Recovery Growth Following Water Deficits of Different Duration in Prairie Grass

Abstract

Recovery of rates of leaf emergence, leaf extension, tiller number, leaf number, leaf area and shoot dry weight per plant following water deficits lasting for between 10 and 28 days was measured in Bromus catharticus in a controlled environment. The rate of leaf extension recovered to the rate of control plants within 4-6 days of rewatering and then exceeded the control rate for up to 28 days. During this time, four or five new leaves emerged. The maximum rate of leaf extension for individual leaves during recovery was up to 20% higher than rates typical for leaves of the same insertion on well watered control plants. During an initial recovery phase which followed the 28-day water deficit, and which lasted 20 days from rewatering, the rates of increase in tiller number, leaf number, and leaf area per plant were greater than control rates by 38, 48 and 51%, respectively. Rates for these components of yield then normalized. Relatively small differences among treatments were measured for rate of shoot dry matter accumulation. Final shoot dry weight was approximately proportional to the number of 'non- drought' days, which were defined as those days on which the leaves showed no sign of wilting. This also corresponded to day-time leaf water potentials higher (less negative) than - 1400 kPa.