Moss stem TS Funaria sp. Differential interference contrast (DIC) Nomarski
Funaria is a genus of approximately 200 species of moss. Funaria hygrometrica is the most common species. Funaria hygrometrica is called “cord moss” because of the twisted seta which is very hygroscopic and untwists when moist. The name is derived from Latin word “funis” meaning a rope. Capsules are abundant with the moss surviving as spore when conditions are not suitable. Moss plant Funaria grows in dense patches or cushions in moist shady and cool places during the rainy seasons. It has a height of 3–5 cm, a radial symmetry with a differentiation of an axis or stem, leaves or phylloids. Differential interference contrast (DIC) microscopy, also known as Nomarski Interference Contrast (NIC) or Nomarski microscopy, is an optical microscopy illumination technique used to enhance the contrast in unstained, transparent samples. DIC works on the principle of interferometry to gain information about the optical path length of the sample, to see otherwise invisible features. A relatively complex lighting scheme produces an image with the object appearing black to white on a grey background. This image is similar to that obtained by phase contrast microscopy but without the bright diffraction halo. DIC works by separating a polarized light source into two orthogonally polarized mutually coherent parts which are spatially displaced (sheared) at the sample plane, and recombined before observation. The interference of the two parts at recombination is sensitive to their optical path difference ( the product of refractive index and geometric path length). Adding an adjustable offset phase determining the interference at zero optical path difference in the sample, the contrast is proportional to the path length gradient along the shear direction, giving the appearance of a three-dimensional physical relief corresponding to the variation of optical density of the sample, emphasizing lines and edges though not providing a topographically accurate image.
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Photo credit: © Scenics & Science / Alamy / Afripics
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Keywords: contrast, differential, funaria, interference, micrograph, microscope, moist, moss, nomarski, osmosis, phylloids, sp., stem, ts
