Silicon and Titanium Dioxide Mitigate Copper Stress in Wheat (Triticum aestivum L.) Through Regulating Antioxidant Defense Mechanisms

Copper (Cu), with many documented cases of Cu toxicity in agriculture lands, is becoming an increasingly common issue in the world, but fewer studies have been conducted on its effects and alleviation strategies through the use of titanium dioxide nanoparticles (TiO2-NPs) and silicon (Si). For this purpose, we have conducted a pot experiment to determine the effects of seed priming with TiO2-NPs i.e., 40 mg L-1 and Si i.e., 3 mM on wheat (Triticum aestivum L.) under different levels of Cu in the soil i.e., 0 (no Cu), 100 and 200 mg kg(-1). Results from the present study showed that the increasing concentrations of Cu in the soil caused a significant decrease in the plant growth and biomass, chlorophyll pigments and gas-exchange characteristics, sugar content, essential ions in the roots and shoots of the plant, compared to control. In addition, increasing concentration of Cu also increases oxidative damage, enzymatic and non-enzymatic enzymes along with their gene expression, organic acids exudation patter and Cu concentration in the roots and shoots of the plant. The negative impact of Cu toxicity can overcome the application of TiO2-NPs and Si, which ultimately increased plant growth and biomass by capturing the reactive oxygen species (ROS), and decreased oxidative stress in T. aestivum by decreasing the Cu contents in the roots and shoots of the plants. Research findings, therefore, suggest that the combined application of TiO2-NPs and Si can ameliorate Cu toxicity in T. aestivum, resulting in improved plant growth and composition under metal stress, as depicted by balanced exudation of organic acids. [GRAPHICS]