Ammonium accumulation and glutamine synthetase activity in C3 and C4 plants
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Glutamine synthetase activity was found to be several fold higher in the leaves of a few C3 as compared to C4 plants. Differences in NH 4 + levels were marginal. Methionine sulphoximine inhibition of glutamine synthetase resulted in increased in NH 4 + levels more in wheat than in sorghum. The decrease in methionine sulphoximine induced accumulation of free NH 4 + by photorespiratory inhibitors, isonicotinic acid hydrazide and α-hydroxy methane pyridine sulphate was also several fold higher in wheat than in sorghum. Feeding of glycine and glycolate, intermediates of photorespiration, showed the presence of active glycine decarboxylation system in sorghum but the metabolism of glycolate was more efficient in wheat. Higher glutamine synthetase activity in C3 plants may be a necessary adaptation to a higher photorespiratory NH 4 + production and explain the similar or higher N losses in C4 as compared to C3 plants. These results also support the hypothesis that glutamine synthetase is important in the assimilation of photorespiratory ammonia.
KeywordsGlutamine synthetase NH4+ levels C3 and C4 photorespiratory nitrogen cycle
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- Foster E F and Stutte C A 1986 Glutamine synthetase activity and foliar nitrogen volatilization in response to temperature and inhibitor chemicals;Ann. Bot. 57 305–307Google Scholar
- Maheswari M, Kumar P A, Nair T V R and Abrol Y P 1985 Ammonia accumulation and glutamine synthetase activity in C3 and C4 plants;symposium on nitrogen metabolism in higher plants, Groningen, Netherlands (abstract) p 23Google Scholar
- Novazamsky I, Van Eck R, Ven Schouwenburg J Ch and Wallinger L 1974 To total nitrogen determination in plant material by means of indophenol blue method;Neth J. Agric. Sci. 22 3–5Google Scholar
- Rowe W B, Ronzia R A, Wellner Y P and Meisha A 1970 Glutamine synthetase (sheep brain);Methods Enzymol. (eds) H Tabor and C B Tabor (New York: Academic Press)VIIA 900–910Google Scholar
- Weiland R J and Stutte C A 1985 Oxygen influence of foliar nitrogen loss from soybean and sorghum plants;Ann. Bot. 55 279–282Google Scholar