Question

The role of Bulliform cells in monocotyledonous leaves is :

• A. to prevent excessive transpiration by rolling of leaves
• B. to protect the mesophyll cells of the leaf
• C. in exchange of gases with the surrounding environment.
• D. in storage

Hint:

Associate "Bulliform cells" with "rolling leaves" in grasses. This is a mechanism to combat water stress. Think of it as the leaf folding up to protect itself from drying out.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The question asks for the primary function of bulliform cells, which are specialized cells found in the leaves of many monocots, particularly grasses.
Step 2: Detailed Explanation:
Bulliform cells are large, thin-walled, highly vacuolated, and bubble-shaped cells located in the adaxial (upper) epidermis of the leaf. Their function is directly related to the plant's water status.

Under turgid conditions (sufficient water): The bulliform cells are full of water and swollen (turgid). This keeps the leaf blade flat and fully exposed to sunlight for photosynthesis.
Under flaccid conditions (water stress): When the plant loses water due to excessive transpiration or lack of water absorption, the bulliform cells lose their turgor pressure and become flaccid. This causes the leaf to curl or roll inwards, with the adaxial surface on the inside.
The rolling of the leaf reduces the surface area exposed to the dry, outside air. This in turn reduces the rate of water loss (transpiration) and helps the plant conserve water during periods of drought. This is a hygroscopic movement.
Step 3: Final Answer:
The main role of bulliform cells is to facilitate the rolling and unrolling of the leaf to regulate water loss. Therefore, their function is to prevent excessive transpiration by causing the leaves to roll up.