Determining the fibrillar orientation of bast fibres with polarized light microscopy: the modified Herzog test (red plate test) explained.
Bottom Line: The test has the reputation for never producing false results, but also for occasionally not working.However, so far, no proper justification has been provided in the literature that the 'no false results' assumption is really correct and it has also not been clear up till now, why the method sometimes does not work.We also provide an explanation for why the Herzog test sometimes does not work: According to our model, the Herzog test will not work if none of the three distinct layers in the secondary cell wall is significantly thicker than the others.
Affiliation: Department of Physics and Technology, University of Bergen, Bergen, Norway.Show MeSH
Mentions: The refractive index of the E-ray, and hence the RRTsample, depends sinusoidally on the sample orientation angle relative to the crossed polars (Mea, 2005). It attains its maximum value ( at 90° intervals. It can be shown that the intensity of light emerging from a birefringent sample also depends on the orientation of the sample. Using the notation for the sample orientation angle α, defined in Figure 4(A), maximum intensity and retardation occur at the same angles, namely when , as seen in Figure 4(B) (Petraco & Kubik, 2004; Olympus Microscopy, 2010).
Affiliation: Department of Physics and Technology, University of Bergen, Bergen, Norway.