Enhancing drought tolerance in blackgram (Vigna mungo L. Hepper) through physiological and biochemical modulation by peanut shell carbon dots.

Among the abiotic factors that causes threat to crop production, drought is one of the foremost constraints in the changing climatic era. Hence, a study was conducted to mitigate the effect of drought stress in blackgram with the peanut shell carbon dots (PNS-CDs) as seed priming and foliar spray agent. Blackgram seeds were primed with PNS-CDs at 200 ppm for 3 h and plants were sprayed with PNS-CDs at 50 ppm on 30^th and 45^th DAS under drought stress conditions (30%, 50% and 75% WHC). The imposed treatments included dry seeds (control), water sprayed plants, seed priming with PNS-CDs, foliar spray with PNS-CDs and combination of both. The results demarcate the exemplary performance of plants when given with combined application of priming (200 ppm) and foliar spray (50 ppm) with PNS-CDs in terms of its growth and yield. Further, an increased activity of catalase (12%), peroxidase (12%), superoxide dismutase (22%), glutathione reductase (60%), ascorbate peroxidase (55%), H₂O₂ scavenging (32%) and proline (35%) were noticed over dry seeds, which confirmed the antioxidant defense mechanism offered by PNS-CDs. In addition, the percentage increase in photosynthetic parameters like total chlorophyll (44%), total soluble protein (54%), photosynthetic rate (89%), stomatal conductance (40%), internal CO₂ concentration (74%) and chlorophyll stability index (51%) confirmed the role of PNS-CDs as photosynthesis enhancer under drought stress, which resulted in enhanced stress tolerance, plant growth and yield. Thus, it was found that priming blackgram seeds with 200 ppm PNS-CDs for 3 h followed by foliar spray with 50 ppm on 30 and 45th DAS could serve as a sustainable alternative to chemical inputs, ensuring better crop productivity and stress tolerance in water-limited environments. Further, future research could explore the molecular mechanisms underlying the stress tolerance offered by PNS-CDs. In addition, the application of PNS-CDs to different crops, biotic and abiotic stress conditions will also pave the way for broader agricultural sustainability in an eco-friendly approach.