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 ( Y 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 Y L over a narrow range of water potentials, and that Y L inducing 50% stomatal closure was correlated with both the Y 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 ( Y SC ) amongst species. It was concluded that although both leaf and xylem characters are correlated with the response of stomata to Y 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. Key-words : cavitation; percentage loss of conductivity; pressure–volume curve; stomatal closure; tropical dry forest trees; turgor loss point; water potential.