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Blackman, F.F. Last Updated on 2014-06-30 16:39:52 F.F. Blackman, a British plant physiologist who discovered that photosynthesis is a two-step process (1905), only one of which uses light directly. He cultivated plants under different but controlled carbon dioxide concentrations, different light intensities and different temperatures and noted the effects of these variables on the rate of photosynthesis. Under low light intensity, photosynthesis is enhanced by increasing light, but is unaffected by increases in temperature and carbon dioxide. When light intensity is high, increases in both temperature and carbon dioxide accelerate photosynthesis. Black concluded that the initial "light" reactions are independent of temperature, while the second "dark" reactions are independent of light yet are limited by carbon dioxide and controlled by enzymes. More »
Calvin, Melvin Last Updated on 2014-06-30 16:18:37   Melvin Calvin (1911-1997), American biochemist who first described the photosynthetic process, now known as the Calvin Cycle. Calvin determined the process by tracking radioactive carbon dioxide through its transformation into carbohydrates. He allowed carbon-14 to be absorbed by plants, then mashed up the cells and separated the contents using paper chromatography. He discovered intermediate reaction products of photosynthesis and worked out the reaction scheme. He also discovered that photosynthesis proceeds in the absence of light. Calvin later confirmed which primary elements had formed the atmosphere from which primitive life developed. He received the Nobel Prize in Chemistry in 1961.   Further Reading Melvin Calvin - Biography (The Nobel Foundation) Calvin Photosynthesis Group Subject of History Project (Lawrence Berkeley National Laboratory) More »
Ingenhousz, Jan Last Updated on 2014-06-30 16:14:19   Jan Ingenhousz (1730 - 1799), a Dutch physician and plant physiologist, confirmed in 1779 that in sunlight, plants absorb carbon dioxide and give off oxygen. Ingenhousz's work, published in Experiments On Vegetables, Discovering their Great Power of Purifying the Common Air in Sunshine, and of Injuring it in the Shade or at Night, laid the foundations for the study of photosynthesis. This was the first indication of light's role in the photosynthetic process. Ingenhousz also discovered that only the light of the Sun—and not the heat it generates—is necessary for photosynthesis. He found that plants, like animals, respire all the time and that respiration occurs in all the parts of plants. He further concluded that plants were converting carbon dioxide into oxygen, which animals converted back into carbon dioxide. Ingenhousz also showed that only the green... More »
Kamen, Martin David Last Updated on 2014-06-30 16:09:31 Martin David Kamen, (1913–2002), a Canadian-born American biochemist who discovered carbon-14, the radioactive isotope of carbon used to trace biochemical pathways and mechanisms and to date archeological and anthropological objects. He also carried out extensive research in photosynthesis. Kamen used the isotope oxygen-18 to trace the chemical's role in the process, confirming that that the oxygen created during photosynthesis comes only from the water molecules. Unfortunately, much of his energy at this time was diverted to non-scientific matters; a successful but protracted libel suit against the Chicago Tribune, which falsely accused him of being a communist, as well as a successful, 7-year battle to recover his passport, which had been rescinded by the U.S. government. Further Reading Martin Kamen, Who Discovered Carbon-14, Wins Fermi Award (U. S. Department of Energy,... More »
Fibonacci, Leonardo Pisano Last Updated on 2014-06-30 14:38:11 Leonardo Pisano Fibonacci (c.1170-1250), an Italian mathematician known for his pioneering work in the development of the decimal system that eventually replaced the Roman numeral system. In 1202, he published Liber abaci, which introduced the Hindu-Arabic place-valued decimal system and the use of Arabic numerals in Europe. Fibonacci is perhaps best known for a simple series of numbers, later named the Fibonacci numbers in his honor. The series begins with 0 and 1. After that, use the simple rule: Add the last two numbers to get the next. This produces the series: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987,... Fibonacci numbers show up in a surprising number of natural phenomena, including the branching pattern of some trees, the spiral design of the nautilus shell, the petal... More »