Lv Xiaokang, Ding Yunpeng, Long Mei, Liang Wenxin, Gu Xiaoyan, Liu Yang, Wen Xiaoxia
College of Agronomy, Northwest A&F University, Yangling, China.
Front Plant Sci. 2021 Mar 25;12:645379. doi: 10.3389/fpls.2021.645379. eCollection 2021.
Foliar nitrogen (N) fertilizer application at later stages of wheat () growth is an effective method of attenuating drought stress and improving grain filling. The influences or modes of action of foliar application of various nitrogen forms on wheat growth and grain filling need further research. The objective of this study was to examine the regulatory effects of various forms of foliar nitrogen [NO , NH , and CO(NH)] on wheat grain filling under drought stress and to elucidate their underlying mechanisms. The relative effects of each nitrogen source differed in promoting grain filling. Foliar NH -N application notably prolonged the grain filling period. In contrast, foliar application of CO(NH) and NO -N accelerated the grain filling rate and regulated levels of abscisic acid (ABA), z-riboside (ZR), and ethylene (ETH) in wheat grains. Analysis of gene expression revealed that CO(NH) and NO -N upregulated the genes involved in the sucrose-starch conversion pathway, promoting the remobilization of carbohydrates and starch synthesis in the grains. Besides, activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased, whereas the content of malondialdehyde (MDA) declined under foliar nitrogen application (especially NH -N). Under drought stress, enhancement of carbohydrate remobilization and sink strength became key factors in grain filling, and the relative differences in the effects of three N forms became more evident. In conclusion, NH -N application improved the antioxidant enzyme system and delayed photoassimilate transportation. On the other hand, foliar applications of NO -N and CO(NH) enhanced sink capacity and alleviated drought stress injury in wheat.
在小麦生长后期进行叶面施氮是减轻干旱胁迫和改善籽粒灌浆的有效方法。各种氮形态叶面喷施对小麦生长和籽粒灌浆的影响或作用模式尚需进一步研究。本研究的目的是探讨不同形态叶面氮素[NO₃⁻、NH₄⁺和CO(NH₂)₂]对干旱胁迫下小麦籽粒灌浆的调控效应，并阐明其潜在机制。各氮源在促进籽粒灌浆方面的相对效果有所不同。叶面喷施NH₄⁺-N显著延长了籽粒灌浆期。相比之下，叶面喷施CO(NH₂)₂和NO₃⁻-N加快了籽粒灌浆速率，并调节了小麦籽粒中脱落酸(ABA)、玉米素核苷(ZR)和乙烯(ETH)的水平。基因表达分析表明，CO(NH₂)₂和NO₃⁻-N上调了参与蔗糖-淀粉转化途径的基因，促进了碳水化合物的再转运和籽粒中淀粉的合成。此外，叶面施氮(尤其是NH₄⁺-N)处理下超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的活性增加，而丙二醛(MDA)含量下降。在干旱胁迫下，增强碳水化合物再转运和库强成为籽粒灌浆的关键因素，三种氮形态效应的相对差异更加明显。综上所述，施用NH₄⁺-N改善了抗氧化酶系统并延缓了光合同化物的转运。另一方面，叶面喷施NO₃⁻-N和CO(NH₂)₂增强了库容量并减轻了小麦的干旱胁迫伤害。
