Abstract
Chrysanthemum morifolium plantlets (C3) were cultured on 1/2MS with 3% sucrose and without sucrose in vessels under moistened gas with 0.04% CO2 and either 5, 10, 15 or 21% O2 (the rest being N2) for 30 days. The net photosynthetic rate (NPR) increased and the photorespiration rate decreased with the decrease of O2 concentrations, especially, on the medium without sucrose. Ribulose-1, 5-bisphosphate carboxylase (RuBPCase) activity and content, chlorophyll content and soluble protein content of the plantlets increased in response to the enhancement of NPR in low O2 concentrations. RuBPCase activity and content and NPR were significantly higher in plantlets grown on the medium without sucrose than on the 3% medium, but chlorophyll and soluble protein content were not higher. Photorespiration and dark respiration increaed in plantlets on the medium with 3% sucrose. The results indicate that the repression of photorespiration at low O2 concentrations would promote photosynthesis in C3 plantlets in vitro cultured photoautotrophically.
