Abstract: 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_n) increased first and decreased then, reaching its highest value (15.55 μmol·m^-2·s^-1) in treatment T₂. The ratio of the variable to maximal fluorescence (F_v/F_m), the variable fluorescence quenching (ΔF_v), and the variable fluorescence quenching rate (ΔF_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 PSⅡ reaction center was damaged by drought stress. In conclusion, irrigating per 10 d was favorable to the photosynthetic electron transport and CO₂ assimilation of the tea plants, which would enhance their photosynthesis efficiency.

Key words: Populus ×, euramericana cv. ‘Neva’, drought stress, basal diameter, seedling height, chlorophyll fluorescence, active oxygen metabolism.