Question

Which one is the same between a $C_4$ and a $\mathrm{CAM}$ plant?
I. Leaf anatomy
II. Enzyme catalyzing reaction that fixes ${\mathrm{CO}}_2$
III. Presence of Calvin cycle
IV. Location of $\mathrm{PEP}\mathrm{carboxylase}$ and $\mathrm{RuBisCO}$ in the leaf

• A. Only II
• B. Only II and III
• C. I and II
• D. III and IV

Answer 1

The correct option is B Only II and III

In $C_4$ plants, $C_4$ and $C_3$ cycle occur.

In $C_4$ cycle, $\mathrm{PEP}\mathrm{carboxylase}$ fixes ${\mathrm{CO}}_2$ in mesophyll cells and Calvin cycle (in the presence of the enzyme $\mathrm{RuBisCO}$) occurs in the bundle sheath cells. Hence, the locations of $\mathrm{PEP}\mathrm{carboxylase}$ and $\mathrm{RuBisCO}$ in the leaf are different.

In these plants, there is an inner ring of bundle-sheath cells around the vascular bundles and an outer layer of mesophyll cells. This whole set up which looks like wreath is known as kranz anatomy.

In case of $\mathrm{CAM}$ plants which grow in arid conditions, there is a need to save water and hence, the stomata in the leaves open during the night for the gaseous exchange and remain closed during the day.

The ${\mathrm{CO}}_2$ is concentrated during the night using $\mathrm{PEP}\mathrm{carboxylase}$ and, later during the day, ${\mathrm{CO}}_2$ is extracted in the same cell for Calvin cycle. Hence, the locations of $\mathrm{PEP}\mathrm{carboxylase}$ and $\mathrm{RuBisCO}$ are same in $\mathrm{CAM}$ plants.