Exogenous molybdenum mitigates cadmium-induced toxicity in wheat (Triticum turgidum L.) germinating seeds

Cadmium (Cd) contamination of agricultural soils represents a serious threat to crop productivity and food security due to its phytotoxic effects. In this context, the present study investigates the protective effects of molybdenum (Mo) against Cd-induced oxidative stress in germinating wheat (Triticum turgidum L.) seeds. Seeds were pretreated with ammonium molybdate at 0, 1, 2, or 3 µM for 12 h before germination under control or Cd stress conditions (400 µM CdCl₂). Results indicated that 2 µM Mo was most effective at mitigating Cd-induced growth inhibition; therefore, this concentration was selected for physiological analyses. Mo pretreatment reduced Cd accumulation while increasing tissue Mo content, thereby improving the cellular redox state under Cd stress. This was associated with decreased levels of superoxide anions [Formula: see text], hydroxyl radicals (·OH), and hydrogen peroxide (H₂O₂). Mo also protected membrane integrity, as indicated by reduced lipoxygenase activity and lower levels of malondialdehyde and 4-hydroxy-2-nonenal, thereby decreasing electrolyte leakage and improving cell viability. Improved redox homeostasis was correlated with enhanced antioxidant enzyme activities, including superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, and glutathione reductase. Moreover, Mo enhanced methylglyoxal detoxification by stimulating glyoxalase I and II activities, thereby limiting methylglyoxal accumulation. Likewise, Mo regulated the proline content by modulating its metabolism, particularly through the regulation of Δ¹-pyrroline-5-carboxylate synthase and proline dehydrogenase. These findings highlight the protective role of Mo in mitigating Cd-induced stress, providing insights into potential strategies to enhance seed tolerance to Cd contamination.