An Optical Clearing Technique to Visualize Internal Root Structure

BackgroundRoots play an important role in the foraging and uptake of nutrients and water from soil to support sessile plant growth. Research on root growth and development in plants is very limited due to the thickness and opacity of roots. We developed a tissue clearing technique that enables visualization of crop internal root structure.ResultsThe application of methyl salicylate reduced the time taken for root clearing and accelerated the dye permeation into the tissue; the whole procedure for root clearing was performed within 3 days. We applied our technique on the roots of monocotyledonous plants, such as rice (Oryza sativa L.), wheat (Triticum aestivum L.), and maize (Zea mays L.), and dicotyledonous plants, such as rape (Brassica napus L. var oleifera), tomato (Solanum lycopersicum), and soybean (Glycine max (Linn.) Merr.), and obtained clear root structure. It not only shortens the time for root tissue clearing but also keeps the cell structure of intact roots. The transparent sample can be preserved for more than one year without any structural deformation.ConclusionsOur technique can create a 3-D reconstruction of the entire root structure. In summary, this method is a useful tool for visualizing the structures of thick root tissues and will be a valuable tool for research on root growth and development in plants.