Magnesium oxide nanoparticles and thidiazuron enhance lead phytoaccumulation and antioxidative response in Raphanus sativus L.

An in vitro study was conducted to evaluate the effects of thidiazuron (TDZ) growth regulator and magnesium oxide (MgO) nanoparticles on radish (Raphanus sativus L.) under lead (Pb) stress. Effects of TDZ and MgO on seed germination, growth, biomass, total phenolics and flavonoids, antioxidant potential, and Pb phytoaccumulation in different plant parts were assessed. Nanoparticles of MgO were synthesized with leaf extract of Sageretia thea (Osbeck) plant. Thidiazuron and MgO nanoparticles were added to growth media in individual and in combinations. Lead (50 mg L^-1) was added to growth media. Thidiazuron and MgO nanoparticles increased plant growth, phenolic and flavonoid contents, free radical scavenging activity, and lead phytoaccumulation. The increase was highly significant in TDZ and MgO nanoparticle combination treatments (T5, T6). Treatment (T6) showed a sixfold increase in Pb accumulation (1721.73 ± 17.4 μg g^-1 dry biomass) as compared to control (274.29 ± 4.23 μg^-1g^-1). Total phenolic and dry biomass showed significantly positive correlation in leaves (R² = 0.73), stem (R² = 0.58), and roots (R² = 0.72). The correlation of Pb accumulation and phenolic contents was significantly positive in root (R² = 0.80), stem (R² = 0.92), and leaves (R² = 0.69). Flavonoid showed a positive correlation with dry biomass and Pb accumulation. Antioxidant activity was highly increased in leaves followed by stem and root. Findings show that TDZ in combination with MgO nanoparticles can play a significant role in secondary metabolite production and Pb phytoaccumulation.