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<p>High night-time temperature (HNT) negatively impacts grain yield in wheat that may be alleviated by nitrogen (N) management. However, the regulation of assimilation of supplemented N by the key enzymes of N metabolism i.e., glutamine synthetase (GS) and glutamate synthase/glutamine oxoglutarate aminotransferase (GOGAT), remains elusive. We hypothesize that application of split dose of foliar nitrogen at heading under high night-time temperature can diurnally regulate the nitrogen assimilation pathway in the developing grains and influence nitrogen efficiency indices across different maturity wheat genotypes. A pot experiment was conducted with three wheat genotypes, early maturing (HI 1544, HI 1563) and late maturing (HD 2864), all subjected to HNT (+3&#xa0;°C over ambient) from anthesis to physiological maturity. Nitrogen was applied as urea at 120&#xa0;kg/ha in four split doses [basal: tillering: heading (top dressing): 5&#xa0;days after anthesis (foliar) 2:1:0.5:0.5]. Our results indicate that GS activity followed a developmental pattern, peaking at 7&#xa0;days after anthesis (DAA) in early-maturing genotypes, with a subsequent decline. Diurnal response in GS activity was observed in the tolerant early-maturing genotype (HI 1563), supplemented with foliar supplementing N, particularly under HNT conditions. The late-maturing genotypes showed low GS activity and less responsiveness to supplementing N. This indicates that diurnal regulation of GS is genotype- and temperature-dependent. NADH-GOGAT activity was consistently lower than GS activity, peaking at 14 DAA, but did not exhibit distinct diurnal regulation. Foliar supplementing N did not significantly affect free amino acid (FAA) content at 14 DAA in early-maturing genotypes but reduced soluble protein content, suggesting enhanced protein degradation under HNT stress. Grain N content increased under HNT with foliar supplementing N showing positive correlation with N uptake efficiency (r = 0.83) and nitrogen harvest index (NHI) (r = 0.96), particularly in early-maturing genotypes. Partial factor productivity (PFP) of fertilizer N and grain yield also improved under HNT with supplementing N, with a strong positive correlation to nitrogen use efficiency (NUE) and N uptake. Therefore, our findings suggest that a foliar spray of urea solution at 5 DAA may influence the N assimilation in early maturing wheat genotypes under HNT.</p>

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Interactive effects of post-anthesis foliar nitrogen management and elevated night temperatures on wheat grain nitrogen metabolism

  • 期刊论文

  • 发表日期：

    2025年6月13日

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  • Pandurang Raghunath Divte,
  • Nitin Sharma,
  • Shamima Parveen,
  • D. Sellathdurai,
  • Anjali Anand

摘要

High night-time temperature (HNT) negatively impacts grain yield in wheat that may be alleviated by nitrogen (N) management. However, the regulation of assimilation of supplemented N by the key enzymes of N metabolism i.e., glutamine synthetase (GS) and glutamate synthase/glutamine oxoglutarate aminotransferase (GOGAT), remains elusive. We hypothesize that application of split dose of foliar nitrogen at heading under high night-time temperature can diurnally regulate the nitrogen assimilation pathway in the developing grains and influence nitrogen efficiency indices across different maturity wheat genotypes. A pot experiment was conducted with three wheat genotypes, early maturing (HI 1544, HI 1563) and late maturing (HD 2864), all subjected to HNT (+3 °C over ambient) from anthesis to physiological maturity. Nitrogen was applied as urea at 120 kg/ha in four split doses [basal: tillering: heading (top dressing): 5 days after anthesis (foliar) 2:1:0.5:0.5]. Our results indicate that GS activity followed a developmental pattern, peaking at 7 days after anthesis (DAA) in early-maturing genotypes, with a subsequent decline. Diurnal response in GS activity was observed in the tolerant early-maturing genotype (HI 1563), supplemented with foliar supplementing N, particularly under HNT conditions. The late-maturing genotypes showed low GS activity and less responsiveness to supplementing N. This indicates that diurnal regulation of GS is genotype- and temperature-dependent. NADH-GOGAT activity was consistently lower than GS activity, peaking at 14 DAA, but did not exhibit distinct diurnal regulation. Foliar supplementing N did not significantly affect free amino acid (FAA) content at 14 DAA in early-maturing genotypes but reduced soluble protein content, suggesting enhanced protein degradation under HNT stress. Grain N content increased under HNT with foliar supplementing N showing positive correlation with N uptake efficiency (r = 0.83) and nitrogen harvest index (NHI) (r = 0.96), particularly in early-maturing genotypes. Partial factor productivity (PFP) of fertilizer N and grain yield also improved under HNT with supplementing N, with a strong positive correlation to nitrogen use efficiency (NUE) and N uptake. Therefore, our findings suggest that a foliar spray of urea solution at 5 DAA may influence the N assimilation in early maturing wheat genotypes under HNT.