Lack of Tradeoff between Leaf Hydraulic Efficiency and Safety across Six Contrasting Water-Stress Tolerant Fruit Tree Species

Abstract

Water deficits affect the capacity of leaves to transport water, a process that is related to the obstruction of air in the xylem (embolism). The tolerance to this process has been negatively associated with water-transport efficiency at the xylem level across species, suggesting a tradeoff between hydraulic efficiency and safety. But there is a lack of observation at higher integration levels, i.e., organs. This study aimed to evaluate this tradeoff across six fruit tree species with a wide range of water-stress tolerance: pomegranate, olive, fig tree, mandarin, avocado, and vine. Efficiency was represented by the maximum foliar hydraulic conductance (Kmax) and stomatal conductance, whereas hydraulic security by water potential in which the leaf loses 50% of its water-transport capacity (P50), and at the point of loss of leaf turgor (Ψtlp). Results suggest that the compensation is weak or null at the foliar level. We observed that species with higher hydraulic efficiency tend to be more tolerant to leaf dehydration (higher hydraulic safety), except mandarin, which had lower Kmax and relatively higher P50. Morphological traits associated with carbon investment dynamic (leaf mass per area and petiole density) were highly correlated to water-stress tolerance across fruit tree species.