Genetic Variation and Phenotypic Plasticity of Leaf Minimum Water Conductance in Temperate Tree Species

The survival time of trees under drought is intimately linked to leaf minimum water conductance on the leaf surface (gmin), which determines the residual water loss of trees after maximum stomatal closure. Considerable interspecies variation of gmin in trees has been documented, but intraspecific variation resulting from genetic variation (G) and phenotypic plasticity (E) remains unclear. We measured the temperature response (T) of gmin in different provenances of four temperate tree species growing in three common gardens differing in water availability and assessed G, E and G x E of gmin and T. Additionally, we explored how leaf cuticular and stomatal traits are related to the intraspecific variation of gmin. For all species, our results showed strong T, low G and high E for gmin. Interestingly, E was more pronounced in deciduous angiosperm trees than in evergreen conifers. Surprisingly, there was significant E x T in some species. Contrary to our expectation, we found no significant effect of leaf stomatal and cuticular traits on gmin. Our study suggests that E is the most potent driver of intraspecies variation of gmin, possibly contributing to the acclimation of deciduous trees to a future hotter and dryer climate.