A Novel Analytical Approach for Visualizing and Tracking Organic Chemicals in Plants

Abstract

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.

Phenanthrene uptake by Medicago sativa L. under the influence of an arbuscular mycorrhizal fungus

“…Two-photon excitation microscopy (TPEM) is a technique that enables direct in situ visualization of the movement of compounds that autofluoresce inside living plant tissues and has been pioneered by Wild et al to track the uptake and movement of PAH inside living plant leaves (Wild et al, 2004) and roots (Wild et al, 2005). To further improve our understanding on the influence of mycorrhizal inoculation on plant phenanthrene uptake and translocation, we employed this technique to observe differences between mycorrhizal and non-mycorrhizal lucerne roots in the localization of phenanthrene.…”

Polycyclic aromatic hydrocarbons (PAHs) in soils and vegetation near an e-waste recycling site in South China: Concentration, distribution, source, and risk assessment

“…The mechanisms responsible for the PAH transfer to plant tissues primarily include sorption from soil particles, uptake by the roots through transpiration, and absorption through the waxy leaf cuticle or through stomata (Wild et al, 2004;Meudec et al, 2006). Thus, heavy pollution at an e-waste recycling area may result in an elevated uptake of PAHs into vegetables.…”

Human health risk due to consumption of vegetables contaminated with carcinogenic polycyclic aromatic hydrocarbons

“…In the past, numerous research studies have demonstrated that vegetables grown on PAH-contaminated soils may take up PAHs (Wennrich et al 2002). Several mechanisms including sorption (from soil particles), uptake rate through transpiration, volatilization, and redeposition on plant surfaces are responsible for the PAH transfer from soil ecosystem to plant tissues (Fryer and Collins 2003;Wild et al 2004).…”