Excessive nitrogen in field-grown rice suppresses grain filling of inferior spikelets by reducing the accumulation of cytokinin and auxin
Excessive nitrogen in field-grown rice suppresses grain filling of inferior spikelets by reducing the accumulation of cytokinin and auxin
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DOI：
10.1016/j.fcr.2022.108542
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发表时间：
2022-04-13
影响因子：
5.8
通讯作者：
Ye, Nenghui
中科院分区：
文献类型：
--
作者：
Chen, Yinke;Teng, Zhenning;Ye, Nenghui
在世界许多地区，为了获得更高的水稻产量，经常施用过量的氮肥。然而，过量氮素对弱势粒灌浆的影响及其机理尚不清楚。通过3年田间试验，研究了过量施氮对水稻灌浆的调控机制。结果表明，过量施氮降低了弱势粒的淀粉合成和粒重，但对上级粒无影响。植物激素检测结果表明，在弱势粒灌浆初期，过量氮素使细胞分裂素（CTK）和吲哚乙酸（IAA）含量降低。实时荧光定量PCR结果表明，在过量氮处理条件下，IAA合成基因的抑制导致IAA含量下降，CTK氧化酶基因的上调导致CTK含量下降。外源IAA或CTK的施用显著削弱了过量氮素对弱势粒淀粉积累和粒重的抑制作用。进一步的酶活性测定表明，过量施氮显著抑制了弱势颖花蔗糖合成酶（SuS）、二磷酸腺苷葡萄糖焦磷酸化酶（AGP）和淀粉合成酶（StS）的活性。在过量氮处理下，穗部施用外源IAA或CTK显著提高了SuS、AGP和StS酶活性。综上所述，我们的研究结果表明，过量施氮通过减少细胞分裂素和生长素的积累来抑制弱势颖花的灌浆。
Excessive nitrogen fertilizer is often applied to achieve higher rice yield in many regions of the world. However, the effect of excessive nitrogen on grain filling of inferior spikelets and its underlying mechanisms are still poorly understood. A three-year field experiment was conducted to reveal the mechanisms by which excessive nitrogen application regulated grain filling. We found that excessive application of nitrogen reduced the starch biosynthesis and grain weight of inferior spikelets but not superior spikelets. Plant hormone detection revealed that both cytokinin (CTK) and 3-Indoleacetic acid (IAA) were reduced by excessive nitrogen at the early stage of grain filling in inferior spiekelts. Quantitative real-time PCR results showed that inhibition of biosynthesis genes led to a decrease in IAA content, while elevation of CTK oxidase genes resulted in a lower level of CTK under excessive nitrogen treatment. Application of exogenous IAA or CTK significantly impaired the inhibitory effect of excessive nitrogen on starch accumulation and grain weight of inferior spikelets. Further enzyme assays revealed that excessive nitrogen application significantly suppressed the enzyme activities of sucrose synthase (SuS), adenosine diphosphate glucose pyrophosphorylase (AGP) and starch synthase (StS) in inferior spikelets. Application of exogenous IAA or CTK to the panicle under excessive nitrogen treatment significantly increased the enzyme activities of SuS, AGP and StS. Taken together, our results revealed that excessive nitrogen application in fieldgrown rice suppressed grain filling of inferior spikelets by reducing the accumulation of cytokinin and auxin.