Dynamic Interactions between Root NH_4^+ Influx and Long-Distance N Translocation in Rice : Insights into Feedback Processes

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概要

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• Ammonium influx into roots and N translocation to the shoots were measured in 3-week-old hydroponically grown rice seedlings(Oryza sativa L., cv.IR72) under conditions of N deprivation and NH_4^+ resupply, using, ^<13>NH_4^+ as a tracer. Root NH_4^+ influx was repressed in plants continuously supplied with NH_4^+(at 0.1 mM), but a high proportion of absorbed N(20 to 30%) was translocatd to the shoot in the form of N assimilates during the 13-min loading and desorption periods. Interruption of exogenous NH_4^+ supply for periods of 1 to 3 d caused NH_4^+ influx to be de-repressed. This same treatment caused N translocation to the shoot to decline rapidly, until, by 24 h, less than 5% of the absorbed ^<13>N was translocated to the shoot, illustrating a clear priority of root over shoot N demand under conditions of N deprivation. Upon resupplying 1 mM NH_4^+, root NH_4^+ influx responded in a distinct four-phase pattern, exhibiting periods in which NH_4^+ influx was first enhanced and subsequently reduced. Notably, a 25 to 40% increase in root influx, peaking at 〜2 h following re-exposure was correlated with a 4- to 5-fold enhancement in shoot translocation and a repression of root GS activity. The transient increase of NH_4^+ influx was also observed in seedlings continuously supplied with NO_3^- and subsequently transferred to NH_4^+. Extended exposure to NH_4^+ caused root NH_4^+ influx to decrease progressively, while shoot translocation was restored to 〜30% of incoming NH_4^+. The nature of the feedback control of NH_4^+ influx as well as the question of its inducibility are discussed.

• 日本植物生理学会の論文

著者

• Glass Anthony

  Department Of Botany University Of British Columbia

• Kirk Guy

  International Rice Research Institute(irri) P.o.

• Kronzucker Herbert

  Department of Plant Sciences, University of Western Ontario

• Schjoerring Jan

  Plant Nutrition Laboratory, Royal Veterinary and Agricultural University

• Erner Yair

  Department of Citriculture, ARO The Volcani Center

• Siddiqi M.Yaeesh

  Department of Botany, University of British Columbia

• Erner Y

  Department Of Citriculture Aro The Volcani Center

• Schjoerring Jan

  Plant Nutrition Laboratory Royal Veterinary And Agricultural University

• Siddiqi M.yaeesh

  Department Of Botany University Of British Columbia

• Kronzucker Herbert

  Department Of Plant Sciences University Of Western Ontario:international Rice Research Institute(irr

関連論文

• Regulation of NRT1 and NRT2 Gene Families of Arabidopsis thaliana: Responses to Nitrate Provision
• Dynamic Interactions between Root NH_4^+ Influx and Long-Distance N Translocation in Rice : Insights into Feedback Processes
• Ammonia exchange between plants and the atmosphere : Effects of ammonium supply to the roots, dark-induced senescence and reduced GS activity

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