Plasticity of plant and leaf traits in response to environmental factors

Plants are exposed to heterogeneity in the environment where new stress factors (i.e. climate change, land use change and invasiveness) are introduced. In particular, climate change has been shown to affect abundance and distribution of plant species, as well as plant community composition (1). Nevertheless, adaptation to global change could require the evolution of a number of different traits that may be constrained by correlations between them (2). Thus, it is necessary to identify plant functional traits in which plasticity is likely to be a determinant in plant response to environmental factors change. Moreover, it is important to fully understand the ecological consequences at ecosystem level considering that species with a greater adaptiveness may be more likely to survive in novel environmental conditions. Plasticity is recognized to be a major source of phenotypic variations because it influences natural selection and consequently, patterns of diversification among populations and species (3). Nevertheless, the extent to which phenotypic plasticity may facilitate survival under changing environmental conditions still remains largely unknown. It is important to identify plant traits in which plasticity may play a determinant role in response to environmental changing as well as a fully understanding the ecological consequences at ecosystem level (4). Leaf area index (LAI) is one of the most important variables of ecosystem structure for global researches, and it can be used as a basic descriptor of vegetation to establish the tolerance threshold to perturbations (5). Plants growing in stress conditions tend to have a conservative leaf morphological pattern to avoid the production of structures too expensive to be sustained (6). Moreover, morphological traits are linked to an enhanced plant capacity to grow in forest understories (7) by having an important role in resource acquisition (8). Among plant traits, specific leaf mass area (LMA) is at the center of a nexus of covering traits affecting the ecology of plant species (9-11). It is tightly associated with leaf life-span, both traits being pivotal in the carbon-fixation strategy (12). LMA variability is attributed to changes in both leaf thickness and density (13). Moreover, LMA is related to photosynthesis (14) which generally scales linearly with the leaf biomass investment per unit leaf area making the anatomy the main driver of the light-saturated rate of photosynthesis (13). In spite of a wide variability in both stomatal density and size there is a strong relationship between them independently by the plant groups (grasses and non-grasses) and for different stomatal distributions on either one or both leaf surfaces (15). Moreover, stomatal size and density determine the maximum leaf diffusive conductance to CO2 and water vapor (14) and hence the photosynthetic capacity. Photosynthesis is the basis of carbon assimilation and ecosystem productivity. The ratio between leaf respiration to photosynthesis is indicative of the leaf carbon balance (13). Plasticity for physiological traits may allow plants to grow and reproduce in spatially or temporally variable environments (5). Morphological, anatomical and physiological traits may have a different role in plant adaption to the environmental factors variability. Bibliografia 1) Drenovsky R.E., Grewell B.J., D’Antonio C.M. et al. (2012) A functional trait perspective on plant invasions. Ann. Bot. 110: 141-153. 2) Etterson J. Shaw R.G. (2001) Constraint to adaptive evolution in response to global warming. Science 294: 151-154. 3) Sultan S.E. (2004) Promising directions in plant phenotypic plasticity. Perspect. Plant Ecol. Evol. 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