Abstract:

【Objective】In order to reveal the regulation function of calcium on photosynthesis of tomato leaves under sub-high temperature stress, the effects of CaCl2 on photosynthesis and fluorescence of PS Ⅱand PS Ⅰ under sub-high temperature stress were studied. 【Method】In order to select a appropriate concentration, the tomatoes grown in greenhouse were pretreated with 0, 10 and 30 mg?L-1CaCl2 during the period of sub-high temperature, and then photosynthesis, chlorophyll fluorescence of PS Ⅱand PS Ⅰ were analyzed for the tomatoes pretreated with CaCl2, with the appropriate concentration, Ca2+ chelator EGTA and CaM antagonist TFP. 【Result】 The net photosynthetic rate(Pn) increased at three concentrations of CaCl2 treatments under sub-high temperature stress, especially in the treatment of 10 mg?L-1CaCl2. Under sub-high temperature stress, the maximal photochemical efficiency (FPSII) of PS Ⅱ, photochemical quantum yield of PS Ⅱ and PS Ⅰ[Y(Ⅱ) and Y(Ⅰ)], quantum yield of non-photochemical energy dissipation in PS I due to donor side limitation [Y(ND)] in the tomato leaves pretreated with CaCl2 were much higher than that of control, while quantum yield of non-photochemical energy dissipation in PS I due to acceptor side limitation [Y(NA)] was much less than that of the control. EGTA and TFP treatments had negative effect.【Conclusion】The treatment of 10 mg?L-1 CaCl2 could improve photosynthesis of tomato leaves under sub-high temperature stress. And calcium played an important role in regulating stomatal movements and protecting PS Ⅰ PS Ⅱ not to be injured.

Key words: tomato, photosynthesis, chlorophyll fluorescence, PS Ⅱ, PS Ⅰ, calcium