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Cell functions - Membrane-located activities - Photosynthesis - Light and photosynthetic pigments - Action and Absorption Spectra in Diatoms
Action and Absorption Spectra in Diatoms
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| Description |
The aim of this experiment is to find out whether Navicula favours certain wavelengths of light.
The algae are exposed to monochromatic light at wavelengths of 400 to 670 nm. A shutter covers the upper part of the aquarium, which thus serves as a control. After 48 hours the diatoms are distributed unevenly in the illuminated section. The accumulation maxima occur at wavelengths around 440 and 670 nm. By representing the accumulation densities of the various wavelengths graphically, we can trace an action spectrum of light for the photosynthesis.
Action and absorption spectra are more or less concurrent. The pigments involved in the absorption are now investigated. Chlorophyll a is responsible for the two maxima in blue at 425 and 438 nm, as well as the peak in red at 670 nm. Chlorophyll c shows an absorption maximum at 460 nm and two submaxima at 585 and 635 nm. The absorption at 495 nm is caused by the carotinoids, while the shoulder of the absorption curve around 540 nm is due to fucoxanthin. It follows from a comparison of the absorption and action spectra that in the case of Navicula, chlorophyll a and c, the carotinoids and fucoxanthin are the pigments involved in photosynthesis.
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Sources
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Action Spectrum of Step-down Reaction in Diatoms. WENDEROTH, Klaus, Marburg. IWF, Göttingen, 1984. C 1520.
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Order |
This film is part of the CD-ROM The Cell I - Life from Light and Air. You can order it at the IWF Knowledge and Media gGmbH.
Also available as clip.
Order no.:
C 7145
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