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The uptake of NO3-, NO2-, and NH4+ by intact wheat (Triticum aestivum) seedlings. I. Induction and kinetics of transport systemsThe inducibility and kinetics of the NO3-, NO2-, and NH4+ transporters in roots of wheat seedlings (Triticum aestivum cv Yercora Rojo) were characterized using precise methods approaching constant analysis of the substrate solutions. A microcomputer-controlled automated high performance liquid chromatography system was used to determine the depletion of each N species (initially at 1 millimolar) from complete nutrient solutions. Uptake rate analyses were performed using computerized curve-fitting techniques. More precise estimates were obtained for the time required for the extent of the induction of each transporter. Up to 10 and 6 hours, respectively, were required to achieve apparent full induction of the NO3- and NO2- transporters. Evidence for substrate inducibility of the NH4+ transporters requiring 5 hours is presented. The transport of NO3- was mediated by a dual system (or dual phasic), whereas only single systems were found for transport of NO2- and NH4+. The Km values for NO3-, NO2-, and NH4+ were, respectively, 0.027, 0.054, and 0.05 millimolar. The Km for mechanism II of NO3- transport could not be defined in this study as it exhibited only apparent first order kinetics up to 1 millimolar.
Document ID
Document Type
Reprint (Version printed in journal)
Goyal, S. S.
(University of California Davis 95616, United States)
Huffaker, R. C.
Date Acquired
August 21, 2013
Publication Date
January 1, 1986
Publication Information
Publication: Plant physiology
Volume: 82
ISSN: 0032-0889
Subject Category
Man/System Technology And Life Support
Funding Number(s)
Distribution Limits
NASA Discipline Number 61-10
NASA Discipline Life Support Systems
Non-NASA Center

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