Premium
Kinetics of NH 4 + and K + uptake by ectomycorrhizal fungi. Effect of NH 4 + on K + uptake
Author(s) -
Jongbloed R. H.,
Clement J. M. A. M.,
BorstPauwels G. W. F. H.
Publication year - 1991
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1991.tb00116.x
Subject(s) - kinetics , nuclear chemistry , depolarization , chemistry , biology , biophysics , physics , quantum mechanics
NH 4 + and K + uptake experiments have been conducted with 3 ectomycorrhizal fungi, originating from Douglas fir (Pseudotsuga menziesii (Mirb.] Franco) stands. At concentrations up to 250 μ M , uptake of both NH 4 + and K + follow Michaelis‐Menten kinetics. Laccaria bicolor (Maire) P. D. Orton, Lactarius rufus (Scop.) Fr. and Lactarius hepaticus Plowr. ap. Boud. exhibit K m values for NH 4 + uptake of 6, 35, and 55 μ M , respectively, and K m values for K + uptake of 24, 18, and 96 μ M , respectively. Addition of 100 μ M NH 4 + raises the K m of K + uptake by L. bicolor to 35 μ M , while the V max remains unchanged. It is argued that the increase of K m is possibly caused by depolarization of the plasma membrane. It is not due to a competitive inhibition of K + by NH 4 + since the apparent inhibitor constant is much higher than the K m , for NH 4 + uptake. The possibility that NH 4 + and K + are taken up by the same carrier can be excluded. The K m , values for K + uptake in the two other fungi are not significantly affected by 100 μ M NH 4 + . Except for a direct effect of NH 4 + on influx of K + into the cells, there may also be an indirect effect after prolonged incubation of the cells in the presence of 100 μ M NH 4 + .