Effect of foliar application of nanoparticles on growth, physiology, and antioxidant enzyme activities of lettuce (Lactuca sativa L.) plants under cadmium toxicity.

Nanotechnology has attracted the interest of scientists due to its wide range of application specifically in agriculture. Nanoparticles (NPs) may act as a promising materials to alleviate cadmium (Cd) stress in plants. This study aims to assess the impact of multiple nanoparticles including nSiO (50 mg L:100 mg L), nTiO (20 mg L:60 mg L), nZnO (50 mg L:100 mg L), nFeO (100 mg L:200 mg L), nCuO (50 mg L:100 mg L), and nCeO (50 mg L:100 mg L) in combination with CdCl (5 µM) to mitigate Cd toxicity in lettuce through foliar application in hydroponic solution. Current findings indicate that foliar application of nSiL + Cd (50 mg L), nZnL + Cd (50 mg L), and nTiL + Cd (20 mg L) is more effective in improving growth, biomass, root architecture, and elevated photosynthetic efficiency, which might be attributed to the increasing uptake of essential micronutrient (K, Mg, Ca, Fe, Zn) under Cd stress. Similarly, treatment with nanoparticles leads to reduced accumulation of ROS and MDA in lettuce, while enhancing the SOD, POD, CAT, and APX activities. The results showed that nanoparticles have high tolerance against Cd as depicted by the inhibition in Cd accumulation by 3.2-58% and 10-72% in roots as well as edible parts of lettuce, respectively. In addition, Cd alone reduces the morphological traits, antioxidant enzyme activity, and photosynthetic activity, while increasing the ROS, MDA, and Cd accumulation in lettuce. This comprehensive study suggests the role of nanoparticles in reducing Cd toxicity in lettuce, signifying their importance as stress mitigation agents. However, long-term pot, priming, and field trials are needed to identify the optimal nanoparticle for the lettuce under variable environmental conditions.