Question

In which of the following respects the photosynthetic adaptations of $C_4$ plants and CAM plants are similar?

• A. In both cases, stomata normally close during the day
• B. Both types of plants make their sugar without the Calvin cycle
• C. In both cases, an enzyme other than rubisco carries out the first step in carbon fixation
• D. Neither $C_4$ plants nor CAM plants have grana in their chloroplasts

Answer 1

The correct option is C In both cases, an enzyme other than rubisco carries out the first step in carbon fixation

$C_4$ and CAM plants are plants that use certain special compounds to gather carbon dioxide (CO ₂ ) during photosynthesis. Exploitation of dry and arid habitats required adaptations in the form of $C_4$ and CAM photosynthesis, which independently evolved many times during periods of low atmospheric $C{O}_2$ levels carried out by carried out by a non-rubisco enzyme, PEP carboxylase, that has no tendency to bind $O_2$.

So, the correct option is, 'In both cases, an enzyme other than rubisco carries out the first step in carbon fixation'.