Relations between stomatal closure, leaf turgor and xylem vulnerability in eight tropical dry forest trees

This study examined the linkage between xylem vulnerability, stomatal response to leaf water potential (Psi(L)), and loss of leaf turgor in eight species of seasonally dry tropical forest trees. In order to maximize the potential variation in these traits species that exhibit a range of leaf habits and phenologies were selected. It was found that in all species stomatal conductance was responsive to Psi(L) over a narrow range of water potentials, and that Psi(L) inducing 50% stomatal closure was correlated with both the Psi(L) inducing a 20% loss of xylem hydraulic conductivity and leaf water potential at turgor loss in all species. In contrast, there was no correlation between the water potential causing a 50% loss of conductivity in the stem xylem, and the water potential at stomatal closure (Psi(SC) ) amongst species. It was concluded that although both leaf and xylem characters are correlated with the response of stomata to Psi(L,) there is considerable flexibility in this linkage. The range of responses is discussed in terms of the differing leaf-loss strategies exhibited by these species.