Comparative response of Allium cepa (l.) to the water soluble fraction (WSF) of crude oil and three sources of water
Physicochemical characteristics of three levels (25, 50, and 100%) of the WSF of Erhobahro flow station crude oil, rain river and pond water on Allium cepa were investigated in order to evaluate the toxic level of the different treatments. Root growth parameters were used as an index of toxicity. Physicochemical characteristics were found to increase after exposure to the plant tissues, except for pH, TDS, EC, THC (at 25 and 100%), hardness (at 50 and 100%), HCO-3 (at 25%), Cl- and SO42- of the three different levels of WSF which recorded reduction in values after exposure to the plants. The pH of rain and river water was also found to reduce after exposure to Allium species. The river water had the least values of EC before and after exposure to the plant tissues. Total hydrocarbons (river water), Zn and Ni (pond and rain water) were not detected before exposure to A. cepa, while Zn (pond water) and Ni (50% WSF, rain and pond water) were not detected after exposure to the plant. Allium cepa grown in pond water had the highest number of roots. The results showed that 25% WSF, pond and river water, had improvement in growth over the control treatment. Rain water, 50% and 100% WSF showed reduction in the number of roots as compared to the control treatment. River water had the highest value for root length while the least value was recorded for 100% WSF followed by 50% WSF. Root initiation occurred in pond, rain and river water treatments. At concentrations of 50% and 100% WSF there was inhibition of root growth. The results indicated significant difference in the number of roots exposed to 25% WSF (P<0.01), pond (P<0.01) and control (0.005) treatments while control, rain, pond (25 and 50% WSF) were significantly (P<0.01) different for root lengths. The results were discussed in the broader context of the implications of oil industry in the community.
Key words: Response, Allium cepa, water soluble fraction WSF, crude oil, physicochemical characteristics