Main centers of nitrate and nitrite reduction in young and nodulated yellow lupine (<Emphasis Type="Italic">Lupinus luteus</Emphasis>) |
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Authors: | Władysław Polcyn Robert Luciński |
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Institution: | (1) Institute of Experimental Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland |
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Abstract: | Nitrate and nitrite reduction centers in non-nodulated and symbiotic yellow lupine were analyzed. In young seedlings, nitrate
was exclusively accumulated in roots, which also was shown as the main nitrate reduction center. In contrast, leaves were
shown to play a key role in nitrite reduction. A similar distribution of nitrate reductase (NR) and nitrite reductase was
found in nodulated plants. However, in field conditions characterized by low nitrate content, a disproportionately high level
of NR activity in nodules was also observed during all stages of symbiotic growth. This feature was confirmed in nitrate-fed
hydroponic cultures. Nodule NR activity was one order of magnitude higher than in roots, in spite of the small stored nitrate
pool found inside nodules. This suggests that nodule NR activity had been induced not by nitrate itself but indirectly. Since
bacteroids were shown to be responsible for the vast majority of nodule NR activity, the plausible explanation of this effect
seems to be a dissimilatory nature of rhizobial NR. Considering that environmental nitrate could cause hypoxia inside nodules,
this is the proposed way of the observed nodule NR induction. |
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Keywords: | Lupinus luteus Assimilatory nitrate reductase (EC 1 6 6 1-3) Assimilatory nitrite reductase (EC 1 6 7 1-2) Bacteroids Dissimilatory nitrate reductase (EC 1 7 99 4) Stored nitrate pool size |
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