Exploring the significant contribution of silicon in regulation of cellular redox homeostasis for conferring stress tolerance in plants

Silicon (Si), a bioactive metalloid is beneficial for plant growth and development. It also plays a key role in the amelioration of different abiotic and biotic stresses. Extensive studies have elucidated the morpho-physiological, biochemical and molecular background of Si-mediated stress tolerance in plants. However, the mechanism acquired by Si to enhance stress tolerance in plants is still unheeded. Present review summarized the prospective mechanisms of Si in acquisition of stress tolerance with emphasis on its interactions with secondary messengers. Silicon usually modulates the different gene expressions in plants under stress conditions rather than acting as a direct signal or secondary messengers. Silicon regulates the production and accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in plants under stress conditions. Furthermore, Si also activates the antioxidant defence system in plants; thereby, maintaining the cellular redox homeostasis and preventing the oxidative damage of cells. Silicon also up-regulates the synthesis of hydrogen sulfide (H2S) or acts synergistically with nitric oxide (NO), consequently conferring stress tolerance in plants. Overall, the review may provide a progressive understanding of the role of Si in conservation of the redox homeostasis in plants.