Linking drought strategy to climate of origin in a widespread C4 grass: hydraulic traits, xylem anatomy and stomatal behaviour in Themeda triandra

Abstract

O_LIHydraulic, stomatal and anatomical traits strongly influence drought survival and productivity, but the extent to which these trait-types are coordinated and relate to climate-of-origin in herbaceous species remains poorly understood. C_LIO_LIWe quantified hydraulic, stomatal and anatomical traits in eight populations of Themeda triandra selected from diverse temperature and precipitation regimes across Australia, grown under common conditions and exposed to drought. Trait - climate-of-origin relationships were quantified using multiple linear mixed models. C_LIO_LILeaf xylem embolism resistance (P50) was unrelated to climate-of-origin precipitation. Instead, plants from drier climates exhibited lower maximum stomatal conductance, earlier stomatal closure during drought and higher stomatal safety margins (the difference between water potential at stomatal closure and P50). Plants from warmer climates exhibited greater embolism resistance and higher hydraulic conductance, along with wider vessels and lower vein density, suggesting adaptation to high evaporative demand. C_LIO_LIOur findings highlight two primary hydraulic strategies related to climate-of-origin: 1) conservative water use and drought avoidance in drier climates, and 2) embolism resistance and hydraulic efficiency in warmer climates. These findings provide new insights into the intraspecific differences in traits and adaptive strategies used by C4 grasses to persist in contrasting climates. C_LI