Question

What is the importance of photorespiration in plants?

Answer 1

Photorespiration takes place in the presence of light under high temperature and oxygen concentration. As a result of photorespiration excess amount of carbon dioxide is evolved. Photorespiration always competes with the carbon fixing process. It causes heavy loss of fixed carbon. It does not produce any energy rich compounds. It protects the plants from the photo oxidative damage. When the amount of carbon dioxide is low so as to utilize the light energy, the excess light energy is then used for photorespiration. The increased amount of carbon dioxide favors photosynthesis whereas the increased amount of oxygen and light energy initiates the photorespiration. The photorespiration is negligible or absent in the C₄ plants. 

Answer 2

C3 plants do photosynthesis in dry conditions with daytime temperature in range of 40 degree centigrade  and in these conditions,  rubisvo enjyme shows stronger tendency to oxygenate rubp, thus producing 3 phosphoglycerate and 2 phosphoglycolate 2 PG.

Every two molecules of 2PG produce one molecule of 3 phosphoglycerate, thus 3 carbons are restored to Calvin cycle through oxygenation of rubp in process called photorespiration.