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Products of photosynthetic 14 CO 2 fixation and related enzyme activities in fruiting structures of chickpea
Author(s) -
Singal H. R.,
Sheoran I. S.,
Singh Randhir
Publication year - 1986
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1986.tb05951.x
Subject(s) - phosphoenolpyruvate carboxylase , malate dehydrogenase , photosynthesis , dehydrogenase , biochemistry , pyruvate carboxylase , malic enzyme , biology , carbon fixation , enzyme , nad+ kinase , crassulacean acid metabolism
Fruiting structures of a number of legumes including chickpea are known to carry out photosynthetic CO 2 assimilation, but the pathway of CO 2 fixation and particularly the role of phosphoenolpyruvate carboxylase (EC 4.1.1.31) in these tissues is not clear. Activities of some key enzymes of the Calvin cycle and C 4 metabolism, rates of 14 CO 2 fixation in light and dark, and initial products of photosynthetic 14 CO 2 fixation were determined in podwall and seedcoat (fruiting structures) and their subtending leaf in chickpea ( Cicer arietinum L.). Compared to activities of ribulose‐1,5‐bisphosphate carboxylase (EC 4.1.1.39) and other Calvin cycle enzyme, viz. NADP + ‐glyceraldehyde‐3‐phosphate dehydrogenase (EC 1.2.1.13), NAD + ‐glyceraldehyde‐3‐phosphate dehydrogenase (EC 1.2.1.12) and ribulose‐5‐phosphate kinase (EC 2.7.1.19), the levels of phosphoenolpyruvate carboxylase and other enzymes of C 4 metabolism viz. NADP + ‐malate dehydrogenase (EC 1.1.1.82), NAD + ‐malate dehydrogenase (EC 1.1.1.37), NADP + malic enzyme (EC 1.1.1.40), NAD + ‐malic enzyme (EC 1.1.1.39), glutamate oxaloacetate transaminase (EC 2.6.1.1) and glutamate pyruvate transaminase (EC 2.6.1.2), were generally much higher in podwall and seedcoat than in the leaf. Podwall and seedcoat fixed 14 CO 2 in light and dark at much higher rates than the leaf. Short‐term assimilation of 14 CO 2 by illuminated fruiting structures produced malate as the major labelled product with less labelling in 3‐phosphoglycerate, whereas the leaf showed a major incorporation into 3‐phosphoglycerate. It seems likely that the fruiting structures of chickpea utilize phosphoenolpyruvate carboxylase for recapturing the respired carbon dioxide.