Diurnal Photosynthesis and Transpiration ofFicus benjaminaL. as Affected by Length of Photoperiod, CO2Concentration and Light Level

摘要

The diurnal net photosynthesis ofFicus benjaminaL., cultivar Cleo, was studied at different daylengths (12, 18 and 24 h day#x2212;1), photosynthetic photon flux densities (40 and 120 #x3BC;mol m#x2212;2s#x2212;1PPFD) and CO2concentrations (350 and 700 #x3BC;mol mol#x2212;1). Net photosynthesis increased to a maximum after 5#x2013;6 and 6#x2013;7h of light at 12 and 18h day#x2212;1photoperiods, respectively, followed by a decrease towards the end of the photoperiod. At a photoperiod of 18 h day#x2212;1similar diurnal curves were found at 350 and 700 #x3BC;mol mol#x2212;1CO2, and at 40 and 120 #x3BC;mol m#x2212;2s#x2212;1PPFD. Five days after the photoperiod was changed from 18 to a 24h day#x2212;1the diurnal rhythm disappeared. Transpiration followed the same diurnal rhythm as that for photosynthesis. The water-use efficiency was enhanced by raising the CO2 concentration. A decrease in the CO2concentration from 700 to 350 #x3BC;mol mol#x2212;1after six days at high CO2first significantly decreased the photosynthesis, but three days later it reached the same level as that at high CO2.