Differential sensitivity of stomatal and non-stomatal components to NaCl or Na2SO4 salinity in horsegram, Macrotyloma uniflorum (Lam.) |
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Authors: | P Sreenivasulu Reddy S Ramanjulu C Sudhakar K Veeranjaneyulu |
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Institution: | (1) Department of Botany, Sri Krishnadevaraya University, Anantapur, 515003, India;(2) Regional Sericultural Research Station (CSR & TI), Rapthadu, Anantapur, India;(3) Department of Chemistry, University of Miami, Coral Gable, Florida, 33124, U.S.A |
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Abstract: | 14CO2 assimilation rate (P), leaf diffusive conductance (gs), photosynthetic electron flow, and activities of enzymes of Calvin cycle were studied in a horsegram Macrotyloma uniflorum (Lam.)] in response to salinity induced by NaCl or Na2SO4. A significant reduction in P and gs by both salt treatments was registered. Na2SO4 caused a greater reduction in gs than the NaCl salinity. Studies with isolated chloroplasts confirmed a greater sensitivity to NaCl than to Na2SO4. Salinity inhibited the photosynthetic electron transport. The activity of ribulose-1,5-bisphosphate carboxylase (E.C.4.1.1.39) was under salinity inhibited more than the activities of other three enzymes of the Calvin cycle, ribulose-5-phosphate kinase (E.C.2.7.1.19), ribose-5-phosphate isomerase (E.C.5.3.16), and NADP-glyceraldehyde-3-phosphate dehydrogenase (E.C.1.2.13). These inhibitions lead to a reduced capacity for ribulose-1,5-bisphosphate regeneration. Isolated chloroplasts extracted from salt stressed plants and supplemented with the substrates of Calvin cycle could elevate P, but the P was always lower than in the controls. Decreased P in horsegram exposed to high salinity can be attributed to both stomatal and non-stomatal components, however, the sensitivity to the salt source, NaCl or Na2SO4, was different. |
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Keywords: | CO2 fixation NADP-glyceraldehyde-3-phosphate dehydrogenase photosystem 2 activity ribose-5-phosphate isomerase ribulose-1 5-bisphosphate carboxylase ribulose-5-phosphate kinase salt stress stomatal conductance |
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