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Field investigations of ammonia exchange between barley plants and the atmosphere. II. Nitrogen realiocation, free ammonium content and activities of ammonium‐assimilating enzymes in different leaves
Author(s) -
SCHJOERRING J. K.,
KYLLINGSBAEK A.,
MORTENSEN J. V.,
BYSKOVNIELSEN S.
Publication year - 1993
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1993.tb00858.x
Subject(s) - ammonium , glutamine synthetase , ammonia , nitrogen , glutamate synthase , chemistry , nitrogen cycle , enzyme , glutamine , agronomy , botany , horticulture , biology , biochemistry , amino acid , organic chemistry
The activities of glutamine synthetase (GS) and glutamate synthase (GOGAT) in different leaves of field‐grown spring barley were measured during the reproductive growth phase in 2 consecutive years. Concurrently, the contents of soluble ammonium ions and free amides in the leaves were determined. The studies were carried out to investigate the relationship between variations in these parameters and emission of NH3 from the plant foliage. GS and GOGAT activities declined very rapidly with leafage. The decline in enzyme activities was followed by an increase in soluble ammonium ions and amides in the leaf tissues. During the same period, about 75% of leaf and stem nitrogen was reallocated to the developing ear. The amount of NH 3 volatilized from the foliage during the reproductive growth phase amounted to about 1% of the reallocated nitrogen. The experimental years were characterized by very favourable conditions for grain dry matter formation and for re‐utilization of nitrogen mobilized from leaves and stems. Ammonia volatilization occurring under conditions with declining GS and GOGAT activities and increasing tissue concentrations of NH 4 + may be useful in protecting the plant from accumulation of toxic NH 3 and NH 4 + concentrations in the tissues.