Abstract

Cadmium (Cd) is a highly toxic metal that impairs plant growth and yield. Thus, Cd-mitigating cost-effective and eco-friendly strategy is highly desirable. The aim of the study was to investigate the effects of calcium nanoparticles (N-Ca) at 0.1 mM (N-Ca-1) and 0.2 mM (N-Ca-2) in mitigating Cd toxicity in faba beans. In this study, foliar treatment with N-Ca-1 or N-Ca-2 significantly improved faba bean growth and physio-biochemical parameters by regulating plant growth regulators, antioxidant enzymes, and expression of key antioxidant genes in response to Cd stress. Faba bean plants remarkably induced Cd accumulation, leading to excessive reactive oxygen species (ROS), which caused Cd- induced oxidative damage via elevated lipid peroxidation and ion leakages. However, both N-Ca treatments (N-Ca-1 and N-Ca-2) effectively reduced ROS (O2•– and H2O2) levels and oxidative damage in both Cd-stressed and normal plants compared to N-Ca-0. The application of Cd-2 combined with N-Ca-2 maximized plant antioxidant capacity, indicating the ability to scavenge ROS and enhance photosynthetic performance. Interestingly, both N-Ca treatments enhanced leaf integrity by regulating relative water content and membrane stability index (MSI), as well as enhancing antioxidant enzyme activities, osmoregulation, and phytohormones. Supplementation of Ca-nanoparticles improved Ca content while reducing Cd absorption, thereby lowering Cd levels in both faba bean roots and shoots, which minimized ROS levels and oxidative damage. Expressions of key antioxidant genes (SOD, CAT, APX, and GR) suggest that they were fully active in response to Cd stress, which led to alleviating Cd toxicity. Notably, N-Ca-2 induces better yield compared to N-Ca-1. Therefore, these findings reveal N-Ca-mediated Cd toxicity mitigation is a cost-effective, eco-friendly, and efficient alternative for sustainable faba bean production in Cd-toxic soils.

Key words: Heavy metal stress; faba bean; nanotechnology; antioxidant capacity; sustainable agriculture