Abstract

Heavy metals can have adverse health effects on both humans and biota if they exist in high concentrations in the soil or in water bodies. Rhizofiltration is a specific type of Phytoremediation which involves plants to extract contaminants from large wetland areas that have a low level of contamination. The objective of this research is to elucidate the interaction of the plant species Solanum lycopersicum (tomato plant) with the surrounding zinc contaminated solution, after being subjected to environments of darkness, illumination, and alternate current gradient. To perform this objective, tomato plants were grown in the hydroponic solutions containing 0, 100, 200 and 500 mg/L of zinc under illuminated conditions. Subsequently, these plants were grown in solutions of 100mg/L and were subjected to varied environmental conditions stated earlier. At the end of each experiment, which lasted seven days, concentration of zinc in plant roots, shoots and fruits were analyzed separately. The effects of plants and alternate current on solution pH and electrical conductivity (EC) were also investigated concurrently. It was found that the accumulated amount of zinc in plant roots is proportional to its concentration in hydroponic solution. However, the augmentation of zinc concentration in plant roots attains a plateau with increasing concentration of zinc in the hydroponic solution. As in roots, accumulation of zinc in plant shoots generally reached a saturation level of zinc when zinc concentration increased. However, in the fruit, zinc concentration appears to be not dependent on solution concentration of zinc. It was found that plants subjected to a light environment accumulated more zinc in their roots and shoots than plants subjected to a dark environment. Further, it was also noted that for the specific environment which consisted of an applied alternate current gradient of 1Volt/em at 16HZ, plant capability to extract zinc in both shoot and root was observed to be reduced. A brief series of tests related to the effect of nutrients on the uptake of zinc indicated that they modify the plant uptake of zinc.