Seed priming with silicon quantum dots promotes maize seedling establishment in coastal saline soil

Developing efficient, eco-friendly strategies to enhance crop salt tolerance is essential for sustaining grain productivity in saline soils. Although silicon quantum dots (Si QDs) have been reported to enhance crop stress resilience through soil or foliar application, their potential as seed priming agents to regulate crop salt tolerance remains poorly understood.

To address this question, we synthesized water-soluble Si QDs via a one-step hydrothermal method. Using maize (Zea mays L.) as the model crop, we first performed plate germination assays to compare Si QDs priming effects with those of hydropriming, sodium silicate (Na₂SiO₃), and silica nanoparticles (SiO₂ NPs). We further conducted pot experiments to systematically evaluate the growth-promoting efficacy and physiological basis of Si QDs seed priming in Yellow River Delta coastal saline soil.

At high salinity (125-150 mM), Si QDs seed priming significantly enhanced the germination rate, germination potential, germination index, root length, shoot length, and vigor index in maize. Si QDs seed priming improved the overall germination performance by 132.3% and 39.9% relative to Na2SiO3 and SiO2 NPs priming, respectively. Pot experiments demonstrated that Si QDs seed priming enhanced seedling emergence, biomass accumulation, and root system architecture. Notably, Si QDs seed priming significantly improved seedling responses to salt stress, as reflected by a 19.5% decrease in the Na⁺/K⁺ ratio, a 10.1% increase in superoxide dismutase activity, a 25.4% decrease in malondialdehyde content, and a marked enhancement in photosynthetic capacity. With ultrasmall particle size and abundant hydrophilic functional groups, Si QDs form effective interfacial contact with the seed coat, and are efficiently internalized by seed tissues, thereby enhancing germination. In addition, Si QDs promote maize seedling growth via synergistic regulation of ion homeostasis, enhancement of antioxidant defense, and improvement of photosynthetic efficiency. Collectively, this study not only demonstrates that Si QDs outperform conventional Na2SiO3 and SiO2 NPs as seed priming agents, but also expands the application scope of Si QDs from post-emergence field application to pre-sowing seed priming. These findings provide experimental evidence supporting potential application of Si QDs in Yellow River Delta coastal saline soil.