Silicon Quantum Dots Enhance the Nutritional Quality and Digestive Bioaccessibility of Cherry Radish ( <i>Raphanus sativus</i> L.) via Rhizosphere Modulation

Abstract A 50-day greenhouse pot experiment was conducted to evaluate the effects of soil-applied silicon quantum dots (Si QDs) and SiO2 nanoparticles (SiO2 NPs) at 50 mg kg−1 on cherry radish (Raphanus sativus L.), using unamended soil and ionic Si as comparative controls. Si QDs exhibited higher Si bioavailability and assimilation efficiency, increasing edible taproot biomass by 90.7% relative to the unamended control. Mechanistically, Si QDs enhanced taproot ammonium accumulation (23.1%) by stimulating urease activity and enriching beneficial rhizobacteria (Ramlibacter, Ensifer, Thauera). This promoted nitrogen assimilation, the TCA cycle, and phenylpropanoid metabolism, thereby elevating amino acids, glucosinolates, vitamin C, phenolic acids, and minerals in taproots by 12.0−153.8%. Conversely, SiO2 NPs primarily increased sugars and flavonoids. Furthermore, the INFOGEST model revealed that Si QDs significantly improved the in vitro bioaccessibility of essential amino acids, fatty acids, vitamins, and nucleosides by 34.1−131.9%. This study demonstrates that Si QDs provide an effective nano-agricultural strategy for simultaneously improving crop yield and postharvest nutritional delivery.