Effects of exogenous application of proline and betaine on the growth of tobacco cultured cells under saline conditions

The effects of the application of exogenous proline and betaine on the growth of tobacco cultured cells subjected to salt stress were investigated. Both proline and betaine mitigated the inhibition of growth of tobacco cells under saline conditions, but the harmful effect of salinity was less reduced by betaine than by proline. The amount of intracellular betaine in tobacco cells cultured in the NaCl medium supplemented with 20 mm betaine was larger than that of intracellular proline in the NaCl medium with 20 mm proline. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) experiments showed that proline displayed an antioxidant activity and that the antioxidant activity of betaine was not detectable. The malondialdehyde (MDA) assay demonstrated that exogenous proline but not betaine decreased the amount of MDA in salt-stressed tobacco cells. These results suggest that the difference in the mitigation effects between proline and betaine may be responsible for the difference in the antioxidant activity.