Journal
ACTA PHYSIOLOGIAE PLANTARUM
Volume 33, Issue 2, Pages 325-334Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s11738-010-0551-5
Keywords
Accessions; Glutamine synthetase; Glutamate dehydrogenase; Circadian clocks; NH4+ toxicity
Categories
Funding
- National Basic Research Program of China [2007CB109303]
- National Natural Science Foundation of China [30771285]
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Responses to excessive ammonium (NH4 (+)) were compared between two Arabidopsis ecotypes (Col-0, JA22) with respect to different photoperiods in hydroponics. In this study, we showed that external extra NH4 (+) led to severe growth suppression, accumulations of free NH4 (+) and amino acids and increased the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in shoots of the two Arabidopsis ecotypes. However, the levels of free NH4 (+) and total amino acids increased, whereas the activities of GS, NADH-dependent glutamate synthase and GDH decreased under the continuous light when compared with the light (16 h)-dark (8 h) cycle photoperiod. Statistical analyses suggested that strong correlations exist among the growth reduction, accumulations of free NH4 (+), total amino acids and levels of GS activity in shoots under the high NH4 (+) stress regardless of the photoperiod regimes. Interestingly, under the continuous light, Col-0 showed more resistant to such growth reduction and maintained about onefold higher capability of converting excess free NH4 (+) into amino acids, with onefold higher GS activity induced by the external NH4 (+) when compared with JA22. In contrast, these differences were abolished between Col-0 and JA22 under the light-dark cycle condition. Taken together, our results conclude that the sensitivity to NH4 (+) of Col-0 and JA22 is changed between the continuous light and the light-dark cycle photoperiod, which is correlative to the alteration of the GS activity in shoots.
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