Question

Diagram and describe photorespiration. Why does it occur? Diagram and describe the C4 and CAM pathways and explain how they reduce photorespiration. Why don’t all plants use these pathways?

(no bullet points, essay format)

Answer 1

In photorespiration plants utilize oxygen and from organic compound release carbon dioxide- This process takes place in presence of light and use the enzyme RuBisCO.

Photorepiration occurs due to a higher oxygen concentration in environent and enough corbon dioxide is not present.

C4 pathway

In C4 pathway, CO₂ get converted to a 4C compound which next passed through a area of deeper tissue layer with less oxygen. In this area CO₂ get released and can go into Calvin cycle pathway.

CAM pathway

CAM pathway initiates where water is present in low amount and there is a need that stomata to be closed during day.. During night, CO₂ is converts to C4 which then diffused to leaves when stomata are opened. At day this CO₂ is act as storage to be used and O₂ is not released.

Both C3 and CAM pathway functioning in CO₂ fixation and there by helps and improves photosynthesis and thus reduce photorespiraiton: C3 plants reduce the rate of photorespiration by fixing the CO₂ at different cell types. Whereas, CAM pathway reduces photorepiration by fixing the CO₂ at different time point, day and night.

This do not occur in other plants as most of the plants are chatagorized into C3 group and they do not have any features which can be used to fixed CO_2.