Effects of iron oxide nanocoatings on the seed germination, seedling growth, and antioxidant response of aromatic rice grown in the presence of different concentrations of rice straw extracts

Straw returning to the field has an inhibitory effect on seed germination and the early stage of seedling growth. Nanoparticles may contribute to good seed germination and seedling growth under stress. However, the effects of nanoparticles on seed germination and seedling growth of rice under straw returning remain unknown. Two popular aromatic rice varieties, Xiangyaxiangzhan and Meixiangzhan 2, were used as experimental materials. Three doses of iron oxide nanoparticles (Fe₂O₃ NPs) (i.e., 0 mg L⁻¹, 25 mg L⁻¹, and 50 mg L⁻¹) were used for seed coating, and the nanoparticle-coated seeds were grown at three concentrations of straw extract (i.e., 0 g L⁻¹, 10 g L⁻¹, and 20 g L⁻¹). The seed germination, seedling growth, antioxidant response, and nitrogen metabolism of aromatic rice were studied. The results showed that the aromatic rice varieties responded differently to straw concentration. Straw extract at 10 mg L⁻¹ promoted the germination of Xiangyaxiangzhan but inhibited the germination of Meixiangzhan 2. With increasing straw extract concentration, the antioxidant response of Xiangyaxiangzhan increased. Fe₂O₃ NPs significantly increased seed germination under straw stress by 5–44%. The growth response of aromatic rice to iron oxide nanoparticle coating treatments varied among the different aromatic rice varieties and straw extract treatments. Therefore, iron oxide nanoparticle coating improved seed germination and regulated early growth and physiological parameters in aromatic rice.