OBSERVATIONS ON THE ACCUMULATION OF 5 XENOBIOTIC CHEMICALS IN PHLOEM VERSUS PARENCHYMA TISSUES OF CELERY

The uptake of five xenobiotic chemicals (cinmethylin, cyanazine, hyfor mal, oxamyl and phenylurea) by isolated phloem strands and storage-par enchyma tissues of celery (Apium graveolens L var. dulce) has been ass essed with respect to time, substrate concentration, pH and efflux cha racteristics. Absorption by phloem tissue was by a diffusion-like proc ess which did not become saturated within the time investigated. In co ntrast, uptake by parenchyma tissue approached saturation within 6 h. Uptake of the various chemicals demonstrates different responses to th e pH of the incubation solutions and the chemicals showed different re tention characteristics within the phloem and parenchyma tissues. The use of physicochemical properties (log K(ow) and pK(a)) to predict the behavior of these xenobiotic chemicals within celery tissue is discus sed.