Control of Plant Water Potential in Water Stress Studies

Abstract

Weed seedlings were grown in a composite soil contained within a semipermeable membrane that allowed the development of consistent, reproducible levels of plant water stress. The water content of membrane units with a 1-cm cross section equilibrated most rapidly, within 3 to 5 days, with the external osmotic solution. The water potential (Ψ) of green foxtail grown in plant growth membrane units was curvilinearly related to the external polyethylene glycol (PEG) osmotic solution Ψ. This relationship permitted nondestructive estimation of plant Ψ. Green foxtail shoot growth in membrane units was reduced by decreasing Ψ of the external PEG osmotic solution and was completely arrested by high water stress induced by an −800 kPa external osmotic solution. The technique makes possible precise control and relatively rapid adjustment in the level and duration of plant Ψ of seedlings and small plants.