Exogenous supply of zinc modulates plant growth and physiological attributes of wheat under cadmium and drought stress

Soil contamination with cadmium (Cd) along with drought stress causes severe decline in wheat production around the world. The current study was designed to unravel the role of Zn in modulation of Cd phytotoxicity and phytoremediation in wheat under drought stress. Wheat plants were exposed to Cd (0, 20 mg kg^-1) and Zn (0, 10 mg kg^-1) under moist (70% of water-holding capacity and drought stress (35% of water-holding capacity) conditions. A significant reduction was observed in plant growth (44%), chlorophyll contents (47%), and stomatal conductance (46%) in plants under the dual stress of Cd and drought. The level of oxidative stress markers (H₂O₂ and lipid peroxidation) enhanced under combined Cd and drought stress, resulting in membrane damage. The supplementation of Zn partially alleviated negative effects of Cd and drought on plants. Under the combined treatment of Cd and drought, Zn addition caused a 27%, 24%, and 27% increase in plant growth, chlorophyll contents and stomatal conductance, respectively. Zinc application limited root to shoot transfer of Cd and lowered the oxidative damage by enhancing the activities of catalase, superoxide dismutase, and peroxidase by 16%, 18%, and 17%, respectively. Hence, the exogenous application of Zn proved to be a promising strategy for mitigating the phytotoxicity of Cd and enhancing its phytostabilization under water limited conditions.