[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 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.

[Allelopathic potential and physiological mechanism of Oryza sativa L. under phosphorus deficiency stress].

In this paper, allelopathic rice PI312777 (PI) and non-allelopahtic rice Lemont (Le) were grown in the nutrient solution with two levels of phosphorus (P) supply, and their allelopathic effects on Echinochloa crus-galli L. were studied. The results showed that under phosphorous deficiency stress, the inhibitory effect of PI on E. crus-galli root growth had an obvious increase. After growing in the nutrient solution with low P supply (0.5 mg x L(-1)) for 5, 10 and 15 days, the inhibitory rate of PI on E. crus-galli root dry matter increased by 5.64%, 3.89% and 12.13%, respectively, while that of Le did not show the same trend, compared with normal P supply. With low P supply for 5, 10 and 15 days, PI allelopathic effect on the leaf POD activity of E. crus-galli increased by 20.19%, 15.47% and 6.68%, IAAoase activity increased by 18.08%, 17.71% and 12.50%, while NR activity increased by 13.89%, 18.60% and 2.10%, respectively, suggesting that under P deficiency, PI enhanced its allelopathic potential through two pathways, i.e., to increase the weed POD and IAAoase activities to slow down its growth rate, and to decrease the weed NR activity to affect its N uptake.