Premium
Light and dark assimilation of nitrate in plants
Author(s) -
ABROL Y. P.,
SAWHNEY S. K.,
NAIK M. S.
Publication year - 1983
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/1365-3040.ep11589193
Subject(s) - nitrate , nitrogen assimilation , nitrate reductase , pentose phosphate pathway , assimilation (phonology) , nitrite , darkness , chloroplast , chemistry , nitrite reductase , phosphate , biochemistry , heterotroph , biology , botany , metabolism , bacteria , glycolysis , organic chemistry , linguistics , philosophy , genetics , gene
. Heterotrophic assimilation of nitrate in roots and leaves in darkness is closely linked with the oxidative pentose phosphate pathway. The supply of glucose‐6‐phosphate to roots and chloroplasts in leaves in darkness is essential for assimilation of nitrite into amino acids. When green leaves are exposed to light, the key enzyme, glucoses‐phosphate dehydrogenase, is inhibited by reduction with thioredoxin. Hence the dark nitrate assimilatory pathway is inhibited under photoautotrophic conditions and replaced by regulatory reactions functioning in light. On account of direct photo‐synthetic reduction of nitrite in chloroplasts and availability of excess NADH for nitrate reduclase, the rate of nitrate assimilation is extremely rapid in light. Under dark anaerobic conditions also nitrate is equally rapidly reduced to nitrite on account of abolition of competition for NADH between nitrate reductase and mitochondrial oxidation.