Problem 30 - Objective Biology for NEET

Question

Which of the following is correct about leaf? (a) It has originated from root apical meristem. (b) It is arranged in basipetal order. (c) It arises from axillary bud. (d) It bears a bud in its axil.

Step-by-Step Solution

Answer

The correct answer is (d) It bears a bud in its axil.

Step 1: Identifying the Characteristics of the Options

Parse through each option letter-by-letter and determine the characteristic/s it is stating about leaves. For instance, option (a) refers to leaves originating from root apical meristem; (b) states leaves are arranged basipetally; (c) mentions leaves rising from axillary bud; and (d) claims leaves bear buds in their axils.

Step 2: Evaluating the Validity of Each Statement

Now that we know what each option is saying, we can evaluate the truthfulness of each statement. Here's a brief rundown of each: \n(a) Leaves do not originate from root apical meristem. The root apical meristem is involved in the growth of roots, not leaves. So, this statement is incorrect. \n(b) Basipetal order means the younger structures are arranged towards the base and the older towards the apex. Leaves, in fact, follow an acropetal order. They are younger towards apex and older towards the base. \n(c) Leaves do not arise from axillary buds; instead, they are formed on the node of a stem. \n(d) True statement. The axil, the angle between the leaf and stem, often contains an axillary bud which may develop into a branch or a flower.

Step 3: Select the Correct Statement

With our evaluations from Step 2, we can now identify the correct answer. That is option (d), stating that a leaf bears a bud in its axil.

Key Concepts

Root Apical Meristem

The root apical meristem is a region found at the tip of a plant's root. It plays a crucial role in root growth and formation. This area consists of actively dividing cells, which allow the root to extend and penetrate the soil.
Interestingly, the root apical meristem is highly specialized for its function and solely dedicated to root development. It does not have any association with leaf production.

• Located at the root tip.
• Responsible for root elongation.
• Unrelated to leaf formation.

Understanding this distinction helps clarify why leaves do not originate from the root apical meristem.

Axillary Bud

Axillary buds are small, bud-like structures found in the axil of a leaf, where the leaf stem meets the main stem. These buds have the potential to grow into branches, leaves, or even flowers, depending on the plant's needs.
Leaves themselves do not arise from axillary buds but can support them. Think of axillary buds as growth reserves that can develop if required.

• Located in the leaf axil.
• Potential to grow into various structures.
• Do not produce leaves directly.

Recognizing the role of axillary buds is key to understanding plant growth dynamics.

Basipetal Order

Basipetal order is a term used to describe a pattern of growth or development. It means younger structures are nearer to the base while older structures are towards the tip or apex. This pattern can be observed in certain aspects of plant growth but not in leaves.
For leaves, this arrangement is incorrect since they develop in an acropetal order, meaning newer leaves are closer to the tip.

• Growth from apex to base.
• Not applicable to leaf arrangement.
• Common in certain developmental processes.

Appreciating these growth patterns can aid in understanding plant development thoroughly.

Acropetal Order

Acropetal order refers to the pattern where newer structures are found at the apex or tip, while older ones are located towards the base. This is the typical pattern observed in leaves as they progress up a stem.
This method of growth ensures that the plant can continually expand and reach for resources like sunlight.

• Growth from base to apex.
• Describes leaf development.
• Facilitates efficient resource acquisition.

Recognizing acropetal order is essential for understanding how plants grow and adjust to their environment.