Foliar spray of LaO nanoparticles regulates the growth, antioxidant parameters, and nitrogen metabolism of fragrant rice seedlings in wet and dry nurseries.

Nanoparticles (NPs) have been widely used in agriculture, and lanthanum oxide nanoparticles (LaO) NPs can regulate plant growth. LaO NPs treatment was hypothesized to affect the accumulation and distribution of substances in rice seedlings under wet and dry nursery conditions. The objective of the present study was to ascertain the effects of LaO NPs foliar spray on the morphology and physiology of fragrant rice seedlings under wet and dry nursery conditions. Seedlings of two fragrant rice cultivars, namely 'Xiangyaxiangzhan' and 'Yuxiangyouzhan,' were grown under wet and dry nursery conditions with LaO NPs treatments at three concentrations (CK, LaO NPs 0 mg L; T1, LaO NPs 20 mg L; and T2, LaO NPs 40 mg L). The results showed that the seedling-raising method was significantly associated with LaO NPs application (P < 0.05), affecting the leaf area of both cultivars. Changes in plant morphological parameters, such as dry weight and root-shoot ratio, were the reasons for the differences in cultivars in response to LaO NPs application. Changes were also observed in the plant morphological and physiological parameters of leaf area, specific leaf area, chlorophyll contents, antioxidant properties, and activities of nitrogen metabolism enzymes. The relationship between morphological and physiological processes in fragrant rice was investigated to test the hypothesis. In both wet and dry nursery methods, the T2 concentration of LaO NPs was beneficial for rice seedlings and significantly increased their leaf area due to changes in morphological and physiological parameters. Therefore, the results of this study provide a theoretical basis for expanding the research on LaO NPs application in rice, as well as relevant references for strengthening rice seedlings in the nursery, which has a positive effect on the grain yield improvement in fragrant rice.