[Photosynthetic characters and fluorescence parameters of different grape stocks under water stress]

The study showed that water stress decreased the net photosynthetic rate (Pn), stomatal conductance (Gs), Tr transpiration rate (Tr), maximum fluorescence (Fm), ratio of variable to maximum fluorescence (Fv/Fm), and actual activities of PS II (phiPS II), but increased the minimal fluorescence (Fo). The alterations of test parameters differed with grape stocks. Under adequate water supply and mild water stress, the Pn of 3309C was higher than that of 1103P and 420A, while the chlorophyll fluorescence parameters of these three stocks changed a little. Under moderate water stress,the Pn of 1103P was higher than that of 420A and 3309C,the Fo of 3309C increased by 17.1% while Fv/Fm decreased by 8.5%, and the Fo of 1103P increased by 6.8% while Fv/Fm decreased by 5.8%. Under severe water stress,the Pn of 1103P was the highest (5.6 micromol x m(-2) x s(-1)), which was 24% higher than that of 3309C, and the water use efficiency of 1103P was about 1.95 times as high as that of 3309C. The Fo of 3309C increased by 36.2% while Fv/Fm decreased by 20.1%, and the Fo of 1103P increased by 9. 9% while Fv/Fm decreased by 10.2%. It was implied that there was a close correlation between drought-resistance and the alteration of photosynthetic characters and chlorophyll fluorescence parameters, of which, the correlation index of Fv/Fm and Pn was the highest (r = 0.9883).