Effects of different irrigation treatments on photosynthesis of Tieguanyin tea plants

By using chlorophyll fluorescence kinetics technique, the effects of different irrigation intervals, i.e., 5 d (T1), 10 d (T2), 15 d (T3), 20 d (T4), and 25 d (T5), on the photosynthesis of 2-year Tieguanyin tea plants were investigated in the field, with no irrigation as the control. The results showed that the leaf water potential and chlorophyll content decreased with increasing irrigation interval, while the net photosynthesis (P) increased first and decreased then, reaching its highest value (15.55, micromol x m(-2) x s(-1)) in treatment T2. The ratio of the variable to maximal fluorescence (F(v)/F(m)), the variable fluorescence quenching (deltaF(v)), and the variable fluorescence quenching rate (deltaF(v)/F(o)) all got the highest in treatment T2, being 0.844, 342.5, and 4.03, respectively. The initial fluorescence (F(o)) decreased with increasing irrigation interval, while a reverse changing trend of F(o) was observed in the control, demonstrating that PS II reaction center was damaged by drought stres