Gibberellic Acid and Silicon Ameliorate NaCl Toxicity in <i>Brassica juncea:</i> Possible Involvement of Antioxidant System and Ascorbate-Glutathione Cycle
Pravej Alam | Thamer Al Balawi | Sami Ullah Qadir | Parvaiz Ahmad
This work was carried out to observe the combined impact of exogenous applications of Gibberellic acid (GA<sub>3</sub>) and Silicon (Si) on <i>Brassica juncea</i> under salt (NaCl) stress. Application of GA<sub>3</sub> and Si enhanced the antioxidant enzyme activities of (APX, CAT, GR, SOD) in <i>B. juncea</i> seedlings under NaCl toxicity. The exogenous Si application decreased Na<sup>+</sup> uptake and enhanced the K<sup>+</sup> and Ca<sup>2+</sup> in salt stressed <i>B. juncea</i>. Moreover, chlorophyll-<i>a</i> (<i>Chl-a</i>), Chlorophyll-<i>b</i> (<i>Chl-b</i>), total chlorophyll (<i>T-Chl</i>), carotenoids and relative water content (RWC) in the leaves declined under salt stress, which were ameorialated after GA<sub>3</sub> and Si supplementation individually and in combination. Further, the introduction of Si to NaCl treated <i>B. juncea</i> help in alleviating the negative effects of NaCl toxicity on biomass and biochemical activities. The levels of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) increase significantly with NaCl treatments, subsequently resulting in enhanced peroxidation of membrane lipids (MDA) and electrolyte leakage (EL). The reduced levels of H<sub>2</sub>O<sub>2</sub> and enhanced antioxidantactivities in Si and GA<sub>3</sub> supplemented plants demonstrated the stress mitigating efficiency. In conclusion, it was observed that Si and GA<sub>3</sub> application alleviated NaCl toxicity in <i>B. juncea</i> plants through enhanced production of different osmolytes and an antioxidant defence mechanism.
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