[Regulation function of calcium on photosynthesis of Dimocarpus longana Lour. cv. wulongling under simulated acid rain stress].

Studies on the regulation function of calcium on photosynthesis of Dimocarpus longana under simulated acid rain stress showed that the photoreduction activity of chloroplasts was activated when the concentration of calcium ion in reaction medium ranged from 0 to 5 mmol.L-1, and peaked at the 3.5 mmol.L-1, which was 41.90% higher than that of control. Conversely, the activity of chloroplasts reduced 26.06% in the reaction medium with a concentration of 2 mmol.L-1 EGTA, as compared with the control. Both Mn2+ and Mg2+ could inhibit photoreduction activity. The photophosphorylation activity increased when the concentration of calcium ion in reaction medium ranged from 0 to 6 mmol.L-1, and peaked at the 4.5 mmol.L-1, while superoxidase dismutase (SOD) activity rose from 0 to 6 mmol.L-1 and peaked at 6 mmol.L-1. Calcium ion with the concentration of both 10 mmol.L-1 and 15 mmol.L-1 could increase the content of chlorophyll(Chl), stabilize the membrane structure of leaf discs, and reduce the membrane permeability under simulated acid rain with pH value of 3.0. The effect in 15 mmol.L-1 were better than in 10 mmol.L-1. However, the injury of acid rain to leaves was strengthened when the concentration of calcium was higher than 20 mmol.L-1. Net photosynthesis rate (Pn) rose when leaves sprayed with 15 mmol.L-1 Ca(NO3)2 before treatment of acid rain stress of pH 2.5. All of the results represented the excellent protection function of calcium on D. longana leaves under simulated acid rain.