SUMMARYTwo techniques for collection of water-soluble substances, particularly carbohydrates, from the leaf surfaces (phylloplane) of maize {Zea mays L.) were compared in order to explain the oviposition preference ofthe European corn borer.By dipping the leaves in water, smaller amounts of substances were obtained than by spraying water. The total amounts of three sugars (glucose, fructose and sucrose) collected from maize phylloplane ranged from 0-6 to 3-6 mg m"^ of leaf surface.The quantities of these substances varied with the variety of maize, with leaf position, and with the part of the leaf. Sugar ratios on the phylloplane were quite different from those observed within the leaf.

We have explored cultures of roots transformed by Agrobacterium rhizogenes to test the availability of cadmium in sewage sludges. The toxic effects of Cd and the kinetics of Cd accumulation were examined for three species of transformed roots, grown for 2 weeks in nutrient media, containing Cd as a salt.Roots of sugar beet (Beta vulgaris L.) were highly sensitive, while those of tobacco (Nicotiana tobaccum L.) and morning glory (Calystegia sepium R. Br) were more tolerant. Cd accumulation was higher in sugar beet and morning glory than in tobacco. We developed a non-sterile, 5-day procedure for testing the accumulation (an indication of availability) of Cd from sludge suspensions, using transformed roots of morning glory and tobacco. Cd accumulation varied with plant species and source of sludge. Ranking of Cd availability using this biological assay for Cd accumulation was confirmed by chemical tests with NH 4 acetate and EDTA. Results from transformed roots were also compared with those from normal, excised, tobacco roots and normal and transformed tobacco plantlets. No major alteration in Cd uptake was associated with genetic transformation. We thus demonstrated the feasibility of using transformed roots to estimate the availability of Cd in metal-contaminated materials like sewage sludges.

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