Exploring the deleterious effects of heavy metal cadmium on antioxidant defense and photosynthetic pathways in higher plants

• Adverse effects of cadmium exposure on plant physiology and biochemistry. • Plants activate multiple defense mechanisms to alleviate/avoid/tolerate Cd toxicity. • The role of antioxidant enzymes, osmotic regulating substances, and genetic engineering. • The importance of soil microorganisms in reducing metal phytoavailability and increasing plant growth parameters under Cd stress. Cadmium (Cd) is a highly toxic heavy metal and a major inorganic pollutant in soil ecosystems. Due to its high mobility and solubility, plants easily absorb Cd, affecting their physiological and biochemical processes, crop quality, and ultimately human health through bioaccumulation in the food chain. This review provides a comprehensive analysis of recent advances in understanding Cd toxicity in soil. It studies the influence of Cd on plant growth and development, focusing on disruptions in physiological and biochemical processes, changes in cellular ultrastructure, changes in biomass accumulation, and changes in nutritional quality. The review summarizes current findings on the mechanisms of Cd-induced toxicity, particularly its effects on antioxidant and photosynthetic systems. The broader ecological consequences of Cd contamination on ecosystem health and biodiversity are also examined. In addition, the article discusses new phytoremediation and genetic engineering strategies aimed at increasing plant resistance to Cd stress. Future research directions are suggested to address existing knowledge gaps and improve remediation efforts.