Does homeostasis or disturbance of homeostasis in minimum leaf water potential explain the isohydric versus anisohydric behavior of Vitis vinifera L. cultivars?

Abstract

Due to the diurnal and seasonal fluctuations in leaf-to-air vapor pressure deficit (D), one of the key regulatory roles played by stomata is to limit transpiration-induced leaf water deficit. Different types of plants are known to vary in the sensitivity of stomatal conductance (gs) to D with important consequences for their survival and growth. Plants that minimize any increase in transpiration with increasing D have a tight stomatal regulation of a constant minimum leaf water potential (Ψ_leaf); these plants are termed as ‘isohydric’ (Stocker 1956). Plants that have less control of Ψ_leafhave been termed as ‘anisohydric’ (Tardieu and Simonneau 1998). Isohydric plants maintain a constant Ψ_leaf by reducing gs and transpiration under drought stress. Therefore, as drought pushes soil water potential (Ψ_soil) below this Ψ_leaf set point, the plant can no longer extract water for gas exchange. Anisohydric plants allow Ψ_leaf to decrease with rising D, reaching a much lower Ψ_leaf in droughted plants relative to well-watered plants (Tardieu and Simonneau 1998), so this strategy produces a gradient between Ψ_soil and Ψ_leaf that allows gas exchange to continue over a greater decline in Ψ_soil. Thus, anisohydric plants sustain longer periods of transpiration and photosynthesis, even under large soil water deficit, and are thought to be more drought tolerant than isohydric species (McDowell 2011).

Citation

Domec, Jean-Christophe; Johnson, Daniel M. 2012. Does homeostasis or disturbance of homeostasis in minimum leaf water potential explain the isohydric versus anisohydric behavior of Vitis vinifera L. cultivars? Tree Physiology 32:245–248.