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. 1989 Nov;91(3):1152–1156. doi: 10.1104/pp.91.3.1152

Role of Nitrate and Nitrite in the Induction of Nitrite Reductase in Leaves of Barley Seedlings 1

Muhammad Aslam 1, Ray C Huffaker 1
PMCID: PMC1062133  PMID: 11537455

Abstract

The role of NO3 and NO2 in the induction of nitrite reductase (NiR) activity in detached leaves of 8-day-old barley (Hordeum vulgare L.) seedlings was investigated. Barley leaves contained 6 to 8 micromoles NO2/gram fresh weight × hour of endogenous NiR activity when grown in N-free solutions. Supply of both NO2 and NO3 induced the enzyme activity above the endogenous levels (5 and 10 times, respectively at 10 millimolar NO2 and NO3 over a 24 hour period). In NO3-supplied leaves, NiR induction occurred at an ambient NO3 concentration of as low as 0.05 millimolar; however, no NiR induction was found in leaves supplied with NO2 until the ambient NO2 concentration was 0.5 millimolar. Nitrate accumulated in NO2-fed leaves. The amount of NO3 accumulating in NO2-fed leaves induced similar levels of NiR as did equivalent amounts of NO3 accumulating in NO3-fed leaves. Induction of NiR in NO2-fed leaves was not seen until NO3 was detectable (30 nanomoles/gram fresh weight) in the leaves. The internal concentrations of NO3, irrespective of N source, were highly correlated with the levels of NiR induced. When the reduction of NO3 to NO2 was inhibited by WO42−, the induction of NiR was inhibited only partially. The results indicate that in barley leaves NiR is induced by NO3 directly, i.e. without being reduced to NO2, and that absorbed NO2 induces the enzyme activity indirectly after being oxidized to NO3 within the leaf.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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