Some pioneers of photosynthesis
1. plants need water.
2. Plants produce oxygen
A few years later, in 1777, Antoine Laurent de Lavoisier (1743-1794), French chemist, philosopher and economist (Figure 2), replaced the theory of phlogistics with the “general théorie of combustion ”. It gives the name of oxygen to the gas involved.
3. Plants, oxygen and light
(1) Light is necessary for the plant to restore air (photosynthesis);
(2) only the green parts of the plant are involved in this restoration;
(3) all living parts of the plant “damage” the air, but the extent of air restoration by a green plant far exceeds its harmful effect.
A century later, Theodor Wilhelm Engelmann (1843-1909), a German physiologist (Figure 3), demonstrated the role of the colour of light in an experiment with filamentous algae (spirogynous type) illuminated with coloured spots, then with a prism, in which aerobic bacteria* serve as an indicator of oxygen production. Bacteria density was highest in the areas illuminated by the blue and red lights.
4. Plants use carbon dioxide
Jean Senebier (1742-1809), a Swiss naturalist, meteorologist and pastor (Figure 4), studied gas exchanges between plants and the atmosphere. He showed that plants absorb carbon dioxide and produce oxygen in the presence of light and published a book in 1783 entitled “ Research on the influence of sunlight in transforming fixed air into clean air by vegetation” . These observations are reinforced by those of Nicolas-Théodore de Saussure (1767-1845), a Swiss chemist, biochemist and botanist (Figure 5): de Saussure shows that plants need carbon dioxide, but also water, nitrogen compounds and mineral salts to ensure their nutrition and growth.
Jean-Baptiste Joseph Dieudonné Boussingault (1802-1887), French chemist, botanist and agronomist, is considered the founder of modern agricultural chemistry (Figure 4). After developing air analysis techniques, he demonstrated – around 1860 – that the volume of gaseous oxygen released and the volume of CO2 absorbed are almost identical.
5. Chlorophyll and chloroplasts
Hugo von Mohl (1805-1872), a German botanist (Figure 6), gave the first detailed description of “Chlorophyllkörnern” (chlorophyll granules) in green leaves in 1837.
Arthur Meyer (1850-1922), a German botanist, cell biologist and pharmacognosist (Figure 6), was the first to name and describe chlorophyll-containing structures in chloroplasts (which Meyer called “autoplasts”) known as grana.
6. Plants transform light energy: photosynthesis
Julius von Sachs (1832-1897), a German botanist (Figure 7), participated very actively in the development of plant physiology. In particular, it demonstrates that starch grains present in chloroplasts are formed under the influence of light.
It was finally in 1930 that Cornelis Bernardus van Niel (1897-1985), a Dutch-American microbiologist (Figure 8), demonstrated that photosynthesis is a light-dependent redox reaction, in which the hydrogen of an oxidizable compound (H 2 A) reduces carbon dioxide to cellular material (CH 2 O)x. This reaction is expressed according to the equation:
CO 2 + H 2 A + light → (CH 2 O)x + A 2 + H 2 O
Notes and References
Cover image. Joseph Priestley [Source: Ozias Humphrey (1742-1810) / Public domain]
[1] Lavoisier, very interested in Van Helmont’s work, points out that the word gas comes from the Dutch word ghoast which means spirit. He adds that the English “express the same idea by the word ghost and the Germans by the word geist”.
[2] Phlogistic theory is a chemical theory that explained combustion by postulating the existence of a “flame element” present within combustible bodies.
[3] Gest H. (2002) History of the word photosynthesis and evolution of its definition. Photosynth Res 73(1-3):7-10.
- Pol D. (2007) History of Plant Biology, History of Knowledge of Plant Physiology. Fondation La main à la pâte : https://www.fondation-lamap.org/fr/page/11407/histoire-des-connaissances-sur-la-physiologie-des-plantes
- Website “Photosynthesis education”. https://photosynthesiseducation.com/discovery-of-photosynthesis/
Engelmann bacteria experiment
Engelmann tried to show that photosynthesis and oxygen production are dependent on the wavelength of the light. For his experiment he split light into its individual color components with a prism. Next, he illuminated a filamentous green alga with the individual light colors. To measure the rate of photosynthesis, he added aerotactic bacteria that moved to the oxygen regions. He could see that the density of bacteria was highest in red and blue light, so the photosynthesis rate had to be highest at these wavelengths. Furthermore, he could determine that photosynthesis takes place in chloroplasts: The illumination of the chloroplasts attracted bacteria, while the illumination of other cell components failed in attracting them.
Explanation for children:
Mr. Engelmann discovered that photosynthesis is dependent on the wavelength of light. Plants do not like all kinds of light, but only blue or red light, for example. For his experiment he illuminated an alga with different colors. To measure the rate of photosynthesis, he used very special bacteria that migrate to places where the air is cleanest. He could quickly see that most of the bacteria were in the red and blue light. So that's where the air had to be the cleanest and the rate of photosynthesis had to be very high.
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Early Experiments on Photosynthesis
Table of contents, introduction, photosynthesis discovery – early experiments, experiment to prove carbon dioxide is essential for photosynthesis, other experiments.
Photosynthesis is a light-dependant process that plants use to produce their own food. It is the process by which plants convert light energy into chemical energy, which can be used later for plants’ own processes. During this process, oxygen is produced as a byproduct. Photosynthesis was discovered only in 1800. To prove the existence of photosynthesis in plants, many scientists performed numerous experiments.
Let us have a detailed look at the early experiments on photosynthesis.
Also Read: What is Photosynthesis
Since photosynthesis is a light-dependant process, it only takes place in the presence of sunlight. But along with sunlight, the plant also requires water and carbon dioxide as raw materials for this process to synthesise carbohydrates. Green plants also possess a green pigment known as chlorophyll which helps in capturing light energy. All these key features of photosynthesis were revealed later during the mid-nineteenth century when numerous scientific studies were conducted on photosynthesis.
Below mentioned are the experiments that were conducted by the early scientists in support of photosynthesis.
Materials required: A healthy potted plant, a wide-mouthed glass bottle with a split cork, potassium hydroxide solution (KOH), and starch solution.
Experiment:
- Select a healthy potted plant and place it in the darkroom for two to three days to ensure the leaves are free from starch.
- In a wide-mouthed glass bottle, add 10-15 ml of potassium hydroxide solution and split the cork vertically.
- Now carefully insert half part of a leaf into a glass bottle through the split cork and the other half exposed to air.
- Place the complete unit undisturbed in sunlight for about 3 – 4 hours.
- After 4 hours, detach the leaf from the plant and slowly remove it from the bottle and test it with the starch solution.
- We can observe that the half part leaf which was inside the glass bottle (KOH solution) did not show any colour change, but the other half part exposed to the surroundings turned its colour to dark brown, indicating the presence of starch in it.
Conclusion: In this experiment, we can conclude that carbon dioxide is essential for photosynthesis. Both the portion of the leaf received the same amount of water, chloroplasts , and sunlight but the half part which was inside the glass bottle did not receive carbon dioxide.
After discovering the importance of carbon dioxide in photosynthesis, many experiments were conducted to understand other essential factors for this process. Joseph Priestly was one of the first scientists to perform these experiments.
Experiment by Joseph Priestley
In 1770, after a series of experiments, Joseph Priestley came to a conclusion regarding the essentiality of air for photosynthesis and also for the growth of plants.
Materials required: A bell jar, candle, rat, and a plant.
- Priestley kept a burning candle and a rat together in the single bell jar.
- After some time, the candle was extinguished, and the rat died.
- For the second time, he kept a burning candle, a rat, and a green plant together in the bell jar.
- He observed that neither the candle got extinguished nor did the rat die.
Conclusion: Based on his observations, Priestley concluded that in the first case, the air in the bell jar got polluted by the candle and rat. However, in the second case, the plant reinstated the air that was spoiled by the candle and the rat.
But it took another few years to reveal what was exactly released by the plant to keep the rat alive and the candle burning.
Jan Ingenhousz: He proved that sunlight is essential for the photosynthesis process during which carbon dioxide is used and oxygen is produced.
Jean Senebier: He demonstrated that during photosynthesis, carbon dioxide in the air is absorbed, and oxygen is released by the plant.
Julius Robert Mayer: Mayer proposed the idea that light energy is being converted into chemical energy during photosynthesis.
Julius Von Sachs: He discovered that the photosynthesis process leads to the production of glucose molecules.
T.W.Engelmann: Engelmann was the scientist who discovered the importance of chlorophyll in photosynthesis.
Cornelius van Niel: He introduced the chemical equation of the photosynthesis process when he revealed that the oxygen released by plants at the end of photosynthesis comes from water and not from carbon dioxide.
Also Read: Photosynthesis in Higher Plants
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Home » Agriculture » Contribution to the History of Photosynthesis: Theodor Wilhelm Engelmann and Hugo Von Mohl
Contribution to the History of Photosynthesis: Theodor Wilhelm Engelmann and Hugo Von Mohl
Théodor Wilhelm Engelmann (1843 -1909) was a German botanist and physiologist.
He demonstrated that the site of photosynthesis is the chloroplast , the cytoplasmic organelle in plant cells which is responsible for the green coloration of leaves and other organs.
He also shed important enlightenment on the functions of light in photosynthesis, particularly light quality .
He showed that not all colors or wavelengths of light are effective in photosynthesis.
He therefore made significant addition to Ingenhousz ’ finding that the degree of shade and brightness of the day ( light intensity ) affects the ability of plants to purify the air (photosynthesis).
It is now a well accepted fact that the process of photosynthesis is affected by the properties of light which include light quality, light intensity, and light duration.
But long before Engelmann’s work on Spirogyra which was published in1881, the presence of chloroplasts in plant cells was already discovered.
In 1837, Hugo von Mohl (1805–1872), also a German botanist and the discoverer of the protoplasm in plants, first described the ‘chlorophyllkörnern’ or chlorophyll granules in detail.
It was proposed in 1883 to substitute the term ‘plastid’ for chlorophyll granule, but eventually ‘chloroplast’ was adapted (Staehelin 2003).
Von Mohl also recognized the presence of starch in the chloroplasts and developed the concept that this starch is a reserve food (Spoehr 1926).
In 1881, Theodor Wilhelm Engelmann designed an experiment for the simultaneous study of the light requirements and biochemistry of photosynthesis.
He used the green alga Spirogyra , which has long chloroplast in each cell, as test organism.
He placed the alga first in a drop of water which contained aerophilic (oxygen-requiring) bacterium to serve as indicator of oxygen evolution.
He then illuminated the alga with different colors of light using a prism.
Using a microscope, he discovered that the bacteria gathered around the parts of the chloroplast that were illuminated by red and blue light.
He concluded that the red and blue colors of light were most effective in producing oxygen (Moore et al. 2003; Govindjee and Krogmann 2004).
This means that the wavelengths of light corresponding to the red and the blue colors are most effective in photosynthesis.
It has long been established that some forms of algae constitute the nano-plankton.
These are organisms which form the basis of the food chain from fish to man.
It was estimated that the contribution of planktonic organisms to the overall photosynthetic processes on earth exceeds 90 percent (Boedijn 1968).
As to generation of oxygen, Moore et al. (2003) suggested that unicellular marine algae probably contributes to 50-70% of the oxygen in the earth’s atmosphere.
Note: The lists of contributors and Literature Cited are in the History of Photosynthesis Mainpage.
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Theodor Wilhelm Engelmann
(1843—1909)
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(1843–1909) German physiologist
Engelmann, the son of a publisher, was educated at Jena, Heidelberg, and Göttingen, before obtaining his PhD from the university in his native city of Leipzig in 1867. He immediately joined the faculty of the University of Utrecht, serving there as professor of physiology from 1888 until 1897 when he returned to Germany to a similar chair at the University of Berlin, where he remained until his retirement in 1908.
Between 1873 and 1895 Engelmann published a number of papers on muscle contraction. By this time, following the work of such physiologists as William Bowman, the main anatomical details of striated muscle had been established. However an explanation was needed as to why the anisotropic or A bands refract polarized light quite differently to the isotropic or I bands. Engelmann had noted that in contraction the A bands increased in volume while the I bands decreased. He consequently proposed his ‘imbibition’ theory in which the contraction of striped muscle is attributed to a flow of fluid from the I to the A bands.
Engelmann also worked on the nature and mechanism of the heartbeat and in 1875 devised an experiment that proved the heartbeat is myogenic; that is, the contraction originates in the heart muscle and not from an external nerve stimulus. In 1881 he discovered the chemotactic response of certain bacteria to oxygen, and he also demonstrated that red and blue light is far more effective in stimulating plant chloroplasts during photosynthesis than other parts of the spectrum.
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Pictorial Demonstrations of Photosynthesis
- Published: April 2004
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Theodor Engelmann's experiments in 1882 provided the first recorded visual demonstration of light wavelengths that are absorbed by photosynthetic pigments. Later, starch images in intact leaves were used to demonstrate photosynthesis in green plants. Similarly, light-induced chloroplast movements can form images in leaves as a result of changes in light transmittance through leaves and photoinhibition can form images that can be visualized by whole leaf chlorophyll fluorescence. This paper provides a brief account of how photosynthesis has been used to create an assortment of 'living images' that offer stunning demonstrations of various aspects of photosynthesis.
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THROUGH WILHELM ENGELMANN, an eminent German physiologist, was born at Leipzig on November 14, 1843, the son of a well-known publisher. He received his medical education at Jena, Leipzig, Heidelberg and Göttingen, and qualified at Leipzig in 1867. Directly after qualification he became assistant to Donders at the Physiological Institute at Utrecht, where he was appointed professor of general biology and histology, and succeeded Donders in the chair of physiology in 1888. In 1897 he succeeded Du Bois-Reymond as professor of physiology at Berlin, where he died on May 20, 1909. His most important work was the discovery of the cones and pigment cells of the retina. Besides studying the mechanics and thermodynamics of muscular contractions, he published works on ciliary movement (1868), spectrophotometric observations and an obituary of Helmholtz (1897). He was also co-editor of Archtiv fur Physiological. He was well known to physiologists in Great Britain, where he was elected an honorary member of the Physiological Society in 1898. He was elected an honorary member of the American Physiological Society in 1904.
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Eight years later, von Mohl then characterized the presence and structure of chloroplasts. Despite these advances, the location of photosynthesis was still a matter of ... Engelmann's bacteria experiments (Engelmann 1881) belong to the very first bioassays and are still well known after 140 years. Notably, the work "color and ...
Theodor Engelmann's Experiment Theodor Wilhelm Engelmann was a German scientist. In 1883, he performed his famous action spectrum experiment to learn which wavelengths (colors) of light were the most effective in carrying out photosynthesis in the green alga. He used a modified microscope equipped with a prism in order to produce the visible ...
Theodor Wilhelm Engelmann (14 November 1843 - 20 May 1909) was a German botanist, physiologist, microbiologist, university professor, and musician whose 1882 experiment measured the effects of different colors of light on photosynthetic activity and showed that the conversion of light energy to chemical energy took place in the chloroplast.
Mit diesem Versuch erforschte Theodor Wilhelm Engelmann das Wirkungsspektrum der ... Hi, in diesem Video erkläre ich euch kurz und simpel den Engelmann Versuch.
In 1883, Theodor Wilhelm Engelmann, a German scientist, wrote his essay"color and assimilation. " (Ger.: "Farbe und Assimila-tion ") describing the state of the art in pho-tosynthesis research, his recent findings, and further assumptions based upon his pres-ented results. Nearly 140 years later, many of his assumptions were proven correct.
In 1883, Theodor Wilhelm Engelmann, a German scientist, wrote his essay "color and assimilation" (Ger.: "Farbe und Assimilation") describing the state of the art in photosynthesis research ...
In 1883, Theodor Wilhelm Engelmann, a German scientist, wrote his essay "color and assimilation" (Ger.: "Farbe und Assimilation") describing the state of the art in photosynthesis research, his recent findings, and further assumptions based upon his presented results.
A century later, Theodor Wilhelm Engelmann (1843-1909), a German physiologist (Figure 3), demonstrated the role of the colour of light in an experiment with filamentous algae (spirogynous type) illuminated with coloured spots, then with a prism, in which aerobic bacteria* serve as an indicator of oxygen production. Bacteria density was highest ...
Explanation for children: Mr. Engelmann discovered that photosynthesis is dependent on the wavelength of light. Plants do not like all kinds of light, but only blue or red light, for example. For his experiment he illuminated an alga with different colors. To measure the rate of photosynthesis, he used very special bacteria that migrate to ...
Theodor Engelmann's experiments in 1882 provided the first recorded visual demonstration of light wavelengths that are absorbed by photosynthetic pigments. Later, starch images in intact leaves were used to demonstrate photosynthesis in green plants. Similarly, light-induced chloroplast movements can form images in leaves as a result of ...
Key words: action spectra, chlorophyll fluorescence, chloroplast movement, Theodor Engelmann, Hans Molisch, photoinhibition, photosynthesis, starch, David Walker, Julius von Sachs Abstract Theodor Engelmann's experiments in 1882 provided the first recorded visual demonstration of light wavelengths that are absorbed by photosynthetic pigments.
Experiment: Select a healthy potted plant and place it in the darkroom for two to three days to ensure the leaves are free from starch. ... Julius Von Sachs: He discovered that the photosynthesis process leads to the production of glucose molecules. T.W.Engelmann: Engelmann was the scientist who discovered the importance of chlorophyll in ...
Von Mohl also recognized the presence of starch in the chloroplasts and developed the concept that this starch is a reserve food (Spoehr 1926). In 1881, Theodor Wilhelm Engelmann designed an experiment for the simultaneous study of the light requirements and biochemistry of photosynthesis.
Kompaktlexikon der Biologie Engelmann-Versuch. Engelmann-Versuch. Engelmann-Versuch, das nach T.W. Engelmann (1843-1909) benannte Experiment zum Nachweis des Aktionsspektrums der Fotosynthese. Engelmann nutzte ein Prisma, um das Sonnenlicht in verschiedene Spektralbereiche aufzutrennen und damit die fädige Grünalge Spirogyra zu bestrahlen.
The biographers who would venture to assess Engelmann's place in the history of German science and art must integrate the strands of his career into a balanced whole. A forceful imagination is needed for a full appreciation of his creativity, taking into ac- count both scientific objectivity and artistic insights.
Quick Reference. (1843-1909) German physiologist. Engelmann, the son of a publisher, was educated at Jena, Heidelberg, and Göttingen, before obtaining his PhD from the university in his native city of Leipzig in 1867. He immediately joined the faculty of the University of Utrecht, serving there as professor of physiology from 1888 until 1897 ...
law, A. von Bezold and his brother, Paul, within two years during this time period. Engelmann's personal dilemma was assuaged when he met the pianist Emma Brandes (ne´e Vick), whom he mar-ried in 1870. She retired from a promising career as a concert pianist to raise a family and preside over the household. Emma and Theodor Engelmann
Theodor Engelmann's experiments in 1882 provided the first recorded visual demonstration of light wavelengths that are absorbed by photosynthetic pigments. Later, starch images in intact leaves were used to demonstrate photosynthesis in green plants. Similarly, light-induced chloroplast movements can form images in leaves as a result of changes in light transmittance through leaves and ...
THROUGH WILHELM ENGELMANN, an eminent German physiologist, was born at Leipzig on November 14, 1843, the son of a well-known publisher. He received his medical education at Jena, Leipzig ...
Jan Ingenhousz, The Netherlands, demonstrates that the plant in Priestley's experiment is dependent on light and its green parts. 1782-1804: Several researchers show that carbon dioxide and water are stored as organic matter by plants. 1845: Robert Mayer, Germany, points out that plants store solar energy in organic matter. ca 1915