Supraoptimal Temperature Effects upon Agrostis palustris

Agrostis palustris turfs cut weekly at 1.3 cm were subjected to successive four‐week periods with day‐night temperature regimes of 20–10, 25–15, 30–20, 35–25 and 40–30°C. Plants grown at 40–30°C exhibited a growth character distinctly different from those grown at 20–10°C. They were more upright and bristle‐like in growth habit. The percentage dry weight of leaf blade tissue increased 67% and weight per unit area increased 53% between 20–10 and 40–30°C. Reduced leaf blade width was noted first at 30–20°C while leaf blade length reduction first occurred at 35–25°C. Weekly yields were significantly reduced at the supraoptimal temperature regimes of 35–25 and 40–30°C. Chlorophyll content was lowest at 20–10 and 40–30°C, the lowest and highest temperature regimes studied. Shoot density appeared to decrease under the 35–25°C regime, but no dead plants were observed. The apparent decrease in shoot density was attributed to the upright growth habit. Density decreased at 40–30°C upon death of individual plants. A community of grass plants maintained as a turf was found to change in form quite rapidly in response to temperature.