Question

A plant in your garden avoids photorespiratory losses, has improved water use efficiency, shows high rate of photosynthesis at high temperature and has improved efficiency of nitrogen utilisation. In which of the following physiological groups would you assign this plant?

• A. $C_3$
• B. $C_4$
• C. CAM
• D. Nitrogen fixer

Answer 1

The correct option is B $C_4$

In C${}_4$ plants, chloroplasts exist not only in the mesophyll cells in the outer part of their leaves but in the bundle sheath cells as well. Instead of direct fixation to RuBisCO in the Calvin cycle, CO${}_2$ is incorporated into a 4-carbon organic acid, which has the ability to regenerate CO${}_2$ in the chloroplasts of the bundle sheath cells. C${}_4$ plants have a competitive advantage over plants possessing the more common C${}_3$ carbon fixation pathway under conditions of drought, high temperatures, and nitrogen or CO${}_2$ limitation. This increased water use efficiency of C${}_4$ grasses means that soil moisture is conserved, allowing them to grow for longer in arid environments.