Efficacy of ascorbic acid coated quantum dots in alleviating lead-induced oxidative damage and enhancing growth parameters in rice (Oryza sativa L.) for sustainable cultivation.

Lead (Pb) toxicity impairs the growth, yield, and biochemical traits of rice, making it essential to mitigate Pb stress in soil and restore its growth and production. This study investigated the potential of ascorbic acid-coated quantum dots (AsA-QDs) in alleviating Pb stress in two rice cultivars, Japonica (JP-5) and Indica (Super Basmati), grown in pots under Pb stress (50 mg/kg as lead chloride) with AsA-QD suspensions (50 ppm and 100 ppm) as treatments. The synthesized AsA-QDs were characterized by zeta potential (-14.4 mV), particle size (472.3 nm, PDI 0.745), UV-Vis absorption peak (240 nm), FT-IR analysis revealing functional groups (carboxylic acid and alkene), and TEM showing spherical morphology (average size 9.43 nm). Pb stress reduced key traits in JP-5, including tillers per plant (11.11 %), grain yield (18.22 %), kernel weight (18.22 %), protein (40.19 %), phenolic content (59.66 %), and antioxidant capacity (17.75 %), while 50 ppm AsA-QDs improved these by 33.33 %, 5.73 %, 2.03 %, and 13.19 %, respectively. Similarly, Pb stress reduced plant height, T/P, biomass yield (BY), GY, TKW, total sugars, reducing sugars, non-reducing sugars, starch, proteins, and TPC in Super Basmati by 19.76 %, 21.43 %, 11.01 %, 11.01 %, 7.52 %, 38.09 %, 7.24 %, 13.96 %, 11.97 %, and 40.39 %, respectively, while PbQD1 improved these traits by 14.29 %, 15.49 %, 9.25 %, 109.52 %, 8.31 %, 31.72 %, 25.91 %, and 7.075 %, respectively. The findings demonstrate that AsA-QDs effectively mitigate Pb toxicity by reducing oxidative stress, enhancing growth parameters, and restoring yield components, establishing them as a promising nanomaterial for sustainable crop resilience under Pb stress.