Morphological Traits In Response Research Articles

Morphological and Anatomical Differentiation of Potamogeton gramineus in Relation to the Presence of Invasive Species Elodea nuttallii: A Case Study from Vlasina Lake, Serbia.

Elodea nuttallii represents non-native and highly invasive species in Europe that significantly influence freshwater plant communities by decreasing the diversity of native species. This study aimed to determine whether the morphological and anatomical features of Potamogeton gramineus, a native species in Vlasina Lake, differ between sites where it coexists with E. nuttallii and those where E. nuttallii is not present. Environmental variables such as water depth, temperature, pH, conductivity, saturation, and O2 concentration were included in the analysis. Analyses were conducted on 32 morphological and anatomical features of P. gramineus collected from six sites within Vlasina Lake, comprising three sites where E. nuttallii was present and three sites where it was absent. The datasets containing morphometric and environmental variables underwent analysis using standard univariate techniques (Descriptive, ANOVA), Tukey's Honest Significant Difference (HSD) test, Student's t-test, and the Mann-Whitney U test, as well as multivariate statistical methods such as Canonical Discriminant Analysis (CDA). The results show the presence of morphological differentiation among P. gramineus individuals across the analyzed sites. These findings suggest that morphological and anatomical features, such as epidermis, mesophyll, palisade, and aerenchyma tissue thickness in floating leaves, number, length, width, and the surface area of stomata, as well as the width of submersed leaves and stem aerenchyma tissue thickness, effectively differentiate individuals that coexist with E. nuttallii and individuals that growth without its presence. Moreover, they indicate that P. gramineus exhibits a notable ability to modify its morphological traits in response to invasion.

Phenotypic plasticity of growth ring traits in Pinus hartwegii at the ends of its elevational gradient.

Phenotypic plasticity (PP) could be an important short-term mechanism to modify physiological and morphological traits in response to climate change and global warming, particularly for high-mountain tree species. The objective was to evaluate PP response of growth ring traits to temperature and precipitation in Pinus hartwegii Lindl. populations located at the ends of its elevational gradient on two volcanic mountains in central Mexico (La Malinche and Nevado de Toluca). Increment cores collected from 274 P. hartwegii trees were used to estimate their PP through reaction norms (RN), which relate the ring width and density traits with climate variables (temperature and precipitation). We estimated the trees' sensitivity (significant RN) to climatic variables, as well as the relative proportion of RN with positive and negative slope. We also estimated the relationship between the PP of ring width and density traits using correlation and Principal Component (PC) analyses. Over 70% of all trees showed significant RN to growing season and winter temperatures for at least one growth ring trait, with a similar proportion of significant RN at both ends of the gradient on both mountains. Ring width traits had mostly negative RN, while ring density traits tended to have positive RN. Frequency of negative RN decreased from lower to higher elevation for most traits. Average PP was higher at the lower end of the gradient, especially on LM, both for ring width and ring density traits, although high intrapopulation variation in PP was found on both mountains. Results indicate that P. hartwegii presents spatially differentiated plastic responses in width and density components of radial growth. PP was particularly strong at the lower elevation, which has higher temperature and water stress conditions, putting these populations at risk from the continuing global warming driven by climate change.

Annual Herbaceous Plants Exhibit Altered Morphological Traits in Response to Altered Precipitation and Drought Patterns in Semiarid Sandy Grassland, Northern China.

The frequency and intensity of extreme precipitation events and severe drought are predicted to increase in semiarid areas due to global climate change. Plant morphological traits can reflect plant responses to a changing environment, such as altered precipitation or drought patterns. In this study, we examined the response of morphological traits of root, stem, leaf and reproduction meristems of annual herbaceous species to altered precipitation and drought patterns in a semiarid sandy grassland. The study involved a control treatment (100% of background precipitation) and the following six altered precipitation treatments: (1) P(+): precipitation increased by 30%, (2) P(++): precipitation increased by 60%, (3) P(-): precipitation decreased by 30%, (4) P(--): precipitation decreased by 60%, (5) drought 1 (D1): 46-day drought from May 1st to June 15th, and (6) drought 2 (D2): 46-day drought from July 1st to August 15th. P(++) significantly increased root length, flower length-to-width ratio, both P(+) and P(++) significantly increased stem length and flower number in the plant growing seasons, while all of them decreased under P(-) and P(--). The annual herbaceous plants marginally increased the number of second-level stem branches and stem diameter in order to better resist the severe drought stress under P(--). P(+) and P(++) increased the root, stem, leaf, and flower dry weight, with the flower dry weight accounting for a larger proportion than the other aboveground parts. Under D2, the plants used the limited water resources more efficiently by increasing the root-to-shoot ratio compared with P(-), P(--) and D1, which reflects biomass allocation to belowground increased. The linear mixed-effects models and redundancy analysis showed that the root-to-shoot ratio and the dry weight of various plant components were significantly affected by morphological traits and altered precipitation magnitude. Our results showed that the herbaceous species have evolved morphological trait responses that allow them to adapt to climate change. Such differences in morphological traits may ultimately affect the growing patterns of annual herbaceous species, enhancing their drought-tolerant capacity in semiarid sandy grassland during the ongoing climate change.

Selection of drought-tolerant tomato during the vegetative stage

Drought stress consists of a significant productivity constraint in tomatoes. Two contrasting crosses were performed to estimate physiological and morphological traits in response to drought stress during the vegetative stage, aiming to identify superior genotypes for drought tolerance. Two genotypes (GBT_2037 – sensitive drought-sensitive and GBT_2016 – intermediate drought-tolerant) were used as female parentals, and a commercial hybrid (drought tolerant) was used as a pollen source in both crosses: C1 (GBT_2037 × Commercial hybrid) and C2 (GBT_2016 × Commercial hybrid). The populations of parentals (P), the first generation of descendants (F1), backcrosses (BC), and the second generation of self-pollination (F2) were exposed to drought stress for 20 days when they were analyzed: physiological traits (relative water content of leaves, proline, and relative chlorophyll content) and morphological (plant height, stem diameter, number of leaves, fresh and dry matter of roots and shoot and classification by wilt scale). The means of chlorophyll, root/shoot ratio, and water content in leaves for the F2 generation of C2 were higher than C1, indicating that C2 resulted in plants with greater capacity to maintain turgor under conditions of water stress and presented minor damage to the photosynthetic structures, consequently showing greater tolerance to drought stress.

Impact of habitat variability on phenotypic attributes of Hypericum Perforatum L. along an elevational gradient in Kashmir Himalaya

A number of environmental factors such as mean temperature, precipitation, soil characteristics etc. changes with elevational gradient and thereby, affect the morphological pattern of a plant species. Phenotypic attributes of a particular species varies along different altitudes in order to adapt and also to overcome these changeable and stressful conditions. The present study was undertaken to assess the distribution pattern and impact of habitat variability along an elevational gradient on morphology of an important medicinal plant Hypericum perforatum L. growing in the Kashmir Himalaya. Hypericum perforatum L., member of family Hypericaceae, is a perennial herb and distributed in North Western Himalaya. The species exhibited distinct variability and a peculiar trend in morphological traits in response to different environmental conditions along an elevational gradient.

Geographical Variation in Phenotypic Plasticity of Intertidal Sister Limpet’s Species Under Ocean Acidification Scenarios

Ocean Acidification (OA) can have pervasive effects in calcifying marine organisms, and a better understanding of how different populations respond at the physiological and evolutionary level could help to model the impacts of global change in marine ecosystems. Due to its natural geography and oceanographic processes, the Chilean coast provides a natural laboratory where benthic organisms are frequently exposed to diverse projected OA scenarios. The goal of this study was to assess whether a population of mollusks thriving in a more variable environment (Talcaruca) would present higher phenotypic plasticity in physiological and morphological traits in response to different pCO2 when compared to a population of the same species from a more stable environment (Los Molles). To achieve this, two benthic limpets (Scurria zebrina and Scurria viridula) inhabiting these two contrasting localities were exposed to ocean acidification experimental conditions representing the current pCO2 in the Chilean coast (500 μatm) and the levels predicted for the year 2100 in upwelling zones (1500 (μatm). Our results show that the responses to OA are species-specific, even in this related species. Interestingly, S. viridula showed better performance under OA than S. zebrina (i.e., similar sizes and carbonate content in individuals from both populations; lower effects of acidification on the growth rate combined with a reduction of metabolism at higher pCO2). Remarkably, these characteristics could explain this species’ success in overstepping the biogeographical break in the area of Talcaruca, which S. zebrina cannot achieve. Besides, the results show that the habitat factor has a strong influence on some traits. For instance, individuals from Talcaruca presented a higher growth rate plasticity index and lower shell dissolution rates in acidified conditions than those from Los Molles. These results show that limpets from the variable environment tend to display higher plasticity, buffering the physiological effects of OA compared with limpets from the more stable environment. Taken together, these findings highlight the key role of geographic variation in phenotypic plasticity to determine the vulnerability of calcifying organisms to future scenarios of OA.

Phenotypic Plasticity of Drought Tolerance Traits in a Widespread Eucalypt (Eucalyptus obliqua)

Long-term studies of tree responses to drought stress help us to understand the capacity of species to adapt to their environment. In this study, we investigated how Eucalyptus obliqua adjusts physiological and morphological traits in response to seasonal and multi-year droughts. We monitored physiological and morphological traits over multiple years in undisturbed control and throughfall reduction plots in a eucalypt forest in south-eastern Australia. The throughfall reduction treatment did not induce significantly lower soil moisture in the throughfall reduction plots compared with the control plots. However, natural variability in precipitation and evaporative demand induced drought stress of varying intensity each summer in all plots. We observed a significant relationship between seasonal precipitation and leaf pre-dawn water potential (ΨPD), with less precipitation over summer, resulting in a decline in ΨPD and drought stress when ΨPD fell below −0.75 MPa. Eucalyptus obliqua responded to short-term summer drought through rapid leaf osmotic adjustment which lowered the leaf water potential at the turgor loss point beyond the minimum leaf water potential. Morphological adjustments, such as the reduction of leaf area to sapwood area (higher Huber Value) were moderate during the measurement period and only occurred under severe drought stress (pre-dawn water potential < −1.2 MPa). Overall, E. obliqua responded to short-term mild drought stress through physiological trait plasticity, while morphological adjustment only occurred under a more severe water deficit.

Selfing and Drought-Stress Strategies Under Water Deficit for Two Herbaceous Species in the South American Andes.

Angiosperms are highly diverse in their reproductive systems, including predominantly selfing, exclusive outcrossing, and mixed mating systems. Even though selfing can have negative consequences on natural populations, it has been proposed that plants having a predominantly selfing strategy are also associated with fast development strategies through time limitation mechanisms that allow them to complete their life cycle before the onset of severe drought. This relationship might be affected by the challenges imposed by global change, such as a decrease in pollinator availability and the earlier and more severe onset of droughts. In this work, our aim was to investigate whether selfing is correlated with a dehydration avoidance strategy, and how this could affect drought resistance and survival in two species with different types of selfing: pollinator-independent delayed selfing (Schizanthus grahamii) and pollinator-dependent selfing (Schizanthus hookeri), representing a gradient in selfing rates. We hypothesize that delayed selfing species and highly selfing populations will show “fast” plant traits whereas we will find no pattern in more outcrossed populations of the pollinator-dependent species. However, we predicted that high selfing populations would have lower survival rates when exposed to chronic drought early in their development since fast traits imply physiological compromises that will affect their drought survival. To evaluate these hypotheses, we characterized different physiological and morphological traits in response to two contrasting treatments (moist and dry) in a total of six populations of the two species. We found a relationship between the delayed selfing species and a dehydration avoidance strategy and also with low drought survival. Our work offers evidence to support the importance of abiotic factors, such as drought, on the possible variation in selfing rates on natural populations, and the effect that this mating system could have in their ability to face new environmental conditions such as those imposed by climate change.

Highlighting convergent evolution in morphological traits in response to climatic gradient in African tropical tree species: The case of genus Guibourtia Benn.

Adaptive evolution is a major driver of organism diversification, but the links between phenotypic traits and environmental niche remain little documented in tropical trees. Moreover, trait‐niche relationships are complex because a correlation between the traits and environmental niches displayed by a sample of species may result from (a) convergent evolution if different environmental conditions have selected different sets of traits, and/or (b) phylogenetic inertia if niche and morphological differences between species are simply function of their phylogenetic divergence, in which case the trait‐niche correlation does not imply any direct causal link. Here, we aim to assess the respective roles of phylogenetic inertia and convergent evolution in shaping the differences of botanical traits and environmental niches among congeneric African tree species that evolved in different biomes.This issue was addressed with the tree genus Guibourtia Benn. (Leguminosae and Detarioideae), which contains 13 African species occupying various forest habitat types, from rain forest to dry woodlands, with different climate and soil conditions. To this end, we combined morphological data with ecological niche modelling and used a highly resolved plastid phylogeny of the 13 African Guibourtia species.First, we demonstrated phylogenetic signals in both morphological traits (Mantel test between phylogenetic and morphological distances between species: r = .24, p = .031) and environmental niches (Mantel test between phylogenetic and niche distances between species: r = .23, p = .025). Second, we found a significant correlation between morphology and niche, at least between some of their respective dimensions (Mantel's r = .32, p = .013), even after accounting for phylogenetic inertia (Phylogenetic Independent Contrast: r = .69, p = .018). This correlation occurred between some leaflet and flower traits and solar radiation, relative humidity, precipitations, and temperature range.Our results demonstrate the convergent evolution of some morphological traits in response to climatic factors in congeneric tree species and highlight the action of selective forces, along with neutral ones, in shaping the divergence between congeneric tropical plants.

Root nutrient concentration and biomass allocation are more plastic than morphological traits in response to nutrient limitation

Understanding the magnitude of phenotypic plasticity within a species is important, particularly when comparing species from diverse habitats or when using traits from global databases. Our objective was to quantify the magnitude of intraspecific variability of fine root, stem, and leaf traits in response to nutrient availability. We measured growth rates and traits from fine roots, stems, and leaves on replicate seedlings of four species grown in two treatments: low and high soil nutrient availability. We used ANOVA to test for effects of fertilizer, species, and their interaction on trait expression, and ranked intraspecific trait variation using the coefficient of variation. Root nutrient concentration, relative growth rate, and biomass allocation exhibited the most plastic responses to nutrient availability. Specific root length, specific leaf area, root diameter, and wood density were the least variable traits within species. Nutrient limitation only induced greater root branching in the non-mycorrhizal Proteaceae species that produced more cluster roots. Woody plants respond to nutrient limitation by increasing root mass fraction, rather than by adjusting root morphology or structure. We urge caution when using root tissue chemistry traits obtained from global databases in local studies, as this is one of the most plastic traits in response to nutrient availability.

Precipitation, not air temperature, drives functional responses of trees in semi‐arid ecosystems

Summary Model scenarios of climate change predict that warming and drought will occur simultaneously in the future in many regions. The capacity of woody species to modify their physiology and morphology in response to environmental conditions is widely recognized, but little is known about the responses of trees to reduced precipitation and increased temperature acting simultaneously. In a semi‐arid woodland, we assessed the responses in physiological (needle emergence, maximum photosynthesis, stomatal conductance, water use efficiency (WUE) and shoot elongation) and morphological (needle length and thickness, and leaf mass per area (LMA)) foliar traits of piñon pine (Pinus edulis) in response to three years of a 45% reduction in precipitation, a 4.8 °C increase in air temperature and their simultaneous effects. A strong change in physiological and morphological traits in response to reduced precipitation was observed. Precipitation reduction delayed needle emergence, decreased photosynthesis and stomatal conductance, increased WUE, decreased shoot elongation and induced shorter needles with a higher LMA. Trees subjected to simultaneous reductions in precipitation and warming demonstrated a similar response. However, atmospheric warming did not induce a response in any of the measured traits. Physiological and morphological traits of trees in this semi‐arid climate were more responsive to changes in soil moisture than air temperature. Long‐term exposure to seasonal drought stress in arid sites may have resulted in strong plastic responses to this first stressor. However, atmospheric warming probably was not experienced as a stress for trees in this warm and dry climate. Overall, our results indicate that in semi‐arid ecosystems where tree functioning is already highly limited by soil water availability, atmospheric warming as anticipated with climate change may have less impact on foliar trait responses than previously thought.

Plasticity of morphological traits in response to social conditions in a simultaneous hermaphrodite

According to sex allocation theory, hermaphrodites allocate a fixed amount of resources to their male and female functions, and the proportion of resources invested in each sex depends on the mating group size. Measures of trade-offs between male and female functions are usually made directly by estimating the number of gametes or the size of the gonads. In this study, we focused on the effect of social conditions (i.e. mating opportunities) on the expression of some morphological traits and on their plasticity in the protandrous simultaneously hermaphrodite Ophryotrocha diadema. We investigated whether in O. diadema the morphological traits, which are dimorphic in Ophryotrocha dioecious species – upper-jaw size, prostomium size, body size and number of rosette glands − are plastic when they respond to variations in social conditions and whether variations in these traits are associated with variations in male and/or female reproductive success. Plasticity of the traits was analysed during both the juvenile and the adult phases in order to check whether phenotypic plasticity is limited to the developmental phase or can be manifested throughout the whole lifespan of the animals. Our results showed that the number of rosette glands, the upper-jaw size and the prostomium size are traits that are plastic in O. diadema. Indeed, the number and size of these traits changed according to the variation of social conditions. However, we found no association between the plastic morphological traits and male or female reproductive success.

Plant zonation patterns reflected by the differences in plant growth, biomass partitioning and root traits along a water level gradient among four common vascular plants in freshwater marshes of the Sanjiang Plain, Northeast China

Water level is important in determining plant zonation distribution patterns in freshwater wetlands. However, the role of whole-plants’ morphological traits in response to water level gradients in accounting for the distribution of marsh species is far from clear. Four typical dominant vascular plants with different distribution patterns (high-elevation species Deyeuxia angustifolia, mid-elevation species Carex lasiocarpa and Glyceria spiculosa, and low-elevation species Carex pseudocuraica) in freshwater marshes in the Sanjiang Plain of Northeast China were treated with four static water level conditions (−5, 0, +5, and +15cm relative to the soil surface), and each plant’s growth characteristics, biomass allocation and root traits were investigated. With the rising water level, the growth of D. angustifolia performed worse than other species, whereas the total biomass, plant height and relative growth rate (RGR) of C. pseudocuraica increased steadily. Compared with the other three species, C. pseudocuraica showed a distinct pattern with increasing water levels in the biomass allocation to photosynthetic and non-photosynthetic organs, as well as for coarse and fine roots. Flooding stress significantly reduced root diameter and C/N ratio but simultaneously increased the specific root length (SRL), specific root area (SRA) and root nitrogen concentration (RNC) for both coarse roots (1st order, >0.2mm) and fine roots (2nd and 3rd orders, <0.2mm). However, these root parameters of C. pseudocuraica exhibited an opposite response with the increase in the water level between such two different branching orders. Our results indicate that wetland plants could acclimate to flooding stress through resource trade-off among different tissues and trait-coordinated variation within the root system. Furthermore, species-specific shifts in above- and below-ground traits could help to better understand and predict the vegetation zonation patterns in temperate freshwater wetlands.

Crescimento e distribuição de raízes de soja em diferentes densidades de plantas

A cultura da soja apresenta alta plasticidade fenotípica da parte aérea, alterando a sua morfologia em função da densidade de plantas. No entanto, os seus efeitos no crescimento e na distribuição de raízes no perfil do solo ainda não estão elucidados. O objetivo do presente trabalho foi avaliar o efeito de três densidades de plantas de soja sobre variáveis relacionadas ao crescimento de raízes, em diferentes camadas de solo e posições (linha e entrelinhas). Foram conduzidos dois experimentos na safra 2014/2015 em Londrina, PR, um com a cultivar BRS 359 RR e outro com a cultivar BMX Potência RR. O delineamento experimental foi de blocos casualizados, com três repetições e parcelas subsubdivididas. Nas parcelas principais, foram alocadas três densidades de semeadura (150, 300 e 450 mil sementes ha-1); nas subparcelas, cinco camadas de solo (0-10, 10-20, 20-30, 30-40 e 40-50 cm); e nas subsubparcelas, três posições (linha, entrelinha à esquerda e entrelinha à direita). O aumento da densidade de plantas provoca a formação de raízes mais finas, com tendência de haver maior ocupação das entrelinhas e das camadas subsuperficiais do solo, mas a magnitude dessa resposta é dependente da cultivar

Growth, morphological traits and mycorrhizal colonization of fine roots respond differently to nitrogen addition in a slash pine plantation in subtropical China

Background and aims Growth, morphological traits, and mycorrhizal colonization of fine roots show high degree of plasticity in response to changes in nutrient availability, causing shifts in root nutrient-foraging strategy. However, little is known about how this plasticity associated with root branching orders respond to atmospheric nitrogen (N) deposition in subtropical coniferous forests. Methods We used soil block sampling method to examine the responses of six key root functional parameters (including three morphological traits (specific root length (SRL), root tissue density (RTD), and root diameter), two growth indices (total root length (TRL) and biomass) on an areal basis across five root orders, and ectomycorrhizal (EM) tip colonization) to different doses and species of N addition in a slash pine (Pinus elliottii) plantation in subtropical China. Results TRL, root biomass in all root orders, and EM tip colonization increased significantly with N addition. However, SRL, RTD, and root diameter did not change in any root orders. In comparison to low doses of N input, high doses of N input exerted greater effects on lower-order roots. In regard to species of N added, stronger responses in lower-order roots were observed under ammonium-based than nitrated-based N input. Foliar P content was significantly decreased and stoichiometric N:P ratio was markedly increased in response to high dose of ammonium-based N input. Conclusions Fine root growth and EM tip colonization displayed higher degree of plasticity than morphological traits in response to N addition. The plastic responses were not root-order dependent, but dependent on both N dose and species, especially for ephemeral lower-order roots that are mostly like to be the main nutrient acquisition structures. Our results imply that while N limitation was alleviated by exogenous N input, P limitation may persist or even be exacerbated, thus causing an increase of absorptive root length, biomass, and dependence on ectomycorrhizae for nutrient acquisition in subtropical slash pine plantation forests.

Nitrogen Uptake and Use Efficiency of Invasive Spartina alterniflora and Native Phragmites australis: Effect of Nitrogen Supply

AbstractPlant roots play a vital role in acquisition of resources, while their potential role in plant successful invasions has been largely overlooked. Spartina alterniflora is an invasive grass that has expanded dramatically on the Chinese coast, outcompeting native plant Phragmites australis and resulting in serious negative consequences for invaded ecosystems. In this study, we evaluated differences between S. alterniflora and P. australis in nitrogen uptake and use efficiency as well as plasticity of nitrogen characteristics and additional morphological traits in response to increased nitrogen supply. We grew two species in monoculture and mixed‐culture pots under two nitrogen levels in a greenhouse environment. After growing for 17 weeks, plants were exposed to 15N‐labeled ammonium chloride for 48 h and harvested to compare the uptake of nitrogen. Invasive S. alterniflora showed significantly higher biomass, root mass ratio, and nitrogen use efficiency but lower 15N uptake rate than native P. australis in both monocultures and mixed‐cultures, regardless of nitrogen levels. Nitrogen supply significantly increased biomass, total 15N uptake, and 15N uptake rate but decreased root mass ratio and nitrogen use efficiency of both species regardless of culture form, with biomass and total 15N uptake of S. alterniflora responding more strongly to nitrogen supply than the corresponding traits of P. australis when the two species were grown in a mixed culture. Our results suggested that the greater root mass ratio and nitrogen use efficiency of S. alterniflora played a greater role than root nitrogen capture capacity in its successful invasion.

Genetic vs. non‐genetic responses of leaf morphology and growth to elevation in temperate tree species

SummaryAt high elevation, temperate trees generally exhibit adaptive genetic differentiation in their morphological and physiological traits. On account of this directional selection, we hypothesized that tree populations growing near their upper cold elevational limits exhibit lower phenotypic plasticity of growth and leaf morphological traits in response to temperature changes than populations growing at lower elevations.Seedlings of six common deciduous tree species originating from low and high elevations were transplanted into eight common gardens along two elevational gradients in the Swiss Alps. The aim of the experiment was to evaluate the genetic differentiation in growth and leaf morphology between populations from low and high elevations and to quantify the phenotypic plasticity of these traits to temperature changes.In contrast to growth that decreased with increasing elevation, leaf mass per area (LMA) showed no significant change with elevation of common garden, except for a decrease inLaburnum alpinumfor both low‐ and high‐elevation provenances. Interestingly, leaf density was found to decrease with elevation of the gardens for all species. Genetic differentiation between low‐ and high‐elevation populations was found in both leaf morphology and growth: high‐elevation populations tended to have slower growth rate than low‐elevation populations, while no consistent trend was found forLMAacross species. Interestingly, forAcer pseudoplatanusandFraxinus excelsiorhigh‐elevation populations exhibited a lower phenotypic plasticity of growth in response to temperature compared to lower populations, whereas no interactions between the elevation of a provenance and the elevation of the garden was detected for the four other species.Hence, during young life stages, the expected increase in tree growth in future warmer climates might be lower in populations living in the coldest part of the species distribution range in temperate species such asAcer pseudoplatanusandFraxinus excelsior, but similar in other tree species, disregarding other environmental changes.

Physiological and morphological short-term responses to light and temperature in two Nothofagus species of Patagonia, South America

The study of plant responses to environmental stress factors is essential for management of plant systems and for anticipating their response to climate change. The main goal of this study was to determine morphological and physiological responses of Nothofagus obliqua and N. nervosa seedlings to light and temperature, two of the main stress factors acting in their current natural distribution in NW Patagonia. Responses to light were evaluated analyzing growth and survival, as well as morphological and physiological traits related to them, in seedlings subjected to three contrasting light conditions (full-sun conditions, 50% of sunlight and 20% of sunlight) during one growth season. Temperature photosynthetic responses were evaluated in seedlings subjected to temperature treatments between −5 and 40°C for 2 and 4 h. Growth rate and biomass partition were similar between light treatments in both species. High apical meristem damage and decreased photosynthetic capacity of preformed leaves were observed under full-sun conditions, suggesting that high light levels have a deleterious effect on plant yield. Both species produced neoformed leaves during the growing season with better photosynthetic capacity than preformed leaves under full sun conditions, contributing to plant acclimation. Almost no plasticity was observed in morphological traits in response to shade. Both species differed in optimum temperature for photosynthesis, with a wider temperature range at which high photosynthesis is maintained in N. obliqua. In both species the higher values of net photosynthetic rate were found at higher temperatures than the mean annual temperature of its current natural distribution range. Under no water-stress conditions, future higher temperatures could increase carbon fixation of these species, with a little advantage of N. obliqua if temperature variance is high. Synergy effect of various environmental stress factors, particularly considering cultivation of these species outside their current natural distribution sites require further studies.

Selection on phenotypic plasticity of morphological traits in response to flooding and competition in the clonal shore plant Ranunculus reptans

Adaptive evolution of phenotypic plasticity requires that plastic genotypes have the highest global fitness. We studied selection by spatial heterogeneity of interspecific competition and flooding, and by temporal heterogeneity of flooding on morphological plasticity of 52 genotypes of the clonal shore plant Ranunculus reptans. Competition reduced clone size, rosette size, leaf length and stolon internode thickness. Flooding had similar effects and reduced competition. Differences in selection between environments imply potential for either local adaptation or for indirect evolution of phenotypic plasticity. We also detected direct selection for plastic reductions in internode length in response to flooding and for a plastic increase in internode length in response to competition. Plastic responses of some morphological traits to flooding were in line with selection thereon, suggesting that they indeed are adaptive and might have evolved in response to direct selection on plasticity.

Plastic responses to temporal variation in moisture availability: consequences for water use efficiency and plant performance

The ability to appropriately modify physiological and morphological traits in response to temporal variation should increase fitness. We used recombinant hybrid plants generated by crossing taxa in the Piriqueta caroliniana complex to assess the effects of individual leaf traits and trait plasticities on growth in a temporally variable environment. Recombinant hybrids were used to provide a wide range of trait expression and to allow an assessment of the independent effects of individual traits across a range of genetic backgrounds. Hybrid genotypes were replicated through vegetative propagation and planted in common gardens at Archbold Biological Station in Venus, Florida, where they were monitored for growth, leaf morphological characters, and integrated water use efficiency (WUE) (C isotope ratio; delta(13)C) for two successive seasons. Under wet conditions only leaf area had significant effects on plant growth, but as conditions became drier, growth rates were greatest in plants with narrow leaves and higher trichome densities. Plants with higher WUE exhibited increased growth during the dry season but not during the wet season. WUE during the dry season was increased for plants with smaller, narrower leaves that had higher trichome densities and increased reflectance. Examination of alternative path models revealed that during the dry season leaf traits had significant effects on plant growth only through their direct effects on WUE, as estimated from delta(13)C. Over the entire growing season, plants with a greater ability to produce smaller and narrower leaves with higher trichome densities in response to reduced water availability had the greatest growth rate. These findings suggest that plants making appropriate changes to leaf morphology as conditions became dry had increased WUE, and that the ability to adjust leaf phenotypes in response to environmental variation is a mechanism by which plants increase fitness.