Photosynthesis as a biological process
Definition and main principles of photosynthesis
Photosynthesis is a process of producing organic agents out of carbon dioxide and water with the help of sunlight and special photosynthetic pigments (chlorophyll in plants and bacteriochlorophyll or bacteriorhodopsin in bacteria). Plants, many algae and bacteria (with the exception of archaea) are able to feed themselves with the help of photosynthesis, that is why they are called photoautotrophs. Since the waste product of this process is oxygen, photosynthesis is vital for all the living and breathing organisms on the Earth.
History of photosynthesis
Jan Baptist van Helmont in the17th century was the first who, having observed the growth of a tree during 5 years, made an assumption that rain water was the main element owing to which the tree was able to grow. Shortly afterwards, Joseph Priestley with the reference to a series of experiments announced that green plants are able to perform the same process of breathing as animals. In 1817 two French scientists – Joseph Bienaimé Caventou and Pierre Joseph Pelletier – extracted green substance out of plants and gave it the name of chlorophyll. Only in 1905 English physiologist Frederick Blackman undertook a study and identified the main processes of photosynthesis.
Light and dark phases
On the basis of the studies, undertaken by Blackman, it was concluded, that the process of photosynthesis can be divided into two main phases. The first phase mostly depends on the level of lighting, but not upon the temperature, whereas the second phase is greatly defined by the temperature, regardless of the light level. These two processes are formally named the light and the dark phases, though these terms are not completely correct, since it turned out that even though the reactions of the dark phase can be going on without light, the products of the light phase are necessary for them.