic traits, whereas leaf longevity and many leaf functional traits remained unchanged. In CL, both provenances had lower gs, higher RGR, increased shoot:root ratio and increased sink-sizes (more branching, more leaves, increased total plant DW) compared to NCL. In NCL, 67°N ceased height growth earlier than in CL, which altered biomass accumulation and distribution patterns. Northern conditions impose challenges for plant growth and physiology. Whether a provenance inhabits and is adapted to an area with or without CL can also affect its response to the changing climate. Northern birches may have adapted to CL and the short growing season with a ‘polar day syndrome’ of traits, including relatively high gas exchange rates with low leaf biomass and growth traits that are mainly limited by the environment and the earlier growth cessation (to avoid frost damage).
Harsh environmental conditions affect both leaf structure and root traits. However, shoot growth in high‐latitude systems is predominately under photoperiod control while root growth may occur for as long as thermal conditions are favorable. The different sensitivities of these organs may alter functional relationships above‐ and belowground along environmental gradients. We examined the relationship between absorptive root and foliar traits of Scots pine trees growing in situ along a temperate‐boreal transect and in trees grown in a long‐term common garden at a temperate latitude. We related changes in foliar nitrogen, phosphorus, specific leaf area, needle mass and 13C signatures to geographic trends in absorptive root biomass to better understand patterns of altered tree nutrition and water balance. Increased allocation to absorptive fine roots was associated with greater uptake of soil nutrients and subsequently higher needle nutrient contents in the northern provenances compared with more southern provenances when grown together in a common garden setting. In contrast, the leaf δ13C in northern and southern provenances were similar within the common garden suggesting that higher absorptive root biomass fractions could not adequately increase water supply in warmer climates. These results highlight the importance of allocation within the fine‐root system and its impacts on needle nutrition while also suggesting increasing stomatal limitation of photosynthesis in the context of anticipated climatic changes.
Lycium chinense, belonging to the Solanaceae family and Lycium genus, is an important healthy resource with abundant nutritional and functional components, which leaves has been developed as popular medicinal vegetable and healthy herbal tea. However, little systemic evaluation has been taken on the germplasm quality of L. chinense leaves in China. In this study, the contents variation of the main active compounds (polysaccharides, flavonoids, rutin and chlorogenic acid) and nutrients (crude protein, amino acids, mineral elements and reducing sugar) of different L. chinense populations among different regions and different years and seasons were investigated by common-garden experiment. The results indicated a significant difference in the contents of functional components among the different populations. The SS (Shishou) population has the highest average contents and stability of total flavonoid (64.25 mg RE/g dw), rutin (16.95 mg/g dw), and chlorogenic acid (7.19 mg/g dw), followed by the LT (Luotian) population. The steadily highest contents of crude protein (6.25 g/100 g fw) and total amino acids (44.92 g/100 g fw) contents were detected in the XS (Xinshan) population. Little changes in the components contents of L. chinense leaves were showed in different growth stages, which indicated that L. chinense leaves could have the longer harvesting period. Moreover, there was a significant correlation between the functional components and the geographic location. For example, we found flavonoids and polysaccharides of L. chinense showed the highest content in Central and South China, respectively. In addition, the mean annual temperature (MAT) was the environmental factor with the highest degree of correlation with most of the functional components. This study provides important information on the exploration of quality resources and further breeding of L. chinense germplasm resources.
Sheath senescence is an important part of bamboo shoot development during the fast growth stage. However, no information has been reported about this distinctive process until now. Using multiple approaches, we found that sheath senescence is a complex process that occurs sequentially with chloroplast corruption, chlorophyll degradation, and water loss. Reactive oxygen species (ROS), salicylic acid, and abscisic acid also accumulate in the senescing sheath. Transcriptome analysis showed that NAC and WRKY transcription factors, such as NAC2 and WRKY75, as well as their possible downstream target genes, such as those involved in ROS production, proteolysis, and nutrition recycling, constitute the gene network of the bamboo sheath senescence process. Furthermore, the initiation of sheath senescence might be triggered by hexokinase genes, such as HXK6, which is localized to the mitochondrion and could promote leaf senescence when overexpressed in Arabidopsis. Sheath senescence occurs after the growth decrease of the internodes, which provides assimilates. The slowing of internode growth possibly results in sugar accumulation, such as glucose, in the sheath, which finally upregulates hexokinase genes and initiates sheath senescence. These findings reveal that sheath senescence is a multilevel regulation process and has a close link to the corresponding internode growth, which provides new insights into the shoot development of bamboo during the fast growth stage.
Clarifying the coordination of leaf hydraulic traits with gas exchange across closely‐related species adapted to varying rainfall can provide insights into plant habitat distribution and drought adaptation. The leaf hydraulic conductance (Kleaf), stomatal conductance (gs), net assimilation (A), vein embolism and abscisic acid (ABA) concentration during dehydration were quantified, as well as pressure‐volume curve traits and vein anatomy in ten Caragana species adapted to a range of mean annual precipitation (MAP) and growing in a common garden. We found a positive correlation between the Ψleaf at 50% loss of Kleaf (Kleaf P50) and maximum Kleaf (Kleaf‐max) across species. Species from low‐MAP environments exhibited more negative Kleaf P50 and turgor loss point, higher Kleaf‐max and leaf‐specific capacity at full turgor, along with higher vein density and midrib xylem per leaf area, and higher ratio of Kleaf‐max to maximum gs. Tighter stomatal control mediated by higher ABA accumulation during dehydration in these species resulted in an increase in hydraulic safety and intrinsic water use efficiency (WUEi) during drought. Our results suggest that high hydraulic safety and efficiency combined greater stomatal sensitivity triggered by ABA production and leading to greater WUEi provides drought tolerance in Caragana species adapted to low‐MAP environments.
Climate is known to be a critical factor controlling the broad-scale distribution of plants but often the physiological basis for species distribution limits is not well understood, nor is the extent to which populations within species are locally adapted to climate. Reciprocal transplant experiments designed to test for local adaptation are difficult to conduct and interpret in long-lived species, like oaks. Linking the physiological tolerances of species to their climatic distributions is an alternative approach to understanding adaptation to climate, and is important in predicting future distributions of species under changing climatic conditions. Here we synthesize a series of studies in a single lineage of American oaks that span the temperatetropical divide and encompass a range of precipitation and edaphic regimes, to determine (1) the physiological basis for adaptation to seasonal winter and seasonal drought and (2) the variation among populations that associated with climate variation and can be interpreted as local adaptation. We focus primarily on a series of common gardens that allow us to determine the genetically based differences in functional and physiological traits as well as the genetically based responses to contrasting temperature or precipitation regimes. We show that variation in freezing tolerance among closely related species is greater than variation among populations within species. Nevertheless, freezing tolerance varies predictably with climate of origin and is negatively associated with growth rate. In contrast, drought tolerance mechanisms vary more among populations within a single species, at least for the most widely distributed species, Quercusoleoides, than between species. Within this species, climate of origin predicts a suite of leaf physiological traits, and there is evidence for evolutionary trade-off between desiccation avoidance and desiccation resistance. Combined, these results show evidence for local adaptation to both freezing and drought stress within species, as well as adaptive differentiation between closely related species, despite phylogenetic conservatism in functional traits and highly similar physiognomy across the American live oak clade. The results inform conservation efforts aimed at preventing extinction of tree species in the face of global change.
Nonlinear relationships between species and their environments are believed common in ecology and evolution, including during angiosperms’ rise to dominance. Early angiosperms are thought of as woody evergreens restricted to warm, wet habitats. They have since expanded into numerous cold and dry places. This expansion may have included transitions across important environmental thresholds. To understand linear and nonlinear relationships between angiosperm structure and biogeographic distributions, we integrated large datasets of growth habits, conduit sizes, leaf phenologies, evolutionary histories, and environmental limits. We consider current‐day patterns and develop a new evolutionary model to investigate processes that created them. The macroecological pattern was clear: herbs had lower minimum temperature and precipitation limits. In woody species, conduit sizes were smaller in evergreens and related to species’ minimum temperatures. Across evolutionary timescales, our new modeling approach found conduit sizes in deciduous species decreased linearly with minimum temperature limits. By contrast, evergreen species had a sigmoidal relationship with minimum temperature limits and an inflection overlapping freezing. These results suggest freezing represented an important threshold for evergreen but not deciduous woody angiosperms. Global success of angiosperms appears tied to a small set of alternative solutions when faced with a novel environmental threshold.
Leaf size varies by over a 100,000-fold among species worldwide. Although 19th-century plant geographers noted that the wet tropics harbor plants with exceptionally large leaves, the latitudinal gradient of leaf size has not been well quantified nor the key climatic drivers convincingly identified. Here, we characterize worldwide patterns in leaf size. Large-leaved species predominate in wet, hot, sunny environments; small-leaved species typify hot, sunny environments only in arid conditions; small leaves are also found in high latitudes and elevations. By modeling the balance of leaf energy inputs and outputs, we show that daytime and nighttime leaf-to-air temperature differences are key to geographic gradients in leaf size. This knowledge can enrich "next-generation" vegetation models in which leaf temperature and water use during photosynthesis play key roles.
Leaf size varies by over a 100,000-fold among species worldwide. Although 19th-century plant geographers noted that the wet tropics harbor plants with exceptionally large leaves, the latitudinal gradient of leaf size has not been well quantified nor the key climatic drivers convincingly identified. Here, we characterize worldwide patterns in leaf size. Large-leaved species predominate in wet, hot, sunny environments; small-leaved species typify hot, sunny environments only in arid conditions; small leaves are also found in high latitudes and elevations. By modeling the balance of leaf energy inputs and outputs, we show that daytime and nighttime leaf-to-air temperature differences are key to geographic gradients in leaf size. This knowledge can enrich " next-generation " vegetation models in which leaf temperature and water use during photosynthesis play key roles.
Environmental stresses experienced by individual parents can influence offspring phenotypes in ways that enhance survival under similar conditions. Although such adaptive transgenerational plasticity is well documented, its transmission mechanisms are generally unknown. One possible mechanism is environmentally induced DNA methylation changes. We tested this hypothesis in the annual plant Polygonum persicaria, a species known to express adaptive transgenerational plasticity in response to parental drought stress. Replicate plants of 12 genetic lines (sampled from natural populations) were grown in dry versus moist soil. Their offspring were exposed to the demethylating agent zebularine or to control conditions during germination and then grown in dry soil. Under control germination conditions, the offspring of drought-stressed parents grew longer root systems and attained greater biomass compared with offspring of well-watered parents of the same genetic lines. Demethylation removed these adaptive developmental effects of parental drought, but did not significantly alter phenotypic expression in offspring of well-watered parents. The effect of demethylation on the expression of the parental drought effect varied among genetic lines. Differential seed provisioning did not contribute to the effect of parental drought on offspring phenotypes. These results demonstrate that DNA methylation can mediate adaptive, genotype-specific effects of parental stress on offspring phenotypes.
The remnants of the Caledonian Native Pinewood are distributed across a relatively narrow geographic area in the Scottish Highlands yet inhabit a steep environmental gradient in terms of rainfall, temperature and altitude. Previous work based on common garden trials has demonstrated that native pine populations (Pinus sylvestris (L.)) exhibit differentiation in terms of growth, phenology and frost resistance. However, despite their important role in plant fitness, no such information is available on leaf traits, which have shown both plastic and adaptive genetic responses to environmental variation in other species. We analysed a subset of 11 needle characters in 192 saplings grown in a population-progeny common garden trial based on seedlots from eight native pinewoods. Narrow-sense heritability (h
2) was estimated for each trait and found to be particularly high (1.30 ± 0.33) for resin canal density. The majority of the phenotypic variation found was within populations, although interpopulation differentiation was detected for needle length (ΔAICc = 2.55). Resin canal density was positively correlated with longitude (β = 0.45, ΔAICc = 4.23), whereas stomatal row density was negatively correlated (β =−0.12, ΔAICc = 2.55). These trends may reflect adaptation for differences in moisture availability and altitude between eastern and western populations in Scotland.
The competitive equilibrium between deciduous and evergreen plant species to a large extent depends on the intensity of the reduction in carbon gain undergone by evergreen leaves, associated with the leaf traits that confer resistance to stressful conditions during the unfavourable part of the year. This study explores the effects of winter harshness on the resistance traits of evergreen leaves. Leaf mass per unit area (LMA), leaf thickness and the concentrations of fibre, nitrogen (N), phosphorus (P), soluble protein, chlorophyll and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) were determined in three evergreen and two deciduous species along a winter temperature gradient. In the evergreen species, LMA, thickness, and P and structural carbohydrate concentrations increased with the decrease in winter temperatures. Nitrogen and lignin concentrations did not show definite patterns in this regard. Chlorophyll, soluble proteins and Rubisco decreased with the increase in winter harshness. Our results suggest that an increase in LMA and in the concentration of structural carbohydrates would be a requirement for the leaves to cope with low winter temperatures. The evergreen habit would be associated with higher costs at cooler sites, because the cold resistance traits imply additional maintenance costs and reduced N allocation to the photosynthetic machinery, associated with structural reinforcement at colder sites.
Pinus yunnanensis Franch. is a major component of coniferous forests in southwestern China. Little is known about its intraspecific variation. Morphological variations in needle and cone traits of P. yunnanensis were analyzed to quantify variability among and within natural populations. Seven traits were measured on 10 needles collected from 30 trees in each of the 18 sampled populations of P. yunnanensis. Four cone traits were measured in 221 individual trees from nine populations. The results showed that there were significant differences (p < 0.01) both among populations and within populations in each needle and cone trait. The proportion of phenotypic variation of nearly all needle and cone traits was over 50 % within populations, which showed trees within populations accounted for a majority of the total variation. The needle traits showed higher variability within population than cone traits. Variability in the needle traits was correlated with geo-climatic parameters (longitude, latitude, altitude, temperature, and precipitation). Needle length and the ratio of needle length to fascicle sheath length showed clinal variation in response to latitudinal and altitudinal gradients. A hierarchical classification of all populations based on needle traits led to the formation of four major groups. The findings provide important genetic information for the evaluation of variation. Moreover, it will assist in management of genetic diversity of P. yunnanensis. © 2015 GovernmentEmployee: USDA Forest Service, Northern Research Station, HTIRC
Pinus yunnanensis Franch. is an particular conifer tree species in Yunnan–Guizhou plateau in southwest China. The morphological and anatomical traits of needles are important to evaluate geographic variation and population dynamics of conifer species. Seedlings from seven populations of P. yunnanensis were analyzed, looking at 22 morphological and anatomical needle traits. The results showed that variations among and within populations were significantly different for all traits and the variance components within populations were generally higher than that among populations in the most tested needle traits. The proportions of three-needle fascicle were significantly different among populations. The traits related to needle size in both morphology and anatomy were positive with latitude and negative with annual temperature and precipitation. Ratio indices, including mesophyll area/vascular bundle area, mesophyll area/resin canals area, vascular bundle area/resin canals area and mesophyll area/(resin canals area and vascular bundle area), were negatively correlated with elevation and positively correlated with the annual mean temperature, showing some fitness feature for the populations. Needle traits were more significantly correlated with longitude than with other four environmental factors. Needle length was significantly correlated with almost all environmental factors. First four principal components accounted for 81.596 % of the variation with eigenvalues >1; the differences among populations were mainly dependent on needle width, stomatal density, section areas of vascular bundle, total resin canals, and mesophyll, as well as area ratio traits. Seven populations were divided into three categories by Euclidean distance. Variations in needle traits among the populations have shown systematic microevolution in terms of geographic impact on P. yunnanensis. This study would provide empirical data to characterize adaptation and genetic variation of P. yunnanensis, which would be helpful for management of genetic resources and reasonable utilization of them in future. © 2015 Northeast Forestry University and Springer-Verlag Berlin Heidelberg
Conifers exhibit a number of chemical and anatomical mechanisms to defend against pests and pathogens. Theory predicts an increased investment in plant defences under limited nutrient availability, but while this has been demonstrated for chemical defences, it has rarely been shown for anatomical defensive structures. In a long-lived woody plant, we tested the hypothesis that limited nutrient availability may promote an improved differentiation of persistent anatomical defences. We also hypothesized that the costs of differentiation of those long-term anatomical structures may be determined by genetic constraints on early growth potential. Using Pinus pinaster Ait. juveniles, we performed a greenhouse study with 15 half-sib families subjected to experimental manipulation of phosphorus (P) availability and herbivory-related induced responses. When plants were ∼30 cm high, half of the plant material was treated with methyl jasmonate to induce defences, and 2 weeks later plants were harvested and the abundance of resin canals in the cortex and xylem was assessed. Density of constitutive resin canals in the cortex and the total canal system was ∼1.5-fold higher in plants under limited P availability than in fully fertilized plants. Availability of P did not significantly influence the inducibility of resin canal traits. We found negative genetic correlations between plant growth and the density of constitutive canals in the xylem and total canal system, but only under conditions of limited nutrition. These results demonstrate for the first time that differentiation of constitutive anatomical-based defences is affected by P limitation. Moreover, results also evidence the existence of genetic constraints between plant growth and constitutive defensive investment, where lineages with the highest growth potential showed the lowest investment in constitutive resin canals.
The phloem vascular system facilitates transport of energy-rich sugar and
signaling molecules in plants, thus permitting long range communication within
the organism and growth of non-photosynthesizing organs such as roots and
fruits. The flow is driven by osmotic pressure, generated by differences in
sugar concentration between distal parts of the plant. The phloem is an
intricate distribution system, and many questions about its regulation and
structural diversity remain unanswered. Here, we investigate the phloem
structure in the simplest possible geometry: a linear leaf, found, for example,
in the needles of conifer trees. We measure the phloem structure in four tree
species representing a diverse set of habitats and needle sizes, from 1 cm
(\textit{Picea omorika}) to 35 cm (\textit{Pinus palustris}). We show that the
phloem shares common traits across these four species and find that the size of
its conductive elements obeys a power law. We present a minimal model that
accounts for these common traits and takes into account the transport strategy
and natural constraints. This minimal model predicts a power law phloem
distribution consistent with transport energy minimization, suggesting that
energetics are more important than translocation speed at the leaf level.
Evergreen plants are an important component of many ecosystems of the world and occur in numerousevolutionary lineages. In this article we review phenotypic traits of evergreen woody angiosperms occurring in habitats that regularly experience frost. Leaf anatomical traits such as sclerenchymatic tissues or prominent cuticles ensure mechanical strength while often enhancing tolerance of water deficit. The low ratio of photosynthetic to nonphotosynthetic tissues as well as modified cell wall structure and nitrogen allocation patterns in evergreen leaves result in lower mass-based photosynthetic rate and photosynthetic nitrogen use efficiency in comparison with deciduous leaves. Their photosynthetic apparatus is adapted for the survival of frost in a down-regulated state with potential for photosynthetic activity in winter during periods of permissive temperatures. Leaf structure interacts with the mechanisms of frost survival. Stem xylem in evergreen plants tends to contain smaller diameter conduits incurring greater resistance to freeze/thaw induced cavitation than in deciduous plants, although at the cost of reduced hydraulic efficiency. In contrast, no such differences in hydraulic conductivity have been documented at the leaf level. There is evidence for reduced structural plasticity of evergreen leaves in response to variability in irradiance, however photosynthetic downregulation occurs in mature leaves in response to self shading. Some evergreen species exhibit slow leaf development and “delayed greening”, while in many species aging is also a very protracted process. Finally, evergreen leaves may participate in carbohydrate and, less obviously, in nitrogen storage for the support of spring shoot and foliage growth, although the importance of this function is under debate. In conclusion, the evergreen leaf habit is correlated with numerous structural and functional traits at the leaf and also at the stem level. These correlations may generate trade-offs that shape the ecological strategies of evergreen plants.
Maternal effects, the effect of the maternal environment during development on offspring growth, can complicate the interpretation of common garden studies. Growing one or more generations in a common environment can help minimize maternal effects, but is often not practical with long-lived species. In Pinus aristata Engelm. and Pinus flexilis James, we assessed maternal effects by growing offspring sourced over multiple years from the same mother trees, comparing growth traits between source years. Additionally, we explored the effect of maternal environment on seed characteristics by collecting five twig clippings from each mother tree and measuring characteristics indicative of the relative vigor of the tree during each seed source year. The effect of year was significant for twig growth characteristics, seed size, and seedling performance. For both species, there were significant relationships between the relative inter-annual (RIA) variation in seed mass and the RIA variation in numerous seedling traits including cotyledon length, seedling total dry mass, and needle length. Variation in seed mass was not predicted by yearly variation in the maternal plant’s phenotypic traits. These results support the hypothesis that maternal effects translate into variation in early seedling growth and suggest possibilities to statistically account for them in common garden studies involving long-lived species.
To evaluate the geographic variability of Pinus sylvestris populations seven morphological traits of needles of pines from IUFRO 1982 provenance trial have been analyzed. The studied populations originated from northern (>55°N in Russia, Sweden and Latvia), central (55-47°N in Poland, Germany, Belgium, France, Slovakia) and southern (<47°N in Hungary, Bosnia, Montenegro and Turkey) European ranges of Scots pine. The analyzed provenance trial experimental areas were located in Kórnik (western Poland) and in Supraśl (north-eastern Poland). The greatest variation was found in needle length and number of stomata rows on the flat and convex side of a needle, whereas number of stomata per 2 mm of needle length on flat and convex side of a needle was stable, with minor interpopulational variation. Biometrical analyses revealed a significant population × location interaction and a geographical pattern in interpopulational differentiation in both experimental sites, with the northern and southern European Scots pine groups of provenances differ-ing significantly from the group of central origin. The results obtained are compatible with previous results of studies on provenance variability of the Scots pine from IUFRO 1982. In the light of available data, the influ-ence of the Balkan glacial refugia of Pinus sylvestris on a present genetic diversity of this species in Europe and the reconstruction of Scots pine migration routes after the last glacial period are discussed.
Significance
How evergreen tree needle longevity varies from south to north in the boreal biome is poorly quantified and therefore ignored in vegetation and earth system models. This is problematic, because needle longevity translates directly into needle turnover rate and profoundly affects carbon cycling in both nature and computer models. Herein we present data for five widespread boreal conifers, including pines and spruces, from >125 sites along a 2,000-km gradient. For each species, individuals in colder, more northern environments had longer needle life span, highlighting its importance to evergreen ecological success. Incorporating biogeography of needle longevity into a global model improved predictions of forest productivity and carbon cycling and identified specific problems for models that ignore such variability.
Angiosperm hydraulic performance is crucially affected by the diameters of vessels, the water conducting conduits in the wood. Hydraulic optimality models suggest that vessels should widen predictably from stem tip to base, buffering hydrodynamic resistance accruing as stems, and therefore conductive path, increase in length. Data from 257 species (609 samples) show that vessels widen as predicted with distance from the stem apex across angiosperm orders, habits and habitats. Standardising for stem length, vessels are only slightly wider in warm/moist climates and in lianas, showing that, rather than climate or habit, plant size is by far the main driver of global variation in mean vessel diameter. Terminal twig vessels become wider as plant height increases, while vessel density decreases slightly less than expected tip to base. These patterns lead to testable predictions regarding evolutionary strategies allowing plants to minimise carbon costs per unit leaf area even as height increases.
Many studies have recorded phenotypic changes in natural populations and attributed them to climate change. However, controversy and uncertainty has arisen around three levels of inference in such studies. First, it has proven difficult to conclusively distinguish whether phenotypic changes are genetically based or the result of phenotypic plasticity. Second, whether or not the change is adaptive is usually assumed rather than tested. Third, inferences that climate change is the specific causal agent have rarely involved the testing - and exclusion - of other potential drivers. We here review the various ways in which the above inferences have been attempted, and evaluate the strength of support that each approach can provide. This methodological assessment sets the stage for 11 accompanying review articles that attempt comprehensive syntheses of what is currently known - and not known - about responses to climate change in a variety of taxa and in theory. Summarizing and relying on the results of these reviews, we arrive at the conclusion that evidence for genetic adaptation to climate change has been found in some systems, but is still relatively scarce. Most importantly, it is clear that more studies are needed - and these must employ better inferential methods - before general conclusions can be drawn. Overall, we hope that the present paper and special issue provide inspiration for future research and guidelines on best practices for its execution.
Early flowering plants are thought to have been woody species restricted to warm habitats. This lineage has since radiated into almost every climate, with manifold growth forms. As angiosperms spread and climate changed, they evolved mechanisms to cope with episodic freezing. To explore the evolution of traits underpinning the ability to persist in freezing conditions, we assembled a large species-level database of growth habit (woody or herbaceous; 49,064 species), as well as leaf phenology (evergreen or deciduous), diameter of hydraulic conduits (that is, xylem vessels and tracheids) and climate occupancies (exposure to freezing). To model the evolution of species' traits and climate occupancies, we combined these data with an unparalleled dated molecular phylogeny (32,223 species) for land plants. Here we show that woody clades successfully moved into freezing-prone environments by either possessing transport networks of small safe conduits and/or shutting down hydraulic function by dropping leaves during freezing. Herbaceous species largely avoided freezing periods by senescing cheaply constructed aboveground tissue. Growth habit has long been considered labile, but we find that growth habit was less labile than climate occupancy. Additionally, freezing environments were largely filled by lineages that had already become herbs or, when remaining woody, already had small conduits (that is, the trait evolved before the climate occupancy). By contrast, most deciduous woody lineages had an evolutionary shift to seasonally shedding their leaves only after exposure to freezing (that is, the climate occupancy evolved before the trait). For angiosperms to inhabit novel cold environments they had to gain new structural and functional trait solutions; our results suggest that many of these solutions were probably acquired before their foray into the cold.
Unlabelled:
•
Premise of the study:
Plant species differ widely in the leaf biomass invested per unit area (LMA). LMA can be explained by variation in leaf thickness and/or density, both of which are influenced by anatomical tissue composition. The aim of this study is to quantify the anatomical characteristics that underlie variation in LMA in a range of woody species. •
Methods:
Twenty-six woody species, forming 13 species pairs with a deciduous and evergreen species from the same genus or family, were grown in a glasshouse. The youngest full-grown leaves were analyzed for LMA and morpho-anatomical characteristics at leaf, tissue, and cell level. •
Key results:
Considered over all species studied, leaf thickness and density were equally important to explain the variation in LMA, but the class difference between deciduous and evergreen species was mainly determined by thickness, whereas variation within each group was largely due to density. Evergreens had thicker leaves, predominantly caused by a larger volume of mesophyll and air spaces, whereas the higher leaf density within each group was due to a lower proportion of epidermis and air spaces, and overall smaller cells. •
Conclusions:
The anatomical basis for variation in LMA in woody species depends on the contrast made. Higher LMA in evergreens is mainly due to a greater leaf thickness, caused by a larger volume of mesophyll and air spaces. Within deciduous species and evergreens, higher LMA is caused by a higher density, due to higher volumetric fractions of mesophyll and lower fractions of air spaces and epidermis.
Background: Broad-scale analysis of interspecific trait variation is a fundamental approach in comparative ecology to investigate general species-environment relationships, but inferences from environmental and phylogenetic signals are still controversially discussed. Aim: To analyse in a global study of the genus Pinus the interspecific variation of morphological traits with latitude as a surrogate of broad-scale environmental changes, and to compare latitudinal trait correlations with biogeographic, environmental, and phylogenetic signals in trait variation. Methods: Based on native range maps of 103 Pinus species, the latitudinal correlations of nine morphological traits, including needle characters, cone length and tree height were calculated. Principal component analysis was used to explore trait covariation. Variation partitioning was applied to disentangle environmental and phylogenetic signals in trait variation. Results: Strong latitudinal correlations were detected for traits, such as needle length:width ratio or needle longevity, with similar trends for different taxonomic species subsets and geographic regions. Strong latitudinal correlations were related to a decrease in the pure phylogenetic signal and to an increase in the phylogenetically structured environmental variation (PSEV), whereas the pure environmental signal was almost negligible. Conclusions: Besides a ranking of traits which differ in environmental and phylogenetic signals, our results showed a general relationship between increasing latitudinal trait correlation and an increase in PSEV which indicates phylogenetic niche conservatism. Thus, for the investigated morphological traits of the genus Pinus both environmental and phylogenetic signals are directly linked by PSEV to broad-scale spatial patterns in trait variation.
With data from 15 species in eight families of tropical dry forest trees, we provide evidence of coordination between the stem and leaf economic spectra. Species with low-density, flexible, breakable, hydraulically efficient but cavitationally vulnerable wood shed their leaves rapidly in response to drought and had low leaf mass per area and dry mass content. In contrast, species with the opposite xylem syndrome shed their costlier but more drought-resistant leaves late in the dry season. Our results explain variation in the timing of leaf shedding in tropical dry forests: selection eliminates combinations such as low-productivity leaves atop highly vulnerable xylem or water-greedy leaves supplied by xylem of low conductive efficiency. Across biomes, rather than a fundamental trade-off underlying a single axis of trait covariation, the relationship between leaf and stem economics is likely to occupy a wide space in which multiple combinations are possible.
In several growth chamber and field experiments we examined the growth response of Scots pine (Pinus sylvestris L.) populations from a wide latitudinal range to temperature and photoperiod. The duration of the shoot elongation period of on-year-old seedlings was affected by temperature and photoperiod. In contrasting temperatures, 23/20°C, 20/17°C, and 17/14°C (day/night), shoot elongation period for all populations was shortest in the high and longest in the low temperature treatments. The northern populations from 61-57°N ceased height growth earlier than the other populations in the southern 50°N photoperiod. The order of growth cessation among populations at 50°N in the chamber experiment and at 52°N in the field experiment was similar and related to observed population differences in terminal leader growth and total tree height. Since the length of growing season is under strong environmentally-mediated genetic control in Scots pine, potential climatic changes such as increasing temperature will probably alter the length and timing of growth in aboveground tree parts, but likely in the opposite direction (a shorter growing season) than has been often hypothesized (a longer growing season). Tree-ring analyses of a provenance experiment established in 1912 indicate that the main climatic factors that limited ring-width growth in Scots pine were air temperatures in the winter months of December through March. Low winter temperatures were followed by the formation of narrow rings over the next summer. Based on responses to temperature, Scots pine populations from the continuous European range can be divided in several geographic groups along a latitudinal gradient. Our results suggest that in developing new models to predict the response of Scots pine to changing environmental conditions, it is necessary to include intraspecific differentiation in acclimation and adaptation to environmental factors.
Aim This first global quantification of the relationship between leaf traits and soil nutrient fertility reflects the trade-off between growth and nutrient conservation. The power of soils versus climate in predicting leaf trait values is assessed in bivariate and multivariate analyses and is compared with the distribution of growth forms (as a discrete classification of vegetation) across gradients of soil fertility and climate.
Location All continents except for Antarctica.
Methods Data on specific leaf area (SLA), leaf N concentration (LNC), leaf P concentration (LPC) and leaf N:P were collected for 474 species distributed across 99 sites (809 records), together with abiotic information from each study site. Individual and combined effects of soils and climate on leaf traits were quantified using maximum likelihood methods. Differences in occurrence of growth form across soil fertility and climate were determined by one-way ANOVA.
Results There was a consistent increase in SLA, LNC and LPC with increasing soil fertility. SLA was related to proxies of N supply, LNC to both soil total N and P and LPC was only related to proxies of P supply. Soil nutrient measures explained more variance in leaf traits among sites than climate in bivariate analysis. Multivariate analysis showed that climate interacted with soil nutrients for SLA and area-based LNC. Mass-based LNC and LPC were determined mostly by soil fertility, but soil P was highly correlated to precipitation. Relationships of leaf traits to soil nutrients were stronger than those of growth form versus soil nutrients. In contrast, climate determined distribution of growth form more strongly than it did leaf traits.
Main conclusions We provide the first global quantification of the trade-off between traits associated with growth and resource conservation ‘strategies’ in relation to soil fertility. Precipitation but not temperature affected this trade-off. Continuous leaf traits might be better predictors of plant responses to nutrient supply than growth form, but growth forms reflect important aspects of plant species distribution with climate.
We explored the relationship between leaf specific mass (LSM) and its two components, leaf density and thickness. These were assessed on the leaves of (a) the moderately sclerophyllous tree Arbutus menziesii distributed along a natural nutrient/moisture gradient in California, (b) eight sclerophyllous shrub species on four substrates in south-western Australia, and (c) seedlings of two morphologically contrasting Hakea species grown under varying soil nutrient, moisture and light regimes in a glasshouse experiment. Leaf area, mass, LSM, density and thickness varied greatly between leaves on the same plant, different species, and with different nutrient, moisture and light regimes. In some cases, variations in LSM were due to changes in leaf density in particular or thickness or both, while in others, density and thickness varied without a net effect on LSM. At lower nutrient or moisture availabilities or at higher light irradiances, leaves tended to be smaller, with higher LSM, density and thickness. Under increased stress, the thickness (diameter) of needle leaves decreased despite an increase in LSM. We concluded that, while LSM is a useful measure of sclerophylly, its separation into leaf density and thickness may be more appropriate as they often vary independently and appear to be more responsive to environmental gradients than LSM.
Metrosideros polymorpha, a dominant tree species in Hawaiian ecosystems, occupies a wide range of habitats. Complementary field and common-garden
studies of M. polymorpha populations were conducted across an altitudinal gradient at two different substrate ages to ascertain if the large phenotypic
variation of this species is determined by genetic differences or by phenotypic modifications resulting from environmental
conditions. Several characteristics, including ecophysiological behavior and anatomical features, were largely induced by
the environment. However, other characteristics, particularly leaf morphology, appeared to be mainly determined by genetic
background. Common garden plants exhibited higher average rates of net assimilation (5.8 μmol CO2 m−2 s−1) and higher average stomatal conductance (0.18 mol H2O m−2 s−1) than their field counterparts (3.0 μmol CO2 m−2 s−1, and 0.13 mol H2O m−2 s−1 respectively). Foliar δ13C of most common-garden plants was similar among sites of origin with an average value of −26.9‰. In contrast, mean values
of foliar δ13C in field plants increased substantially from −29.5‰ at low elevation to −24.8‰ at high elevation. Leaf mass per unit area
increased significantly as a function of elevation in both field and common garden plants; however, the range of values was
much narrower in common garden plants (211–308 g m−2 for common garden versus 107–407 g m−2 for field plants). Nitrogen content measured on a leaf area basis in common garden plants ranged from 1.4 g m−2 to 2.4 g m−2 and from 0.8 g m−2 to 2.5 g m−2 in field plants. Photosynthetic nitrogen use efficiency (PNUE) decreased 50% with increasing elevation in field plants and
only 20% in plants from young substrates in the common garden. This was a result of higher rates of net CO2 assimilation in the common garden plants. Leaf tissue and cell layer thickness, and degree of leaf pubescence increased significantly
with elevation in field plants, whereas in common garden plants, variation with elevation of origin was much narrower, or
was entirely absent. Morphological characteristics such as leaf size, petiole length, and internode length decreased with
increasing elevation in the field and were retained when grown in the common garden, suggesting a potential genetic basis
for these traits. The combination of environmentally induced variability in physiological and anatomical characteristics and
genetically determined variation in morphological traits allows Hawaiian M. polymorpha to attain and dominate an extremely wide ecological distribution not observed in other tree species.
Pine needles reflect some of the most outstanding xeromorphic characteristics of sclerophyllous plants. Detailed descriptive
studies about their anatomy and morphology were carried out since the beginning of the past century but the role the different
tissues play in adaptation to diverse environments is still little known. In this work we analyzed morphological and anatomical
needle traits of seventeen natural populations of Pinus canariensis Chr. Sm. Ex DC to identify adaptive traits related to drought resistance and determine their variability throughout a wide
range of ecological conditions. A Principal Component Analysis revealed two groups of traits, one related to drought adaptation:
maximizing gas exchange, avoiding water loss and storing water and the other to photosynthesis. Results support a predominantly
mechanical function of hypodermis and a possible role of transfusion tissue to withstand dry conditions, thanks to its water
storing capacity. The inversion of the patterns of the relative area of the dermal and transfusion tissues in the xeric region
was justified due to the influence of the extreme dry Saharan wind from the East. A clear adaptation of Pinus canariensis needles to contrasted environments is evidenced suggesting distinct phenotypic needle features in the most xeric stands.
A study was conducted on the variation in growth, biomass, juvenile wood anatomy, and needle morphology of Pinus
halepensis Mill. from three Spanish regions of provenance characterized by environmental differences, without the influence of the site factor. Seeds collected from two progenies in each region were planted in a single plot, and the trees were felled at the age of 7 years. The results showed significant differences between provenances, as well as the genetic or environmental influence on the traits analyzed. Trees adapted to moderate summer drought conditions (Inland Catalonia region) are primarily characterized by higher average values for height, diameter, biomass, cell wall thickness, inter-tracheid wall strength, pit membrane diameter, torus diameter, bordered pit aperture diameter, and ray tracheid abundance in comparison with trees adapted to severe summer drought conditions (Southern region and Balearic Islands region). The greater structural requirements of trees from the Inland Catalonia region, subjected to higher weight and wind loads, resulted in thick cell walls. Moreover, the large pits and more abundant ray tracheids in trees from this provenance would allow more efficient water transport and greater water storage capacity, respectively. The differences found between provenances suggest the adaptive nature of the anatomy of this species, which demonstrates the importance of the region of provenance when choosing reproduction material for reforestation.
Water transport in leaf vasculature is a fundamental process affecting plant growth, ecological interactions and ecosystem productivity, yet the architecture of leaf vascular networks is poorly understood. Although Murray's law and the West–Brown–Enquist (WBE) theories predict convergent scaling of conduit width and number, it is not known how conduit scaling is affected by habitat aridity or temperature. We measured the scaling of leaf size, conduit width and conduit number within the leaves of 36 evergreen Angiosperms spanning a large range in aridity and temperature in eastern Australia. Scaling of conduit width and number in midribs and 2° veins did not differ across species and habitats (P > 0.786), and did not differ from that predicted by Murray's law (P = 0.151). Leaf size was strongly correlated with the hydraulic radius of petiole conduits (r2 = 0.83, P < 0.001) and did not differ among habitats (P > 0.064), nor did the scaling exponent differ significantly from that predicted by hydraulic theory (P = 0.086). The maximum radius of conduits in petioles was positively correlated with the temperature of the coldest quarter (r2 = 0.67; P < 0.001), suggesting that habitat temperature restricts the occurrence of wide‐conduit species in cold habitats.
Occupancy of cold habitats by evergreen species requires structural modification of photosynthetic organs for stress resistance and longevity. Such modifications have been described at inter-specific level while intra-specific variation has been underexplored. 2.To identify structural and anatomical traits that may be adaptive in cold environments, we studied intra-specific variability of needles of Scots pine (Pinus sylvestris L.), a wide-ranging tree, along a 1900 km temperate-boreal transect in Europe. 3.Needles from 20 sites representing mean minimum winter temperatures between -4.0°C and -19.9°C and mean annual temperatures between 8.3°C and -1.7°C were sampled for measurements of leaf mass per area (LMA, g m−2), leaf density (LD, g cm−3) and 30 other morpho-anatomical traits. 4.Needles from cold sites lived longer, were shorter, showed higher LMA and LD, had narrower and more collapse-resistant tracheids, thicker epidermal cells with thicker cell walls, and wider resin ducts occupying larger fraction of needle volume in comparison to needles from warmer sites. 5.Along the steep climatic gradient, needles presented a coordinated phenotypic spectrum of external and internal traits that are largely interpretable in functional, adaptive terms. This intra-specific pattern of co-varying traits provides insight into the adaptive syndrome associated with stress tolerance and extended needle longevity under cold conditions of high latitudes. This article is protected by copyright. All rights reserved.
Leaf anatomical traits may reflect plant's adaption to environmental changes and influence ecosystem functions, as they regulate light absorption and gas exchange to some extent. Here, we hypothesized that leaf anatomical traits were closely related to gross primary productivity (GPP) because photosynthesis commonly occurs in the chloroplasts of palisade and spongy tissues in leaf. 2. Eight leaf anatomical traits were measured in 916 plant species inhabiting from tropical to cold-temperate forests in eastern China: adaxial epidermis thickness (AD), abaxial epidermis thickness (AB), leaf thickness (LT), palisade tissue thickness (PT), and spongy tissue thickness (ST), palisade-spongy tissue ratio (PT/ST), palisade tissue-leaf thickness ratio (PT/LT), and spongy tissue-leaf thickness ratio (ST/LT). 3. Leaf anatomical traits showed significant latitudinal patterns at species, plant functional groups (PFGs), and communities levels (P < 0.05), and they differed between PFG and community. Temperature and precipitation were the main factors influencing AD, AB, PT/ST, and PT/LT, explaining 33–72% of the total variation at large scale. Furthermore, AB, LT, PT/ST, and PT/LT were significantly correlated with the aridity index. 4. Our findings filled the data gap of plant anatomical traits at regional scales, and broadened current knowledge on the adaptation strategies of plant anatomical traits, which also provided new evidence for linkages of plant traits and functioning across natural communities. This article is protected by copyright. All rights reserved.
Epigenetic signals can affect plant phenotype and fitness and be stably inherited across multiple generations. Epigenetic regulation plays a key role in the mechanisms of plant response to the environment without altering DNA sequence. As plants cannot adapt behaviourally or migrate instantly, such dynamic epigenetic responses may be particularly crucial for survival of plants within changing and challenging environments, such as the Mediterranean-Type Ecosystems (MTEs). These ecosystems suffer recurrent stressful events (warm and dry summers with associated fire regimes) that have selected for plants with similar phenotypic complex traits, resulting in similar vegetation growth forms. However, the potential role of epigenetics in plant adaptation to recurrent stressful environments such as the MTEs has been most often ignored. To understand the full spectrum of adaptive processes in such contexts, it is imperative to prompt the study of the causes and consequences of epigenetic variation in natural populations. With this purpose, we review here current knowledge on epigenetic variation in natural populations and the genetic and epigenetic basis of some key traits for plants in the MTEs, namely those traits involved in adaptation to drought, fire and oligotrophic soils. We conclude there is still much to be learned about 'plant epigenetics in the wild' and, thus, we propose future research steps in the study of natural epigenetic variation of key traits in the MTEs at different scales. This article is protected by copyright. All rights reserved.
Plant leaf size varies by more than three orders of magnitude, from a few millimeters to over one meter. Conifer leaves, however, are relatively short and the majority of needles are no longer than 6 cm. The reason for the strong confinement of the trait-space is unknown. We show that sugars produced near the tip of long needles cannot be exported efficiently, because the pressure required to drive vascular flow would exceed the greatest available pressure (the osmotic pressure). This basic constraint leads to the formation of an inactive region of stagnant fluid near the needle tip, which does not contribute to sugar flow. Remarkably, we find that the size of the active part does not scale with needle length. We predict a single maximum needle size of 5 cm, in accord with data from 519 conifer species. This could help rationalize the recent observation that conifers have significantly smaller leaves than angiosperms, and provide a biophysical explanation for this intriguing difference between the two largest groups of plants.
Patterns of plant biomass allocation and functional adjustments along climatic gradients are poorly understood, particularly belowground. Generally, low temperatures suppress nutrient release and uptake, and forests under such conditions have a greater proportion of their biomass in roots. However, it is not clear whether 'more roots' means better capacity to acquire soil resources. Herein we quantified patterns of fine-root anatomy and their biomass distribution across Scots pine (Pinus sylvestris) populations both along a 2000-km latitudinal gradient and within a common garden experiment with a similar range of populations. We found that with decreasing mean temperature, a greater percentage of Scots pine root biomass was allocated to roots with higher potential absorptive capacity. Similar results were seen in the common experimental site, where cold-adapted populations produced roots with greater absorptive capacity than populations originating from warmer climates. These results demonstrate that plants growing in or originated from colder climates have more acquisitive roots, a trait that is likely adaptive in the face of the low resource availability typical of cold soils.
The degree of herbivory and the effectiveness of defenses varies widely among plant species. Resource availability in the environment is proposed as the major determinant of both the amount and type of plant defense. When resources are limited, plants with inherently slow growth are favored over those with fast growth rates; slow rates in turn favor large investments in antiherbivore defenses. Leaf lifetime, also determined by resource availability, affects the relative advantages of defenses with different turnover rates. Relative limitation of different resources also constrains the types of defenses. The proposals are compared with other theories on the evolution of plant defenses.
This book is an illustrated comprehensive account of living and fossil gymnosperms in 24 chapters. Chapters 1 and 2 (Introduction; and Seed development) give a general account and describe similarities and dissimilarities with pteridophytes and angiosperms. Chapter 3 deals with classification. The next 19 chapters (4-21) deal sequentially with fossil and living taxa: Progymnospermopsida (4), Gymnospermopsida (5), Gymnospermopsida - Cycadophytes (6-8), Gymnospermopsida - gymnosperms of uncertain relationship (9-12), Gymnospermopsida - Coniferophytes (13-16), Gnetopsida (17), Ephedrales (18), Welwitschiales (19), and Gnetales (20). Phylogenetic relationships are considered for each order, but chapter 21 specifically discusses phylogenetic considerations in Ephedra, Welwitschia and Gnetum. Chapter 22 describes in vitro experimental studies on the growth, development and differentiation of vegetative organs and tissues. Chapter 23 discusses the economic importance of gymnosperms, and chapter 24 presents concluding remarks. Overall, there is complete coverage of significant findings concerning morphology, anatomy, reproduction, embryology, cytology (chromosome numbers), and evolutionary trends and phylogeny. Ultrastructural and histochemical details are given where considered necessary.
The leaf economics spectrum is a general concept describing coordinated variation in foliage structural, chemical and physiological traits across resource gradients. Yet, within this concept, the role of within-species variation, including ecotypic and plastic variation components, has been largely neglected. This study hypothesized that there is a within-species economics spectrum within the general spectrum in the evergreen sclerophyll Quercus ilex which dominates low resource ecosystems over an exceptionally wide range. An extensive database of foliage traits covering the full species range was constructed, and improved filtering algorithms were developed. Standardized data filtering was deemed absolutely essential as additional variation sources can result in trait variation of 10–300%, blurring the broad relationships. Strong trait variation, c. two-fold for most traits to up to almost an order of magnitude, was uncovered. Although the Q. ilex spectrum is part of the general spectrum, within-species trait and climatic relationships in this species partly differed from the overall spectrum. Contrary to world-wide trends, Q. ilex does not necessarily have a low nitrogen content per mass and can increase photosynthetic capacity with increasing foliage robustness. This study argues that the within-species economics spectrum needs to be considered in regional- to biome-level analyses.
The leaf economics spectrum (LES) provides a useful framework for examining species strategies as shaped by their evolutionary history. However, that spectrum, as originally described, involved only two key resources (carbon and nutrients) and one of three economically important plant organs. Herein, I evaluate whether the economics spectrum idea can be broadly extended to water – the third key resource –stems, roots and entire plants and to individual, community and ecosystem scales. My overarching hypothesis is that strong selection along trait trade-off axes, in tandem with biophysical constraints, results in convergence for any taxon on a uniformly fast, medium or slow strategy (i.e. rates of resource acquisition and processing) for all organs and all resources.
Differences in terms of depth of dormancy have been revealed in the provenace trial of Scots pine based on an analysis of parameters of the zero fluorescence level, as well as the content of chlorophylls and abscisic acid, which corresponds to the results of studying the pine-needle morphological traits and phenological observations. Trees of the southern climatype different in terms of needle morphological traits and the length of phenological stages are characterized by a deeper dormancy than those of the northern climatype. It is assumed that, due to climate change, northern climatypes would be more vulnerable during winter-spring thaws, which were not typical of these regions in former times.
Spatial variation in filters imposed by the abiotic environment causes variation in functional traits within and among plant species. This is abundantly clear for plant species along elevational gradients, where parallel abiotic selection pressures give rise to predictable variation in leaf phenotypes among ecosystems. Understanding the factors responsible for such patterns may provide insight into the current and future drivers of biodiversity, local community structure and ecosystem function.In order to explore patterns in trait variation along elevational gradients, we conducted a meta‐analysis of published observational studies that measured three key leaf functional traits that are associated with axes of variation in both resource competition and stress tolerance: leaf mass:area ratio (LMA), leaf nitrogen content per unit mass (Nmass) and N content per unit area (Narea). To examine whether there may be evidence for a genetic basis underlying the trait variation, we conducted a review of published results from common garden experiments that measured the same leaf traits.Within studies, LMA and Narea tended to decrease with mean annual temperature (MAT) along elevational gradients, while Nmass did not vary systematically with MAT. Correlations among pairs of traits varied significantly with MAT: LMA was most strongly correlated with Nmass and Narea at high‐elevation sites with relatively lower MAT. The strengths of the relationships were equal or greater within species relative to the relationships among species, suggesting parallel evolutionary dynamics along elevational gradients among disparate biomes. Evidence from common garden studies further suggests that there is an underlying genetic basis to the functional trait variation that we documented along elevational gradients.Taken together, these results indicate that environmental filtering both selects locally adapted genotypes within plant species and constrains species to elevational ranges based on their ranges of potential leaf trait values. If individual phenotypes are filtered from populations in the same way that species are filtered from regional species pools, changing climate may affect both the species and functional trait composition of plant communities.
Freeze avoidance has evolved in plants in response to selection pressures brought about by exposure to freezing temperatures. It is a multifaceted adaptive mechanism with many attributes. Despite the prevalence of freeze avoidance as an adaptive mechanism little research has been devoted in recent times to understanding the underlying mechanisms and regulation of freeze avoidance. Therefore, there is no shortage of questions that need to be addressed. Inherent in understanding how plants respond to freezing temperatures is the need to know the properties of water at different temperatures and how the interaction of water with biological substances affects these properties. This review provides an overview of the subject of biological ice nucleation and propagation and how various aspects of plant structure and composition can affect the freezing process. Deep supercooling of plant tissues represents the most extreme example of freeze avoidance. The potential role of anti-nucleating substances in defining the ability to deep supercool is also discussed. The importance of studying intact plants in their natural environments is emphasized. Although, this adds a high degree of complexity to investigations, it is in this context that adaptive mechanisms have evolved and play a role in the biology and survival of plants.
Seedlings of 24 European populations of Scots pine were grown from seed for 4 months in controlled environments under photoperiod conditions of 50° or 60°N, but with similar temperatures and total daily quantum flux in both photoperiods. During the experiment the photoperiod was continually changed to simulate the photoperiod from 1 May to 1 September at each latitude. Secondary needle length, plant height and dry mass at harvest were greater at 60° than at 50°N photoperiod. All populations allocated significantly greater proportions of their biomass to roots at 50° than 60°N photoperiod, yet central populations allocated less to roots than nothern ones in both photoperiods. Northern populations (origin >55°N latitude) stopped height growth up to 50d earlier than the other populations when grown under 50°N photoperiod conditions. Under the 60°N photoperiod, all populations, except the most southern one, developed terminal leader buds and ceased growth in height between 87 and 105 d after sowing. Using cluster analysis, populations with similar growth and photoperiod responses were assigned to two major groups; northern (61-56°N from Sweden and Russia), and central (55-40°N from Russia, Poland, Germany, Belgium, France, Czechoslovakia, Yugoslavia, and Turkey). Findings support the hypothesis that northern plants respond to a combination of increasing night length and accumulated degree-days, but central and southern populations do not respond to increased night length as they all ceased growth earlier in the 60° than the 50° photoperiod. Central and southern populations are either photoperiodically insensitive or respond to short nights or to accumulated degree-days at their native latitudes. -from Authors
Leaf dry mass per unit area (LMA) is a product of leaf thickness (T) and of density (D). Greater T is associated with greater foliar photosynthetic rates per unit area because of accumulation of photosynthetic compounds; greater D results in decreased foliage photosynthetic potentials per unit dry mass because of lower concentrations of assimilative leaf compounds and decreases in intercellular transfer conductance to CO2. To understand the considerable variation in T and D at the global scale, literature data were analyzed for 558 broad-leaved and 39 needle-leaved shrubs and trees from 182 geographical locations distributed over all major earth biomes with woody vegetation. Site climatic data were interpolated from long-term world climatologies (monthly precipitation, surface temperature) or modeled using the Canadian Climate Center Model (monthly global solar radiation). Influences of total annual precipitation (W-T), precipitation of the driest month (W-min), monthly mean precipitation of the three driest months in the year (W-3min), highest monthly precipitation (W-max), precipitation index ([W-max - W-min]/W-T), mean, minimum, and maximum annual monthly temperatures, and daily annual mean global solar radiation (R) on LMA, D, and T were tested by simple and multiple linear and log-linear regression analyses. In broad-leaved species, LMA and T increased with increasing R and mean temperature and scaled weakly and negatively with precipitation variables, but D was negatively related only to precipitation. Similar relationships were also detected in needle-leaved species, except that, in multiple regression analysis, precipitation did not significantly influence leaf thickness, and R was positively related to D. Given that increases in LMA and T are compatible with enhanced photosynthetic capacities per unit leaf area, but also with greater costs for construction of unit surface area, positive effects of solar irradiance and surface temperature on these variables are indicative of shorter leaf pay-back times in conditions of higher irradiance and temperature allowing construction of leaves with higher photosynthetic potential. To gain insight into the scaling of leaf density with site aridity, correlations of D with the leaf elastic modulus close to full turgor (epsilon) and with the leaf osmotic potentials (pi) at full and zero turgor were analyzed. Both low pi, which is compatible with low leaf water potential, and high epsilon, which permits large adjustment of leaf water potential with small changes in leaf water content, may facilitate water uptake from drying soil. Leaf elastic modulus was independent of T and was weakly related to LMA; but there were close positive associations of epsilon with D and leaf dry to fresh mass ratio, which is an estimate of apoplastic leaf fraction. Consequently, changes in D bring about modifications in leaf elasticity and allow tolerance of water limitations. Across all the data, epsilon and the estimates of pi were negatively related. However, given that pi varied only fourfold, but epsilon 10-fold, I conclude that osmotic adjustment of leaf water relations is inherently limited, and that elastic adjustment resulting from changes in leaf structure may be a more important and general way for plants to adapt to water-limited environments.
Shoot and needle growth of 20-year-old Pinus sylvestris trees was studied in relation to the temperature of the current and previous seasons at three localities in Northern Fennoscandia over a 10-year period. Leader length and the number of needle fascicles per leader had highly significant positive correlation coefficients with the mean June-August temperature of the previous season. A low number of needle fascicles per leader was associated with a high frequency of fascicles with three needles. Needle length showed a significant positive correlation with the mean temperature of the current growing season, particularly June-August temperature. Use of heat sums or respiration equivalents instead of mean temperatures did not significantly improve correlation coefficients. A highly significant positive correlation was also found between needle length and next year's leader growth. Forest Sci. 27:423-430.
Needle mass, length, and nitrogen concentration, and their relation to site index were studied for lodgepole pine (Pinus contorta Dougl.) and Scots pine (Pinus sylvestris L.). Needles were collected at 53 locations throughout Sweden where the two species, of the same age, were growing on adjacent, comparable sites. Sampling was done throughout the growing season, with a pause during the period of most active growth. Needles of lodgepole pine had a higher mass, were longer, and had a lower nitrogen concentration than those of Scots pine. Site index was positively correlated to needle length and weight for both species, and to nitrogen concentration for lodgepole pine. For the characteristics studied, the relative differences between needles of the two species decreased with increasing site index.
The Digital Climatic Atlas and the Ecological and the Forestry Inventory of Catalonia (NE Spain) were analysed to study the climate effect on leaf mass per area (LMA) and leaf area index (LAI) on Quercus ilex L., one of the most widely spread tree species in the Mediterranean region. 195 sites in this region of 31,895km2 were considered. The relationship between climatic variables (total annual rainfall, mean annual temperature, mean minimum winter temperatures, and mean annual solar radiation) and LMA and LAI were analysed by simple and multiple regressions. LMA was higher in the drier sites and specially in the colder sites. There was also a significant correlation between solar radiation and LMA. On the contrary, LAI values, which were negatively correlated with LMA values, were lower in drier and colder sites, and were not significantly affected by solar radiation. The results highlight that high LMA values do not seem to be a specific protection to dry conditions but to a wide range of environmental stress factors, including low temperatures.
The natural ratio of stable carbon isotopes (δ13C) was compared to leaf structural and chemical characteristics in evergreen conifers in the north-central Rockies, United
States. We sought a general model that would explain variation in δ13C across altitudinal gradients. Because variation in δ13C is attributed to the shifts between supply and demand for carbon dioxide within the leaf, we measured structural and chemical
variables related to supply and demand. We measured stomatal density, which is related to CO2 supply to the chloroplasts, and leaf nitrogen content, which is related to CO2 demand. Leaf mass per area was measured as an intermediate between supply and demand. Models were tested on four evergreen
conifers: Pseudotsuga menziesii, Abies lasiocarpa, Picea engelmannii, and Pinus contorta, which were sampled across 1800 m of altitude. We found significant variation among species in the rate of δ13C increase with altitude, ranging from 0.91‰ km–1 for A. lasiocarpa to 2.68‰ km–1 for Pinus contorta. Leaf structure and chemistry also varied with altitude: stomatal density decreased, leaf mass per area increased, but leaf
nitrogen content (per unit area) was constant. The regressions on altitude were particularly robust in Pinus contorta. Variables were derived to describe the balance between supply and demand; these variables were stomata per gram of nitrogen
and stomata per gram of leaf mass. Both derived variables should be positively related to internal CO2 supply and thus negatively related to δ13C. As expected, both derived variables were negatively correlated with δ13C. In fact, the regression on stomatal density per gram was the best fit in the study (r
2=0.72, P<0.0001); however, the relationships were species specific. The only general relationship observed was between δ13C and LMA: δ13C (‰)=–32.972+ 0.0173×LMA (r
2=0.45, P<0.0001). We conclude that species specificity of the isotopic shift indicates that evergreen conifers demonstrate varying
degrees of functional plasticity across environmental gradients, while the observed convergence of δ13C with LMA suggests that internal resistance may be the key to understanding inter-specific isotopic variation across altitude.
Evergreen boreal plant species express high variability in their leaf traits. It remains controversial whether this within-species
variability is constrained to the same leaf trait relationships as has been observed across species. We sampled leaves of
three boreal evergreen woody species along a latitudinal gradient (from 57º56′N to 69º55′N). Leaf longevity (LL) of Pinussylvestris L. and Vacciniumvitis-idaea L. correlated negatively with mean annual air temperature (MAT), whereas the LL of Ledumpalustre L. was not affected by MAT. V.vitis-idaea and L.palustre had a negative relationship between leaf mass per area (LMA) and MAT. In P.sylvestris, the LMA–MAT relationship was positive. A negative correlation between LL and LMA was significant only for P.sylvestris. Leaf nitrogen concentration was positively related to leaf phosphorus concentration in all three species. Leaf potassium
concentration was related to nitrogen concentration only in L.palustre, and to phosphorus concentration in P.sylvestris and L.palustre. Our results demonstrate that although within the studied species the variation in some of the leaf traits may have the same
degree as interspecific variation, there is no such intercorrelation of leaf traits within the studied species as has been
observed across species.
KeywordsBoreal forest-Evergreen plants-Leaf traits-Nutrients-Temperature
Morphophysiological and anatomical characters of needles that are used for characterizing infraspecific taxa have been studied Morphophysiological and anatomical characters of needles that are used for characterizing infraspecific taxa have been studied
in Scotch pine geographic cultures established in the forest-steppe zone of Siberia. Variation in these characters has been in Scotch pine geographic cultures established in the forest-steppe zone of Siberia. Variation in these characters has been
revealed, which reflects the polymorphic structure of the species and the effect of natural selection on the composition of revealed, which reflects the polymorphic structure of the species and the effect of natural selection on the composition of
populations in new natural-cimatic conditions. populations in new natural-cimatic conditions.