Impact of mercury toxicity on plant growth and development: an overview on physiological, biochemical, and mitigation...

Mercury is one of the major environmental contaminants that affect plant metabolism, growth, and development. Mercury is released into the environment because of anthropogenic activities like mining and industrial emissions, along with natural causes like weathering of rocks and volcanic eruptions. This can interfere with physiological and biochemical interactions of plants associated with impairment or poorly developed plants. Globally, mercury pollution is of critical relevance due to its release from industrial sources such as mining, fossil fuel combustion, and manufacturing; its persistence and mobility allow bioaccumulation and biomagnification across ecosystems, ultimately entering the food chain. Depending on its chemical form (Hg⁰, Hg²⁺, or Me-Hg), mercury can persist in soil and water systems associated with accumulation in plant tissues. According to studies, long-term exposure to HgCl₂ at concentrations as low as 20-30 µM can stunt the growth of seedlings, while long-term soil contamination beyond 1000 mg kg^-1 significantly hinders plant development. This review focuses on the effects of mercury toxicity across plant growth stages like germination, vegetative development, reproductive function, and physiological processes such as photosynthesis and metabolism. The sustained exposure to mercury leads to decreased root and shoot length, inhibits the efficiency of photosynthesis, causes oxidative stress, and reduces germination rates. It also lowers chlorophyll content, alters enzyme activity, carbohydrate, and protein metabolism, resulting in reduced growth and yield. Understanding these aspects is important to maintain and mitigate the stress by introducing or adopting recent approaches and developments to reduce the contamination of mercury and its impact on plant productivity. Therefore, creating efficient, field-relevant remediation requires a clear understanding that connects Hg speciation, molecular responses, physiological damage, and emerging mitigation techniques. Protecting crop yield and guaranteeing food safety in agroecosystems affected by mercury will require bridging process-based understanding with proper solutions.