Question

Explain how photorespiration is avoided in C-4 plants.

Answer 1

Photorespiration is the process when the level of carbon dioxide is very less. C4 plants generally minimize the respiration by splitting the original carbon dioxide and Calvin cycle.

Complete answer:
Respiration is the process which leads to oxygen metabolism and carbon dioxide production. Cellular respiration is a positive term which is very important for survival but photorespiration is a negative term because it leads to loss to the method of using light energy in photosynthetic organisms to fix carbon for subsequent carbohydrates.
It is a trend seen in C3 Plants like oats, wheat where an increase in the carbon dioxide concentration and decrease in photosynthesis occurs.
In C4 photosynthesis, a four carbon compound is produced and carbon dioxide concentrates in the bundle sheath cells around the Rubisco. These bundle sheaths help to deliver the carbon dioxide directly to Rubisco which effectively removes its contact with oxygen and the need for photorespiration.
Plants which are adapted to tropical dry regions have C4 pathways like sugarcane, corn etc. C4 plants require carbon dioxide to be available for Rubisco. So these are provided in the separate compartment of leaves. Photorespiration does not occur in C4 plants as they have a mechanism which increases the carbon dioxide concentration at the enzyme site.
It happens when the mesophyll C4 acid is broken down in the bundle sheath cells to release carbon dioxide this results in high intracellular carbon dioxide concentration which ensures that Rubisco acts as a carboxylase which minimizes the oxygenase activity.
Hence C4 plants lack photorespiration but show high temperature tolerance.

Note: C4 plants avoid photorespiration because they have the enzyme called PEP during the first step of carbon fixation. Hence the carbon dioxide regenerated during photorespiration is recycled through PEP.