Question

\[{C_4}\] plants are adapted to
A. Temperate humid climate
B. Tropical humid climate
C. Temperate dry climate
D. Tropical dry climate

Answer 1

Hint: \[{C_4}\] plants have been adapted to dry tropic regions. Sugarcane, sorghum and maize are examples of \[{C_4}\] plants. These kinds of plants. They possess a special kind of anatomy known as Kranz anatomy. They are able to tolerate higher temperatures due to that anatomy. Kranz means wreath, which is a reflection of the arrangement of cells. The anatomy is characterized by possessing a number of chloroplasts.

Complete answer
The active site of the Rubisco enzyme catalyzes carboxylation and oxidation of ribulose \[1,5\]-bisphosphate, hence the two processes compete with each other. The rate of oxidation increases with the increase in temperature, which is much faster than the rate of carboxylation reaction, thereby causing enhanced rate of photorespiration at higher temperatures.
Spatial separation of fixation of carbon dioxide and rubisco activity happens in mesophyll cells and bundle sheath cells respectively. This avoids photorespiration by concentrating carbon dioxide in bundle sheath cells to scale down the oxygenase activity of rubisco, which enhances the rubisco efficiency even when the stomata are in a closed position for a long time to avoid loss of transpiration. These leads make the plants adapted to hot and dry conditions, which persist in tropical regions.
Grana are absent in chloroplast. The thick walls of cells are impervious to gaseous exchange and there are no extracellular spaces.
Option A Temperate humid climate: Temperature climate is not that hot.
Option A is not correct
Option B Tropical humid climate: Humidity leads to more water flow.
Hence, Option B is not correct
Option C Temperate dry climate: Temperate climate has some moisture.
So, Option C is not correct
Option D Tropical dry climate: Tropical dry climate is the driest of the four climates given in the options.
Option D is correct

Hence, Option D is the correct answer

Note:
\[{C_4}\] plants maintain lower levels of oxygen since they live in hot and dry climates. Through closing the stomata, they attain this and prevent the loss of water. The occurrence of the Calvin cycle takes place in the mesophyll cells. Usually, stomata is used by plants for losing water vapour and the photosynthesis process. For the purpose of prevention of dehydration, these plants mainly close stomata.