Photosynthesis: The Power Plant and the Chemical Factory of Life

Literally, photosynthesis means " synthesis with the help of light." This covers a variety of processes in organic and inorganic chemistry. However? the term is usually applied to one reaction only- the synthesis of organic matter by plants in light- a process also called " carbon assimilation."
This is the basic process of life ( at least as we know it on earth ).It creates living matter out of inert inorganic materials? replenishes the reservoir of oxygen in the atmosphere, and stores the energy of sunlight to support the life activities of organisms.Its discovery is a thrilling chapter in the history of science.
   About 1648, a Dutchman, van Helmont, grew a willow tree in a bucket of soil and found that the amount of soil did not diminish significantly, although a big tree was formed. He guessed that the material of the tree must have come from water used to wet the soil. In a book published in 1727 ( called Statical Essays, Containing Vegetable Statics, or, an Account of Some Statical Experiments on the Sap in Vegetation) , the great English minister-naturalist, Stephan Hales, surmised that plants drew a part of their nutrition from the air. Both views ran contrary to the long-accepted, Aristotelian view that plants feed on "humus" of the soil. Stephan Hales also suggested that sunlight may play a role in "ennobling the principles of vegetables."