Are There Other Enzymes Involved in Nitrite Metabolism in Plants

It has long been known that soybean can produce X (NO and NO,) gases from nitrite by the action of the so-called constitutive NRs (Dean and Harper, 1988 Klepper, 1990). Since then, it has been found that many plants have the ability to emit nitrogen oxide(s) (Wildt et al., 1997), a denitrifying capability closely associated with nitrate availability. Interestingly, Goshima et al. (1999) have found emission ofN Oby transgenic tobacco plants expressing an antisense NiR construct (line 271...

References

Abrol YP (ed) (1993) Nitrogen-Soils, Physiology, Biochemistry, Microbiology, Genetics, Indian National Science Academy, New Delhi Abrol YP, Chatterjee SR, Kumar PA and Jain V (1999) Improvement in nitrogen use efficiency Physiological and molecular approaches. Curr Sci 76 1357-1364 Ahmad A and Abdin MZ (2000) Photosynthesis and its related physiological variables in the leaves of Brassica genotypes as influenced by sulphur fertilization. Physiol Plant 110 144149 Badger MR and Price GD (1994)...

Introduction Of Nitrate Reductase

Overview of Nitrogen Metabolism and Its Regulation Nitrogen (N) is the most limiting element for crop plant growth, after factors like light and water. Nitrogen fertilizer had a major impact on agricultural crop productivity in the second half of the Twentieth Century (Smil, 1997) and is likely to be a big factor in the Twenty-First. Another impact of N fertilizers has been the contribution to nutrient run-off and pollution ofnatural ecosystems with excess N, which has upset the natural...

Regulation of Nitrogen Responsive Genes for Carbon Assimilation

The balance of the C N ratio relies on the interdependent and interconnected regulation of the metabolism. This is achieved through regulatory signals and processes that include metabolites, allosteric effectors, protein phosphorylation, and redox regulation. At the level of gene expression, many genes in photosynthesis are N-responsive (Table 1). These genes include the Rubisco small subunit (rbcS) and the light harvesting chlorophyll a, -binding protein(Cab) in Chlamydomonas reinhardtii...

Regulatory Phosphorylation of the C3 Form Importance in Anaplerosis

In the plant leaf, PEPc is not directly involved in photosynthesis, but fulfils a variety of physiological roles. In the anaplerotic pathway, which must also occur in plants, it contributes to the replenishment of tricarboxylic acid (TCA) cycle intermediates when organic acids are directed towards other metabolic processes such as amino acid and protein synthesis (Huppe and Turpin, 1994). During amino acid synthesis, organic acids are used for assimilation through glutamine synthetase (GS) and...

Approaches to Improving Nitrogen Use Efficiency in Crops

Rubisco is a major sink for N supplied in the form of fertilizers. Manipulation of crops to improve NUE would have economic and environmental benefits, reducing pollution of water supply by nitrates. It has been suggested that improvement of cereal NUE is not a useful goal because the N is needed in the grain (Sinclair and Sheehey, 1999). However, if NUE is improved, N uptake could benefit from greater root growth and grain quality can be maintained by adding N fertilizer during grain...

Selection of Photorespiratory Mutants

During the past two decades our knowledge and understanding of photorespiratory metabolism has been refined by the selection and study of mutant plants lacking the specific isozymes involved. Mutant plants have been selected on the principle that, a Fig. 1. Photorespiratory carbon and nitrogen metabolism. Oxygenation of two molecules ofRuBP yields two molecules of glyccrate-3-P C3 and two molecules by converting it intoglycerate3-P in the photorespiratory cycle. This can then re-enter the RPP...