Conferring Drought and Salinity Stress Tolerance in Horticultural Crops by Si Application

Due to climate change, and increasing environmental stresses the foliar and soil application of Si, as well as genetic engineering application to increase Si uptake, has gained special importance. Anatomical, biochemical, and metabolic changes in plant tissues that result from the accumulation and transport of Si in the cell are responsible for its beneficial role. Although Si has been introduced as a quasiessential element, its effectiveness in increasing the activity of the antioxidant system, altering the biosynthesis or signaling pathways of hormones, and controlling reactive oxygen species (ROS) indicate its importance and necessity beyond a quasi-essential element in plant nutrition. Si is also involved in absorbing and transporting other elements, and Si nutrition is effective in improving plant growth under both deficiency and toxicity of elements such as iron and manganese. This element decreases stress intensity through non-chemical mechanisms, such as reducing the transfer of toxic elements from the roots to the shoots and improving plant water relations through mechanical changes caused by Si deposition in plant tissues, which in turn alter gene expression through hormonal signals. In this review, we have provided useful information on the application of Si in horticultural crops. However, the effect of silicon on metabolic processes is not well understood and requires a comprehensive study.