What is Solar Energy?
In sun, the nuclear reaction converts hydrogen atom to helium atom and by doing so radiant energy is produced. This radiant energy passes through space as electromagnetic spectrum (wavelength of 380 nm -760 nm). The electromagnetic radiation is composed of small packets of energy called photons or quanta. These photons or quanta are the source of energy for photosynthesis. The energy of photons depends upon its wavelength. The energy of photon at shorter wavelength is higher than that of it at longer wavelength.
Amount of Solar Energy Used
only 1.2% of solar energy is available to plants for photosynthesis. A good portion of the solar energy is reflected back by cloud, dust particles of the atmosphere, surface of the earth and leaf surface etc., a portion is utilised is transportation and another portion is absorbed by leaves as coloured body. Moreover, 60% of the solar energy reaching earth surface comprises of far-red and infra-red radiation which are not used for photosynthesis.
Amount of Carbon Assimilated
Although water covers 70% of the earth surface, the productivity of aquatic environment is low compared to terrestrial environment. Against 2-3 kg of carbon dioxide fixed per square km in terrestrial part only 0.07 kg. of it is fixed in aquatic part. It is estimated that I30x10^8 metric tons of carbon dioxide are fixed in land and 34×10^8 metric tons are fixed in water bodies (Odum 1971).