高粱根系能分泌抑制土壤亚硝化细菌的物质,称为生物硝化抑制剂.在铵态氮存在时,这类物质会大量分泌,而以硝态氮为氮源时则分泌很少.目前还不清楚,这是因为不同氮素代谢的差异所引起的,还是根系吸收铵态氮后根际酸化影响了硝化作用.因此本研究通过砂培试验,用铵硝营养处理高粱根系,并且控制pH,最后收集根系分泌物,利用一种荧光标记的亚硝酸细菌来测定高粱分泌的硝化抑制剂活性,计算其分泌速率.结果发现,铵态氮是导致根系大量分泌硝化抑制剂的主要原因,并且在根际pH＜6时,硝化抑制剂的活性与分泌速率随着根系分泌氢离子数量的增加而增强.研究表明,铵态氮营养下高粱根系分泌生物硝化抑制剂高于硝态氮营养可能是高粱根系保护根际铵氧化,提高氮素利用率的一个重要生理机制.%The ability to suppress soil nitrification through the release of nitrification inhibitors from sorghum roots is termed "biological nitrification inhibitor" (BNI). It was reported that the release of BNI from sorghum roots under ammonium nutrition was much more than under nitrate nutrition. It is not understood whether the nitrogen metabolism or the rhizosphere pH in relation to the uptake of ammonium and nitrate is the effect on the release of BNI. In this study, sorghum plants were cultivated in sands with ammonium or nitrate. The root medium pH was controlled by pH-stat system and root exudation was collected to test the BNI activity and release rate by gene modified Nitrosomonas with florescence. The results showed that nitrogen form was the major factor which affected the release of BNI. Moreover, under the pH 6.0, the release of BNI was related to the release of proton by sorghum roots. Our study indicated the release of BNI by sorghum roots under ammonium nutrition rather than under nitrate nutrition might be a potential to suppress ammonium oxidation in soil, which could improve nitrogen use efficiency (NUE).
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