Foliar application of rice husk derived nanosilica for mitigating drought stress in hybrid maize by boosting antioxidant defense system

The increasing frequency and intensity of drought magnified by the climate change, pose significant challenge to global food security and agricultural productivity. Chemically synthesized nanosilica have emerged as a promising solution for managing drought stress, enhancing crop growth and stress resilience but, its production involves harmful chemicals which results in adverse impacts on soil, plant and environment. Hence, the present study aimed to green synthesize and characterize silicon nanoparticles from rice husk and to evaluate their potential for improving plant growth, development and stress mitigation in hybrid maize. The rice husk derived nanosilica has spherical morphology, amorphous nature, siloxane bonds and high purity (99 %). Five different levels of nanosilica (0.05, 0.10, 0.15, 0.20 and 0.25 %) were sprayed on hybrid maize grown under irrigated and drought conditions and the results revealed that, nanosilica spray has improved the stress tolerance, growth and photosynthetic parameters. An optimum response was noted with the nanosilica spray upto 0.10 % in irrigated plants and 0.15 % in drought stressed plants, where greater increase in plant height (27.7 and 28.9 %), total biomass (55.7 and 39.1 %), chlorophyll a (36.7 and 54.5 %), relative water content (12.5 and 24.9 %) and superoxide dismutase (23.0 and 35.7 %) activity was observed. This was ascribed to the alleviation of membrane damage by reduced melondialdehyde content (18.9 and 21.4 %) and electrolyte leakage (21.9 and 26.7 %) under irrigated and drought regimes. However, higher doses of nanosilica caused slight reduction in plant growth and antioxidant activity. We conclude that, foliar spraying of nanosilica synthesized from rice husk at a concentration of 0.10 % for irrigated and 0.15 % for hybrid maize exposed to drought stress has shown a positive effect on plant growth and stress mitigation. Nanosilica synthesised from rice husk is economical, environmentally feasible and efficiently boosts plant growth and stress tolerance. Further, to confirm the role of rice husk derived nanosilica in plant stress tolerance, the comprehensive molecular mechanisms underpinning the stress mitigation has to be studied in detail.