Photosynthesis is the process of preparation of carbohydrate by green plants from CO2 and H2O in the presence of sunlight. It has been defined as the capture of photons by the green plants and conversion of their radiant energy into chemical energy in the form of organic foods.
It is of common occurrence among green plants, green, red and brown algae, blue-green algae, diatoms, dinoflagellates, purple bacteria and sulphur bacteria. Nearly 90% of the global photosynthesis is carried out by marine and fresh water algae. CO2 and H2O are the raw materials used in photosynthesis. It is the single largest chemical process and provides energy for the various life activities.
It is of common occurrence among green plants, green, red and brown algae, blue-green algae, diatoms, dinoflagellates, purple bacteria and sulphur bacteria. Nearly 90% of the global photosynthesis is carried out by marine and fresh water algae. CO2 and H2O are the raw materials used in photosynthesis. It is the single largest chemical process and provides energy for the various life activities.
The overall process of photosynthesis can be represented by the formula
History of Photosynthesis
These are the pioneers who explained the life sustaining chemical reaction; photosynthesis on this planet.Aristole and Theophrastus (320 BC)
The great philosophers believe that plant absorb all the materials, inorganic, organic directly from the soil.Jan Baptista Van Helmont (1648 AD)
His experiments concluded that the dry weight of plant increases due to water absorbed by them and not due to soil. He concluded that the major constituent of all vegetation is water.Stephan Hales (1727)
The father of plant physiology recognised the importance of air and sunlight in the nutrition of green plants.Joseph Priestly (1772)
Showed that plants have the ability to take up CO2 from the atmosphere and release O2.Jan Ingenhousz (1779)
Discovered that release of O2 by plants was possible only in sunlight, and only by the green parts of the plants. He also confirmed Joseph Priestley’s work.Jean Senebier (1782)
He noted that air restoring activity of plants depends on the presence of fixed air or he showed that as the concentration of CO2 is increased, the rate of oxygen evolution also increases.Nicolas de Saussure (1804)
He verified Jan Ingenhousz´s hypothesis that plants assimilate CO2 from the air while nitrogen and other nutrients are derived from the soil. He realized the importance of H2O in photosynthesis.Von Mayer (1842)
He considered sun as the source of energy and revealed that green plants can convert solar energy to chemical energy in the form of organic matter.Leibig (1845)
He indicated that the organic matter was derived from CO2and H2O was used in photosynthesis.Sachs (1864)
He reported that carbohydrates are the products of photosynthesis and also that chloroplast are the centres where CO2 and H2O are utilized and O2 is released.Engelmann (1888)
He demonstrated the correspondence between the action spectrum of photosynthesis and the absorption spectrum of chlorophyll.F.F. Blackmann (1905)
Formulated the “law of limiting factors”Van Niel (1924)
He showed that bacteria use H2S instead of H2O in photosynthesis and he gave a simplified equation of photosynthesis.Emerson and Arnold (1932)
Revealed the occurrence of light and dark reactions in photosynthesis.Robert Hill (1937)
Demonstrated photolysis of water.Photolysis or Hill's Reaction: In the presence of light water(H2O) gets dissociated into hydrogen (H+) ions and hydroxyl ions(OH)-.
Samuel Ruben and Martin Kamen (1941)
The role of water (H2O) in the formation of molecular oxygen (O2) was clearly explained by using labelled isotope of oxygen,18O.Arnon, Allen and Whatley (1954)
Demonstrated the reduction or fixation of CO2.Melvin Calvin (1954)
Traced the path of carbon (CO2 assimilation) in photosynthesis and awarded the Nobel Prize in 1961.Hatch and Slack(1965)
Reported the C4 pathway.Robert Huber, Hartmut Michael and Johann Dissenhofer (1985)
Crystallization of the light-harvesting complex and photosynthetic reaction centre of the bacterium Rhodobacter. For this work they were awarded the Nobel prize in 1988.Learn more:
