【摘要】 随着全球气候变化的不断加剧,大气CO2浓度呈明显增加趋势,这将间接影响土壤-植物-微生物系统的氮循环过程.为研究典型水稻土壤反硝化细菌对CO2浓度升高的响应规律和机制,借助水稻密闭培养箱,运用实时荧光定量聚合酶链式反应(Real-Time q PCR)分子技术,设置不施氮(0 mg/kg)和常规施氮(100 mg/kg) 2个处理,研究CO2倍增对水稻不同生长期土壤关键反硝化功能细菌(nar G、nir K和nir S型)丰度的影响.结果表明:①在2种施氮水平,CO2倍增显著促进了水稻分蘖期、孕穗期、扬花期和成熟期水稻根系生长(增幅为2. 96%～28. 4%)、地上部生物量增加(增幅为7. 1%～107. 3%)以及成熟期籽粒干质量的增加(增幅为19. 5%和38. 0%),具有显著的增产效应.②反硝化细菌丰度对CO2倍增的响应与生育期及施氮水平有关,CO2倍增在2个施氮水平均抑制分蘖期反硝化细菌的繁殖,显著增加孕穗期反硝化细菌数量;在水稻扬花期,CO2倍增促进了施氮处理nar G和nir S型反硝化细菌数量的增加,在成熟期抑制未施氮处理下nar G、nir K和nir S型反硝化细菌的生长.另外,nar G、nir K、nir S型反硝化细菌丰度整体表现为nar G>nir S>nir K,且随水稻的生长,其在成熟期的丰度均呈降低趋势. nir K和nir S基因同属亚硝酸还原酶,但nir S基因丰度高于nir K,且对CO2倍增和施氮的响应有所差异.研究显示,CO2倍增可显著增加水稻生长和产量,不同施氮水平对稻田土壤反硝化细菌丰度的影响存在差异.更多还原

【Abstract】 The atmospheric CO₂ concentration has an obvious rising trend with the increasing global climate change,which will indirectly affect the nitrogen cycling process of the soil-plant-microbe system. In order to investigate the mechanisms of the rising CO₂ effect on denitrifying bacteria in paddy soil,we used the airtight rice incubator and the real-time PCR technology to investigate the effect of the elevating CO₂ concentration on the abundance of nar G-,nir K-and nir S-containing bacterial communities at two nitrogen levels. The results showed that the elevating CO₂ concentration significantly increased the biomass of roots and aboveground parts（ 2. 96%-28. 4%,7. 1%-107. 3%） at the tillering,booting,blooming and maturing stages either without nitrogen or with regular nitrogen application.Meantime,the dry weight of grains at the two levels of nitrogen application increased（ 19. 5%,38. 0%） at the maturing stage,indicating that the rice yield was stimulated by the elevating CO₂ concentration; Response of denitrifying bacteria to elevating CO₂ concentration was related to growth stage and nitrogen application level: the elevating CO₂ decreased the number of denitrifying bacteria at tillering stage,but increased that at booting stage; The elevating CO₂ obviously increased the abundance of nar G-,nir S-containing communities in nitrogen application treatment at the booting stage,and decreased the abundance of nar G-,nir K-and nir S-containing communities at the maturing stage. In addition,the abundance of nar G-,nir K-and nir S-containing communities were nar G>nir S>nir K,and they decreased with the increase of rice growth. Both nir K and nir S genes belong to nitrite reductase,but the abundance of nir S gene was higher than that of nir K,and their responses to elevating CO₂ and nitrogen application were different. Overall,the results showed that the elevating CO₂ significantly increased rice growth and yield,and the effects of CO₂ on the abundance of denitrifying bacteria in paddy soil were different with different nitrogen application.更多还原