Abstract
Plants have gained importance in situ bioremediation of heavy metals. In the present study, different concentrations of zinc (Zn2+) (0.5, 5, 10, 15, 20 mg/l) and lead (Pb2+) (1, 2, 4, 6, 8 mg/l) were used to evaluate metal tolerance level of Lemna minor. L.minor were exposed to metals for 4 days and tested for its dry to fresh weight ratio (DW/FW), photosynthetic pigments production and protein content. The oxidative damage was detected by measuring catalase activity. L.minor showed tolerance against Zn2+ and Pb2+ at a concentration of 10 and 4 mg/l, respectively. Among the metals, Pb2+ showed a significant toxicity at 8 mg/l. High concentration (20 mg/l of Zn2+ and 8 mg/l of Pb2+) of the metals displayed a considerable negative effect on soluble proteins (13 fold decrease with Zn2+ and 4 fold decrease with Pb2+) and photosynthetic pigments (twofold decrease with Zn2+ and onefold decrease with Pb2+) and lead to a consequent reduction in number of fronds. Further, the catalase was greatly increased (twofold decrease with Zn2+ and sixfold decrease with Pb2+) under metal stress. The results indicate that L.minor withstands Zn2+ and Pb2+ toxicity up to the concentration of 10 and 4 mg/l, respectively. Hence, the metal tolerant property of this plant shall be exploited for bioremediation of Zinc and Lead in polluted water. Further, the detailed and wide range of heavy metal toxicity studies should be done to reveal the possible use of this plant on large scale bioremediation purpose.
Highlights
Urbanization and industrialization had triggered extreme water pollution by draining effluents directly into water bodies without prior treatment
The zinc at lower concentration promotes the growth of duckweeds, but it becomes toxic to the duckweed at higher concentration
The lead induced stress had a negative impact on the growth of L. minor
Summary
Urbanization and industrialization had triggered extreme water pollution by draining effluents directly into water bodies without prior treatment. Industries such as smelters, tanneries, metal refineries and mining operations are the major sources of metal release into the environment (Gardea et al 2004; Srivastava and Thakur 2006). These effluents generally contain metals that can be toxic even in trace amounts and it is very difficult to purify these water bodies due to its large volume. Metals induce deleterious effect on physiology of aquatic plants by effecting some of the essential phenomenon such as photosynthesis, enzymatic activity, etc. (Teisseire and Vernet 2000; Appl Water Sci (2017) 7:1247–1253
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