Silicon and Its Application Methods Improve Physiological Traits and Antioxidants in Triticum aestivum (L.) Under Cadmium Stress

Plants are exposed to various abiotic stressors in agricultural systems, especially cadmium (Cd) stress, which hinders plant growth and development. The current study was conducted to assess the protective role of silicon (Si) application in two methods and to identify the optimum method of Si application for wheat plants grown hydroponically under the same levels of Cd stress. For this purpose, we used two different silicon (Si; 1 mmol L-1 Na2SiO3) application methods (i.e., root application and foliar spray) on growth, chlorophyll contents, cell membrane injury contents, enzymatic and non-enzymatic antioxidants, and membrane permeability contents of winter wheat (Triticum aestivum L.) against four levels of cadmium (Cd), normal, 50 mu mol L-1, 100 mu mol L-1, and 200 mu mol L-1, in 2-repeated greenhouse experiments. Results showed that Cd stress markedly affects growth, chlorophyll contents, and physiological traits and boosted up anti-oxidative defense system activity, osmoprotectants, and Cd contents. However, Si application as foliar or root induced reversibility of Cd toxic effects by significantly increasing growth, chlorophyll contents, membrane stability index, and Si contents and significantly reducing membrane injury contents measured as electrolytic leakage (EL) contents, lipid peroxidation measured as malondialdehyde (MDA) contents, and osmotic pressure measured as hydrogen peroxide (H2O2) contents and increased in enzymatic and non-enzymatic anti-oxidative defense system's activity. Being an effective beneficial element, Si with the preference of root application improved leaf area, plant biomass, membrane characteristic, photosynthetic rate, and anti-oxidative defense system of wheat plants by alleviating Cd toxicity.