Foliar Application of Silica Nanoparticles Positively Influences the Early Growth Stage and Antioxidant Defense of Maize Under Low Light Stress

Low light reduces growth and adversely affects the antioxidant defense system. At the same time, the silica nanoparticles (SiO2 NPs) mitigate the biotic and abiotic stresses and improve plant growth. Therefore, this study investigated whether SiO2 NPs alleviates the low light stress by measuring the biomass and physiological indices of maize seedlings. A hydroponic experiment was set up with two maize varieties, Yuebaitiannuo10 and Yuebaitiannuo12, grown under two light treatments, namely normal light (NL) and low light (LL) and three SiO2 NPs foliar treatments (SiO2 NPs at doses of 0 mg L- 1 (Si0), 150 mg L- 1 (Si1), and 300 mg L- 1 (Si2)). The plant growth, antioxidant responses, nitrogen metabolism, and photosynthetic pigments in the maize seedlings were determined. The results showed that the low light treatment significantly reduced the maize seedling growth in both varieties. However, the SiO2 NPs slightly increased the biomass and altered the growth, with the highest aboveground dry weight/plant height detected in the Si1 treatment, irrespective of the maize variety and light treatment. Compared to the Si0 treatment, Si1 significantly increased the aboveground dry weight/plant height by 35.38% in Yuebaitiannuo12 at low light. Various changes in antioxidant response, photosynthesis pigments, and nitrogen metabolism were recorded in the different maize varieties and light treatments in response to the SiO2 NPs treatments. Correlation analysis suggested that the maize seedling growth parameters and biomass were related to the superoxide dismutase (SOD) activity and ascorbic acid content in the root, SOD activity and malondialdehyde content in the stem, and nitrate reductase activity in the leaves (P<0.05). The results of this study provide a theoretical basis for expanding the research on the application of SiO2 NPs in maize. It also provides the relevant reference for elucidating the response mechanism of maize seedlings under fluctuating light environments to lay a foundation for improving maize yield at later growth stages.