The relation between pressure-volume curve traits and stomatal regulation of water potential in five temperate broadleaf tree species

Key messageIn the five temperate tree species, leaf turgor loss point and the stringency of stomatal regulation are not related to each other and to the drought sensitivity of radial growth, suggesting that additional factors exert a large influence on the species' drought tolerance.ContextHow trees are responding to drought will largely determine their fitness and survival in a warmer and drier world. Much of our understanding of the drought response strategies of woody plants has been based on the study of either plant hydraulics or leaf water status dynamics or stomatal behavior, while the interaction of these components is less often studied.AimsTo examine the relatedness of leaf tissue osmotic and elastic properties to the isohydry-anisohydry syndrome in adult trees of five co-occurring broadleaf tree species (Acer pseudoplatanus L., Carpinus betulus L., Fagus sylvatica L., Fraxinus excelsior L., and Tilia cordata Mill.), which differ in the stringency of stomatal regulation.MethodsAdult trees of the five species were accessed with a mobile canopy lift and pressure-volume (p-v) curves of sun leaf tissue analyzed for species differences and seasonal change in p-v curve parameters. The extent of seasonal fluctuation in daily leaf water potential ((l)) minima served to position the species along the isohydry-anisohydry continuum.ResultsThe five species differed greatly in the bulk modulus of elasticity (epsilon) (12MPa to 33MPa) and, to a lesser extent, in leaf water potential at turgor loss ((tlp)) (-2.3MPa to -2.9MPa), exhibiting species-specific combinations of p-v parameters with the extent of (l) fluctuation. However, (tlp) and epsilon were only weakly, or not at all, related to the species' position along the isohydry-anisohydry continuum. Anisohydric Fagus sylvatica with high epsilon and relatively low (tlp) had a more drought-sensitive radial growth than the fairly isohydric Tilia cordata with low epsilon and relatively high (tlp).ConclusionThe five coexisting tree species exhibit largely different drought response strategies, which are partly determined by species differences in leaf tissue elasticity and the stringency of stomatal regulation.