Silicon and Strigolecton Application Alleviates the Adversities of Cadmium Toxicity in Maize by Modulating Morpho-Physiological and Antioxidants Defense Mechanisms

Abstract

Cadmium (Cd) toxicity is a serious threat to agronomic crop productivity worldwide. It raises severe concerns about the food and nutrient security required to meet the demands of a rapidly growing population, while also creating grave challenges for agriculture. Silicon (Si) and strigolecton (SL) are reported to impart multiple benefits to plants exposed to abiotic stress. Therefore, the current experiment was performed to evaluate the effects of silicon (4.0 mM) and strigolecton (20 µM) on the amelioration of cadmium (25 mg kg−1 soil) stress in maize seedlings via intervention in morphological attributes, photosynthetic pigments, enzymatic antioxidant mechanisms, and osmolyte accumulation. The results indicated that morphological attributes and photosynthetic pigments were significantly reduced in Cd-exposed seedlings. However, foliar application of Si and SL, both individually and in combination, significantly improved the growth attributes and photosynthetic pigments of maize seedlings under both control and Cd-stress conditions. Exposure of maize seedlings to Cd stress increased H2O2 levels, malondialdehyde content, and electrolyte leakage and reduced cell membrane stability. These effects were significantly negated by Si and SL supplementation, both individually and in combination. Moreover, enzymatic antioxidants, including catalase, superoxide dismutase, peroxidase, and ascorbate peroxidase, were activated after Cd stress, but their activity was further increased with foliar application of Si or SL. In Cd-contaminated seedlings, the combined application of Si and SL enhanced soluble proline, sugars, and total phenolic contents as compared to the control treatment. Furthermore, Si and SL applications increased Si accumulation in Cd-exposed seedlings and decreased Cd uptake. It was concluded that the combined application of Si and SL improved Cd tolerance in maize seedlings by modulating morpho-physiological attributes, photosynthetic pigments, and osmolytes accumulation, and by supporting the antioxidant defense system. The findings of this study suggest that Si and SL could be safe and effective strategies for reducing Cd toxicity in maize seedlings.