水稻内源油菜素甾醇对施氮量的响应及其对颖花退化的调控作用

为探明油菜素甾醇(brassinosteroids,BRs)是否介导氮肥对水稻颖花退化的影响。水稻品种扬稻6号和甬优2640种植于盆钵,全生育期设置3种施氮水平,观察了不同氮肥处理下水稻减数分裂期幼穗中氮含量、BRs、过氧化氢(H2O2)和总抗氧化能力(totalantioxidantcapacity,T-AOC)水平及其与颖花退化的关系。结果表明,颖花退化率的降低与稻穗中增加的24-表油菜素甾酮(24-epicastasterone,24-epiCS)和28-高油菜素内酯(28-homobrassinolide,28-homBL)含量密切相关。当稻穗的氮含量为1.25%时,幼穗中BRs(24-epiCS和28-homBL)含量显著增加,颖花退化率显著降低。稻穗中T-AOC水平与BRs含量变化趋势相同,且均与水稻颖花退化率显著负相关,而H_2O_2含量与BRs含量和T-AOC变化趋势相反。施用外源BRs(24-epiCS或28-homBL)可显著提高稻穗中内源BRs(24-epiCS和28-homBL)含量与T-AOC水平,并显著降低稻穗中H_2O_2含量和颖花退化率,施用BRs合成抑制剂则效果相反。表明BRs可以介导氮肥对水稻颖花退化的调控,在减数分裂期适宜的稻穗含氮量(1.25%)可有效提高幼穗中的BRs含量,并通过提高抗氧化能力来抑制颖花退化。

Response of endogenous brassinosteroids to nitrogen rates and its regulatory effect on spikelet degeneration in rice

In order to investigate whether and how brassinosteroids(BRs)mediate the effect of nitrogen(N)rates on spikelet degeneration of rice,rice cultivars Yangdao 6 and Yongyong 2640 were grown in pots subjected to three N rates in the whole growth periods.The contents of N,BRs,hydrogen peroxide(H2O2)and total antioxidant capacity(T-AOC)in young rice panicles at meiosis stage and their relationship with spikelet degeneration rate were observed.The results showed that the decreased spikelet degeneration rate was closely associated with enhanced 24-epicastasterone(24-epiCS)and 28-homobrassinolide(28-homBL)contents in young panicles.When N content of rice panicle was 1.25%,the BRs(24-epi CS and 28-hom BL)content in young panicle increased significantly,and the spikelet degeneration rate decreased.The variation trend of T-AOC level was very consistent with BRs,and T-AOC was significantly negatively correlated with spikelet degeneration rate,whereas the variation trend of H2O2 content was opposite to that of T-AOC and BRs contents in the young panicles.Application of exogenous BRs(24-epiCS or 28-homBL)to young panicles could significantly increase the T-AOC level and contents of endogenous 24-epiCS and 28-homBL,but significantly reduce the H2O2 content and spikelet degeneration rate,while application of BRs synthesis inhibitor had the opposite effect.In summary,BRs mediated the effects of N application rates on spikelet degeneration,and elevated BRs contents in young panicles could inhibit spikelet degeneration by elevating antioxidant capacity under a proper panicle N content(1.25%)at meiosis stage in rice.