Comparative Study of Heavy Metal Toxicity on Chlorophyll and Carotenoid Levels in Vigna radiata L. Seedlings

Abstract

Rapid industrialization and urbanization have resulted in the contamination of natural resources, particularly water bodies and agricultural soils. This pollution has severely disrupted ecological balance and agricultural productivity, posing a serious threat to global food security. Among the various pollutants, heavy metals such as cadmium (Cd), lead (Pb), and nickel (Ni) are of particular concern due to their high toxicity, persistence in the environment, and tendency to accumulate in plant tissues. This study examines the effects of these heavy metals on the photosynthetic pigments of Vigna radiata L. (mung bean) seedlings, a nutritionally important legume crop. Seedlings were exposed to different concentrations of Cd, Pb, and Ni, and their total chlorophyll and carotenoid contents were measured. The results showed that all three heavy metals significantly reduced pigment levels, with the degree of reduction increasing alongside concentration. At 1000 ppm, cadmium caused the greatest decline in both chlorophyll and carotenoid levels, followed by lead and then nickel, establishing a toxicity order of Cd > Pb > Ni. The substantial decrease in photosynthetic pigments indicates impaired photosynthetic activity, leading to reduced plant growth and productivity. These findings underscore the urgent need for effective monitoring and management of heavy metal pollution to safeguard agricultural systems and promote sustainable food production.