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Photosynthetic Research Throughout History
Transcript of Photosynthetic Research Throughout History
(384 B.C - 322 B.C) René Dutrochet
(1776 – 1847) Aristotle was a Greek philosopher (Waggoner, 2006) who, in 350 B.C, proposed that plants, like animals, need food (Brennan, 2008). Aristotle believed that plants could obtain nutrients directly from the earth by using their roots. (Janick, 200).
This idea was the beginning of the humus theory of plant nutrition, which stated that plants consume organic matter in soil. ("Plant nutrition," 2011) Sculpture of Aristotle in the National Museum of Rome. (Nguyen, 2006). 350 B.C. 1648 Jan Baptista van
Helmont (1577 - 1644) Jan Baptista van Helmont was a Flemish scientist. He performed an experiment where he placed 200 lbs of dried soil into a clay pot. He then inserted the stem of a willow tree, weighing 5 lbs, into the soil. (Bareja, 2012). After growing the plant in a controlled environment for 5 years, he discovered that the tree gained around 163 lbs, but the soil, dried again, lost merely 2 ounces. (Rubin, 2012). From this, he concluded that most of the plant's mass came from water. (Brennan, 2008). In addition, van Helmont created the term "gas" for fluid substances that were neither liquid nor solid. (Bareja, 2012). He also discovered carbon dioxide, which he named "gas sylvestre." (Cleveland, 2006). -Continued- Summary of van Helmont's experiment observations. (Ong, 2010). Portrait of Jan Baptista van Hemont (Bassett, 2012). 1699 John Woodward
(1665 - 1728) 2.2 cm = 50 years John Woodward was an English scientist who, in 1699, grew mint only in water, without soil. (Bareja, 2012). He measured the amount of water plants absorbed compared to their increase in mass. For one mint plant, 76 kg of water was supplied over a course of 77 days. However, the plant only gained 1 gram of mass. (Rubin, 2012). After performing many of these experiments, Woodward learned that plants needed more than just water to survive and that a large amount of the water a plant absorbed was expelled through pores in the leaves. -Continued- From these findings, he concluded that water does not account for most of a plant's mass, refuting van Helmont's claims. Instead, Woodward suggested that soil was part of a plant's mass. (Bareja, 2012). Portrait of John Woodward. (Humphrey, 1774). Woodward discovered that water left through a plant's pores. ("Transpiration scheme (plants)," 2012). 1727 Stephen Hales
(1677 - 1761) Stephen Hales was the first to propose that plants obtained nutrients from the air through leaves ("Landmarks in studies," 2012) and sunlight was somehow involved. (Brennan, 2008). In his experiments, he measured the amount of water vapor that was released from plants in closed environments. Hales noticed that the air volume above the water in which the plant grew decreased by about 15%. From these results, he hypothesized that plants released some kind of substance that combined with air, causing air volume to decrease. (Govindjee & Krogmann, 2004) Portrait of Stephen Hales. (Day, 2012). 1772 Joseph Priestley
(1773 - 1804) Joseph Priestley, an English chemist, tried to isolate air. When he heated mercuric oxide with focused sun rays, the reaction produced oxygen; he named this gas "dephlogisticated air." ("Joseph Priestley," 2012). He also experimented with mice, mint, and candles. When a mouse was placed in a container of dephlogisticated air, it lived twice as long as a mouse in normal air. ("Landmarks in studies," 2012). In addition, air that was made unbreathable by burning candles could be purified by a plant. In a closed space, a candle will burn out and a mouse will suffocate. However, when a plant is added, the candle will continue to burn and the mouse will live. (Govindjee & Krogmann, 2004). Painting of Joseph Priestley. (Ford, 2004). Priestley's experiment. Without plants, candles and mice cannot exist. ("Priestley's experiment," 2012). 1779 Jan Ingen-Housz (1730 - 1799) Jan Ingen-Housz was a Dutch physician who showed that plants needed sunlight (Govindjee & Krogmann, 2004) to produce oxygen. (Brennan, 2008). In one of his experiments, he placed plants underwater. He noticed that, when sunlight was available, gas bubbles formed on the underside of the leaves. Similarly, when there was no sunlight, no bubbles formed. While trying to identify the gas, he discovered that it will reignite a dying flame. He named this gas "oxygen." From his observations, he concluded that plants release oxygen in sunlight and carbon dioxide in darkness. ("Jan Ingenhousz," 2011) -Continued- Although plants release both oxygen and carbon dioxide, they release oxygen in much greater amounts. Hence, Ingen-Housz found that the purifying effect of plants outweighs their damaging effect.(Jan Ingenhousz, 2012) Portrait of Jan Ingen-Housz. (Olsen, 2012). Oxygen bubbles on the leaves of an aquatic plant. ("The pearling effect," 2010). 1782 Jean Senebier
(1742 - 1809) Jean Senebier was a Swiss scientist who believed that carbon dioxide, which he called "fixed air", was essential to photosynthesis. (Govindjee & Krogmann, 2004). He knew that, in sunlight, plants will take in carbon dioxide and release oxygen gas. (Jean Senebier, 2012). Thus, he concluded that the carbon dioxide was decomposed into oxygen and carbon. Oxygen was released into the atmosphere and carbon became part of the plant as organic matter. ("Discovering the secrets," 2011). Painting of Jean Senebier from the 18th century. ("Jean Senebier," 18th century). 1783 Antoine Lavoisier (1743 - 1794) The French chemist Antoine Lavoisier created the Law of Conservation of Mass, which states that the mass in a closed system is constant. (Weisstein, 2007). He suggested that combustion was merely a reaction with oxygen. (Govindjee & Krogmann, 2004). To prove this, he burnt sulfur and phosphorus and measured the mass of the products. He found that the products weighed more than the reactants. Thus, he deduced that the weight gained was from taken the air.(Weisstein, 2007).
He also gave the name "carbon dioxide" to what Senebier called "fixed air." ("Landmarks in studies," 2012).
In addition, he realized that animals need oxygen for respiration. (Brennan , 2008). Antoine Lavoisier. ("Antoine Lavoisier," 1785) 1804 Nicolas de Saussure (1767 - 1845) Nicolas de Saussure, a Swiss scientist, proposed that water is a reactant in photosynthesis (Govindjee & Krogmann, 2004) and that carbon and water combined accounted for the increase in a plant's weight. (Brennan, 2008). He put many plants in glass containers and weighed both the plant and the amount of carbon dioxide in the container. He found that plants absorb carbon from the atmosphere in the form of carbon dioxide. De Saussure also proved that the amount of carbon dioxide taken in was nearly equal to the amount of oxygen released. Additionally, he studied plant ashes and discovered that the mineral composition of the ashes was different than that of the soil. Thus, he concluded that plants are selective in terms of which nutrients they absorb. (Robinson, 2012) Nicolas de Sassure. ("Nicolas-Théodore de Saussure," 2012). 1837 René Dutrochet, a French physiologist, discovered the process of osmosis. He believed that all basic metabolic processes of living things could be explained by physical and chemical forces. (Henri Dutrochet, 2012).
He also named the pores of plant leaves "stomata." Through his observation of plants, he realized that chlorophyll played a part in plants' ability to use carbon dioxide. (Brennan, 2008). Upon further observation, he discovered that only cells with chlorophyll could perform photosynthesis. (Rezende, 2006). Portrait of René Dutrochet. ("Naissance d'Henri Dutrochet," 2012) 1845 Julius Robert von Mayer (1814 - 1878) Julius Robert von Mayer, a Germany physicist and physician, proposed the Law of Conservation of Energy. (Govindjee & Krogmann, 2004). He suggested that sunlight was the main source of energy for living organisms and plants could change light energy into chemical energy through photosynthesis. (Brennan, 2008).
He performed experiments in a paper factory, where he saw a horse stirring a cauldron of pulp. By measuring the change in pulp temperature, he was able to obtain a figure for the amount of heat produced by a given amount of mechanical work done by the horse. (Fisher, 2011) Portrait of Julius Robert von Mayer. ("Julius Robert von," 2012) 1862 Julius von Sachs
(1832 - 1897) Julius von Sachs was a German botanist who, throughout his years of tending to plants, found starch grains in leaves. He claimed this to be the first visible product of photosynthesis. (Govindjee & Krogmann, 2004). He also proved that chlorophyll was found in chloroplasts. From his studies, he created his imbibition theory: plants have tubes that carry water from their roots to their tips, and this system can function without the help of living cells. (Julius von Sachs, 2012). Julius von Sachs. (Sengbusch, 2003). 1864 Jean Baptiste Boussingault (1802 - 1887) Jean Baptiste Boussingault was a French chemist who proved that plants obtain nitrogen, in the form of nitrates, from the soil. Moreover, he was able to created a basic schematic for the nitrogen cycle. (Jean-Baptiste Boussingault, 2012).
Boussingault also made accurate measurements of the amount of carbon dioxide and oxygen a plant takes in and produces. This led him to form a balanced equation for photosynthesis: 6CO2 + 12H2O + light energy ---> C6H12O6 + 6O2. (Brennan, 2008) Portrait of Jean Baptiste Boussingault. (Petit, 2009). The completed nitrogen cycle. ("The nitrogen cycle," 2007). 1957 Daniel Arnon
(1910 – 1994) Daniel Arnon performed experiments to prove that ATP was synthesized only when light was present. This process was called photophosphorylation. (Brennan, 2008). He also showed that NADP+ was reduced photochemically, which caused the carboxylation of pyruvic acid into malic acid. (Govindjee & Krogmann, 2004). Photograph of Daniel Arnon as he works in the University of California. (Reinhard, 1988). 1956 Melvin Calvin
(1911 - 1997) Melvin Calvin, an American biochemist, traced the path of carbon through photosynthesis by using radioisotope carbon-14. (Benson & Seaborg, 2012). Calvin added carbon dioxide and carbon-14 to a single-celled green alga. He was able to identify different radioactive compounds with the help of paper chromatography, which then allowed him to determine the types of chemical reactions that occurred when carbon dioxide was turned into carbohydrates. He also discovered that the compounds formed during light-dependent reactions were used in light-independent reactions (Melvin Calvin, 2012) and sunlight acted on chlorophyll to create organic compounds. (Yarris, 1997). -Continued- Calvin made several important discoveries. Firstly, he learned that, from carbon dioxide reduction, phosphoglyceraldehyde was the first stable product. Secondly, he found that ribulose bisphosphate is a carbon dioxide acceptor. Lastly, he noticed that this acceptor was regenerated in a cycle (Govindjee & Krogmann, 2004). These discoveries allowed him to create the Calvin cycle, which details how carbon dioxide is converted into an organic compound. (Melvin Calvin, 2012) Photograph of Melvin Calvin. ("Calvin, Melvin") Simplified version of the Calvin cycle. ("Calvin cycle"). 1954 Robert Emerson
(1903 – 1959) Robert Emerson was an American biophysicist who, in 1957, discovered that there exists two types of light reactions. He performed experiments in which flashes of blue and red light were shone at a green alga. With each type of light, the amount of oxygen produced was measured. Emerson found that when both lights were used, the amount of oxygen created was much greater than with one light alone; this led him to believe that there are two types of light reactions and they are most efficient when they work together. (Photosynthesis, 2012).
While shining the lights at the alga, Emerson deduced that only one of many chlorophyll molecules participate directly in photosynthesis. This led to another conclusion that there are hundreds of accessory pigments and only one reaction center chlorophyll. (Govindjee & Krogmann, 2004). Robert Emerson. ("Understanding photosynthesis," 2009). 1960 Robert Hill
(1899 - 1991) Robert Hill was an English biochemist who took isolated chloroplasts and tried to recreate photosynthesis; however, only part of photosynthesis was completed. ("Landmarks in studies," 2012). Despite this, Hill saw that isolated chloroplasts could create oxygen as long as there was light and an electron acceptor, such as iron oxalate. He called this the Hill reaction, which showed that oxygen was created in photosynthesis due to the breakdown of water, as opposed to carbon dioxide. (Sengbusch, 2003). Following this logic, he proved that the breakdown of water and carbon dioxide fixation are independent processes. (Cleveland, 2009). -Continued- Hill created the "Z-scheme" for the two photosystems that use different wavelengths of light. (Brennan, 2008) Photograph of Robert Hill. ("Robert hill (biochemist)," 2012) 1985 Robert Huber
(1937 – present) Robert Huber was the first person to find the 3D shape of the reaction center in chloroplasts. He, along with his associates, used x-ray crystallography and created a 3D structural diagram of a photosynthetic reaction center. Robert Huber.
("Prof. Dr.," 2011) 2000 Zu-Hua Yin and Giles N. Johnson (2000) Zu-Hua Yin and Giles N. Johnson published a journal article about their experiment with a plant's ability to adapt to fluctuating light. The two grew plants in an environment where the irradiance was 100 μmol m̄² s̄¹ for 4-6 weeks. After that time period, the plants were moved to an area with irradiance of either 475 or 810 μmol m̄² s̄¹. Most of the plants were able to adjust to the changes and maximize their rate of photosynthesis. (Yin & Johnson, 2000) 2010 Gregory D. Scholes
(2010) Gregory D. Scholes is a chemistry professor at the University of Toronto. (Scholes, 2003). During his studies, he found that photosynthesis uses the laws of quantum mechanics and other biological systems may also be doing the same in order to optimize processes.("Quantum laws discovered," 2010). Photograph of Gregory Scholes.
("Gregory Scholes," 2012) Janet Wong
November 26, 2012