| Abstract
| - Vegetation plays a key role in the environmental fate ofmany organic chemicals, from pesticides applied to plants,to the air−vegetation exchange and global cycling ofatmospheric organic contaminants. Our ability to locatesuch compounds in plants has traditionally relied on inferencesbeing made from destructive chemical extractiontechniques or methods with potential artifacts. Here, forthe first time, two-photon excitation microscopy (TPEM) iscoupled with plant autofluorescence to visualize andtrack trace levels of an organic contaminant in living planttissue, without any form of sample modification ormanipulation. Anthracene−a polynuclear aromatic hydrocarbon (PAH)−was selected for study in living maize(Zea mays) leaves. Anthracene was tracked over 96 h,where amounts as low as ∼0.1−10 pg were visible, as itmoved through the epicuticular wax and plant cuticle, andwas observed reaching the cytoplasm of the epidermalcells. By this stage, anthracene was identifiable in fiveseparate locations within the leaf: (1) as a thin (∼5 μm)diffuse layer, in the upper surface of the epicuticular wax;(2) as thick (∼28 μm) diffuse bands extending from theepicuticular wax through the cuticle, to the cell walls ofthe epidermal cells; (3) on the external surface of epidermalcell walls; (4) on the internal surface of epidermal cellwalls; and (5) within the cytoplasm of the epidermal cells.This technique provides a powerful nonintrusive tool forvisualizing and tracking the movement, storage locations,and degradation of organic chemicals within vegetationusing only plant and compound autofluorescence. Manyother applications are envisaged for TPEM, in visualizingorganic chemicals within different matrixes.
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