Significance of plant metabolism in the mutagenicity and toxicity of pesticides.

Abstract

In an attempt to gain an overall estimate for the influence of plant metabolism on environmental mutagenesis, the mutagenicity of an assortment of agricultural pesticide preparations in the Salmonella bio-assay was evaluated using both rat liver S9 and plant enzyme homogenates as activating systems. The study indicates that plant metabolism can alter the results of this short-term mutagenicity test: some compounds which are non mutagenic in the Salmonella bio-assay (e.g. diquat) give positive responses, some preparations such as captan become more or less mutagenic, and some, such as triallate, become significantly more toxic to the tester strains. Furthermore, dose response curves suggest that even when both plant homogenates and rat liver S9 supernatant activate a compound, the mutagens which are formed may differ. Five-day old alfalfa (Medicago sativa L.), corn (Zea mays L. var. Golden Jubilee), bean (Vicia faba L), pea (Pisum sativum L. var. Laxton's Progress), sunflower (Helianthus annuus var. Krasnodarets), tobacco (Nicotiana tobaccum L. var. Wisconsin 58), and wheat (Triticum aestivum L.) were tested and compared as activating systems; these were prepared by an assortment of cell disruption techniques including blending, homogenizing, sonication, and high pressure disruption methods. For routine testing, filter sterilized, blended, S14 supernatants of corn or wheat were the most promising. No correlation was observed between levels of activation by the various plant species and their protein contents, catalase, or peroxidase activities. The preparations, however, could be standardized using specific chemical compounds in the bio-assay.