Abstract: With two years old Wisteria sinensis as test material, this paper measured the light response of its leaves net photosynthetic rate (P_n), transpiration rate (T_r) and water use efficiency (WUE) under different soil moisture conditions, aimed to ascertain the optimal soil moisture and light conditions of W. sinensis growth. The results showed that the P_n, T_r and WUE had evident threshold responses to the variations of soil moisture and light intensity. To maintain the normal growth and higher levels P_n and WUE of W. sinensis, soil volumetric moisture content (W_v) and relative moisture content (W_r) should be within the range of 15.3%-26.5% and 46.4%-80.3%, and the optimal W_v and W_r were 23.3% and 70.6%, respectively. W. sinensis leaves had stronger adaptability to light conditions. When the photosynthetic active radiation (PAR) was 600-1 600 μmol·m^-2·s^-1, the P_n and WUE were at higher level, and the light saturation points of P_n and WUE were all at about 800-1 000 μmol·m^-2·s^-1. The appearance of non-stomatal limit was significantly correlated with soil moisture and light intensity. When W_v ranged from 18.4% to 26.5%, the decline of P_n was mainly caused by stomatal limit rather than PAR. Out of this range, P_n was obviously affected by PAR, and the critical turning point of PAR was observed with the change from stomatal limit to non-stomatal limit. The minimal values of W_v and W_r for the normal growth of W. sinensis were 11.9% and 36.1％,respectively, and the maximal PAR was 1 000 μmol·m^-2·s^-1, the critical point of detriment in leaf photosynthetic organ.

Key words: Macrobrachium nipponense, Lead, Ultrastructure, Histochemistry