Effects of moisture stress on the multiplication and expansion of cells in leaves of sugar beet.

Sugar beets were subjected to moisture stress by decreasing the water potential of the culture solution osmotically with polyethylene glycol by a known amount, ΔΨ π , and, alternatively by applying matric potential, Ψ τ , at the plant roots. Lowering the water potential at the root surface less than 200 millibars by either method resulted in significant decreases in the rate of cell multiplication. The final number of cells per leaf at Ψ π = -372 mb the final was 165% of that at Ψ π = -473 mb (ΔΨ τ = -101 mb); similarly at Ψ τ = -15 mb the final cell number was 198% of that at Ψ τ = -196 mb (ΔΨ τ = -181 mb). The mean cell volume of leaves was not significantly affected by these levels of moisture stress.