[Effects of enhanced UV-B radiation on culm charateristics and lodging index of two local rice varieties in Yuanvang terraces under field condition].

Two local rice varieties (Baijiaolaojing and Yuelianggu) were cultivated in situ in Yuanyang terraces, China, in 2012 and 2013 to investigate the effect of enhanced UV-B radiation condition (0, 2.5, 5.0 and 7.5 kJ . m2) on internode characteristics including length, culm diameter, culm wall thickness from the first to the fourth internode, as well as the lodging index. The results showed that UV-B radiation had no significant influence on internode length and culm, but significanly reduced the culm wall thickness, with that of the fourth internode region decreased by 11.6% to 19.6% under 7.5 kJ . m2 UV-B radiation. The enhanced UV-B radiation increased the lodging index of rice varieties, making them more prone to lodging. The fourth internode had the highest lodging index which was higher than the lodging critical value (200). The decrease in culm wall thickness due to the enhanced UV-B radiation could be responsible for the increasing lodging risk of rice varieties grown in Yuanyang terraces.