Effect of short-term exposure to NaCl on photochemical activity and antioxidant enzymes in Bruguiera parviflora, a non-secretor mangrove

Abstract

Effect of short-term (6 days) exposure to high salinity (500 mM NaCl) was studied in Bruguiera parviflora, a tree mangrove. NaCl treatment decreased photochemical activity, but had no effect on growth. Thylakoid protein profile and spectral characteristic were not changed. There was no significant effect on chlorophylls and carotenoids content, total proteins and total free amino acids. However, there was an increase in free proline. The activity of antioxidant enzymes like catalase, ascorbate peroxidase was enhanced, but no significant change in guaiacol peroxidase was observed. Salinity did not cause any alteration in malondialdehyde formation indicating intactness of membrane integrity upon high salinity. We conclude that the effect of high NaCl stress is not revealed in morphology of the plants, but in the metabolic changes as increase in proline and antioxidant enzyme activity. These effects are the adaptive mechanisms that operates under high salt stress in this mangrove; however, the decrease in photochemical activity may be due to onset of senescence which helps plant in remobilization of photosynthate to new leaves after adaptation.