EVALUATION OF PHYTOREMEDIATION POTENTIALS OF Phytolacca dodecandra, Adhatoda schimperiana AND Solanum incanum FOR SELECTED HEAVY METALS IN FIELD SETTING LOCATED IN CENTRAL ETHIOPIA. by ALEMU SHIFERAW DEBELA Submitted in accordance with the requirements for the degree of DOCTOR OF PHILOSOPHY in the subject ENVIRONMENTAL SCIENCE at the UNIVERSITY OF SOUTH AFRICA SUPERVISOR: DR. MEKIBIB DAVID DAWIT CO-SUPERVISOR: PROF. MEMORY TEKERE