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ASSIMILATION AND TRANSLOCATION OF NITRATE IN PLANTS AND SIGNIFICANCE OF NITRATE REDUCTION IN ROOTS

Research Project

Project/Area Number 63480051
Research Category

Grant-in-Aid for General Scientific Research (B)

Allocation TypeSingle-year Grants
Research Field 土壌・肥料
Research InstitutionKOBE UNIVERSITY

Principal Investigator

SHIGA Hitoichi  KOBE UNIVERSITY, FACULTY OF AGRICULTURE, PROFESSOR, 農学部, 教授 (50187340)

Co-Investigator(Kenkyū-buntansha) OJI Yoshikiyo  KOBE UNIVERSITY, FACULTY OF AGRICULTURE, ASSOCIATE PROFESSOR, 農学部, 助教授 (90031195)
Project Period (FY) 1988 – 1989
Project Status Completed (Fiscal Year 1989)
Budget Amount *help
¥5,300,000 (Direct Cost: ¥5,300,000)
Fiscal Year 1989: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1988: ¥4,300,000 (Direct Cost: ¥4,300,000)
KeywordsNitrate reduction / Nitrogen Translocation / ^<15>N Tracer / NAD(P)H Nitrate Reductase / NADH Nitrate Reductase / Nitrogen Metabolism / 重窒素トレーサー
Research Abstract

In vivo nitrate reduction in roots and shoots and exchange of reduced N between organs were quantitatively estimated in intact 13-day-old barley seedlings using the ^<15>NO^-_-incorporation model. N-depleted seedlings were exposed to media containing both nitrate (1.8 mM) and nitrite (0.2 mM) under a light-dark cycle of 12:12 h at 20゚C; the media contained different amounts of ^<15>N labeling. Experiments were started either immediately after the beginning or immediately prior to the end of the light period, and plants were sampled subsequently at each light-dark transition throughout 36 h. We also assayed the activities of NAD(P)H nitrate reductase and NADH nitrate reductase in roots and shoots at each 4 h interval throughout the same experimental period.
In vivo nitrate reduction in roots was higher in the dark than in the light, and the reverse was the case in shoots. Roots were responsible for most nitrate reduction during the initial nitrate utilization, particularly in darkness. H … More owever, thereafter the shoots were generally the main organ for reducing nitrate, particularly in the light. When in vivo nitrate reduction in the root decreased, shoot nitrate reduction increased, with downward translocation of reduced N by way of phloem increasing. Xylem translocation of nitrate drastically decreased in the dark, but that of reduced N rather increased, with phloem translocation of reduced in decreasing. In root tissues, NAD(P)H nitrate reductase was present as much as NADH nitrate reductase. On the other hand, almost all of the nitrate reductases was NADH-specific enzyme in shoot tissues. NAD(P)H enzyme also functioned well in root tissues.
We conclude that the cycling of reduced N through the plant is important for N feeding of each organ, and that the transport system of reduced N by way of xylem and phloem, as well as nitrate reduction by root and shoot, can be modulated in response to the relative magnitude of reduced-N demands by the root and shoot, with the one or the other predominating under different circumstances. We also confirm that root nitrate reduction plays an important role in transporting reduced N to shoot when nitrate reduction in shoots is low. Less

Report

(3 results)
  • 1989 Annual Research Report   Final Research Report Summary
  • 1988 Annual Research Report
  • Research Products

    (8 results)

All Other

All Publications (8 results)

  • [Publications] Y.Oji,Y.Otani,Y.Hosomi,N.Waiuchi,H.shiga: "Nitrate reduction in root and shoot and exchange of reduced nitrogen between organs in two-row barley seedlings nuder light-dark cycles" Planta. 179. 359-366 (1989)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1989 Final Research Report Summary
  • [Publications] Y.Oji,N.Wakiuchi,H.Shiga: "Root nitrate reduction and reduced-N exchange in inttact barley seedilngs" Plant Physiology. 89. 197 (1989)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1989 Final Research Report Summary
  • [Publications] 日本土壌肥料学会監修: "植物栄養実験法(植物酵素取扱い法の項)分担執筆,(予定)" 博友社, (1990)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1989 Final Research Report Summary
  • [Publications] Y. Oji et al.: "Nitrate reduction in root and shoot and exchange of reduced nitrogen between organs in two-row barley seedlings under light-dark cycles." Planta 179 (3), 359-366 (1989).

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1989 Final Research Report Summary
  • [Publications] Y. Oji et al.: "Root nitrate reduction and reduced-N exchange in intact barley seedlings." Plant Physiology 89 (4) 197 (1989).

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1989 Final Research Report Summary
  • [Publications] Y.Oji,Y.Otani,Y.Hosomi,N.Wakiuchi,H.Shiga: "Nitrate reduction in root and shoot exchange of reduced nitrogen between organs in two-row barley seedlings under light-dark cycles" Planta. 179. 359-366 (1989)

    • Related Report
      1989 Annual Research Report
  • [Publications] Y.Oji,N.Wakiuchi,H.Shiga: "Root nitrate reduction and reduced-N exchange in intact barley seedlings" Plant Physiology. 89. 197 (1989)

    • Related Report
      1989 Annual Research Report
  • [Publications] 日本土壌肥料学会監修: "植物栄養実験法(植物酵素取扱い法の項)分担執筆" 博友社, (1990)

    • Related Report
      1989 Annual Research Report

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Published: 1988-04-01   Modified: 2016-04-21  

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