Question

In the given figure, which component has thin outer walls and highly thickened inner walls?

• A. C
• B. D
• C. A
• D. B

Answer 1

The Correct Option is A

Guard cells are specialized cells found in the epidermis of plant leaves and stems. These cells control the opening and closing of stomata, which are pores on the surface of the plant that allow gas exchange (oxygen and carbon dioxide) and water vapor to pass in and out. 

The unique structure of the guard cells plays a crucial role in this function. Guard cells have thin outer walls and thickened inner walls. This differential wall thickness is essential for the opening and closing mechanism of the stomata.

- The thin outer walls of the guard cells are more flexible, allowing the cells to stretch and bend outward as they accumulate water and become turgid.

- The thickened inner walls are more rigid and less flexible, which helps create a ”bowing” effect when the cells swell. As water enters the guard cells, the thick inner walls prevent them from expanding evenly. Instead, the outer walls expand more, and the inner thickened walls restrict this movement, causing the stomata to open. When the guard cells lose water, the inner walls’ rigidity causes the cells to collapse, closing the stomatal pore. 

This mechanism helps regulate water loss through transpiration while allowing necessary gas exchange for photosynthesis and respiration.

Answer 2

Xylem Vessel Structure

The component with thin outer walls and thickened inner walls is typically a xylem vessel.

Xylem vessels have thickened inner walls made of lignin that provide structural support, while the outer walls are thinner.

Conclusion

The correct answer is: (1) C.