Silicon-Mediated Drought Tolerance: An Enigmatic Perspective in the Root–Soil Interphase

Drought is one of the major yield-limiting factors under climatic adversaries. The positive role of silicon (Si) in drought tolerance of plants has unfolded a new avenue for enhancing crop productivity through better Si use efficiency. It is hence interesting to understand the mechanistic insights pertaining to its beneficial roles under drought stress conditions. Higher plants sense drought stress via roots which, regulate aboveground plant growth under stress. Cellular and molecular modulations occurring at the root and soil interphases influence the survival and growth of plants under drought stress; therefore, it is intriguing to know how Si influences the soil–root interphase and how this interaction augments overall plant growth under drought. In this review, we summarised the roles of Si in the root systems, rhizosphere and their interactions that could improve plant's growth and development under drought conditions. We have discussed the direct and indirect effects of Si-induced belowground changes on plant roots, soil physical, chemical and biological properties, and their mutual interactions in eliciting defence signalling, including hormone signalling pathways. A mechanistic model of Si-induced beneficial effects in water-limited environments is suggested, which could help improve the management of rainfed croplands through Si fertilisation.