The combination of soil drying and a high transpiration rate causes severe water stress in plants. In their Viewpoint article, Carminati et al. develop a biophysical model to describe how low soil moisture and high transpiration rates result in dramatic reduction of xylem water potential occurring across the rhizosphere as the soil dries, eventually leading to root dehydration and loss of contact with the soil.
Plants adopt several mechanisms that could attenuate such drops in water potential and facilitate root water uptake. In particular, mucilage exudation and root hairs can act as a bridge between the root surface and the adjacent bulk soil, thereby maintaining the hydraulic connection across the rhizosphere.
This paper is part of the Root Biology Special Issue.