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- Title
GLUTAMINE SYNTHETASE AND AMMONIUM ASSIMILATION IN ROOTS OF ZINC-TOLERANT AND NON-TOLERANT CLONES OF DESCHAMPSIA CESPITOSA (L.) BEAUV. AND ANTHOXANTHUM ODORATUM L.
- Authors
Smirnoff, N.; Stewart, G. R.
- Abstract
The influence of zinc on glutamine synthetase (GS) activity and ammonium assimilation in roots of zinc-tolerant and non-tolerant clones of Deschampsia cespitosa (L.) Beauv. and Anthoxanthum odoratum L. was studied. One isoform of GS was resolved by ion exchange chromatography in D. cespitosa roots. However, two isoforms were found in A. odoratum roots; one of these was attributed to fungal contamination and was not studied further. There was no difference in the sensitivity of partially purified GS from zinc-tolerant and non-tolerant clones to inhibition by zinc. Inhibition of GS by Zn was reversible and the kinetics of inhibition were studied. Methionine sulphoximine (an inhibitor of GS) induced ammonium accumulation in the roots of control and zinc-grown roots of Zn-tolerant D. cespitosa. Zinc inhibited incorporation of [[SUP15]N]ammonium into free amino acids (determined by combined gas chromatography-mass spectrometry) in both clones of D. cespitosa, but higher concentrations were required to achieve inhibition in the tolerant clone. The labelling pattern was unaffected by zinc in both clones. The results suggest that zinc has no effect on the pathway of ammonium assimilation in zinc-grown roots and that assimilation is via the glutamine synthetase-glutamate synthase pathway. There was no evidence to support the hypothesis that glutamate dehydrogenase functions preferentially in ammonium assimilation under conditions of environmental stress.
- Subjects
GLUTAMINE synthetase; AMMONIUM; PLANT roots; ZINC; PLANT clones; AMINO acids
- Publication
New Phytologist, 1987, Vol 107, Issue 4, p659
- ISSN
0028-646X
- Publication type
Article
- DOI
10.1111/j.1469-8137.1987.tb00904.x