Mitigation of Salinity Stress and Lead Toxicity in Maize by Exogenous Application of the Sorghum Water Extract

The increased concentration of lead (Pb) in soils is a serious threat to human beings and plants all over the world. Salinity stress is also a major issue across the globe, which limits crop productivity. The use of allelochemicals has become an effective strategy to mitigate the toxic effects of abiotic stresses. Sorghum is an important crop grown across the globe, and it also possesses an appreciably allelopathic potential. Therefore, this study was planned to determine the impacts of the sorghum water extract (SWE) on improving maize growth under Pb and salinity stress. The experiment included different treatments; control, SWE (3%), and different levels of Pb and salinity stress; T₁: control, T₂: 50 mM NaCl, T₃: 100 mM NaCl, T₄: 250 μM Pb, and T₅: 500 μM Pb. Lead and salinity stress reduced the maize growth by the genesis of reactive oxygen species (ROS), as evidenced by higher production of malondialdehyde (MDA: 39.1 and 32.28%) and hydrogen peroxide (H₂O₂: 20.62 and 17.81%). Spraying plants with SWE improved the maize growth by increasing antioxidant activities (ascorbate peroxidase: APX, catalase: CAT, peroxidase: POD and superoxide dismutase: SOD), photosynthetic pigments, relative water contents (RWC), osmolyte accumulation (proline, total soluble proteins: TSP, free amino acids: FAA), potassium accumulation, and decreasing MDA, H₂O₂, sodium, chloride, and Pb accumulation. In conclusion, the application of SWE mitigates adverse impacts of Pb and salinity stresses by improving chlorophyll synthesis and osmolyte accumulation, activating the antioxidant defense system, and preventing the entry of toxic ions.