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The History of Photosynthesis

By Patricia Wright,2014-06-23 11:26
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The History of Photosynthesis

The History of Photosynthesis

384-322 (BC) Aristotle compared the soil (earth) to the stomach and concluded that the earth is like the stomach of plants as they gain their nutrients directly from earth and water without having a proper digestive system. 1648 Johan Baptist van Helmont (from Brussels) considered water to be the source of life and the basic nutrient for plants. Therefore he devised an experiment by which he showed that small potted willows can thrive on soil and water alone while they gain their substance (weight) solely from the water as the weight of the soil in the pots did not decrease significantly. He published his conclusion in his book Ortus medicinae wherein he also used the term gas for the first time. 1675 Marcellus Malphigi (from Bologna) was the first to study the anatomy of plants (and insects) concisely by making use of the microscope and he claimed that plants take up nutrients which are dissolved in water via their roots. 1679 In a letter to a friend which was later published in 1717 Edmé Mariotte (from Dijon) summarized the current knowledge about the composition and nutrition of plants and thus provided the first theory of metabolism by stating that all plants are made up of certain basic substances (principes: like sulphur,salt, oil, ammonia and nitre) which must be contained in the soil, where from they are consequently taken up by the plants and transformed into their metabolites. As plentiful different plants can grow from the same soil and water he concluded that each plant must provide its own specific metabolism in order to create its substances and form. 1684 In this year the Irishman Robert Boyle who was a prominent proponent of the Corpuscular Philosophy published his Memoirs for the Natural History of Human Blood in which he documented that the changing colour of blood during its passage through the capillaries of the lung (from dark to light red) was due to a certain ingredient of air which was consumed by fire or breathing. 1703 The German G.E. Stahl (later the physician of Friedrich Wilhelm I. in Berlin) put forward his Phlogiston Theory according to which an element called phlogiston was given off by combustible materials when they burned. Air in which things had been burned became less able to support combustion because, it was thought, it was saturated with phlogiston which, according to the current belief, could then also mix with other substances. It was assumed that phlogiston ought to have a negative weight because substances which had been burned were lighter than before. 1727 Stephan Hales (an English clergyman) described the leaves as organs of transpiration and he postulated that plants exchange gases with their surrounding air. Furthermore, he was the first to point out a possible role of light in plant nutrition by quoting Newton: Könnte nicht eine beiderseitige ineinander wirckende Verwandlung (transformation reciproque) zwischen dicken Körpern und Lichte vorgehen ? und die Körper einen grossen Theil ihrer Activität von denen Lichtparticuln haben, die in ihren Zusammensatz mit kommen. Daß Körper in Licht und Licht in Körper verwandelt werde, ist doch der Natur Lauf gar gemäß, welche am liebsten mit Verwandlungen (transformations) zu schaffen hat. 1772 Joseph Priestley (from Yorkshire) published his Experiments and Observations on different kinds of air and was the first to prove the different qualities of the gases released by plants and the one?s exhaled by animals (mice). He discovered that, although a candle burned out in a closed container, when he added a living sprig of mint to the container, the candle would continue to burn. At the time, Priestley did not know of O, but he correctly concluded that the mint sprig restored the air that 2the burning candle (or mice which he used in a similar set of experiments) had depleted. As he still believed in the Phlogiston Theory he called the gas which was given off by plants dephlogisticated air because a candle would burn brightly in it. 1779 Jan Ingenhousz (from Breda, Netherlands): Experiments upon vegetables, discovering their great power of purifying the common air in the sunshine and of injuring it in the shade and at night, to which is joined a new method of examining the accurate degree of the atmosphere systematically investigated the release of dephlogisticated air from green parts of plants during day time especially from the lower side of leaves, while he also discovered that this depends on the effects of light as plants give off noxious air during night time. 1783 Priestley divulged his discovery personally to the eminent French chemist Antoin-Laurent Lavoiser who immediately understood the theoretical implications of it, as Priestly did not. Lavoiser had already announced, in 1772, that he was destined to bring about a revolution in physics and chemistry. Unlike the older scientists he realized that atmospheric air was not an element but a compound of gases, and he identified Priestley?s discovery as the active component of air for which he had been searching. He called it oxygen (Greek: acid former), in the belief that all acids contained it. 1796 After Ingenhousz learned about the findings of Lavoiser he elaborated on his on investigations and stated that green plants absorb carbon dioxide and release oxygen during day time. 1793-98 Hedewig, Schrank and Humboldt discuss the function of stomata. 1804 N. Theodore de Saussure (Switzerland):Recherche chimiques sur la végétation. He verified Ingenhousz?s hypothesis that plants assimilate carbon dioxide from the air while nitrogen and other nutrients are derived from the soil. Furthermore he was the first to distinguish systematically between the principles of assimilation and dissimilation. 1817 Pelletier and Caventou isolated the green substance in leaves and named it chlorophyll. 1840 Liebig?s findings help to establish the use of fertilizers in agriculture. 1845 Robert Mayer: Plants transform energy of sunlight into chemical energy. Energy can be transformed but not created or destroyed (first law of thermodynamics or energy conservation). See also: Hermann v. Helmholtz, “Über die Erhaltung der Kraft, 1847. 1845 Mohl: Discovery of starch associated with chlorophyll. 1851 L. Garreau: again delineated the differences between dissimilation and assimilation and emphasizes that dissimilation continuously takes place in all parts of a plant. 1864 Bossingault made the first accurate measurements of the gas exchange and found that the volume of O evolved and CO 22used up is almost unity. 1862-64 Julius Sachs (from Breslau) investigated the synthesis of starch under the influence of light and in relation to chlorophyll. He worked out the overall equation of photosynthesis: 6 CO + 6 HO + solar energy ; CHO + O. 22612621869-71 K.A. Timirjazev (from St. Petersburg) developed a method to investigate the spectrum of light and against the background of the law of energy conservation he stressed the pivotal role of green plants for the transformation of light energy into chemical energy. 1872 W. Pflüger defined respiration as a process located on the cellular level. 1883 The replication of chloroplasts was observed by F. Schmitz and A.F.W. Schimper. 1883 An elegant experiment was first performed by the German botanist Thomas Engelmann. He illuminated a filamentous alga with light that had been passed through a prism, thus exposing different segments of the alga to different wavelengths of light. Engelmann used aerobic bacteria, wich seek oxygen, to determine which segments of the plant were releasing the most O. 2Bacteria congregated in greatest density around the parts of the alga illuminated with red and blue light. He also demonstrated the correspondence between the action spectrum of photosynthesis and the absorption spectrum of chlorophyll. 1887 Sachs reviewed the current knowledge and concluded: the most definite proof that ... the chlorophyll body [chloroplast] itself is the organ which decomposes carbon dioxide and consequently assimilates this organic substance, is afforded by the fact ... that the first recocnizable products of assimilation [starch] appear not in any haphazard place in the green cell, but in the chlorophyll body itself. Until the findings of Hill and van Niel scientists now believed that chloroplasts are the site of

complete photosynthesis because it was still thought that oxygen evolution and CO assimilation were inseparable events. 21888 Pfeffer: Handbuch zum Stoffwechsel und Kraftwechsel in der Pflanze 1900 R.Höber establishes the measurement of pH-values. 1901 K.A. Timirjazev studied drought tolerance and was the first to reveal the antagonism between transpiration and assimilation. 1902 Max Rubner was able to prove that th first law of thermodynamics (energy conservation) is also applicable to organisms (Gesetze des Energieverbrauchs im Organismus). 1905 The British plant physiologist Blackman interpreted the shape of the light-saturation curves by suggesting that photosynthesis is a two-step mechanism involving a photochemical or light-dependent reaction and a non-photo-chemical or light-independent reaction. th1895-06 Until the end of the 19 century scientists still assumed that the synthesis and degradation of intracellular substances would require the living protoplasm of intact cells. However, this changed with the discovery of isolated biological enzymes which were still active (Bertrand, 1895 and Buchner, 1897). Thus, the enzyme theory of metabolism was established and the field of Plant Biochemistry developed rapidly. Among the founding fathers were F. Czapek (Biochemie der Pflanzen, 1905) and F.F. Blackman (1906) who wrote about the function of the protoplasm: [It is] ... a complicated congeries of catalytic agents, adapted to the metabolic work that the cell has to do. 1905 F.F. Blackman and G.L.C. Matthaei investigated the influence of the factors light and temperature on the assimilation of CO 2and were able to distinguish between a temperature-dependent but light-independent and a light-dependent but temperature-independent reaction. They suggested a two-step mechanism involving a photochemical or light reaction and a non-photochemical with a high temperature coefficient (indicative of an enzymatic reaction). 1905 K.S. Merezkovskij first claimed an endosymbiotic origin of chloroplasts. 1905-36 Between 1905 and 1916 Albert Einstein published his theory of relativity while the uncertainty principle was formulated in 1927 by the German Werner Heisenberg, and consequently the mathematical formulation of quantum theory was developed in the preceding years which also enabled physicists to calculate and predict the emission of energy from the sun. Accordingly the sun is considered to be a giant thermonuclear reactor. The energy it emits comes from fusion reactions much like those that occur in a hydrogen bomb. Four hydrogen atoms fuse to form one helium, which has a mass less than the total mass of the hydrogen atoms. The lost mass is converted to energy, and by means of Albert Einstein?s famous formula (E=mc?) it was calculated that each minute about 120 million tons of solar matter are converted to a colossal amount of energy that radiates out into space. A small fraction of that energy reaches Earth in the form of electromagnetic energy (waves/particles), taking only a few minutes to make the trip (the speed of light is about 300000 km/sec). 1906 M.S. Cvet (or Tswett from Italy) introduced chromatography by separating the pigments of leaves. 1909 Michaelis first invented electrophoresis. 1909 C. Correns identified inheritable factors in plastids. 1913 R. Willstätter determined the overall structure of chlorophyll. 1915 Dixon established his hypothesis on transpiration and the ascent of sap in plants (Kohäsonstheorie). 1923 Hevesy was the first to use to apply the tracer technique to plant physiology as he followed the passage of radioactive isotopes through plants. 1926 E.Münch studied source-sink-relation and proposed his hypothesis (Druckstromtheorie). 1926 Warburg postulated that CO molecules remain adsorbed on the chloroplast surface until succesive step-wise reduction by 2light-activated chlorophyll converts them to glucose and liberates oxygen. 1927 Osterhout is the first to measure a membrane potential. 1927 Warburg and Negelein developed spectrophotometry. 1929 ATP described by K. Lohmann. 1930 Prior to about 1930, many investigators in the field believed that the primary reaction in photosynthesis was splitting of CO by 2light to carbon and O, while the carbon would subsequently be reduced to carbohydrates by water in a different set of 2reactions. 1930-41 It was found that some bacteria can assimilate CO and synthesize carbohydrates without the use of light energy. Subsequently, 2the Dutch microbiologist van Niel who worked mostly in California showed that some bacteria can assimilate CO in light without 2evolving O. After manifold experiments with these sulphur bacteria C.B. van Niel concluded that the basic principle of 2photosynthesis was a light-driven exchange of hydrogen from a donator (HA) which was to be oxidised to CO (acceptor) 22which would consequently be reduced. On the basis of this he postulated that in plants the hydrogen had to be derived from the splitting of water. Formerly, many investigators believed that the primary reaction in photosynthesis was splitting of CO by light 2to Carbon and O. 21932 Emerson and Arnold measure the length of the light-independent reaction with light flashes lasting less than a millisecond. Flash saturation occurred in normal cells when one molecule of O evolved from 2500 chlorophyll molecules. Emerson and 2Arnold concluded that the maximum yield of photosynthesis was not determined by the number of chlorophyll molecules capturing the light but by the number of enzyme molecules that carry out the light-independent reactions. 1935 Danielli and Davson?s first model of a membrane containing proteins. 1937 R. Hill successfully isolated chloroplasts and separated them from the respiratory particles (the first mitochondria were purified in 1951 by A. Millerd) by differential centrifugation. By using the affinity of haemoglobin to oxygen he was able to measure the release of oxygen from isolated chloroplasts by the use of spec