Safety-efficiency tradeoffs? Correlations of photosynthesis, leaf hydraulics, and dehydration tolerance across species

The tradeoffs between carbon assimilation and hydraulic efficiencies and drought-tolerance traits on different scales are considered a central tenet in plant ecophysiology; however, no clear tradeoff between these traits has emerged in previous studies using woody angiosperms or grasses by investigating several hydraulic tolerance and gas exchange efficiency and/or water transport efficiency traits. In this study, we measured numerous efficiency, resistance, and leaf anatomical traits, including light-saturated gas exchange, leaf hydraulic vulnerability curves, pressure-volume curves, and leaf anatomical traits, in seven species with diverse drought tolerance. A substantial variation in photosynthetic rate, stomatal conductance, mesophyll conductance, maximum leaf hydraulic conductance (K-max), mesophyll anatomical traits, and leaf vein density across species was observed. Both mesophyll conductance and K-max were related to leaf anatomical traits, but other gas exchange traits were decoupled from K-max. Although the efficiency and tolerance traits varied widely across estimated species, no clear trade-off between safety traits and efficiency traits was observed. These findings suggested that postulated leaf-level drought tolerance-carbon assimilation and hydraulic efficiency tradeoff does not exist among distant species and that the fact that different leaf anatomical traits determine efficiency and tolerance capacity might contribute to the lack of such tradeoffs.

Automated summary

This study investigated the tradeoffs between carbon assimilation and hydraulic efficiencies and drought-tolerance traits in seven species with diverse drought tolerance. The results showed significant variation in efficiency and resistance traits across species, but no clear tradeoff between safety traits and efficiency traits was observed. The findings suggest that the postulated tradeoff between drought tolerance and carbon assimilation and hydraulic efficiency does not exist among distant species.