Excessive nitrogen in field-grown rice suppresses grain filling of inferior spikelets by reducing the accumulation of cytokinin and auxin

Yinke Chen, Zhenning Teng, Youqing Yuan, Zhenxie Yi, Qin Zheng, Huihui Yu, Jiahan Lv, Yuxing Wang, Meijuan Duan*, Jianhua Zhang, Nenghui Ye

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

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 field-grown rice suppressed grain filling of inferior spikelets by reducing the accumulation of cytokinin and auxin.

Original languageEnglish
Article number108542
JournalField Crops Research
Volume283
DOIs
Publication statusPublished - 1 Jul 2022

Scopus Subject Areas

  • Agronomy and Crop Science
  • Soil Science

User-Defined Keywords

  • High nitrogen fertilizer
  • Inferior grains
  • Oryza sativa L
  • Plant hormone
  • Starch biosynthesis

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