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Exogenous gibberellic acid (GA₃) alleviates lead-induced phytotoxicity by modulating growth and antioxidant defence in spinach (Spinacia oleracea L.)
Abstract
Lead (Pb) contamination is a serious threat to vegetable production as it adversely affects plant growth, disrupts physiological and oxidative balance. To assess the effects of Pb stress (20 mg L-1) and the mitigating role of gibberellic acid (GA3; 100 mg L-1) on Spinacia oleracea L., a pot experiment was conducted, laid out in a completely randomized design (CRD) with 5 replications. A significant reduction was observed in plant height, root length, fresh weight and dry weight by 34.6%, 20.7%, 25.3%, and 25.2%, respectively under Pb exposure, compared with the control (p ≤ 0.05). Photosynthetic pigments also reduced with Pb stress, chlorophyll a (0.02 mg g⁻¹ FW), chlorophyll b (0.28 mg g⁻¹ FW), carotenoids (0.24 mg g⁻¹ FW) and relative water content (56.2%), resulting in disruption of photosynthetic activity. Importantly, GA₃ application to plants grown under Pb stress significantly alleviated Pb-induced oxidative damage by restoring growth traits. Application of GA₃ significantly increased chlorophyll content, carotenoids and relative water content. Pb stress triggered the antioxidant enzymatic activities, including superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase, reflecting enhanced oxidative stress. GA₃ application under Pb stress further strengthened antioxidant defence, resulting in more efficient reactive oxygen species detoxification
