Question

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

Answer 1

$C_4$ plants

Plants lacking Kranz anatomy are susceptible to photorespiration under higher oxygen concentration in the mesophyll cells resulting in decreased productivity.

In Kranz anatomy, RuBisCO is present in the bundle sheath cells. These cells possess thick walls impervious to gaseous exchange with no intercellular spaces thereby preventing escape of $C{O}_2$.

$C_4$ plants

Malic acid gets transported to the bundle sheath cells from mesophyll cells and is broken down to release $C{O}_2$. $C{O}_2$ gets accumulated in the bundle sheath cells. High concentration of $C{O}_2$ minimises photorespiration.

These plants also have increased efficiency for nitrogen usage.

$C_4$ plants have a higher temperature maximum. These plants are adapted to dry, high temperature conditions.

$C_4$ plants

Due to the efficient $C_4$ pathway, the plants do not have to keep their stomata open for long duration during the day. This reduces transpiration and minimises water loss.

Hence, the garden plant is most likely to be of $C_4$ type.

Final answer

(B) $C_4$