Synthesis of organic compounds (carbohydrates) from inorganic raw materials (CO2 and Hydrogen donor) by green plants in the presence of light (solar energy).

This equation was given by C.B. Van Niel for photosynthesis.

i. Only 0.2% of the light energy falling on earth is utilised by photosynthetic organisms.

ii. Cyanobacteria: Where photosynthesis was first appeared.

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History :

1. Aristotle (320 BC):

Plants get their food only from the soil.

2. Von Helmont (1648):

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All the substance of the plant was produced from water and none from the soil.

3. Stephen Hales (1727):

Air and light are important for nourishment of plants.

4. Joseph Priestley (1772):

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Plants have ability to take up CO2 from the atmosphere and release O2.

5. Jan Ingenhousz (1779):

Recognize importance of sunlight and chlorophyll.

6. Senebier (1782):

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Rate of purification of air depends upon concentration of foul air.

7. Theodore de Saussure (1804):

Water also participates in photosynthesis.

8. Pelletier and Caventou (1818):

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Discovered chlorophyll due to which leaves are green in colour.

9. Von Mayer (1845):

Solar energy is changed into chemical energy.

10. Sachs (1862):

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Starch is formed as a reserve product of photosynthesis.

11. Engelman (1888):

Blotted the action spectrum of photosynthesis.

12. Blackman (1905):

Proposed law of limiting factors and possibility of two phases of photosynthesis.

13. Emerson and Arnold (1932):

Light reaction consists of two distinct photochemical reactions.

14. Robert Hill (1937):

Evolution of oxygen does not require carbon dioxide; photolysis of water; light produces assimilatory power.

15. Ruben, Hassid and Kamen (1941):

Oxygen evolved in photosynthesis comes from water by using heavy isotope of oxygen i.e., H 2 18O.

16. Calvin (1954):

Calvin cycle/C, cycle/Calvin Benson cycle with the help of 14CO2 discovered cycle involved in carbon assimilation.

17. Arnon, Allen and Whatley (1954):

Demonstrated fixation of CO, by chloroplast using 14CO2, discovered photophosphor- lylation.

18. Emerson et.al. (1957):

Emerson effect, proposed two photosystems.

19. Hatch and Slack (1965):

C4 cycle for CO2 fixation.

20. Huber et.al. (1985):

Crystallised photosynthetic reaction centre of bacterium Rhodobacter and got Nobel Prize in 1988.