EFFECTS OF COPPER AND LEAD ON THE PHYSIOLOGY OF SALVINIA MOLESTA, PISTIA STRATIOTES AND LEMNA TRISULCA AND THEIR PHYTOREMEDIATION POTENTIALS

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Date
2015-10
Authors
ADELANWA, ESTHER BOSEDE
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Abstract
In the developing countries heavy metal pollution becomes serious due to mining, mineral, smelting, tannery and textile industries. Phytoremediation is a newtechnology in which plants are used to remove pollutants or reduce their effects from water and soil. The use ofmetalaccumulating plants to clean environments contaminated with heavy metals is the most rapidly developing component of this environmentally friendly and cost-effective technology.The effects of copper and lead on the physiology of Salvinia molesta, Pistia stratiotes and Lemna trisulca and their phytoremediation potentials were therefore investigated. The experiments were conducted in vitro and the parameters evaluated were content of Chlorophyll a and b, the enzymatic activity of catalase and peroxidase, morphology of the plant (visual signs of chlorosis)and the metal concentration in tissues of Salvinia molesta, Pistia stratiotes and Lemna trisulca.There were significant differences (P≤0.05) in the content of chlorophyll a and b in the three aquatic macrophytes used for this study. In this study, higher contents of chlorophyll a and b were recorded for the control and treatments with lower concentrations (0.5mg/L of copper and 0.05mg/L of lead). Copper and Lead at higher concentrations (1mg/L and 1.5mg/L) reduced the chlorophyll a and b contents in the three species. As the concentration of metals increased, the content of chlorophyll a and b reduced drastically. Also, increase in the number of days the plantswere exposed to the metals led to decrease in the content of chlorophyll a and b.The activities of catalase and peroxidase weresignificantly different (P≤0.05) in Salvinia molesta, Pistia stratiotes and Lemna trisulca.The higher the concentration of copper and lead, the higher the activities of the antioxidant enzymes. The phytotoxicity effects of the accumulated metals were responsible for a reduction in the pigment content (chlorophyll a and b); high activity of the catalase and peroxidase in the three macrophytes species. It was also responsible for the visual toxicity symptoms (chlorosis and necrosis) observed in P. stratiotes and L. trisulca; although nobserved in P. stratiotes and L. trisulca; although no toxicity symptom/sign was observed in S. molesta.All the studied species accumulated copper and lead in their tissues. Also, it was observed that, the accumulation was dependent on the concentrations of the metal(s) in solution and time of exposure to the metals. There was significant difference (P≤0.05) between the accumulation potentials by the aquatic macrophytes and between the various treatments.S. molesta showed highest accumulation of metals (concentrations) in the tissues. S. molesta accumulated 1510.71±166.83mg/l of copper, followed by L. trisulca (1178.39±146.81mg/l) and the least was in P. stratiotes (866.18±101.41mg/l) on day 18after metal application. For lead, the highest accumulation was found in S. molesta with 872.22±126.73mg/l followed by P. stratiotes (378.44±92.14mg/l) and then L. trisulca with 194.77±49.04mg/l on day 18after metal application.Salvinia molesta proved to be the best phytoremediator among the aquatic macrophytes used in this study because it accumulated copper and lead more than the other species and there was no change in the morphology of the plants in all the concentrations that the plant was exposed to.
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A DISSERTATION SUBMITTED TO THE SCHOOL OF POST GRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA,IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF DOCTOR OF PHILOSOPHY DEGREE IN BOTANY (PLANT ECOLOGY). DEPARTMENT OF BIOLOGICAL SCIENCES, FACULTY OF SCIENCE, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
EFFECTS,, COPPER,, LEAD,, PHYSIOLOGY,, SALVINIA MOLESTA,, PISTIA STRATIOTES,, LEMNA TRISULCA,, PHYTOREMEDIATION POTENTIALS,
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