THE EFFECTS OF Cd AND Zn INTERACTIONS ON THE CONCENTRATION OF Cd AND Zn IN SWEET BUSH BASIL (Ocimum basilicum L.) AND PEPPERMINT (Mentha piperita L.)

Experiments were conducted on sweet bush basil (Ocimum basilicum L.) and on peppermint (Mentha piperita L.) plants grown in pots under glasshouse conditions to study the interaction between Cd and Zn on the concentration of these metals in plant leaves. A factorial experiment with two factors (Cd and Zn) at four concentrations (0, 1, 5, 10 mg kg(-1)) was carried out for each plant species. Cadmium was applied as CdSO(4)8/3H(2)O and Zn as ZnSO(4)7H(2)O. Increasing Cd additions to the growth medium resulted in an increase in Cd concentration in leaves of sweet bush basil and increasing Zn additions to the growth medium resulted in an increase in Zn concentration in the leaves of peppermint. No significant effects were observed of Zn on Cd and Cd on Zn in the leaves of sweet bush basil and peppermint, respectively. Cd concentration increased significantly at each Cd level with increasing Zn additions in leaves of peppermint. Cd concentration increased significantly at each Cd level with increasing Zn additions in leaves of sweet bush basil. The Cd concentration in the leaves of peppermint increased with increasing Zn additions to the growth medium but the Zn concentration was not affected by Cd addition to the growth medium. The amounts of Cd and Zn extracted by Diethylene triamine penta acetic acid - triethanol amine (DTPA-TEA) increased significantly with increasing amounts of Cd and Zn additions to the growth medium and also showed significant interaction. DTPA-TEA extractable Cd and Zn significantly correlated with the Cd and Zn concentrations within the leaves of both species studied indicating that this extractant could be used to predict Cd and Zn concentrations in the plant tissues of sweet bush basil and peppermint.