[Light response of Wisteria sinensis leaves physiological parameters under different soil moisture conditions]

With two years old Wisteria sinensis as test material, this paper measured the light response of its leaves net photosynthetic rate (Pn), transpiration rate (Tr) 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 Pn, Tr and WUE had evident threshold responses to the variations of soil moisture and light intensity. To maintain the normal growth and higher levels P. and WUE of W. sinensis, soil volumetric moisture content (Wr) and relative moisture content (Wv) should be within the range of 15.3%-26.5% and 46.4%-80.3%, and the optimal Wv and Wr were 23.3% and 70.6%, respectively. W. sineasis leaves had stronger adaptability to light conditions. When the photosynthetic active radiation (PAR) was 600-1600 micromol x m(-2) x s(-1), the Pn and WUE were at higher level, and the light saturation points of Pn and WUE were all at about 800-1000 x micromol x m(-2) x s(-1). The appearance of non-stomatal limit was significantly correlated with soil moisture and light intensity. When W, ranged from 18.4% to 26.5%, the decline of Pn was mainly caused by stomatal limit rather than PAR. Out of this range, Pn 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 Wv and Wr for the normal growth of W. sinensis were 11.9% and 36.1%, respectively, and the maximal PAR was 1000 micromol x m(-2) x s(-1), the critical point of detriment in leaf photosynthetic organ.