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3.4 outline the discoveries of Englemann and explain why Englemann’s work led to the description of the action spectrum of photosynthesis
outline the discoveries of Englemann and explain why Englemann’s work led to the description of the action spectrum of photosynthesis
- Englemann performed two experiments. In 1894 he used a modified microscope condenser to shine thin rays of light on the green alga Spirogyra, which has chloroplasts arranged in spirals (hence the name) with clear cytosol between them. Englemann dispersed the Spirogyra in a bacteria suspension and found that the bacteria migrated to the areas where the Spirogyra was green or where there were chloroplasts. The bacteria were attracted to the oxygen produced by photosynthesis.
- In an earlier experiment in 1882, Englemann split white light into its spectral components using a prism made for him by Carl Zeiss. He shone the spectrum onto the green alga, Chladophora. In Chladophora, unlike Spirogyra, the cells are completely and evenly filled with chloroplasts. The bacteria accumulated in the violet and red wavelengths of the spectrum, attracted by the regions of high oxygen concentration. Englemann had produced an action spectrum, showing the regions in which chlorophyll absorbs light.