Components of growth and dark respiration of kikuyu (Pennisetum clandestinum Chiov.) at various temperatures

Growth and dark respiration were measured in dense, miniature swards of kikuyu grass grown at constant temperatures of 15, 20, 25 and 30 °C. Total respiration over the first 12 h of darkness was very high and CO2 efflux per unit surface area varied from 2.4 to 3.9 g CO2 m−2 h−1 at 15 and 30 °C respectively. Such rates were consistent with the correspondingly high net growth rates of 24 and 63 g d. wt m−2 d−1 and the heavy yields of herbage. When plants were kept in the dark, CO2 efflux subsequently declined rapidly to a lower, constant rate which was taken to be the maintenance respiration rate. The half-life of the declining phase of respiration averaged 10.9 and 6.0 h at 15 and 30 °C respectively, and was curvilinearly related to the specific maintenance respiration rate (m). The rapid decline in respiration was consistent with the low concentrations of total soluble carbohydrate and starch in the herbage. Values of m for lamina and top growth increased with temperature with a Q10 of 2.6 and 1.42 respectively, but m of stems alone was not affected by temperature. Using results from this study for kikuyu and from McCree (1974) for sorghum and white clover, it was noted that all three species have similar m when grown at temperatures which are near their respective optimums for growth.