The ~ 5 nm degradable carbon dots (CDs) were synthesized directly from carbon rod by a one-step electrochemical method at room temperature. The as-prepared CDs can effectively enhance the ribulose bisphosphate carboxylase oxygenase (RuBisCO) activity, and then promote the dicotyledons growth (soybean, tomato, eggplant and so on) and finally increase their yields. Here, we used Arabidopsis thaliana and Trifolium repens L. as model plants to systematically study the beneficial effects of CDs on plant growth. These include: (i) accelerating seed germination; (ii) enlarging root elongation; (iii) increasing metal ions absorption and delivery; (iv) improving enzymes activity; (v) enhancing the carbohydrate content; (vi) degradation into plant hormone analogues and CO₂; and finally (vii) enhancing the grain production by about 20%.