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Light stimulate plant nitrogen uptake ability under interrupted N supply
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  • Mehedi Hassn,
  • Gibril Dumbuya,
  • Habtamu Assega,
  • Uzuki Matsushima,
  • Maya Matsunami,
  • Hiroyuki Shimono
Mehedi Hassn
Iwate University
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Gibril Dumbuya
Iwate University
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Habtamu Assega
Iwate University
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Uzuki Matsushima
Iwate University
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Maya Matsunami
Iwate University
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Hiroyuki Shimono

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Abstract

Plants take up nitrogen (N) both day and night. However, the molecular regulation of diurnal changes in N uptake is poorly understood. To test the hypothesis that light stimulates N uptake during the day, we examined the long-term effects of interrupted N supply (day only or night only) under hydroponic conditions. Seedlings experienced 32 days under daytime-fed (DF), nighttime-fed (NF), or continuous (CT) N supply. The root N uptake rate (NUR) differed between DF and NF from day 3 of treatment, after which NUR was significantly increased (by up to 82%) in DF and NF plants. The increased NUR during each half-day did not fully compensate for lost access to N during the other half-day, resulting in lower N accumulation by the end of the treatment. The reduction was smaller in DF plants, supporting the hypothesis that light promotes uptake. The root expression of ammonium transporter genes (OsAMT1;1, 1;2, 1;3) and a nitrogen-assimilation gene (OsGS1;2) was upregulated by 10% to 200% in both DF and NF plants relative to CT plants from day 15, more so in NF plants. No significant effect on OsG6PDH1 (in the pentose phosphate pathway) was detected.