Plant Tissue as Liquid Crystal under Polarized Optical Microscope

Yue-Ching Huang¹, Jieh-Wen Tsung^1*

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Jieh-Wen Tsung, email:jiehwen.tsung@nycu.edu.tw

Polarizing optical microscope (POM) is a powerful tool to record the birefringence color of a material. The orientation of the molecules or the fibers (director field) can be derived based on the spectrum of the birefringence color. POM is often for mineral identification, liquid crystal phase identification and topological defect identification. Microscope lovers, science youtubers and even artists love to observe the biological tissues, starch grains or soap film under POM, mainly for the beautiful colors and patterns. Lots of artworks are published on the internet. In fact, the colors are not just about beauty, and they are useful to derive the direction of the polymer molecules or the fibers. The birefrinegnece can be from the molecule itself. The the crystalized starch and cellulose show structural birefrinegnece, too. We collected plant samples, including grass stems, leaf skins, bark, thorns, fruit skin and starch in root vegetables. We observed these samples under a POM to check if they show significant birefringence colors. The techniques of liquid crystal phase identification and topological defect identification (Schlieren texture, finger print texture, focal conic domains, etc.) are applied to the biological samples, and the structure of the tissue is derived in three dimensions.

Keywords: polarized optical microscopy, tissue formation, liquid crystal, starch, cellulose