ABSTRACT
Inherent in the term ‘‘osmotic potential’’ is a measure of the capacity to do work. Typically in plant systems, that work involves the movement of water across cellular membranes and tissues for hydration, expansion growth, leaf movements, and stomatal opening. The osmotic potential of a cell is determined primarily by the concentration of solutes confined within the symplastic water volume (cytoplasm þ vacuole). Therefore, solute transport across cellular membranes and cellular metabolism are essential components of osmotic regulation. Passive concentration of solutes due to dehydration or inhibition of metabolism under severe environmental conditions also can contribute to the ‘‘adjustment’’ of cellular osmotic potential. Whether active or passive, the accumulation of solutes has been shown to support expansion growth, maintain photosynthesis, and improve reproductive success under severe drought conditions in a number of plant systems. This article presents a brief overview of the physical origin of the term osmotic potential and its application to quantifying the response of plants to changing environmental conditions.
