Silicon-functionalized nanotherapeutics modulate physio-biochemical functions and soil enzyme profile for curtailing cadmium toxicity in rice (Oryza sativa L.) at vegetative phase

Abstract

Cadmium (Cd) contamination severely threatens agricultural productivity and food safety. This study examines the ability of biogenic silicon nanoparticles (SiNPs) as nanotherapeutics to mitigate Cd stress in rice (Oryza sativa L.) by enhancing physiological and biochemical responses. A controlled greenhouse experiment demonstrated that SiNPs (250 mg kg⁻¹) significantly improved plant growth under Cd stress. The application of SiNPs increased plant height, fresh and dry weight by 22.98 %, 25.18 %, and 30.01 %, respectively, as compared to the control. Photosynthetic efficiency was also improved, as evidenced by increase in chlorophyll a and b content (17.02 % and 56.86 %, respectively). SiNPs strengthened the plant defense system by enhancing the activities of antioxidant enzymes, such as superoxide dismutase (23.18 %), peroxidase (41.98 %), and ascorbate peroxidase (11.29 %), while simultaneously reducing reactive oxygen species accumulation. SiNPs also enhanced the absorption of various essential nutrients and reduced Cd accumulation (by 61.04 %) in rice leaves compared to Cd-stressed plants without SiNPs treatment. Gene expression analysis showed that SiNPs upregulated genes associated with silicon transport, antioxidant activity, and phyto-chelation, further validating the Cd detoxification in rice plants. Moreover, soil enzyme activities and nutrient cycling improved upon SiNPs exposure. Leaf ultrastructure analysis revealed that SiNPs preserved normal cellular morphology and minimized Cd-induced damage. These findings highlight biogenic SiNPs (as nanotherapeutics) are effective and environmentally friendly solution for reducing Cd toxicity in rice.