Toxicological Effects of Mercury-Induced Biochemical Alterations in Curry Leaves (Murraya koenigii) Plants

Heavy metals, including mercury (Hg), accumulate in the environment via atmospheric deposition, aquatic transport, and terrestrial pathways, eventually settling in soil and sediments. Once these metals become bioavailable, they pose significant ecological and toxicological risks. Upon exposure, plants absorb them, leading to harmful agronomic, physiological, and biochemical effects. The present study aims to assess the toxicological effects of mercury on the biochemical alterations in Murraya koenigii (curry leaves) plants. M. koenigii plants were assigned to four groups: Group 1 (control) in uncontaminated soil, and Groups 2, 3, and 4 exposed to 50 mg, 100 mg, and 200 mg of Hg, respectively. All plants were kept under controlled environmental conditions to promote optimal growth. The results revealed that elevated mercury concentrations significantly impaired critical growth parameters, including seed germination, root and shoot length, fresh and dry weight, and vigour index, all of which reflect suppressed plant growth and productivity. Biochemical analysis further demonstrated substantial reductions in primary metabolites, such as carbohydrates and proteins, with the most pronounced decreases observed at higher mercury concentrations. These alterations suggest that Hg-induced oxidative stress causes cellular damage, disruption of nutrient assimilation, and disturbances in enzyme activity. Additionally, significant reductions in chlorophyll a, chlorophyll b, and total chlorophyll content were observed, further indicating impaired photosynthetic capacity. Overall, the findings underscore the detrimental effects of mercury on plant metabolic processes, highlighting its potential to cause long-term growth inhibition and metabolic dysfunction, with broader implications for plant productivity, nutrient cycling, and ecosystem health.