Confocal laser scanning microscopy - an attractive tool for studying the uptake of xenobiotics into plant foliage

The application of confocal laser scanning microscopy (CLSM) to the study of xenobiotic uptake into plant foliage is explored in this paper. Three fluorescent dyes of low molecular weight and contrasting polarities (hydrophilic, moderately lipophilic and lipophilic) were selected to represent foliage-applied pesticides. These model compounds were applied as droplets to the surfaces of various leaves and/or fruits according to the particular experiment. The transcuticular diffusion behaviour, the compartmentation into epidermal cells and the influence of a surfactant on the uptake of these fluorescent compounds were visualized by CLSM. Distinct differences in diffusion speed across the cuticle and distribution in cell compartments were found between different fluorescent compounds. The presence of a surfactant significantly accelerated the uptake of the moderately lipophilic dye into both thin- and thick-cuticled leaves. The results are discussed in relation to the current knowledge on pesticide uptake and translocation. The advantages and limitations of this technique are highlighted.