SiO₂-based composite nanomaterials outperform single SiO₂: effects for alleviating drought stress in spring wheat

Drought stress has become a major obstacle to achieving high and stable yields in spring wheat. Although nanomaterials have been widely studied as a strategy to alleviate drought, the relative effectiveness of different SiO₂-based composite nanomaterials and their cultivar-dependent responses remain unclear. To address this issue, this study investigated five nanocomposites (NCs), Fe₃O₄@SiO₂, Fe₂O₃@SiO₂, ZnO@SiO₂, MgO@SiO₂, and Al₂O₃@SiO₂, were evaluated in two spring wheat cultivars, Ningchun 16 and Dingxi 48, under different concentration gradients. Growth traits, water status, germination characteristics, photosynthetic pigments, and antioxidant-related parameters were measured to determine the optimal application concentrations and elucidate the underlying physiological responses. The results confirmed the successful construction of core-shell Fe₃O₄@SiO₂ NCs and identified the optimal concentrations as 75 mg L^-1 Fe₃O₄@SiO₂, 25 mg L^-1 Fe₂O₃@SiO₂, ZnO@SiO₂, and MgO@SiO₂, and 100 mg L^-1 Al₂O₃@SiO₂. Among them, Fe₃O₄@SiO₂, MgO@SiO₂, and Al₂O₃@SiO₂ exhibited the most stable and pronounced promotive effects. Compared with single nanomaterial treatments, composite treatments significantly improved seedling growth, relative water content, germination performance, and photosynthetic pigment accumulation, while reducing malondialdehyde content and antioxidant enzyme activities by 10.7-32.9% and 25.2-79.6%, respectively. In contrast, SiO₂ alone did not result in significant improvement, confirming that the incorporation of substances like Fe₃O₄ was critical for enhancing the drought-alleviating efficacy of SiO₂ nanomaterials. Comparison between cultivars showed that Ningchun 16 exhibited a greater degree of recovery than Dingxi 48. Overall, SiO₂-based composite nanomaterials, especially Fe₃O₄@SiO₂, MgO@SiO₂, and Al₂O₃@SiO₂, can effectively enhance drought tolerance in spring wheat by strengthening the photosynthetic system and antioxidant defense system.