Question

Which of the following plants economizes transpiration loss of water
A)${ C }_{ 3 }$ plants
B)${ C }_{ 4 }$ plants
C)both equally
D)${ C }_{ 2 }$ plants

Answer 1

Hint: They are native to the tropics and warm temperate zones with high light intensity and high temperature. include many tropical kinds of grass and are among the world's most important crop species (maize and sugarcane).

Complete answer:
-Due to the incorporation of another type of carbon fixation forming a four-carbon sugar before undergoing the Calvin cycle, that's why the ${ C }_{ 4 }$ plants are unique. Due to the presence of four carbon sugars, it is called as ${ C }_{ 4 }$ plants.
-Sugarcane, corn, Sorghum are some examples of ${ C }_{ 4 }$ plants. ${ C }_{ 4 }$ plants have unique leaf anatomy including two types of photosynthetic cells: bundle-sheath cells and mesophyll cells.
-Stomata are closed during the day and keep the stomata open at night by these special plants. They keep their stomata closed to prevent water loss and also prevent ${ CO }_{ 2 }$ from entering the leaves.
-This is advantageous for the ${ C }_{ 4 }$ plants for their survival in extremely hot and dry conditions by conserving water.
-In this way, ${ C }_{ 4 }$ plants economizes the transpiration loss of water.

Additional Information: ${ C }_{ 3 }$ plants - A "normal" plant—one that lacks the adaptations of photosynthetic adaptations in order to minimize the photorespiration—is called a ${ C }_{ 3 }$ plants
-The fixation of carbon dioxide by rubisco is the first step of the Calvin cycle and many of the plants primarily known as ${ C }_{ 3 }$ plants, use only this standard" mechanism of carbon fixation
Approximately, 85 percent of the plant species found on the planet is ${ C }_{ 3 }$ plants including rice, wheat, soybeans, and all trees.

${ C }_{ 2 }$ plants - The ${ C }_{ 2 }$ photosynthetic pathway is more commonly known as photorespiration. This occurs most commonly when plants are in extremely hot and dry environments, forcing them to keep the pores on their leaves, known as stomata, closed to reduce water loss by transpiration.

So, the correct answer is,”${ C }_{ 4 }$ plants”.

Note: -In ${ C }_{ 4 }$, the light-dependent reactions and the Calvin cycle are physically separated, majorly the mesophyll cells (spongy tissue in the middle of the leaf) are involved in the light-dependent reactions whereas, the Calvin cycle mainly found in special cells around the leaf veins which are known as bundle sheath cells.
-${ C }_{ 4 }$ including maize, sugarcane, and sorghum—avoid photorespiration by using another enzyme called PEP during the first step of carbon fixation. This step takes place in the mesophyll cells that are located close to the stomata where carbon dioxide and oxygen enter the plant.