Do you know the process of photosynthesis? The below article will explain to you the definition and chemical reaction of photosynthesis. You will also find interesting history and the importance of photosynthesis to mankind.
Introduction
Photosynthesis (Gk; photos=light, synthesis=putting together) is the most important phenomenon through which all green plants prepare their food by converting sunlight into chemical energy. The process of unknown till 17th century. Stephen Hales (1927) for the first time pointed out the role of sunlight in the process of photosynthesis, since then significant researches have been made in this connection. In simple term, photosynthesis can be defined as the green plants prepare carbohydrate with the help of carbon dioxide and water in the presence of sunlight and chlorophyll. Green plants prepare glucose which is converted into starch.The chemical equation of photosynthesis is as below: 6CO2 +12H2O = C6H12O6 +6H2O +6O2
During the process of photosynthesis, light energy is converted into chemical energy and is stored as organic matter, which is usually carbohydrates, along with oxygen forms the end products of photosynthesis. One molecule of glucose ( C6H12O6), contains about 673 Kcal of energy. Carbon dioxide and water constitute raw materials for this process. Thus photosynthesis is a mean of autotrophic nutrition.
History of significant discoveries in photosynthesis
The history of photosynthesis is much interesting. It can be traced back to the period of Aristotle and Theophrastus (320 B.C.). However, these pieces of information were based on philosophical ideas and bot correct on scientific ground. Enormous workers have contributed their efforts to the discoveries of processes related to photosynthesis. Some of the important discoveries have been presented here:
Aristotle and Theophrastus (320 B.C.) believed that plants absorb all their nourishment directly from the soil with the help of their roots.
Stephen Hales (1727) discovered that green plants absorb air from the atmosphere and make their food with the help of light.
Joseph Priestley (1772) demonstrated that green plant purifies the foul air and covert it into pure air. He carried out an interesting experiment in which he put two mice inside separate bell jars. Inside the first bell jar, the mouse was alone and inside the second bell jar, a plant of mnt was also kept with the mouse. After sometimes, he observed that the mouse kept inside the first bell jar dies while the mouse inside the second bell jar remain alive. On the basis of this result, Priestley (1772) concluded that green plants release oxygen during photosynthesis.
Jan Ingen Housz (1779) discovered the role of light and green parts of the plants in purifying noxious air.
Jean Senebier (1782) proved that green plants absorb carbon dioxide and release oxygen in the presence of light. He also showed that the rate of oxygen evolution depends upon the rate of carbon dioxide consumption.
Nicolas de Saussure (1804) showed the importance of water and carbon dioxide in the process of photosynthesis.
Dutrochet (1837) showed the importance of green pigment chlorophyll in photosynthesis.
Liebig stated that the chief source of carbon for plants is carbon dioxide found in the environment.
Von Mayer (1845) proposed that green plants convert solar energy into chemical energy of organic matter.
Julius Von Sachs (1864) discovered that the product of photosynthesis is starch.
Blackman (1905) discovered light and the dark reaction of photosynthesis and proposed the law of limiting factor.
Willstatter and Stoll (1913) investigated the structure of chlorophyll.
Emerson and Arnold (1932) showed the existence of light and dark reaction.
Robert Hill (1937) demonstrated that the isolated chloroplast cause photolysis of water in the presence of light.
Ruben, Hassid and Kamen (1941) Used Oxygen 18 and reported that oxygen evolved during photosynthesis comes from water and not from carbon dioxide.
Calvin and Benson (1954) traced the path of carbon in the dark reaction of photosynthesis and gave C3 cycle and awarded the Nobel prize in 1961.
Hill and Bendall (1960) proposed a 'Z' scheme of light reaction of photosynthesis.
Arnon (1961) discovered photophosphorylation.
Hatch and Slack (1966) discovered C4 pathway (Hatch Slack cycle) for carbon dioxide fixation in certain tropical grasses.
Rauhani and associates (1973) discovered the pathway of Crassulacean Acid Metabolism (CAM) in succulent plants.
Importance of photosynthesis to mankind
The significance of photosynthesis to mankind are as below:
Photosynthesis maintains the equilibrium of oxygen in the atmosphere.
Photosynthesis provides food either directly as vegetables or indirectly as meat or milk of animals which in turn are fed on plants.
Besides providing energy in the form of food, photosynthesis has also provided vast reserves of energy to man as fuel such as coal, oil, peat and also wood and dung.
All useful plants products are derived from the process of photosynthesis. E.g., timber, rubber, resins, drugs, oils, fibres, etc.
Photosynthesis decreases the concentration of carbon dioxide which is being added to the atmosphere by the respiration of organisms and burning of organic fuels.
Article by Hakimuddin Kuwakhedawala Hakimuddin Kuwakhedawala is based in India with over 15 years experience as a teacher. Teaching and writing are his passion. Most of the articles of Hakimuddin are related to education, exam, environmental problems, etc.
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