Ecophysiological acclimation to different soil moistures in plants from a semi-arid sandland

In order to explore the functional significance of ecophysiological heterogeneity among three arid microhabitats (sand dune, lowland and wetland), we investigated the stomatal and photosynthetic acclimation to soil moistures in different plants of highly diversified Hunshandak Sandland, Inner Mongolia, China. Wetland was found to have the highest soil water potential (0-40 cm), while the fixed sand dune had the lowest (P<0.001). The three microhabitats appeared in a similar pattern in leaf water potential (Ψleaf), stomatal conductance (gs), photosynthetic rate (Pn) and photochemical efficiency of photosystem II(Fv/Fm) with that of soil water potential, i.e. wetland>lowland>fixed sand dune (p<0.01). Inversely, however, root depths in both fixed sand dune and lowland was 58% deeper (p<0.05) than wetland. Photosynthetic characteristics (e.g. gs, Pn, and Fv/Fm) were found to be linearly correlated with Ψleaf in fixed sand dune and lowland (p<0.05), but no linear relation among these traits were noted in wetland. Such a result indicated that water played an important role in controlling the ecophysiological process. Stomata sensitivity to leaf water potential changes increased with drought. In the microhabitats with contrasting soil water availabilities, plants may display feedback responses to the arid environment through elongating their root lengths and/or reducing their stomatal conductance.