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Root-shoot ratio and SOD activity are associated with the sensitivity of common bean seedlings to NaCl salinization

Abstract:

The response of two common bean (Phaseolus vulgaris) varieties with different sensitivities to salinity (Montalbán: sensitive; I-193: moderately sensitive) was studied to determine some phytometric and physiological characteristics that could be associated with their differential sensitivities. Plants were sown in a greenhouse during the seedling stage and irrigated with a nutrient solution to which NaCl of 60 mol m<sup>−3</sup> was added, while a control group was maintained in parallel. In Montalban, salinity caused a significant reduction in root biomass while shoot biomass and leaf area decreased with salt stress in both genotypes. The root/shoot ratio slightly increased in I.193 and decreased in Montalban salinized plants. Chlorophyll content increased with salinity in both genotypes. The presence of O<inf>2</inf>·<sup>-</sup> (superoxide radicle) in root apex decreased under the saline condition which did not occur in the case of H<inf>2</inf>O<inf>2</inf>. Superoxide dismutase (SOD) activity increased in roots and primary leaves under salt stress to a greater extent in I-193 than in Montalban. Four SOD isoenzymes were detected, one MnSOD, one FeSOD, and two Cu/ZnSOD, but their expression varied according to the variety. Catalase (CAT) activity increased only in the roots of stressed Montalban plants. These results suggest that root/shoot ratio and SOD enzyme activity are related to the lower salt sensitivity shown by I-193.