Raw Materials

Raw Materials used in Photosynthesis In Higher Plants

1. Carbon Dioxide. In land plants, carbon dioxide is obtained from the atmosphere through the stomata. Hydrophytes get their carbon dioxide supply from the aquatic environment as bicarbonates. Bicarbonates are absorbed by the hydrophytes through their general surface.

2. Water. Van Niel (1931), while working on a type of photosynthetic bacteria, found that they required hydrogen sulphide for their carbon fixation. There was no evolution, of oxygen. Obviously in these photosynthetic bacteria carbon dioxide did not split up as there was no evolution of oxygen. 

6CO₂ + 12H₂S  C₆H₁₂O₆ + 6H₂O +12 S

He also propounded that oxygen is evolved from water.

3. Light. Light is the visible part of electromagnetic radiations. Electromagnetic spectrum consists of 8 types of radiations – cosmic rays, gamma rays,  X-rays, ultra-violet radiations, light spectrum, infra-red rays, and radio waves. Visible light consists of radiations having a wavelength 390–760 nm (or 3900 – 7600 Å). Photosynthetically Active Radiation (PAR) is 400 – 700 nm.

Longer than those of red are called infra-red. They have wave length of more than 760 nm. Sunlight or solar radiations reaching the earth have wavelength between 300 nm ( in the ultraviolet range) to 2600 nm ( in the infra-red range).

Fig. The electromagnetic spectrum