Comparative analysis for understanding salinity tolerance mechanism in Indian Mustard (Brassica juncea L.)

Abstract

This study reports a comparison of differential physiological and biochemical changes in two Indian Mustard (Brassica juncea L.) cultivars viz. CS-52 (salinity tolerant) and Ashirwad (salinity susceptible) after 15 days of gradual increase in NaCl concentration in the nutrient solution. The increase in the NaCl concentration in the nutrient solution was as follows: 25 mM for 2 days, 50 mM for 2 days, 75 mM for 2 days, 100 mM for 2 days, 125 mM for 2 days, and 150 mM for 5 days. After 15 days of salinity stress, we observed a sharp decline in dry matter content and leaf area in Ashirwad. These effects were, however, less pronounced in CS-52. Under high salinity conditions, CS-52 maintained a better physiological status as determined by higher relative water content, higher water use efficiency, and lower leaf temperature and electrolytic leakage ratio, compared to Ashirwad. CS-52 was also observed to be more efficient regarding gas-exchange parameters (stomatal conductance and transpiration) and photosynthetic capacity. Moreover, salt-induced changes in accumulation and distribution patterns, and the ratios of major macro- and microelements were recorded to be more favorable in CS-52 compared to Ashirwad. The study also revealed that salinity-induced relative changes in the concentrations and compositions of biomolecules such as lipids, proteins, and carbohydrates, and structural rearrangements in the side chains of proteins were less prominent in CS-52 indicating better preparedness and thus more adaptability of CS-52 towards salinity.