Problem 109 - Objective Biology for NEET

Question

Vascular cambium is formed by I. Interfascicular cambium II. Intrafascicular cambium. III. Cork cambium (a) I and III only (b) II and III only (c) I, II and III only (d) I and II only

Step-by-Step Solution

Answer

The correct answer is (d) - I and II only. Vascular cambium is formed by both Interfascicular cambium and Intrafascicular cambium, but not by Cork cambium.

Step 1: Understanding Interfascicular Cambium

Interfascicular cambium, as its name implies, is the cambium that develops from parenchyma cells located between the vascular bundles (inter-fascicular). It contributes to the formation of the vascular cambium ring.

Step 2: Understanding Intrafascicular Cambium

The Intrafascicular cambium is located within the vascular bundle (intra-fascicular) and it forms the part of cambium ring. It also contributes to the formation of the vascular cambium.

Step 3: Understanding Cork Cambium

The cork cambium, also known as phellogen, is a lateral meristem and it is responsible for the production of the outer bark of a tree. However, it does not contribute to the formation of the vascular cambium.

Step 4: Analyzing the Options

By understanding the roles of each type of cambium, we can see that the vascular cambium is formed by both Interfascicular cambium (I) and Intrafascicular cambium (II). However, Cork cambium (III) does not contribute to the formation of vascular cambium. Therefore, by comparing with the options provided in the exercise, the correct answer is option (d) - I and II only

Key Concepts

Interfascicular Cambium

Interfascicular cambium emerges from the parenchyma cells situated between the vascular bundles. This area between the bundles is referred to as the 'interfascicular' region. Interfascicular cambium is an essential part of the secondary growth process in plants. It merges with the intrafascicular cambium to form a continuous ring of vascular cambium.

The formation of this cambium is crucial for increasing the girth of stems and roots. As this cambium ring develops, it starts producing secondary xylem (wood) and secondary phloem, contributing significantly to the plant's structural strength.

In essence, interfascicular cambium bridges gaps between the bundles, aiding the plant in forming a complete vascular ring that facilitates effective nutrient and water transport throughout the plant. Without this interaction, the plant might struggle to support more extensive secondary growth.

Intrafascicular Cambium

Intrafascicular cambium is located within the vascular bundle itself, hence the prefix 'intra-' meaning 'within.' This cambium is usually primary in origin and exists in the immature stages of plant growth.

As plants mature, the intrafascicular cambium becomes active and continues dividing to facilitate the growth of secondary vascular tissues. It plays a pivotal role in a plant's ability to thicken and is part of the deeper central core that participates directly in forming the vascular cambium ring.

In conjunction with the interfascicular cambium, it substantially contributes to the production of secondary xylem and phloem, leading to increased plant girth and strength.

• Produces secondary vascular tissues
• Essential for circular cambium formation
• Facilitates plant thickening

Thus, the intrafascicular cambium, together with the interfascicular cambium, makes up the full vascular cambium that arises during the secondary growth of a woody plant.

Cork Cambium

Unlike interfascicular and intrafascicular cambium, cork cambium, or phellogen, does not contribute to the formation of the vascular cambium. Instead, it is involved in creating the protective outer layer known as bark.

Cork cambium is also a lateral meristem but serves a different function. It generates cork cells that eventually replace the epidermis. These cork cells are crucial for protecting the plant against environmental damage, disease, and water loss.

The development of the cork cambium is a significant adaptation for terrestrial plants, allowing them to survive in various climates. As it produces the periderm, it facilitates the healing of wounds and the prevention of pathogen entry.

• Produces outer protective bark
• Does not contribute to vascular cambium
• Protects against environmental threats

This differentiation in role highlights the importance of cork cambium in plant survival, ensuring longevity and health through its protective measures.