Green synthesis of silica nanoparticles using chia seeds boosts rice germination and physiological responses

Abstract

This study aimed to synthesize silicon nanoparticles (SiNPs) using two different approaches: chemical (Chem-SiNPs) and biological (Bio-SiNPs) methods, utilizing chia (Salvia hispanica L.) seed extract as a capping agent and bulk silica (SiO2) as a precursor (Bulk-Si). Both routes were employed to compare the conventional chemical method with an eco-friendly, plant-based approach, enabling a comprehensive evaluation of how the fabrication technique influences the physicochemical properties and biological effectiveness of the resulting SiNPs. The synthesized SiNPs were characterized using UV-spectrophotometer, TEM, FTIR, XRD, and zeta potential analysis. Also, the impact of nano-priming with two concentrations (30 and 100 ppm) of Bulk-Si, Chem-, and Bio-SiNPs on the germination and key physiological mechanisms of Oryza sativa L. var. Sakha 108 seedlings were investigated. Characterization results showed that Bio-SiNPs surpassed Chem-SiNPs, exhibiting greater stability and a higher surface area, likely due to the available bioactive phytochemicals in the chia extract. This phytochemical capping layer enhances the stability and bioactivity of Bio-SiNPs, thereby activating key metabolic and physiological responses in rice seedlings. Bio-SiNPs at 100 ppm exhibited the highest improvement in germination rate (97.3%), germination index (65.3%), germination rate index (130.73), seedling vigour index (18.68), seedling biomass (0.033 g), and water uptake (31.53%) compared to Chem-SiNPs and Bulk-Si treatments. Likewise, Bio-SiNPs at 100 ppm concentration significantly increased total soluble sugars, α-amylase, radicle dehydrogenase activities, and Si content in rice seedlings. All SiNPs treatments induced significant changes in proline, malondialdehyde, hydrogen peroxide accumulation, glutathione level, and the antioxidant enzyme activities compared to the bulk material. This research reveals substantial variations in many critical physiological and biochemical parameters, which explain the varying responses of rice seedlings to various nano-synthesis protocols. It illustrates the efficacy of using chia seed extract as a green capping agent for nano priming as a sustainable approach to enhance germination and boost future rice productivity.