Leaf water storage determines foliar water uptake capacity along the isohydric-anisohydric continuum.

Abstract

Foliar water uptake (FWU) capacity of more anisohydric species is significantly higher than that of relatively isohydric species, yet the underlying mechanisms remain unclear. While leaf nutrient elements may modulate the FWU process, this relationship remains understudied. In this study, we investigated four typical species from the arid region of northwest China and measured their FWU parameters along with various associated traits. The results showed obvious differences in FWU capacity and traits along the isohydric-anisohydric continuum, with more anisohydric species exhibiting higher FWU capacity. Structural equation modeling revealed that leaf water storage structures were the primary factor contributing to the high FWU capacity in more anisohydric species (total effect = 0.25), followed by epidermal traits (total effect = 0.18). Leaf phosphorus affected FWU indirectly via leaf water storage structures (standardized path coefficient = 0.35). This study reveals key drivers and mechanisms underlying the FWU capacity of more anisohydric species, providing a theoretical framework for plant water use strategies in arid environments. It also helps to predict the water adaptation strategies of different plant functional types under future climate change scenarios.