FIGURE 2.

The silicon-induced mechanism for regulating abiotic stresses. (A) Silicon is taken up through anion transporters. (B) Drought and salinity stress induce osmotic stress and osmotic imbalance. Si enhances the synthesis of osmoprotectants like proline, glycine, and betaine. (C) Stress induces the formation of ROS. Si enhances the expression of CAT, SOD, and POD for protection against oxidative damage. (D–F) Si supplementation results in transcriptional regulation of genes related to photosynthesis, such as overexpression of PsaH, which encodes essential polypeptide subunits of photosystem-I (PSI) dimer, the PsbY (Os08g02530) gene encoding polyprotein component of Photosystem II and the PetC gene, encoding Rieske Fe-S center-binding polypeptide of cytochrome bf complex. (G) Si modulates the synthesis of plant growth regulators to alleviate stress. Si induces the S-adenosyl-L-methionine decarboxylase (SAMDC) gene, encoding essential enzymes responsible for synthesizing polyamines. (H) Salinity stress negatively affects plant growth by increasing the accumulation of ions up to toxic levels. Due to a higher influx of NaCl, plants experience more severe oxidative and ionic stress. Sodium-ion accumulation up to toxic levels triggers ROS production, which, in turn, severely damages the cellular components and accelerates senescence in mature leaves, leading to reduced growth and metabolism. Si administration improves uptake of K⁺, which, in turn, stimulates H+-ATPase enzymes in the plasma membrane that helps to overcome salt stress.