ISSN:
1573-9058
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
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1006830100627
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