Problem 123 - Objective Biology for NEET

Question

At certain region, the phellogen cuts off closely arranged parenchymatous cells on the outer side instead of cork cells. These parenchymatous cells soon rupture epidermis, forming a lensshaped opening called (a) Hydathodes (b) Stomata (c) Lenticels (d) None of these

Step-by-Step Solution

Answer

The correct answer is (c) Lenticels

Step 1: Understanding Phellogen

Phellogen, also known as the cork cambium, is a meristematic tissue that cuts off cells on both its sides. Under normal circumstances, it cuts off cork cells on the outside.

Step 2: Understanding Parenchymatous Cells

Parenchymatous cells are a type of plant tissue made up of thin-walled cells that make the bulk of most non-woody structures. They are also involved in photosynthesis, storage, and transport.

Step 3: Identifying the Resulting Structure

When the phellogen cuts off closely arranged parenchymatous cells on the outer side instead of the cork cells and these cells rupture the epidermis, they form a lenticel - a lens-shaped opening.

Step 4: Select the Correct Alternative

From the given options i.e. Hydathodes, Stomata, Lenticels, and None of these, Lenticels is the correct plant structure formed under this circumstance. So, the correct answer is (c) Lenticels

Key Concepts

Phellogen

Phellogen, commonly referred to as cork cambium, is a vital meristematic tissue in plants. It plays a key role in forming the protective outer layer of stems and roots.
The cork cambium is responsible for producing cells towards its outer side, typically the cork cells that contribute to the formation of bark.
However, in some situations, when it produces closely packed parenchymatous cells instead, the plant tissue behaves differently.

• These scenarios usually occur during specific developmental stages.
• The phellogen doesn’t always produce the same type of cells on its outer side.

This variability in cell production by the phellogen significantly impacts the type of structures formed, such as lenticels, which are crucial for gas exchange in the absence of stomata.

Parenchymatous Cells

Parenchymatous cells are among the most versatile and widespread types of plant cells. They possess thin walls and can take on a multitude of functions depending on their location and role in the plant.
These cells typically have a large central vacuole and are alive at maturity, contributing to numerous processes.

• Involved in photosynthesis, primarily in their chloroplast-rich form found in leaves.
• Play a critical role in nutrient and water storage in different parts of the plant.
• Assist in the repair and injury response as they can readily divide and differentiate.

When the phellogen produces parenchymatous cells rather than cork cells, these often contribute to creating structures like lenticels by disrupting the epidermal layer.

Plant Tissue

The complex organization of plant tissue is integral to the plant's functionality and survival. Plant tissues comprise various cell types organized into tissue systems that perform specific roles.
These can be broadly categorized into meristematic and permanent tissues.

• Meristematic tissue: Responsible for plant growth and includes tissues like phellogen.
• Permanent tissue: Fully differentiated and specialized, such as parenchymatous cells.

Each type of tissue works together to maintain overall plant health. For instance, the interaction between phellogen and parenchymatous cells under specific conditions results in the formation of lenticels - crucial features for facilitating gas exchange in woody plants where stomata are absent. Understanding these tissues helps explain how plants adapt and thrive in diverse environments.