REGULATION OF NITRATE ASSIMILATION BY LIGHT IN HIGHER PLANTS.
Abstract
Assimilation of nitrate in plants is strictly light dependent. Light regulates the activity of the first enzyme, namely, nitrate reductase, indirectly by blocking the mitochondriat oxidation of NADH, thus making it available for nitrate reduction. Subsequent assimilation of nitrite is carried out in the
chlo•oplasts by nitrite reductase, glutamine synthetase and glutamate synthase which are all light dependent. Recent evidence also suggests that NADH for nitrate reduction is generated by the mitochondrial citric acid cycle dehydrogenases and NAD+-malic enzyme. It has also been shown that in light, carbon skeleton for citric acid cycle turnover is perhaps provided by 2-carbon compounds generated during photorespiration. Thus, combined activities of chloroplasts, mitochondria, cytoplasm and perhaps peroxisomes regulate nitrate assimilation in plants.
chlo•oplasts by nitrite reductase, glutamine synthetase and glutamate synthase which are all light dependent. Recent evidence also suggests that NADH for nitrate reduction is generated by the mitochondrial citric acid cycle dehydrogenases and NAD+-malic enzyme. It has also been shown that in light, carbon skeleton for citric acid cycle turnover is perhaps provided by 2-carbon compounds generated during photorespiration. Thus, combined activities of chloroplasts, mitochondria, cytoplasm and perhaps peroxisomes regulate nitrate assimilation in plants.
Keywords
Nitrate assimilation, regulation by light ATP and mitochondria, source of NADH, higher plants.
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