Abstract
In this study we tested the negative effects of lead (Pb) and cadmium (Cd) at the concentrations of 5 – 500 µg/L and 1 – 100 µg/L, respectively, on the germination, fresh weight, root and shoot length of broccoli, Brassica oleracea L., and okra, Abelmoschus esculentus L. over the period of 7 days. Two other tests were also conducted as control in which the seeds of these two plants were watered with distilled water only. For each concentration of exposures, 10 seeds were put into a plastic container and nine replicates (n = 9) for each treatment were prepared. The results revealed slight effects of the metals on the germination of B. oleracea and A. esculentus. However, fresh weight of the sprouts was decreased upon metal exposures especially the significant reduction of A. esculentus fresh weight in the Pb incubations. Pb slightly affected on the root prolongation of both plants. There was no significant difference on the shoot length of B. oleracea in control and Cd treatments. Furthermore, Cd tended to stimulate the prolongation of root and inhibit the extension of shoot of A. esculentus. Besides, Cd (100 µg/L) and Pb (500 µg/L) caused the leaf abnormality in B. oleracea. Our results contribute more understanding on the toxicity of Pb and Cd at environmentally relevant concentrations on the seedling of plants. Further investigations on the toxicity of other pollutants as well as their mixture on seedling of plants are recommended.
Highlights
In nature, the occurrence of heavy metals is extremely varied in many habitats
In this study we tested the negative effects of lead (Pb) and cadmium (Cd) at the concentrations of 5 – 500 μg/L and 1 – 100 μg/L, respectively, on the germination, fresh weight, root and shoot length of broccoli, Brassica oleracea L., and okra, Abelmoschus esculentus L. over the period of 7 days
The results revealed slight effects of the metals on the germination of B. oleracea and A. esculentus
Summary
The occurrence of heavy metals is extremely varied in many habitats. They exist in the soil, atmosphere and water environment. The emission of heavy metals into the environment happens through various processes and different paths upon the naturally geographic processes and human activities. Heavy metals are emitted into the environment through combustion, mining and processing (Jarup 2003). Heavy metals contaminate the ground and surface water through the transportation process in the water currents. Leaking heavy metals into the soil could be occurred through the geochemical processes of weathering of parent materials, mining waste, leaded gasoline and paint, animal manure, sewage sludge, fertilizers, pesticides, irrigation wastewater and atmospheric deposition (Wuana and Okieimen 2011)
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