Interactions of NH4+ and L-glutamate with NO3- transport processes of non-mycorrhizal Fagus sylvatica roots

J Kreuzwieser, C Herschbach, [No Value] Stulen, P Wiersema, W Vaalburg, H Rennenberg

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    Abstract

    The processes of NO3- uptake and transport and the effects of NH4+ or L-glutamate on these processes were investigated with excised non-mycorrhizal beech (Fagus sylvatica L,) roots, NO3- net uptake followed uniphasic Michaelis-Menten kinetics in a concentration range of 10 mu M to 1 mM with an apparent K-m of 9.2 mu M and a V-max of 366 nmol g(-1) FW h(-1), NH4+, when present in excess to NO3- or 10 mM L-glutamate inhibited the net uptake of NO3-. Apparently, part of NO3- taken up was loaded into the xylem, Relative xylem loading of NO3- ranged from 3.2 +/- 1,6 to 6.4 +/- 5,1% of NO3- net uptake, It was not affected by treatment with NH4+ or L-glutamate. N-15/N-13 double labelling experiments showed that NO3- efflux from roots increased with increasing influx of NO3- and, therefore, declined if influx was reduced by NH4+ or L-glutamate exposure, From these results it is concluded that NO3- net uptake by non-mycorrhizal beech roots is reduced by NH4+ or L-glutamate at the level of influx and not at the level of efflux.

    Original languageEnglish
    Pages (from-to)1431-1438
    Number of pages8
    JournalJournal of Experimental Botany
    Volume48
    Issue number312
    Publication statusPublished - Jul-1997

    Keywords

    • nitrate transport
    • net uptake
    • influx
    • efflux
    • ammonium
    • Fagus
    • Fagaceae
    • PINE PINUS-PINASTER
    • VULGARE L SEEDLINGS
    • SPRUCE PICEA-ABIES
    • NITRATE UPTAKE
    • BARLEY SEEDLINGS
    • EXCISED ROOTS
    • AMINO-ACIDS
    • AMMONIUM
    • KINETICS
    • INFLUX

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