Plasticity In Traits Research Articles

Plasticity of the anatomical traits of Rhododendron L. (Ericaceae) leaves and its implications in adaptation to the plateau environment

Abstract There is a variety of Rhododendron plants in the Tibetan plateau; yet, little is known about their variations in leaf anatomical traits and the implications for environmental adaptation. In this study, we investigated the anatomical traits of leaves in five Rhododendron L. species from Shergyla Mountain on the Tibetan plateau. The results showed that the five species have notable intraspecific and interspecific differences in the thickness of leaves, cuticle thickness, adaxial epidermis thickness, palisade parenchyma thickness, spongy parenchyma thickness, and tightness of leaf palisade parenchyma (P < 0.05). There are autocorrelations among these anatomical traits of the leaves, indicating the existence of synergistic changes. The interspecific variations in leaves’ anatomical structures illustrated their spectrum of plasticity to habitat heterogeneity. Our findings demonstrated that Rhododendron plants have developed typical ectopic leaves to adapt to harsh conditions of the Tibetan plateau.

Complementary trade-offs between plant roots and mycorrhizal fungi traits across four alpine grasslands along a precipitation gradient in the northern Xizang Plateau

Abstract The mechanisms of plant adaptation to environmental gradients have been the focus of ecological research, with environmental stresses driving coordinated or differentiated regulation of plant functional traits. Plant resource acquisition involves root trait plasticity and mycorrhizal symbiosis. However, root trait plasticity along precipitation gradients and root-mycorrhizal trade-offs remain unclear. We conducted community surveys along a west-east precipitation gradient in four natural grassland communities (alpine desert steppe, ADS; alpine steppe, AS; alpine meadow steppe, AMS; and alpine meadow, AM) on the plateau in northern Xizang Plateau. Six key root traits (root diameter, RD; root dry matter content, RDMC; root tissue density, RTD; specific root length, SRL; root branching intensity, RBI; and root length colonization percentage, RLC) were measured in 18 alpine plant species to investigate the coordination and trade-offs between root traits and mycorrhizal fungi along the precipitation gradient. Our results showed community-level declines in RDMC, RD, RTD, and RLC with increasing precipitation, contrasting with elevated RBI and SRL. Functional groups exhibited distinct patterns: grasses and legumes demonstrated root-mycorrhizal trade-offs, sedges displayed synergy, and forbs showed inconsistent responses. Divergent trends in plant root traits and mycorrhizal fungi were observed at the species level. Alpine plants in humid eastern meadows favored root elongation, while those in arid western desert steppe relied on radial growth and mycorrhizal fungal cooperation for resource acquisition. These findings highlight varied root absorption strategies among alpine plants along environmental gradients, supporting the importance of ecological niche diversification in maintaining alpine ecosystem diversity and stability.

Trait plasticity and adaptive strategies of vascular epiphytes to a large-scale experimental reduction of fog immersion in a tropical montane cloud forest.

Tropical montane cloud forests (TMCF) are characterized by frequent fog immersion and host a rich epiphyte community. Epiphytes rely on atmospheric inputs of water, making them susceptible to reductions in fog immersion, which are predicted with climate change. We experimentally reduced the fog in a Peruvian TMCF to examine the ability of eight abundant species of vascular epiphytes in the families Orchidaceae, Bromeliaceae, Ericaceae, Dryopteridaceae, Piperaceae and Clusiaceae to respond to reduced fog immersion via plasticity in morphological and physiological traits. We found that across all species combined, fog reduction led to a decrease in stomatal length (SL) and foliar water uptake (FWU) capacity. Disterigma sp. (Ericaceae), an epiphytic shrub, reduced leaf thickness (LT) with fog reduction, likely a result of reduced water storage. Comparing across species, we found significant differences in traits related to drought tolerance, including the turgor loss point (TLP), relative water content at TLP (RWCTLP) and osmotic potential at full saturation (πo) indicating that two studied fern species in the Elaphoglossum genus (Dryopteridaceae) may tolerate low water potentials. Our results revealed that some vascular epiphyte species can adjust certain morphological and physiological traits to acclimate to reduced fog immersion. Additionally, our findings support differences in ecological strategies across epiphyte functional groups to either maximize water storage in specialized tissue or to increase drought tolerance. These results give early indications of the likely vulnerability of some epiphyte groups to projected shifts in fog immersion across TCMFs globally.

Extensive Variation in Thermal Responses and Toxin Content Among 40 Strains of the Cold-Water Diatom Pseudo-nitzschia seriata-In a Global Warming Context.

Phytoplankton are single-celled microorganisms with short generation times that may comprise high diversity in genetic and phenotypic traits, allowing them to acclimate to changes rapidly. High intraspecific genetic variation is well known in phytoplankton, but less is known about variation in physiological traits. To investigate variability and plasticity in genetic, morphological, and physiological traits of the toxigenic diatom genus Pseudo-nitzschia in a global warming scenario, we exposed 40 strains of the cold-water P. seriata to different temperatures (2 °C, 6 °C and 10 °C). The maximum growth rate and cellular toxin content showed extensive intraspecific variation, whereas morphological and genetic variation was minor. Thermal reaction norms showed a general increase in growth rate with increasing temperature; however, three distinct types of thermal responses were found among the 40 strains. All 40 strains contained toxins (domoic acid) in both exponential and stationary growth phase, and toxin content increased significantly with temperature. Most strains (>87%) contained measurable levels of domoic acid at all three temperatures. In conclusion, P. seriata shows extensive intraspecific variation in measured physiological traits like growth and toxin content, a variation exceeding the response of each strain to increases in temperature. Intraspecific variation in harmful species thus needs attention for the future understanding of food web dynamics, as well as the management and forecasting of harmful blooms.

Responses of leaf traits of plantation tree species in South China under long-term nitrogen deposition

Abstract Nitrogen (N) deposition alters the soil environment for forest trees, particularly in tropical regions, leading to variations in leaf traits. However, the adaptive responses of plantation tree species to chronic N deposition, via leaf traits modifications, remains poorly understood. We conducted a decade-long experiment involving N additions in two typical plantations dominated by Eucalyptus urophylla (EU) and Acacia auriculiformis (AA) in South China, to investigate species-specific leaf trait plasticity under N deposition. Our results showed that long-term N addition did not affect N and phosphorus (P) concentrations, sugar and starch levels, intrinsic water use efficiency (iWUE) and leaf mass per area (LMA), but lowered leaf total C content in both EU and AA. Moreover, it resulted in divergent traits between them, showing an increase in tannin and phenolics but a decrease in leaf water content (LWC) in AA but no such variations in EU. These differential responses were attributed to their unique leaf traits that EU contains high chemical defensive compounds and AA, as an N-fixing tree species, exhibits higher resource levels. The reduced leaf total C was redirected towards defense, without compromising iWUE through unchanged sugar and starch levels, particularly in AA. Our findings demonstrate that long-term N addition intensifies the coupling between C and water, resulting in a shift in C allocation in trees. Consequently, long-term N addition triggers different defensive strategies: a conservative defense in EU and an active defense in AA. This offers new insights into the adaptive mechanisms of forest plants under global change scenarios.

Cryptic genetic variation in brain gene expression precedes the evolution of cannibalism in spadefoot toad tadpoles

The origins of novel behaviors are poorly understood, despite behavior's hypothesized roles in evolution. One model, "genetic accommodation," proposes that selection on ancestral phenotypic plasticity may precede the evolution of novel traits. A critical assumption of genetic accommodation is that ancestral lineages possess heritable genetic variation for trait plasticity that is revealed in novel environments, thereby providing the raw materials for subsequent refinement of the novel trait in derived lineages. Here, we use a combination of behavioral and RNA-seq approaches to test this assumption in the context of a novel tadpole behavior: predatory cannibalism. Cannibalism evolved in the spadefoot genus Spea, where an invertebrate diet induces a carnivorous tadpole morph capable of consuming live conspecific tadpoles. In contrast, closely related Scaphiopus tadpoles do not induce this carnivorous phenotype. Through species comparisons, we found that ancestral Spea likely expressed behavioral plasticity and harbored latent (i.e., "cryptic") genetic variation in brain gene expression plasticity associated with cannibalism-inducing cues. Further, we found that this cryptic genetic variation includes genes specifically associated with a dietary response and cannibalism in derived Spea. Our results suggest that novel behaviors, alongside novel morphologies, can evolve via the process of genetic accommodation. More generally, our results provide key evidence for the plausibility of genetic accommodation, revealing that cryptic genetic variation-the raw material for the evolution of novel traits-exists in natural populations at the level of gene expression.

Evolution of plasticity and character displacement in a fluctuating environment.

Species that compete for the same resource may undergo ecological character displacement (CD), where the phenotype of each species evolves to deviate from its optimum in the absence of competition. As natural habitats are rarely static, interspecific competition is likely to occur in environments that fluctuate over time. Such environmental fluctuations can in turn cause the evolution of phenotypic plasticity for traits mediating the competition. However, the interplay of environmental fluctuations, evolution of plasticity, and character displacement, has been little investigated. We use a quantitative genetic model to study theoretically how a randomly fluctuating environment and evolution of plasticity influence the outcome of ecological CD between two competing species. We show that environmental fluctuations make the conditions for CD more stringent, requiring stronger competitive selection relative to stabilizing selection. This occurs because environmental fluctuations reduce the average population size, and thereby competition intensity. Evolving plasticity can restore CD by buffering the impact of environmental fluctuations through phenotypic tracking, to a degree that depends on environmental predictability. Somewhat paradoxically, competition that favors phenotypic divergence among species can cause convergence in plasticity, when this reduces the load caused by fluctuations in phenotypic divergence. Our results shed light on how competition and plasticity influences evolution of the fundamental niche in a fluctuating environment.

Small-scale genetic differentiation in mean flowering time, but not in plasticity, along a geothermal heating gradient.

Genetic differentiation in traits is assumed to frequently occur in response to divergent natural selection. For example, developmental traits might respond to differences in climate. However, little is known about when and at which spatial scales environmental differences lead to genetic differentiation, and to what extent there is genetic differentiation also in trait plasticity. Using a crossing design and a greenhouse heating experiment, we investigated genetic differentiation in thermal sensitivity of flowering time in a perennial herb along small-scale gradients in geothermal soil heating in Iceland. We found additive genetic variation in both flowering time and thermal plasticity of flowering time. Genetic differentiation in the median flowering date of individuals showed a counter-gradient pattern; flowering being earlier at higher greenhouse temperatures, while at a given temperature individuals originating from warmer soils flowered later than individuals from colder soils. We found no corresponding pattern for plasticity, suggesting that genetic differentiation in phenology in response to soil heating has occurred through changes in trait means rather than in plasticity. Findings such as these identifying genetic trait differentiation along an environmental gradient are key to understand how environmental variation can drive the process of local adaptation, and to predict responses to future environmental changes.

Patterns of Adaptation to Drought in Quercus robur Populations in Central European Temperate Forests.

In order to predict the future of European forests, it is crucial to assess the potential of the dominant perennial species to adapt to rapid climate change. The aim of this study was to reconstruct the pattern of distribution of drought tolerance in Quercus robur in the current center of the species' range. The distribution and plasticity of drought-related traits in German populations of Q. robur were assessed and the effects of spring phenology and species demographic history on this distribution were evaluated using a drought stress experiment in a common garden. We show that variation of drought-related functional traits, including intrinsic water use efficiency (iWUE), leaf osmotic potential (π), and rate of drought-induced defoliation, is high within Q. robur populations. However, frequency of trees with high estimated constitutive drought tolerance increases with decreasing water availability in the regions of population origin, indicating local adaptation to drought. A strong correlation between the distribution of drought-related traits and spring phenology observed in Q. robur suggests that adaptation to water deficit interacts with adaptation to the strong seasonality of the central European climate. The two processes are not influenced by the history of post-glacial recolonisation of central Europe. The results of this study provide a basis for optimistic prognoses for the future of this species in the center of its current distribution range.

Call production and wingbeat coupling is flexible and species-specific in echolocating bats.

Echolocation and flight are two key behavioral innovations that contribute to the evolutionary success and diversification of bats, which are classified phylogenetically into two suborders: Yinpterochiroptera and Yangochiroptera. Considerable research has identified a coupling between call production and wingbeat in flying bats, although only a few have quantified the relationship and all were restricted to bats from the suborder Yangochiroptera. Here, we quantitatively compared the coupling between call production and wingbeat in two representative species of bats, Hipposideros pratti of the suborder Yinpterochiroptera and Myotis pilosus of the suborder Yangochiroptera, under identical experimental settings. We found that (1) both species exhibited the temporal coupling of call production and wingbeat; (2) the degree of coupling is species-specific, with M. pilosus showing a tighter coupling between call timing and wingbeat cycle than H. pratti; (3) the coupling is a plastic trait, as evidenced by the effect of environmental clutter in H. pratti; and (4) there is no evidence that the coupling of call production and wingbeat limits the source level control in either species. We suggest that the coupling between call production and wingbeat is flexible and species-specific, which may not compromise precise echolocation control in bats.

Geographic Variation in Epigenetic Responses to Hypoxia in Deer Mice (Peromyscus maniculatus) Distributed Along an Elevational Gradient.

Lowland and highland Peromyscus maniculatus populations display divergent, locally adapted physiological phenotypes shaped by altitudinal differences in oxygen availability. Many physiological responses to hypoxia seem to have evolved in lowland ancestors to offset episodic and localised bouts of low internal oxygen availability. However, upon chronic hypoxia exposure at high elevation, these responses can lead to physiological complications. Therefore, highland ancestry is often associated with evolved hypoxia responses, particularly traits promoting tolerance of constant hypoxia. Environmentally induced DNA methylation can dynamically alter gene expression patterns, providing a proximate basis for phenotypic plasticity. Given each population's differential reliance on plasticity for hypoxia tolerance, we hypothesised that lowland mice have a more robust epigenetic response to hypoxia exposure, driving trait plasticity, than highland mice. Using DNA methylation data of tissues from the heart's left ventricle, we show that upon hypoxia exposure, lowland mice chemically modulate the epigenetic landscape to a greater extent than highland mice, especially at key hypoxia-relevant genes such as Egln3. This gene is a regulator of the gene Epas1 that is frequently targeted for positive selection at high elevation. We find higher methylation among wild highland mice at gene Egln3 compared to wild lowland mice, suggesting a shared epigenetic ancestral response to episodic and chronic hypoxia. These findings highlight each population's distinct reliance on molecular plasticity driven by their unique evolutionary histories.

Physiological and Ecological Responses of Anoectochilus formosanus to Different Light Intensities

Anoectochilus formosanus is a rare medicinal plant with anti-inflammatory, antioxidant, hepatoprotective, and immunomodulatory properties. Its morphological growth and accumulation of medicinal compounds are strongly influenced by environmental factors such as light intensity. To investigate the physiological and ecological responses of Anoectochilus formosanus to varying light intensities, we examined physiological, morphological, and growth parameters across different growth stages under five different light intensities. Correlation, plasticity, and principal component analysis (PCA) were performed. The results showed that high and low light intensities altered physiological and biochemical indicators at different stages. Leaf area, fresh weight, dry weight, stem thickness, and non-photochemical quenching (NPQ) increased with increasing light intensity, whereas chlorophyll fluorescence parameters (Fv, Fm, and Fv/Fm) and flavonoid content decreased, reflecting reduced light capture and consumption under high light intensities. The phenotypic plasticity index of the morphological traits (<0.5) was lower than that of the photosynthetic physiological parameters (>0.5), indicating a greater plasticity of the photosynthetic traits. Biomass indicators—leaf area ratio and relative growth rate—were strongly correlated, driving the response to light intensity. Growth and biomass allocation peaked at moderate light intensity (70 μmol·m−2·s−1). These findings highlight the conservative strategy employed by A. formosanus for slow carbon use under low-light conditions, and the adventurous strategy employed for rapid carbon use under strong light, offering insights into efficient cultivation practices.

Temporal constraints on leaf-level trait plasticity for next-generation land surface models.

Dynamic global vegetation models (DGVMs) are essential for quantifying the role of terrestrial ecosystems in the Earth's climate system, but struggle with uncertainty and complexity. Eco-evolutionary optimality (EEO) theory provides a promising approach to improve DGVMs based on the premise that leaf carbon gain is optimized with resource costs. However, the timescales at which plant traits can adjust to environmental changes are not yet systematically incorporated in EEO-based models. Our aims were to identify temporal constraints on key leaf photosynthetic and leaf functional traits, and develop a conceptual framework for incorporation of temporal leaf trait dynamics in EEO-based models. We reviewed scientific literature on temporal responses of leaf traits associated with stomata and hydraulics, photosynthetic biochemistry, and morphology and lifespan. Subsequent response times were categorized from fast to slow considering physiological, phenotypical (acclimation), and evolutionary (adaptation) mechanisms. We constructed a conceptual framework including several key leaf traits identified from the literature review. We considered temporal separation of dynamics in the leaf interior to atmospheric CO2 concentration (ci:ca) from the optimal ci:ca ratio χ(optimal), and dynamics in stomatal conductance within the constraint of the anatomical maximum stomatal conductance (gsmax). A proof-of-concept was provided by modelling temporally-separated responses in these trait combinations to CO2 and humidity. We identified 15 leaf traits crucial for EEO-based modelling and determined their response mechanisms and timescales. Physiological and phenotypical response mechanisms were considered most relevant for modelling EEO-based trait dynamics, while evolutionary constraints limit response ranges. Our conceptual framework demonstrated an approach to separate near-instantaneous physiological responses in ci:ca from week-scale phenotypic responses in χ(optimal), and to separate minute-scale physiological responses in stomatal conductance from annual-scale phenotypic responses in gsmax. We highlight an opportunity to constrain leaf trait dynamics in EEO-based models based on physiological, phenotypical and evolutionary response mechanisms.

Plastic Responses of Iris pumila Functional and Mechanistic Leaf Traits to Experimental Warming.

Phenotypic plasticity is an important adaptive strategy that enables plants to respond to environmental changes, particularly temperature fluctuations associated with global warming. In this study, the phenotypic plasticity of Iris pumila leaf traits in response to an elevated temperature (by 1 °C) was investigated under controlled experimental conditions. In particular, we investigated important functional and mechanistic leaf traits: specific leaf area (SLA), leaf dry matter content (LDMC), specific leaf water content (SLWC), stomatal density (SD), leaf thickness (LT), and chlorophyll content. The results revealed that an elevated temperature induced trait-specific plastic responses, with mechanistic traits exhibiting greater plasticity than functional traits, reflecting their role in short-term acclimation. SLA and SD increased at higher temperatures, promoting photosynthesis and gas exchange, while reductions in SLWC, LDMC, LT, and chlorophyll content suggest a trade-off in favor of growth and metabolic activity over structural investment. Notably, chlorophyll content exhibited the highest plasticity, emphasizing its crucial role in modulating photosynthetic efficiency under thermal stress. Correlation analyses revealed strong phenotypic integration between leaf traits, with distinct trait relationships emerging under different temperature conditions. These findings suggest that I. pumila employs both rapid physiological adjustments and longer-term structural strategies to cope with thermal stress, with mechanistic traits facilitating rapid adjustments and functional traits maintaining ecological stability.

The Role of Phenotypic Plasticity and Within-Environment Trait Variability in the Assembly of the Nectar Microbiome and Plant-Microbe-Animal Interactions.

The study of the rules that govern the relationship between phenotypic plasticity, genetic structure, and ecological success has traditionally focused on animals, plants, and a few model microbial species, whereas non-model microorganisms have received much less attention in this regard. The floral nectar of angiosperms is an ephemeral, island-like habitat for different highly adapted yeasts and bacteria. The growth of microorganisms in floral nectar depends on their ability to efficiently use the available nutrients and tolerate challenging physicochemical conditions, including high osmotic pressures, unbalanced carbon-to-nitrogen ratios, and the presence of diverse defensive compounds of plant origin. The production of alternative phenotypic states in response to environmental cues (i.e., phenotypic plasticity) or independently from these (within-environment trait variability) might be particularly relevant in floral nectar, in which rapid growth is needed for population persistence and to improve the chance of animal-mediated dispersal. In this article, we use the nectar microbiome as an example to encourage further research on the causes and ecological consequences of phenotypic plasticity and within-environment trait variability of microbes. We review previous work on the mechanisms and potential ecological significance of the phenotypic plasticity and within-environment trait variability displayed by nectar yeasts and bacteria. Additionally, we provide an overview of some topics that require further attention, including potential trade-offs between different traits that are relevant for adaptation to dynamic nectar environments and the direct and indirect effects of phenotypic variability on the fitness of plants, flower-visiting animals, and other nectar microbes. We conclude that further research on the causes and ecological consequences of phenotypic plasticity and within-environment trait variability of microbes is essential to get a better understanding of community assembly and the establishment of ecological interactions in floral nectar and other similar highly dynamic and strongly selective microbial habitats.

The role of phenotypic plasticity of physiological and agronomic traits on the adaptation of spring wheat genotypes to Mediterranean environments

The role of phenotypic plasticity of physiological and agronomic traits on the adaptation of spring wheat genotypes to Mediterranean environments

Phenological sensitivity of Bromus tectorum genotypes depends on current and source environments.

Plants respond to their environment with both short-term, within-generation trait plasticity, and long-term, between-generation evolutionary changes. However, the relative magnitude of plant responses to short- and long-term changes in the environment remains poorly understood. Shifts in phenological traits can serve as harbingers for responses to environmental change, and both a plant's current and source (i.e., genotype origin) environment can affect plant phenology via plasticity and local adaptation, respectively. To assess the role of current and source environments in explaining variation in flowering phenology of Bromus tectorum, an invasive annual grass, we conducted a replicated common garden experiment using 92 genotypes collected across western North America. Replicates of each genotype were planted in two densities (low = 100 seeds/1 m2, high = 100 seeds/0.04 m2) under two different temperature treatments (low = white gravel; high = black gravel; 2.1°C average difference) in a factorial design, replicated across four common garden locations in Idaho and Wyoming, USA. We tested for the effect of current environment (i.e., density treatment, temperature treatment, and common garden location), source environment (i.e., genotype source climate), and their interaction on each plant's flowering phenology. Flowering timing was strongly influenced by a plant's current environment, with plants that experienced warmer current climates and higher densities flowering earlier than those that experienced cooler current climates and lower densities. Genotypes from hot and dry source climates flowered consistently earlier than those from cool and wet source climates, even after accounting for genotype relatedness, suggesting that this genetically based climate cline is a product of natural selection. We found minimal evidence of interactions between current and source environments or genotype-by-environment interactions. Phenology was more sensitive to variation in the current climate than to variation in source climate. These results indicate that cheatgrass phenology reflects high levels of plasticity as well as rapid local adaptation. Both processes likely contribute to its current success as a biological invader and its capacity to respond to future environmental change.

Genetic Variation of Growth Traits and Seed Production in a Patagonian Native Pasture in Semiarid Rangelands Under Different Environmental Settings.

Rangelands play a crucial socioeconomic and environmental role worldwide. In South America, desertification and overgrazing has led to their deterioration and declining productivity. Breeding programs that use native forage species of economic and ecological importance, such as Festuca pallescens (St. Yves) Parodi, may provide locally adapted germplasm that enhances productivity without threatening local biodiversity. These programs may even promote the conservation of native species. To this end, we characterized the phenotypic variation of nondestructive variables (growth and reproductive traits) related to forage and seed production during spring and early summer (growth and reproductive periods). Plants from ten populations were grown under common garden conditions in two environmental settings (sites) over two years. By early summer of the second year, most populations maintained a consistent relative performance with higher values for basal diameter, height and synflorescence production at site 2. This suggests more favorable environmental conditions for the species and highlights their potential for enhancing both seed and forage production. The growth and reproductive traits were probably largely influenced by micro-environmental cues (i.e., soil type and moisture), showing predominantly plastic patterns. The populations displaying phenotypic plasticity and above-average values for both traits were selected for further evaluation in breeding programs.

Structural-functional signs of Typha angustifolia leaves plasticity depending on the growth conditions

The results of the study of leaf anatomy and leaf epidermal ultrastructure of the heliophytic plant Typha angustifolia L. (Typhaceae), which grew in natural conditions: in the water on the bank of the Venetian Strait of the Dnipro River (Kyiv) and on land near the Strait, using light microscopy and scanning electron microscopy are presented. The common and distinctive features of the anatomical signs and the ultrastructure of epidermal cells of T. angustifolia leaves in the phase of vegetative growth of plants were revealed. The anatomical and morphological characteristics of leaves of two ecotypes of T. angustifolia that grew in water and on the terrestrial soil did not differ; the type of mesophyll and the presence of two zones in the epidermis (the zone of cоnvex vault and stomata zone) is stable features for this species. Differences in the size of the leaf blade, the density of stomata, and the density of wax coating on the surface of epidermal cells of the cоnvex vault zone, and also the presence of amorphous silicon in the cell walls of the epidermis are adaptive, and plastic traits that vary depending on the conditions of cattail growth. Besides, scanning electron microscopy of the leaf epidermis of cattail grown in water and on terrestrial soil revealed that growth in water causes the formation of stomata that are deepened into the epidermis, as well as the presence of closed stomata on the lower epidermis, while in the leaves of terrestrial cattail, all stomata were open and located at the same level as the regular epidermal cells. It is assumed that the deepening of stomata into the epidermis contributes to the optimal water balance of leaves under wave action of Strait and high humidity around the leaves of air-water cattail. The obtained results are discussed as a manifestation of phenotypic plasticity and the possible use of epidermal wax as an adaptive marker of heliophytes for growth in different water supply conditions.

Tree species mixing causes shifts in nitrogen acquisition and utilization strategies of Mongolian pine and Simon poplar

BackgroundEstablishing mixed-species plantations is increasingly recognized as an important silvicultural measure because they are more productive than monocultures. This over-yielding is attributed to the complementary resource use between component tree species, yet it remains largely unknown whether and how component tree species adjust nutrient acquisition and utilization strategies to achieve complementary nutrient use. Here, we measured soil nitrogen (N) availability and transformation rates, leaf N resorption efficiency and proficiency, and nine root morphological, physiological and mycorrhizal traits tightly related to N acquisition in 20-year-old pure and mixed stands of Pinus sylvestris var. mongolica (Mongolian pine) and Populus simonii (Simon poplar), northeast China.ResultsTree species mixing had negative effects on soil nitrate concentration and net N mineralization rate, but had positive effects on absorptive fine root biomass. Compared to growing alone, Mongolian pine in mixed stands had higher leaf N resorption efficiency, and produced more absorptive fine roots with more-efficient morphological features in nutrient acquisition characterized by higher specific root length and lower root tissue density. Additionally, Simon poplar had greater root length density, root area index, and the relative abundance of ectomycorrhizal fungi with genetic potential to produce class II peroxidases in mixed than pure stands.ConclusionsThese findings highlight that component species express high plasticity in nutrient acquisition and utilization traits in response to tree species mixing, and suggest that this high plasticity could be responsible for the over-yielding of mixed-species plantations.