PubMed · 13867700
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F J BERGERSEN. 1961-09-02. Nitrate reductase in soybean root nodules.. https://doi.org/10.1016/0006-3002(61)90922-2
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Nitric oxide (NO) is a diffusible, very reactive gas that is involved in the regulation of many processes in plants. Several enzymatic sources of NO production have been identified in recent years. Nitrate reductase (NR) is one of them and it has been shown that this well-known plant protein, apart from its role in nitrate reduction and assimilation, can also catalyse the reduction of nitrite to NO. This reaction can produce large amounts of NO, or at least more than is needed for signalling, as some escape of NO to the outside medium can be detected after NR activation. A role for NO and NR in stomata functioning in response to abscisic acid has also been proposed. The question that remains is whether this NR-derived NO is a signalling molecule or the mere product of an enzymatic side reaction like the products generated by the oxygenase activity of RuBisCO.
Over the last 10 years, during the lifetime of the nitrogen cycle meetings, structural biology, coupled with spectroscopy, has had a major impact of our understanding enzymology of the nitrogen cycle. The three-dimensional structures for many of the key enzymes have now been resolved and have provided a wealth of information regarding the architecture of redox active metal sites, as well as revealing novel structural folds. Coupled with structure-based spectroscopic analysis, this has led to new insight into the reaction mechanisms of the diverse chemical transformations that together cycle nitrogen in the biosphere. An overview of the some of the key developments in field over the last decade is presented.
To fractionate the contribution of plant to N2O emission from soil-plant system, the N2O emissions from soybean seedling, maize seedling, sand, soil, sand-plant system and soil-plant system were measured by closed chamber method in greenhouse. At the same time the correlation of plant N2O emission with nitrate reductase activity, nitrate content and nitrite content of the plant leaves was also analyzed. The results clearly indicated that N2O could be a by-product of plant metabolism. The emissions of N2O from maize and soybean accounted for 93%-100% of the total N2O emissions in the sand-plant systems, and 79.18%-92% in the soil-plant systems. The flux of plant N2O emission was significantly correlated (R2 > or = 0.97, n = 6) with the nitrate reductase activities, nitrate content and nitrite content of the maize and soybean leaves.