4. is an enzyme that acts both as a carboxylase and oxygenase. Why do you think carries out more carboxylation in plants?
RuBisCO functions as oxygenase only when there is a higher concentration of oxygen and a lower concentration of carbon dioxide. Both these conditions are not found in bundle sheath cells of C4 plants. These do not have a photolytic evolution of oxygen. They receive a regular supply of carbon dioxide even when the stomata are closed. Therefore, RuBisCO of C4 plants functions only as a carboxylase and not as oxygenase.