Leaf rehydration capacity: Associations with other indices of drought tolerance and environment

Clarifying the mechanisms of leaf and whole plant drought responses is critical to predict the impacts of ongoing climate change. The loss of rehydration capacity has been used for decades as a metric of leaf dehydration tolerance but has not been compared with other aspects of drought tolerance. We refined methods for quantifying the percent loss of rehydration capacity (PLRC), and for 18 Southern California woody species, we determined the relative water content and leaf water potential at PLRC of 10%, 25%, and 50%, and, additionally, the PLRC at important stages of dehydration including stomatal closure and turgor loss. On average, PLRC of 10% occurred below turgor loss point and at similar water status to 80% decline of stomatal conductance. As hypothesized, the sensitivity to loss of leaf rehydration capacity varied across species, leaf habits, and ecosystems and correlated with other drought tolerance traits, including the turgor loss point and structural traits including leaf mass per area. A new database of PLRC for 89 species from the global literature indicated greater leaf rehydration capacity in ecosystems with lower growing season moisture availability, indicating an adaptive role of leaf cell dehydration tolerance within the complex of drought tolerance traits.