Carbon dots improve the nutritional quality of coriander (Coriandrum sativum L.) by promoting photosynthesis and nutrient uptake

Coriander (Coriandrum sativum L.) seedlings were cultivated in 50% Hoagland's nutrient solution amended with carbon dots (CDs) at different concentrations (0, 10, 20, 30 and 40 mg L-1) for 7 days to mechanistically explore impacts on carbohydrate, protein, vitamin C, and mineral nutrient content in the edible tissues. Amendment with 40 mg L-1 CDs increased the soluble sugar and protein content in coriander leaves by 17.0 and 27.1% in comparison with controls, respectively. Also, 30 and 40 mg L-1 CDs significantly increased the vitamin C content in coriander leaves by 22.8 and 26.0%, respectively. These increases are likely due to CDs promotion of photosynthesis. Further investigation revealed that CDs treatment increased chlorophyll content, rubisco activity, and photosystem II (PSII) activity by accelerating the electron transfer rate. Furthermore, in coriander shoots, CDs at 30 mg L-1 significantly increased K and Mn content by 25.7 and 16.3%, respectively. CDs at 40 mg L-1 increased the content of K by 64.3%, Ca by 21.0%, Mg by 26.2%, P by 12.8%, Mn by 56.0% and Fe by 125%, relative to untreated controls; these increases appear to be related to an increased transpiration rate with CDs amendment. Antioxidant response analysis revealed that CDs enhance plant stress resistance, which also benefits plant growth and productivity. These findings show that CDs promote photosynthesis and the uptake of essential elements, thereby improving crop nutritional quality, and may be a novel nano-enabled strategy to increase agricultural production.