Effect of silver nanoparticles on rice (Oryza sativa L. cv. KDML 105) seed germination and seedling growth

•The larger sizes of AgNPs had more negative effects on rice seedling growth.•Better penetration of the smaller AgNPs into roots was found.•But the smaller AgNPs were less efficiently transported through shoots.•The higher concentration of AgNPs had more negative effect on rice seedling growth.•Overnight AgNP treatment during seed germination cause cell deformation in leaves.

With the advances in nanotechnology, silver nanoparticles (AgNPs) have been applied in many industries, increasing their potential exposure level in the environment, yet their environmental safety remains poorly evaluated. The possible effects of different sized AgNPs (20, 30–60, 70–120 and 150 nm diameter) on jasmine rice, Oryza sativa L. cv. KDML 105, were investigated at different concentrations (0.1, 1, 10, 100 and 1000 mg/L) upon seed germination and seedling growth. The results revealed that the level of seed germination and subsequent growth of those seedlings that germinated were both decreased with increasing sizes and concentrations of AgNPs. Based on the analysis of AgNPs accumulation in plant tissues, it implied that the higher uptake was found when the seeds were treated with the smaller AgNPs, 20 nm diameter AgNPs, but it was trapped in the roots rather than transported to the leaves. These resulted in the less negative effects on seedling growth, when compared to the seed soaking with the larger AgNPs with 150 nm diameter. The negative effects of AgNPs were supported by leaf cell deformation when rice seeds were treated with 150-nm-diameter AgNP at the concentration of 10 or 100 mg/L during seed germination. These results further strengthen our understanding of environmental safety information with respect to nanomaterials.