Responses of Subterranean Clover Communities to Temperature. I. Dry Matter Production and Plant Morphogenesis

Abstract

Subterranean clover communities were grown in temperature-controlled naturally lit glasshouses at 15, 20, 25 and 30°C. Dry matter yield, leaf area and the distribution of dry matter between plant parts were determined at about 14-day intervals for up to 130 days from planting. Leaf appearance, leaf death, leaf number and growth of laterals were observed for individual plants in the community over a similar time period. A logistic growth curve was found for each temperature and crop growth rate calculated from the equation fitted for each growth curve. The optimum temperature for growth was relatively high (20-25°C) when plants were young, but decreased during growth so that after 100 days total dry matter was inversely related to temperature over the range 15-30°C. Both the rate of leaf appearance and the rate of leaf death on the main stem were constant at each temperature during the experimental period and were directly related to temperature. The number of leaves per unit ground area was determined mainly by the rates of leaf appearance and leaf death on the main stem, since the contribution of laterals was small. The proportion of stem and petiole to total dry matter increased, and that of green leaf lamina decreased, with increase in total dry matter. Neither was markedly affected by temperature. An inverse relationship between specific leaf area and temperature resulted in a lower ratio of leaf area to total dry matter at 15°C compared with that at 20, 25 or 30°C.