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| Effects of UV-B radiation on rice roots-exudated LMWOAs and rhizospheric microorganism quantities in a paddy field of Yuanyang Terraces, Yunnan Province |
| Received:November 15, 2015 |
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| KeyWord:elevated UV-B radiation;Yuanyang Terrace;rice rhizosphere;low-molecular-weight organic acids;microbial quantity |
| Author Name | Affiliation | E-mail | | HE Yong-mei | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | ZHAN Fang-dong | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | WU Jiong | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | GAO Zhao-hua | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | LI Yuan | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | liyuan@ynau.edu.cn |
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| Abstract: |
| A local rice variety, "Baijiaolaojing", was grown in a paddy field in the Yuanyang Terrace under ambient and elevated(5.0 and 10.0 kJ·m-2) ultraviolet-B(UV-B, 280~315 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. Rhizospheric 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 rhizospheric 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 correlations were found between oxalic acid exudation and the quantities of rhizospheric azotobacteria and cellulose-decomposing bacteria, between succinic acid and azotobacteria; and very significant positive correlations between succinic acid exudation and the quantity of bacteria, 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. |
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