Current Journal of Applied Science and Technology

Aims: To investigate the biochemical changes that occurred when T. occidentalis seedlings are exposed to some heavy metals [mercury (Hg), lead (Pb) and cadmium Re(Cd)] at varying concentrations: 50, 80 and 100 μg/dm³ respectively over a period of time.
Study Design: Randomized controlled plant experiment.
Place and Duration of Study: Experimental garden farm unit, Department of Crop Science, Federal University of Technology, Owerri, between April and May, 2012.
Methodology: Sixty viable seeds of T. occidentalis were planted into three sets of polythene bags of three groups each containing four viable seeds. Germination which was indicated by the appearance of epicotyls above the soil level was observed at 4 days interval up to 12 days. At the 8^th days, the cotyledons of two seedlings each from A-D were harvested and prepared for the assay of α-amylase. The other seedlings were allowed to grow. When the plants were considered to have matured with enough leaves (after 120 days), the leaves were harvested according to the labeled sets, washed and prepared for the assay of catalase (CAT) activity and malondialdehyde (MDA) concentration determination.
Results: There was a significant (P<0.05) decrease in α-amylase activity in the cotyledons of seedlings from heavy metal–polluted soil samples(A-C).The activity decreased as the concentrations increased in all the heavy metal-polluted soil samples. The activities of catalase also decreased significantly (P<0.05) in the T. occidentalis leaves from 80 and 100  μg/dm³ heavy metal-polluted soil samples relative to the control.
Conclusion: These heavy metals at 80 and 100 μg/dm³ precipitated biochemical changes in tissues of T. occidentalis by causing a significant (P<0.05) decrease in the activities of α-amylase in the cotyledons of T. occidentalis seedlings and the leaves, and a significant (P<0.05) increase in MDA concentrations in the leaves.