The Effects of Lead and Cadmium Individually and in Combinations on Germination and Seedling Growth of Leucaena leucocephala (Lam.) de Wit
Pollution by heavy metals in the environment is a worldwide problem due to anthropogenic, industrial and automobile activities. In present studies, the effects of selected heavy metals (Pb and Cd) individually and in combination on seed germination and seedling growth of Leucaena leucocephala (Lam.) de Wit. were investigated. Germination rate of L. leucocephala showed that increase in concentration of metal treatment from 25 to 100 ppm, significantly (p<0.05) reduced germination percentage which was more prominent for Pb treatments as compared to control. Seedling growth variables i.e. root and shoot length, seedling size, root/shoot ratio, seedling fresh and dry weights also declined significantly (p<0.05) as compared to control treatment. Seedlings growth of L. leucocephala gradually reduced with increased in concentrations of metals especially Pb and Cd as compared to control. The inhibitory effects of metals showed the order as Pb>Cd of effects at different concentrations. The combined metal treatments of Pb+Cd were also found more toxic as compared to individual’s treatment. The seedlins of L. leucocephala were tested for tolerance to lead and cadmium. Tolerance indices and seedling vigor index of L. leucocephala for individuals and combined metal treatment also decreased with increase in concentration of Pb and Cd treatment as compared to control. The more reduction in seedling tolerance indices of L. leucocephala was recorded for combined metal treatment. This reduction was prominent for Pb+Cd at 100 ppm as compared to control treatments.
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