Effects of Enhanced UV-B Radiation on the Nitrogen Metabolism of Rice Leaves and Yield of Traditional Rice in Yuanyang Terraces

PurposeTo study the effects of different UV-B radiation treatments on leaves nitrogen metabolism at different growth stages (tillering stage, jointing stage and heading stage) and yield of rice.

MethodsIn Yuanyang terrace, the local traditional rice variety Baijiaolaojing as research material was cultivated in situ, the effects of UV-B radiation (0, 2.5, 5.0 and 7.5 kJ/m²) on the activities of key enzymes of nitrogen metabolism (NR, GS and GOGAT), the content of nitrogen-containing substances (soluble protein and total free amino acids) in leaves of rice at different growth stages and yield component index (effective panicle number, panicle number, 1 000-grain weight, seed setting rate and yield) were studied.

ResultsCompared with the control, the activity of GS at heading stage, the activity of GOGAT at jointing stage, total free amino acids content at tillering and heading stage of rice were significantly increased at 2.5 kJ/m² UV-B radiation (P<0.05); the activity of NR at tillering stage, the activity of GS and GOGAT, the content of soluble protein and total free amino acids of rice were significantly increased at all growth stages (P<0.05), and the activity of NR was significantly decreased at jointing stage at 5.0 kJ/m² UV-B radiation (P<0.05); the activity of NR, GS and GOGAT, the content of soluble protein and total free amino acids were significantly decreased at different growth stages of rice at 7.5 kJ/m² UV-B radiation treatment (P<0.05). The increase of UV-B radiation inhibited the effective panicle number, grain number per panicle, seed setting rate and 1 000-grain weight of Baijiaolaojing, which led to the decrease of yield, the maximum decrease of yield was 22.8% at 7.5 kJ/m² UV-B radiation intensity.

ConclusionEnhanced UV-B radiation in the field had significant “dose + growth period” effect on the nitrogen metabolism of local rice leaves in Yuanyang terrace, middle and low intensity UV-B radiation could promote nitrogen metabolism of rice, the most significant with UV-B radiation was 5.0 kJ/m², while high intensity UV-B radiation could inhibit it. The increase of UV-B radiation resulted in the decrease of rice yield.