Gibberellic Acid and Silicon Ameliorate NaCl Toxicity in Brassica juncea: Possible Involvement of Antioxidant System and Ascorbate-Glutathione Cycle

Abstract

This work was carried out to observe the combined impact of exogenous applications of Gibberellic acid (GA3) and Silicon (Si) on Brassica juncea under salt (NaCl) stress. Application of GA3 and Si enhanced the antioxidant enzyme activities of (APX, CAT, GR, SOD) in B. juncea seedlings under NaCl toxicity. The exogenous Si application decreased Na+ uptake and enhanced the K+ and Ca2+ in salt stressed B. juncea. Moreover, chlorophyll-a (Chl-a), Chlorophyll-b (Chl-b), total chlorophyll (T-Chl), carotenoids and relative water content (RWC) in the leaves declined under salt stress, which were ameorialated after GA3 and Si supplementation individually and in combination. Further, the introduction of Si to NaCl treated B. juncea help in alleviating the negative effects of NaCl toxicity on biomass and biochemical activities. The levels of hydrogen peroxide (H2O2) increase significantly with NaCl treatments, subsequently resulting in enhanced peroxidation of membrane lipids (MDA) and electrolyte leakage (EL). The reduced levels of H2O2 and enhanced antioxidantactivities in Si and GA3 supplemented plants demonstrated the stress mitigating efficiency. In conclusion, it was observed that Si and GA3 application alleviated NaCl toxicity in B. juncea plants through enhanced production of different osmolytes and an antioxidant defence mechanism.