ABSTRACT
The ubiquity of water as the primary biochemical solvent reflects life’s origin in aqueous solutions, and enables the enhanced reaction rates that underpin life on Earth. Terrestrial plant–water relations therefore exert significant control over the dynamics of unmanaged terrestrial ecosystems and the productivity of agricultural ecosystems. Metabolism occurs in aqueous solutions, so the properties of water are fundamental to life. Small dam schemes have been used to control water flow for agriculture almost from its very beginning. Ancient civilizations across the world had extensive schemes to control, capture, and distribute water, in significant part for agriculture. Plants have had to evolve hydraulic systems that can deliver water at increasing leaf conductance. The axial transport of water through the xylem from root to shoot generally meets much less resistance than radial transport across the root. Water flux across roots has to meet transpiration demand, and control of it is a major determinant of plant susceptibility to dehydration.
