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

Global climate change is threatening natural ecosystems worldwide. Mountain ecosystems are particularly vulnerable because range expansion or shifts are often not a viable strategy for species to adapt to the changing environment. Phenotypic plasticity, the ability of any genotype to produce a variety of phenotypes under different environmental conditions, is therefore critical in determining the ability of plant species in mountain ecosystems to acclimate to future climatic changes. Picea species, which are important components of the alpine and subalpine coniferous forests of the Northern Hemisphere, may be exposed to more frequent drought events as a result of climate change. The growth and survival of plants during these periods of drought depends on plant traits affecting the absorption, transport and conservation of water; including stomatal regulation of water loss, osmotic adjustment of the leaf turgor loss point, and the structure of the xylem and the roots. It is however unclear how the plasticity of stomatal density and size relate to the plasticity of gas exchange capacity in arid climates, especially when focusing on plants belonging to a single genus, such as Picea.

In a recent Editor’s Choice article published in AoBP, Wang et al. compared the physiology of four Picea species from different provenances and climatic conditions and quantified their phenotypic plasticity index under wet and dry conditions. The four species exhibited comparatively high photosynthetic plasticity but low stomatal plasticity when exposed to drought. The results also indicated that site-specific conditions can mask habitat variations, and thus should always be considered in studies of habitat trends in the future. Finally, the authors make a suggestion that one of the four species, P. crassifolia, would survive best under projected climate change scenarios due to enhanced water use efficiency and ratios of photosynthesis to respiration. 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.