Question

Lenticels permit the:

• A. Exchange of water between the outer atmosphere and internal tissue of the stem in most woody trees.
• B. Exchange of gases between the outer atmosphere and internal tissue of the stem in most woody trees.
• C. Exchange of heat between the outer atmosphere and internal tissue of the stem in most woody trees.
• D. Exchange of radiation between the outer atmosphere and internal tissue of the stem in most woody trees.

Hint:

Think of lenticels as the "stomata of the bark." Just as stomata allow leaves to breathe, lenticels allow the woody stem to breathe. Their function is gas exchange.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Lenticels are structures found on the bark of woody stems and roots. The question asks for their primary function.
Step 2: Detailed Explanation:


In young stems, gas exchange occurs through stomata. As the stem undergoes secondary growth, the epidermis is replaced by the periderm (bark), which is largely impermeable to gases and water.

To allow the living cells within the woody stem to respire, specialized pores called lenticels are formed.

A lenticel is a porous tissue consisting of cells with large intercellular spaces. These pores breach the impermeable cork layer of the bark.

Their primary function is to provide a pathway for the direct exchange of gases (oxygen, carbon dioxide, water vapor) between the internal living tissues of the stem and the outer atmosphere.

They are not primarily for the bulk exchange of liquid water (A), heat (C), or radiation (D). While some water vapor is lost (transpiration), their main role is gas exchange for respiration.

Step 3: Final Answer:
Lenticels permit the exchange of gases between the outer atmosphere and the internal tissues of the stem.