Effects of temperature fluctuation, red and far-red light and nitrate on seed germination of five grasses.
Seed germination in Agrostis capillaris, Holcus lanatus, Poa trivialis, Cynosurus cristatus and Festuca rubra was investigated in the dark at temp. ranging from 5 to 30°C for 12 h, alternating with 12 h at 20°C. Germination was opt. for all spp. at 20/10°C. C. cristatus and F. rubra showed min. germination at 30/20°C while H. lanatus and A. capillaris germinated least well when there was little alternation of temp. The effects of exposure to a fully unshaded situation or deep canopy shade was simulated by treatment with red or far-red light, resp., before transfer to the different temp. In general, red light stimulated and far-red light inhibited germination, particularly in A. capillaris; germination of C. cristatus was unaffected. Treatment with 0.002 smallcap˜M potassium nitrate increased germination in all spp. except C. cristatus. Exposure to daylight and alternating temp. of 20/10°C resulted in full germination in all spp. except A. capillaris which showed a GA requirement. The spp. which form persistent seed banks beneath grasslands (A. capillaris, H. lanatus, P. trivialis) showed more specific germination requirements than C. cristatus and F. rubra which occur only transiently in the seed bank.