Abstract:

Taking relative sensitive variety YZX and relative tolerant variety XY-12 as materials, photosynthetic rate of rice, which were pot cultured in the soil treated with cademium, was measured during full heading stage. The results fitted by the non-rectangular hyperbola model, the rectangular hyperbola model and the YE Zi-piao new model were used to reveal the impact of cademium on the different rice leaf photosynthesis light response characteristics and compared. The results showed that under cadmium treatment, the net photosynthetic rate of two rice varieties decreased. There were differences in the effects of Cd on light response characteristic parameters of two rice varieties, the intrinsic quantum yield, maximum photosynthetic rate, and saturation light points were affected by cadmium lower than the control, and the light compensation point was greatly increased. Cadmium promoted the dark respiration of YZX variety but XY-12 variety demonstrated inhibition. Generally, YZX variety was more sensitive to cadmium than XY-12 variety. All the three models performed well in reflecting the light response characteristic of photosynthesis, but there were differences between the results of three models of light response characteristic and measured values. The maximum net photosynthetic rate (P_max) for non-rectangular hyperbola model and rectangular hyperbola model calculated much higher parameter values than the measured ones, and the dark respiration rate (Rd) and light compensation point (LCP) much lower than the measured value. The light saturation point (LSP), determined by the traditional liner regression method, was far lower than the measured value. The light response characteristic parameters for the YE Zi-piao new model was the most close to the measured value. And it was good to make up for the shortcomings of other models. Therefore, the YE Zi-piao new model had greater advantages in reflecting light response characteristics of photosynthesis in leaves of rice under cadmium treatment.

Key words: Rice, Cadmium, Light response curve, Light response characteristic parameters, Model