Influence of Excised Barley Roots and Associated Bacteria on Organic Chemicals in Aqueous Solutions

Abstract

Two factors that could possibly influence the disappearance of organic chemicals from aqueous solutions containing excised barley roots were investigated. There was no evidence of active uptake and accumulation by excised roots of any of 181 representative organic chemicals investigated. The chemicals were selected for testing so as to include all common reactive functional groups, as well as to have variations in molecular size and ionic nature. Bacteria associated with barley roots had no effect on 140 of the chemicals. The loss of 22 chemicals from solution by bacterial degradation was controlled by the simultaneous addition of streptomycin and peni-cillin-G to the test solutions. Aldehydes were readily removed from solution by means of bacterial oxidation to the corresponding carboxylic acids. The oxidizing bacteria were unaffected by the presence of streptomycin and penicillin-G together in the solution. Conversion of three representative aldehydes to the corresponding acids was confirmed by both spectrophotometric means and paper chromatography. Sterile test solutions exhibited no conversion of aldehydes to acids, while sterile test solutions inoculated with certain pure genera of bacteria isolated from the surface of barley roots exhibited aldehyde-to-acid conversion. A growth factor, necessary for rapid development of bacterial cultures, was readily leached from intact barley seedling roots.