Optical properties of diatom silica frustule with special reference to blue light

Using fresh water diatom, identified as Melosira variance which is growing faster than other algae in the ponds, we characterized the ultrastructure of its silica frustule by electron microscopic observations. On hypothesizing that the ultrastructure has some meanings in photosynthesis, behaviors of a single frustule toward light irradiation were analyzed using an optical fiber. We found that the frustule absorbed light mainly in the blue wavelength region. The theoretical analyses of optical properties supported experimental results and suggested a strong interaction between blue light and inner silica materials. It is speculated that the interaction served for partial extinction of excessive irradiation of blue light and for enhancing photosynthesis of the diatom.