Silicon crosstalk with reactive oxygen species, phytohormones and other signaling molecules

Exogenous applications of silicon (Si) can initiate cellular defence pathways to enhance plant resistance to abiotic and biotic stresses. Plant Si accumulation is regulated by several transporters of silicic acid (e.g. Lsi1, Lsi2, and Lsi6), but the precise mechanisms involved in overall Si transport and its beneficial effects remains unclear. In stressed plants, the accumulation of Si leads to a defence mechanism involving the formation of amorphous or hydrated silicic acid caused by their polymerization and interaction with other organic substances. Silicon also regulates plant ionic homeostasis, which involves the nutrient acquisition, availability, and replenishment in the soil through biogeochemical cycles. Furthermore, Si is implicated in modulating ethylene-dependent and jasmonate pathways, as well as other phytohormones, particularly under stress conditions. Crosstalk between Si and phytohormones could lead to improvements in Si-mediated crop growth, especially when plants are exposed to stress. The integration of Si with reactive oxygen species (ROS) metabolism appears to be a part of the signaling cascade that regulates plant phytohormone homeostasis, as well as morphological, biochemical, and molecular responses. This review aims to provide an update on Si interplays with ROS, phytohormones, and other signaling molecules that regulate plant development under stress conditions

Silicon nanoforms in crop improvement and stress management

Although, silicon – the second most abundant element in the earth crust could not supersede carbon (C) in the competition of being the building block of life during evolution, yet its presence has been reported in some life forms. In case of the plants, silicon has been reported widely to promote the plant growth under normal as well as stressful situations. Nanoform of silicon is now being explored for its potential to improve plant productivity and its tolerance against various stresses. Silicon nanoparticles (SiNPs) in the form of nanofertilizers, nanoherbicides, nanopesticides, nanosensors and targeted delivery systems, find great utilization in the field of agriculture. However, the mechanisms underlying their uptake by plants need to be deciphered in detail. Silicon nanoformss are reported to enhance plant growth, majorly by improving photosynthesis rate, elevating nutrient uptake and mitigating reactive oxygen species (ROS)-induced oxidative stress. Various studies have reported their ability to provide tolerance against a range of stresses by upregulating plant defense responses. Moreover, they are proclaimed not to have any detrimental impacts on environment yet. This review includes the up-to-date information in context of the eminent role of silicon nanoforms in crop improvement and stress management, supplemented with suggestions for future research in this field.National Institute of Plant Genome ResearchCrop Nanobiology and Molecular Stress Physiology Laboratory Amity Institute of Organic Agriculture Amity University Uttar Pradesh, Sector-125National Agri-Food Biotechnology Institute (NABI), PunjabDepartment of Biotechnology Panjab UniversityPlant-Microbe Interaction Laboratory Amity Institute of Organic Agriculture Amity University Uttar Pradesh, Sector-125D D Pant Interdisciplinary Research Laboratory Department of Botany University of Allahabad, UPCentre of Advanced Study in Botany Banaras Hindu UniversityDepartment of Biotechnology Motilal Nehru National Institute of Technology, PrayagrajDepartment of Botany C.M.P. Degree College University of AllahabadDepartment of Biology Saint Joseph's University, University City Campus, 600 S, 43rd St. PhiladelphiaSão Paulo State University (UNESP) Department of Physics and Chemistry School of Engineering, Ilha SolteiraDepartment of Chemistry and Biochemistry The University of Texas at El Paso, 500 West University Ave.São Paulo State University (UNESP) Department of Physics and Chemistry School of Engineering, Ilha Solteir