What is the role of large bundle sheath cells found around the vascular bundles in C₄ plants?

Concept:

• Plants that are adapted to dry tropical regions have the C4 pathway.  
• C4 plants have a special type of leaf anatomy, they tolerate higher temperatures, they show a response to high light intensities, they lack a process called photorespiration, and have greater productivity of biomass. 
•  Large cells around the vascular bundles of the C₄ plants are called bundle sheath cells.
• Leaves that have such anatomy are said to have ‘Kranz’ anatomy.

Explanation:  ​

Option 1:  

•  Bundle sheath cells found around the vascular bundles in C4 plants do not protect the vascular tissue from high light intensity.
• Therefore, this is the incorrect option.

​Option 2:  ​

•  Large bundle sheath cells found around the vascular bundles in C4 plants do not provide the site for the photorespiratory pathway.
• In C4 plants photorespiration does not occur. This is because they have a mechanism that increases the concentration of CO2 at the enzyme site. 
• Therefore, this is the incorrect option.

​Option 3: 

• The large cells around the vascular bundles of C₄ plants form bundle sheaths.
• These cells have a large number of chloroplasts to perform the Calvin cycle.​
• Therefore, this is the correct option.

​Option 4:  

• The C₄ plants respond to higher temperatures and show a higher rate of photosynthesis.
• The optimum temperature required for photosynthesis of different plants also depends on the habitat that they are adapted to.
• Tropical plants have a higher temperature optimum than plants adapted to temperate climates. 
• Therefore, this is the incorrect option.​

So, the correct answer is option 3.