Synergistic application of calcium oxide nanoparticles and farmyard manure induces cadmium tolerance in mung bean (Vigna radiata L.) by influencing physiological and biochemical parameters.

Mung bean (Vigna radiata L.) grown under heavy metals such as cadmium stress shows poor growth patterns and yield attributes which can be extenuated by the application of calcium and organic manure to the contaminated soil. The present study was designed to decipher the calcium oxide nanoparticles and farmyard manure-induced Cd stress tolerance through improvement in physiological and biochemical attributes of mung bean plants. A pot experiment was conducted by defining appropriate positive and negative controls under differential soil treatments with farmyard manure (1% and 2%) and calcium oxide nanoparticles (0, 5, 10, and 20 mg/L). Root treatment of 20 mg/L calcium oxide nanoparticles (CaONPs) and 2% farmyard manure (FM) reduced the cadmium acquisition from the soil and improved growth in terms of plant height by 27.4% compared to positive control under Cd stress. The same treatment improved shoot vitamin C (ascorbic acid) contents by 35% and functioning of antioxidant enzymes catalase and phenyl ammonia lyase by 16% and 51%, respectively and the levels of malondialdehyde and hydrogen peroxide decreased by 57% and 42%, respectively with the application of 20 mg/L CaONPs and 2% of FM. The gas exchange parameters such as stomata conductance and leaf net transpiration rate were improved due to FM mediated better availability of water. The FM improved soil nutrient contents and friendly biota culminating in good yields. Overall, 2% FM and 20 mg/L CaONPs proved as the best treatment to reduce cadmium toxicity. The growth, yield, and crop performance in terms of physiological and biochemical attributes can be improved by the application of CaONPs and FM under the heavy metal stress.