Carbon nanodots as modulators of growth, physiological and biochemical responses in forage pea (Pisum sativum L.)

Forage pea (Pisum sativum L.) is an important cool-season legume forage crop, and improving its early vegetative performance is of practical interest. In this study, we investigated the dose-dependent effects of carbon nanodots (CDs) on growth, photosynthetic pigments, and oxidative stress-related biomarkers in forage pea seedlings. We grew seedlings in soil and applied CDs exogenously via foliar spray (20 mL per pot) at 100, 200, and 300 ppm three times at 3-day intervals, with measurements made 14 days after the first application. Each treatment consisted of three pots, with four seedlings per pot. Root and leaf lengths, chlorophyll a, chlorophyll b, total chlorophyll, proline, hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents were determined. CDs treatment resulted in statistically significant differences in root and leaf length. Root length increased from 5.14 cm in the control to 8.50 cm at 300 ppm, whereas leaf length showed the highest numerical value at 100 ppm (1.80 cm) compared with 1.34 cm in the control. Root H2O2 content increased relative to the control (1.555 µmol g⁻¹ FW), with the highest level observed at 200 ppm, while leaf H2O2 decreased with increasing CD concentration from the control value of 1.810 µmol g-1 FW. MDA responses were tissue- and concentration-dependent, with the highest root MDA content recorded at 300 ppm (0.275 nmol g⁻¹ FW) and the highest leaf MDA content at 200 ppm (0.505 nmol g⁻¹ FW). Proline accumulation also varied between tissues, reaching 0.811 mg g⁻¹ FW in roots at 200 ppm, while leaf proline showed a minimum of 0.352 mg g⁻¹ FW at 100 ppm. Statistically significant differences in MDA were detected in both root and leaf tissues, whereas significant differences in proline were detected in leaves (p<0.05). Chlorophyll accumulation increased particularly at 300 ppm, where chlorophyll a and total chlorophyll reached 3.050 and 5.521 mg L⁻¹, respectively. Overall, CDs induced concentration-dependent and tissue-specific changes in growth, pigment accumulation, and redox-related responses in forage pea, underscoring the importance of dose optimization for the agricultural use of carbon nanodots.