Abstract: To investigate the effects of silica nanoparticles （SiO₂ NPs） on rice seed germination, growth and photosynthesis, and provide a reference for the application of SiO₂ NPs in agricultural production, a completely randomized design was used, the surface of rice seeds and leaves was treated with 0.01, 0.10, 1.00 and 10.00 g/L aqueous dispersions of 30 nm SiO₂ NPs, expressed sequentially as T₁, T₂, T₃ and T₄, and deionized water was taken as control （CK）. The effects of SiO₂ NPs on rice seed germination, growth indices and photosynthetic characteristics such as plant height, tillering number, biomass, soluble polysaccharides content, soluble proteins content, free amino acids content, total phenols content, pigment content of chloroplast, photosynthetic rate and photosynthetic fluorescence parameters at tillering stage were investigated. The results showed that the germination potential, germinate index and vitality index of rice seeds under T₃ increased by 6.6%, 32.7% and 43.4% respectively compared to CK. Root biomass of rice under T₂ increased by 43.6% compared to CK, while stem and leaf biomass of rice under T₃ increased by 143.9% and 15.2% respectively. The contents of soluble polysaccharides and total phenols of rice leaves under T₃ were 107.1% and 26.7% higher than those in CK, respectively. The contents of chlorophyll a, chlorophyll b, carotenoid and total chlorophyll of rice leaves under T₄ were 21.3%, 60.3%, 45.6% and 30.6% higher than those in CK, respectively. Photosynthetic rate, the photochemical quenching coefficients qP and qL during the light reaction process, relative photoelectron conduction rate ETR and actual photochemical quantum yield Y（Ⅱ） of rice leaves under T₃ increased by 32.4%, 68.5%, 61.7%, 69.7% and 69.7% compared to CK respectively. It was recommended to use 0.10~1.00 g/L SiO₂ NPs for rice seed soaking and tillering stage treatment.

Key words: silica nanoparticles, rice （Oryza sativa L.）, seed germination, plant growth, photosynthetic properties, tillering stage