Different effects of supplied ammonium on glutamine synthetase activity in mustard (Sinapis alba) and pine (Pinus sylvestris) seedlings |
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Authors: | P Vollbrecht E Klein H Kasemir |
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Institution: | Biological Inst. II, Univ. of Freiburg, Schänzlestrasse 1, D-7800 Freiburg in Breisgau, FRG |
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Abstract: | The activity of glutamine synthetase (GS) in mustard ( Sinapis alba L.) and Scots pine ( Pinus sylvestris L.) seedlings was used as an index to evaluate the capacity to cope with excessive ammonium supply. In these 2 species GS activity was differently affected by the application of nitrogen compounds (NH4+ or NO3?). Mustard seedlings older than 5 days showed a considerable increase in GS activity after NH4+ or NO3? application. This response was independent of the energy flux, but GS activity in general was positively affected by light. Endogenous NH4+ did not accumulate greatly after nitrogen supply. In contrast, seedlings of Scots pine accumulated NH4+ in cotyledons and roots and showed no stimulation of GS activity after the application of ammonium. In addition, root growth was drastically reduced. Thus, the pine seedlings seem to have insufficient capacity to assimilate exogenously supplied ammonium. NO3?, however, did not lead to any harmful effects. |
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Keywords: | Ammonium toxicity glutamine synthetase mustard nitrate nitrogen fertilization Pinus sylvestris Scots pine Sinapis alba |
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