Authors: Akinloye O. A.*, Adamson I., Ademuyiwa O., Arowolo T. A.
International Journal of Plant Physiology and Biochemistry Vol. 3(4), pp. 75-82, April 2011
Available online at http://www.academicjournals.org/ijppb
ISSN 2141-2162 ©2011 Academic Journals
Abstract
Paraquat (PQ) is a toxic chemical that is widely used as herbicide in developing countries. This has led to extensive contamination of the environment, foods and food products. Therefore, this study
investigated possible occurrence of PQ residues in some commonly consumed vegetables and the
mode by which some of them were able to withstand oxidative stress condition associated with PQ
toxicity. Levels of PQ residues and constituent antioxidant enzymes activities were determined
spectrophotometrically. Paraquat residue concentrations in all vegetables were in the range of 0.04 to
0.27 ppm. A significant (p<0.05) increase in the activities of catalase, peroxidase and superoxide
dismutase were observed in PQ-treated Amaranthus caudatus, Celocia argentea and Chorchorus
olitorius as compared to the control groups during the first week of growth. Vegetables treated with
0.50 mM PQ showed initial signs of wilting without necrotic lesions. A progressive increase in
malondialdehyde (MDA) content of PQ-treated vegetables compared to the control was observed. The
chlorophyll content of the treated vegetables decreased with increased PQ concentrations. These
results did not only revealed that these vegetables showed differential sensitivity to PQ, but also
suggested that elevated antioxidant enzyme activities, especially during early stage of growth, is one of the likely mechanistic basis for the observed tolerance withholding capacity of these vegetables to PQ.