中文摘要：

在元阳梯田地方水稻品种——白脚老粳的拔节孕穗期、抽穗扬花期和成熟期,通过小区实验研究不同UV-B辐射强度（0、5.0、10.0 k J·m-2）对水稻根系低分子量有机酸（LMWOAs）分泌量和根际7个类群微生物数量的影响,并对水稻LMWOAs分泌量和根际微生物数量进行相关分析。结果表明：UV-B辐射增强导致水稻根系草酸和琥珀酸分泌量增加,酒石酸和苹果酸分泌量下降。水稻根际细菌、真菌、自生固氮菌、纤维分解菌、无机磷细菌和钾细菌的数量均在成熟期最大,拔节孕穗期次之,抽穗扬花期最小;但放线菌数量在拔节孕穗期最大,抽穗扬花期次之,成熟期最小。UV-B辐射增强不改变根际微生物数量随生育期进程的动态变化规律,但导致水稻根际7个类群微生物的数量显著或极显著增加。水稻根系草酸分泌量与根际自生固氮菌、纤维分解菌数量呈显著正相关,琥珀酸分泌量与自生固氮菌数量呈显著正相关,与细菌、真菌、纤维分解菌、无机磷细菌和钾细菌数量呈极显著正相关。综上可知UV-B辐射增强影响大田水稻根际微生物的数量,与其改变水稻根系低分子量有机酸的分泌量密切相关。

英文摘要：

A local rice variety,＂Baijiaolaojing＂, was grown in a paddy field in the Yuanyang Terrace under ambient and elevated（5.0 and10.0 k J·m-2）ultraviolet-B（UV-B, 280315 nm）radiation. The rice plant and rhizospheric soil were sampled at jointing-booting, headingflowering and maturity stages of rice. The exudation of low-molecular-weight organic acids（LMWOAs）including oxalic acid, succinic acid,tartaric acid, and malic acid by rice roots and the quantity of 7 microbial groups in rice rhizosphere were determined. Results showed that elevated UV-B radiation increased the concentrations of oxalic acid and succinic acid, but decreased tartaric acid and malic acid. Rhizo-spheric bacteria, fungi, azotobacteria, cellulose-decomposing bacteria, inorganic phosphobacteria and potassium bacteria were found to be the highest at the maturity stage, the next at the jointing-booting stage, and the lowest at the heading-flowering stage. The maximum rhizo-spheric actinomycetes was observed at the jointing-booting stage, the second at the heading-flowering stage, and the lowest at the maturity stage. Elevated UV-B radiation didn′t alter the dynamics of rice rhizospheric microorganism quantities along with the rice growth stages, but induced a significant or very significant increase in the quantities of the 7 microbial groups in the rice rhizosphere. Significant positive cor-relations were found between oxalic acid exudation and the quantities of rhizospheric azotobacteria and cellulose-decomposing bacteria, be-tween succinic acid and azotobacteria; and very significant positive correlations between succinic acid exudation and the quantity of bacteri-a, fungi, cellulose-decomposing bacteria, inorganic phosphobacteria and potassium bacteria. These findings indicate that elevated UV-B radiation influences rhizospheric microorganism quantity rice under field, which is closely associated with LMWOAs exudation by rice roots.