Thomas Engelmann

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Thomas Engelmann was a German botanist from the 19th century, known for his 1803 experiment which measured the effects of different colors of light on photosynthesis. In 1803, Thomas Engelmann illuminated a filamenous algea with light that had been passed through a prisim, exposing different segments of the alga to different wavelenghts. he used aerobic bacteria, which concentrate near an oxygen source, to determine which segments of the alga were releasing the most oxygen and thus photosynthesizing most. Bacteria congregated in the greatest numbers around the parts of the alga illumiated with violet-blue or red light.