水稻生育期内红壤稻田氨氧化微生物数量和硝化势的变化

利用荧光定量PCR(Real-timePCR)技术,通过特异引物检测amoA基因拷贝数分析了水稻不同生育期红壤稻田土壤中氨氧化细菌(Ammonia oxidizing bacteria,AOB)和氨氧化古菌(Ammonia oxidizing archaea,AOA)的数量变化,并测定了土壤潜在硝化势。结果显示:红壤稻田土壤中AOA数量显著高于AOB,二者比例在1.6～120.7之间;红壤稻田根层土中AOA数量显著高于表土,随水稻生长根层和表土中AOA数量均逐渐增加,且根层土中增加幅度更大;在水稻生长前期表土中AOB数量较多,孕穗期后根层土中AOB数量显著增加且高于表土。水稻生长期内土壤潜在硝化势也具有逐渐增加趋势,且根层土潜在硝化势增加幅度更大。根层土中潜在硝化势与AOB和AOA数量均呈显著正相关,而表土中潜在硝化势只与AOA数量存在显著正相关。研究表明,红壤稻田土壤中AOA数量更为丰富,且与硝化作用的关联程度更为密切,证实了氨氧化微生物在红壤稻田土壤微生物组成及其生态系统功能中的重要性。

Abundance of ammonia-oxidizer and potential nitrification rate of quaternary red-clay paddy soil during rice growth

The amount of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in quaternary red-clay paddy soils during rice growing season were determined by real-time polymerase chain reaction (RT-PCR) using amoA gene assay copies. The potential nitrification rate of soil was investigated too. Results show that AOA is the dominant ammonia-oxidizer in quaternary red-clay paddy soils, with AOA/AOB amoA gene ratio range of 1.6~120.7. There is a higher abundance of AOA in root-zone soils than in surface soils. The amount of AOA in surface and root-zone soils increases with growth stage of rice, which is more evident in root-zone soils. There is a higher abundance of AOB in surface soils than in root-zone soils at the early growth stage, with obvious enhancement of root-zone AOB after booting stage. Root-zone AOB is much abundant at the late growth stage of rice. Potential nitrification rate gradually increases with time during rice growing season, especially in root-zone soils. Potential nitrification rates in root-zone soils exhibit significant positive correlations with AOB and AOA amounts. However, potential nitrification rates in surface soils are only significantly positively correlated with AOA amount. The findings of this study indicate the dominance of AOA, which is more strongly related with quaternary red-clay paddy soil nitrification. The results further demonstrate the importance of ammonia-oxidizers in microbial composition and ecological functions of paddy soils.