氮素穗肥对水稻幼穗细胞分裂素和生长素浓度的影响及其与颖花发育的关系

以粳稻品种武育粳3号和2401为研究材料，在盆栽条件下，设高(HN)、低(LN)两个穗肥施氮水平，对幼穗发育过程中(颖花分化至抽穗后7 d)细胞分裂素(ZRs、iPAs)和生长素(IAA)含量及其动态分别进行测定和比较分析。结果表明，幼穗发育过程中穗中细胞分裂素和生长素含量均表现先降后升的趋势，穗肥的施用(HN处理)提高了各个时期细胞分裂素的含量，尤其是颖花分化期效果最为明显。而生长素的变化情况较为复杂，从颖花分化期到花粉母细胞减数分裂期前LN处理稍高于HN处理，之后HN处理又逐渐超过LN处理。穗发育期间HN处理的ZRs/IAA和iPAs/IAA均高于LN处理，颖花分化期差距最大，随后逐渐减小，到花粉母细胞减数分裂期差异最小，抽穗时比值差距又再次扩大，两个品种表现相似。水稻氮素穗肥的施用具有延长颖花分化时间、增加每穗颖花数的作用，这可能与其提高幼穗分化期尤其是颖花分化期的细胞分裂素含量及其与生长素的比值有关。

Effect of Panicle Nitrogen Fertilizer on Concentrations of Cytokinin and Auxin in Young Panicles of Japonica Rice and Its Relation with Spikelet Development

Panicle N fertilizer, which is nitrogen fertilizer applied at panicle development stage, has great influence on the development of rice panicle. Studies have revealed that the beneficial response of nitrogen fertilizer on spikelet development is associated with the increase of spikelets number per panicle. However, little is known concerning the effect of panicle N fertilizer on endogenous hormones in rice young panicle. In the present study, two japonica rice cultivars (Wuyujing 3 and 2401) were used, and two panicle N fertilizer treatments, 120 kg N ha^-1 as high nitrogen (HN) and 0 kg N ha^-1 as low nitrogen (LN), were conducted to investigate the relationship between spikelets number and hormonal changes during rice panicle differentiation. The results showed that zeatin + zeatin riboside (ZRs), isopen-tenyl adenine (iPAs), and indole-3-acetic acid (IAA) concentrations were the highest at spikelet differentiation stage, sharply declined and remained almost static till heading, and recovered slightly after heading. Panicle N fertilizer treatment resulted in higher concentrations of ZRs and iPAs, especially at the spikelet differentiation stage. Whereas, IAA displayed lower concentration in HN as compared to LN. Moreover, there were higher ratios of ZRs/IAA and iPAs/IAA for HN as compared to LN during the panicle differentiation stage. The difference between them was the maximum at the spikelet differentiation stage and then declined to the minimum before heading, while there was no significant difference between two cultivars. The results suggested that the effect of panicle N fertilizer on spikelet differentiation and numbers per panicle could be associated with the changes of endogenous hormones such as ZRs, iPAs and IAA, either in their concentrations or in their ratios.