A Simple Instrument for Measuring Leaf Extension in Grasses, and its Application in the Study of the Effects of Water Stress on Maize and Sorghum

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Abstract
The design of a simple instrument to monitor leaf expansion in grasses is described. The instrument was used to compare the effects of water stress on leaf extension of two cultivars of maize and sorghum. The effect of withholding water for 3 days was an appreciable reduction in the rate of leaf expansion in both plants, particularly during the light period. In well-watered plants of both species, leaf extension continued at a steady rate even when leaf turgor fell to around 0.1 MPa. In water-stressed maize plants, leaf turgor during the light period fell to zero and leaf growth ceased. When turgor was restored, following stomatal closure, leaf extension resumed at a slow rate. In unwatered sorghum plants, leaf turgor remained at a value greater than 0.1 MPa but the rate of leaf extension was significantly reduced. The reduction in leaf turgor in the unwanted plants resulted partly from an increase in solute potential.