Phytotoxicity to and uptake of enrofloxacin in crop plants

Phytotoxicity of enrofloxacin on crop plants Cucumis sativus, Lactuca sativa, Phaseolus vulgaris and Raphanus sativus was determined in a laboratory model: the effect of 50, 100 and 5000 mug 1(-1) were evaluated after 30 days exposure by measuring post-germinative growth of primary root, hypocotyl, cotyledons and leaves. Concentrations between 50 and 5000 mug 1(-1) induced both toxic effect and hormesis in plants, by significantly modifying both length of primary root, hypocotyl, cotyledons and the number/length of leaves. A toxic effect is induced by high concentration (5000 mug1(-1)), while hormesis occurs at low concentrations (50 and 100 mug 1(-1)). A continuum between toxic effect and hormesis is found in the four plant species. Both toxic effect and hormesis can be related to an efficient plant drug uptake, in the order of mug g(-1). Plants are able to metabolize enrofloxacin into ciprofloxacin, as also happens in animals; Cucumis, Lactuca and Phaseolus biologically convert about one quarter of stored enrofloxacin. The ecological implication of enrofloxacin contamination in terrestrial environments is discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.