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Effect of methionine sulphoximine on 13 N‐ammonium fluxes in the roots of barley and squash seedlings
Author(s) -
Wieneke Josef,
Roeb Gerhard W.
Publication year - 1998
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.1998.3581610102
Subject(s) - squash , shoot , ammonium , chemistry , chromosomal translocation , methionine , metabolism , assimilation (phonology) , horticulture , botany , biochemistry , biology , amino acid , linguistics , philosophy , organic chemistry , gene
13 N‐Iabelled experiments were carried out with barley and squash seedlings to analyse the effect of methionine sulphoximine (MSO), as an inhibitor of the ammonium assimilation, on NH 4 + fluxes in the roots at the level (150 μM NH 4 + ) of the high affinity uptake system (HATS). MSO pretreatment in the root medium significantly accelerated NH 4 + influx and efflux in NH 4 + ‐fed plants of both species. Concomitantly, the level of NH 4 + extracted from the root and shoot tissues was strongly elevated whereas the translocation of 13 N‐Iabelled organic substances (presumably amino products) into the shoots was markedly reduced. The onset of the increased NH 4 + influx did not occur immediately but was indicated about 1 h after the application of MSO to the nutrient solution. Also, MSO did not directly affect the uptake of 13 NO 3 − . The reason why MSO treatment leads to an acceleration of the NH 4 + influx against an increasing level in the cell tissue remains obscure. In squash, an intermediate of NO 3 − metabolism is thought to suppress NH 4 + uptake since NH 4 + influx was high in N‐free‐ and NH 4 + ‐grown seedlings but was reduced about threefold in NO 3 − ‐fed squash plants; the suppression was not eliminated by MSO treatment.