Question

Which pathway of photosynthesis is more efficient c3 or c4. Give reasons?

Answer 1

c4 pathway is more efficient than c3 because of division of labour

Answer 2

C4 -plants show Kranz anatomy. In the leaves of C4 -plants, the vascular bundles are surrounded by bundle sheath of parenchymatous cells, which in turn are surrounded by mesophyll cells. Chloroplasts in bundle sheath cells are larger and always contain grana whereas chloroplasts in mesophyll cells are smaller. The C4 -plants are photosynthetically more efficient than C3 -plants because they have more chloroplasts.

Photorespiration takes place only in C3 -plants. It occurs in chlorophyllous tissues. At high temperature and high oxygen concentration the affinity of RuBP carboxylase for CO2 decrease and for O2 increases.

Photosynthesis takes CO2 and release O2, while respiration utilizes O2 and release CO2. If the light factor is saturating, there will be certain concentraton of CO2 in the atmosphere at which the rate of photosynthesis will be equal to rate of the respiration. This is called carbon dioxide compensation point. C4 -plants have very low CO2 compensation point.