Phenotypic plasticity of stomatal and photosynthetic features of four Picea species in two contrasting common gardens.

Global climate change is expected to affect mountain ecosystems significantly. Phenotypic plasticity, the ability of any genotype to produce a variety of phenotypes under different environmental conditions, is critical in determining the ability of species to acclimate to current climatic changes. Here, to simulate the impact of climate change, we compared the physiology of species of the genus Picea from different provenances and climatic conditions and quantified their phenotypic plasticity index (PPI) in two contrasting common gardens (dry vs. wet), and then considered phenotypic plastic effects on their future adaptation. The mean PPI of the photosynthetic features studied was higher than that of the stomatal features. Species grown in the arid and humid common gardens were differentiated: the stomatal length (SL) and width (SW) on the adaxial surface, the transpiration rate (Tr) and leaf mass per area (LMA) were more highly correlated with rainfall than other traits. There were no significant relationships between the observed plasticity and the species' original habitat, except in P. crassifolia (from an arid habitat) and P. asperata (from a humid habitat). Picea crassifolia exhibited enhanced instantaneous efficiency of water use (PPI = 0.52) and the ratio of photosynthesis to respiration (PPI = 0.10) remained constant; this species was, therefore, considered to the one best able to acclimate when faced with the effects of climate change. The other three species exhibited reduced physiological activity when exposed to water limitation. These findings indicate how climate change affects the potential roles of plasticity in determining plant physiology, and provide a basis for future reforestation efforts in China.