The seasonal pattern of growth and production of a temperate C4 species, Cyperus longus

Collins, R. P. and Jones, M. B. 1986. The seasonal pattern of growth and production of a temperate C4 species, Cyperus longus.—i. exp. Bot. 37: 1823-1835. Growth and production of the temperate C4 species Cyperus longus L. was measured throughout a growing season in an established plot in Eastern Ireland. The maximum standing live biomass reached was 2-5 kg m~2. Estimates of unit leaf rate (ULR) and leaf area index (LAI) were made. The product of these quantities gave the crop growth rate (CGR) each week. C. longus was found to maintain high values of LAI throughout the summer, with a maximum value of about 13 in early August. CGR reached a peak in early July. The optimum LAI was 11-6. Temperatures at five levels in the plant canopy, and the amount of solar radiation intercepted by the canopy were measured continuously during the summer. The mean daily rate of leaf extension was positively correlated with the mean daily air temperature above the canopy but the temperature coefficient of the process was low compared with other temperate species. The percentage of solar radiation intercepted by the canopy increased rapidly in early summer, and canopy closure had occurred by mid-June. Rates of net photosynthesis were measured on young and old leaf material in situ at the time of peak LAI. In young leaves the maximum rates of net photosynthesis were higher than those published for a range of temperate C3 species, but similar to those found in another temperate C4 species, Spartina townsendii.