A novel analytical approach for visualizing and tracking organic chemicals in plants.
Vegetation plays a key role in the environmental fate of many organic chemicals, from pesticides applied to plants, to the air-vegetation exchange and global cycling of atmospheric organic contaminants. Our ability to locate such compounds in plants has traditionally relied on inferences being made from destructive chemical extraction techniques or methods with potential artifacts. Here, for the first time, two-photon excitation microscopy (TPEM) is coupled with plant autofluorescence to visualize and track trace levels of an organic contaminant in living plant tissue, without any form of sample modification or manipulation. 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 approximately 0.1-10 pg were visible, as it moved through the epicuticular wax and plant cuticle, and was observed reaching the cytoplasm of the epidermal cells. By this stage, anthracene was identifiable in five separate locations within the leaf: (1) as a thin (approximately 5 microm) diffuse layer, in the upper surface of the epicuticular wax; (2) as thick (approximately 28 microm) diffuse bands extending from the epicuticular wax through the cuticle, to the cell walls of the epidermal cells; (3) on the external surface of epidermal cell walls; (4) on the internal surface of epidermal cell walls; and (5) within the cytoplasm of the epidermal cells. This technique provides a powerful nonintrusive tool for visualizing and tracking the movement, storage locations, and degradation of organic chemicals within vegetation using only plant and compound autofluorescence. Many other applications are envisaged for TPEM, in visualizing organic chemicals within different matrixes.
Wild
Edward
E
Departments of Environmental and Biological Sciences, Lancaster University, Lancaster, LA1 4YQ, United Kingdom.
Dent
John
J
Barber
Jonathan L
JL
Thomas
Gareth O
GO
Jones
Kevin C
KC
D000393:Air Pollutants / Q000032:analysis*; D000873:Anthracenes / Q000032:analysis*; D004784:Environmental Monitoring; D021621:Imaging, Three-Dimensional; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods; D018515:Plant Leaves / Q000737:chemistry*; D012984:Software; D003313:Zea mays
D000393:Air Pollutants; D000873:Anthracenes; C034020:anthracene