Evidence of Photosynthesis
Photosynthesis is the process during which a plant’s chlorophyll traps light energy and sugars (glucose) are produced. In plants, photosynthesis occurs only in cells with chloroplasts. Water (H2O), carbon dioxide (CO2) and light energy are required. The light energy is absorbed by the green pigment, chlorophyll, and is converted into chemical energy, which causes the water drawn from the soil to split into molecules of hydrogen and oxygen. The hydrogen combines with the carbon dioxide in the air, forming the sugar. Oxygen from the water molecules is given off in the process. However, how can it be proven that this occurs in plant cells?
Theodor Wilhelm Englemann was a German botanist, physiologist, microbiologist, university professor, and musician who published the first piece of evidence for the existence of photosynthetically active bacteria in 1883 from his results in a physiological study containing red bacteria. He measured the effects of different colours of light on photosynthetic activity through a modified microscope containing a prism that produced a microscopic spectrum on a microscope slide. He could also distinguish and measure different wavelengths of light. He was amazed by the fact that these bacteria accumulated in the spectrum exactly as they did in their absorption spectrum. Their clumping allowed him to see which regions had the highest concentration of oxygen. He concluded that the most photosynthetically active regions would have the highest concentration of bacteria. The bacteria accumulated in the regions of red and blue light, showing that these wavelengths of light generated the most photosynthetic activity. This idea was supported by the photatic behaviour of the organisms, and also by later experiments that showed that no development takes place without the presence of light.
Melvin Calvin, James Bassham, and Andrew Benson studied the radioactive isotope carbon-14 and resulted in the discovery of...
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