Role of silicon on root morphological characters of wheat ( Triticum aestivum L.) plants grown under Cd-contaminated nutrient solution

Heavy metal toxicity causes a remarkable decline in the growth and yield of numerous plant species in the agricultural system. Cadmium (Cd) among the other heavy metals is the most distinguished lethal heavy metal as its higher water solubility, relative mobility, and phytotoxicity. Silicon (Si), as a second most abundant element, has been reported to mitigate numerous abiotic stresses, comprising heavy metal stress in plants. The 2-repeated studies were conducted to disclose the protective role of silica gel derived from sodium silicate (Na 2 SiO 3 ) at the rate of 1 and 3 mmol L −1 on the root morphological characters of wheat plants grown in cultured medium with three levels of Cd toxicities (0, 50, and 200 µmol L −1 ). The results of our studies demonstrated a remarkable alteration in morphological traits of wheat roots with both levels of Cd toxicities through incorporating an excessive amount of reactive oxygen species (ROS), by lipid peroxidation, by limitation of essential nutrient availability, and by the accumulation of the high contents of Cd in root cells. While the introduction of Si nanoparticles at the rate of 1 and 3 mmol L −1 in the cultured medium having Cd toxicities remarkably demolished Cd adversity by shifting the balance between antioxidant enzymes and oxidants of ROS. Moreover, Si significantly increased cations concentrations in root tips that compete with Cd ions for exchange sites and reduced Cd uptake and accumulation by roots. Being an effective beneficial element, Si improved root morphological characters by strengthening the antioxidative defense system and by hindering ROS in root tissues grown in a cultured medium with different toxicities of Cd.