Problem 119 - Objective Biology for NEET

Question

In most of the higher plants, the growing apical bud inhibits the growth of lateral bud. This phenomena is called (a) Apical tolerance (b) Axial intolerance (c) Apical ordinance (d) Apical dominance

Step-by-Step Solution

Answer

The correct answer is (d) Apical dominance

Step 1: Understand the Phenomenon

The phenomenon described in the question is a common behaviour seen among many plants,where the apical bud, or tip, of a stem inhibits the growth of the lateral buds beneath it. This ensures that the plant grows vertically, maximizing exposure to sunlight.

Step 2: Analyze the Answer Options

In this step, one needs to look at each option carefully. Apical tolerance, axial intolerance, apical ordinance and apical dominance are the provided options. By understanding the meanings of these terms, one can identify the correct answer. Apical refers to the tip of the plant, and dominance implies that it takes precedence or inhibits other growth.

Step 3: Select the Appropriate Term

By analyzing each of the terms in the provided answers and comparing them to the original phenomenon mentioned in the question, it's clear that the term which correctly describes this effect is apical dominance.

Key Concepts

Plant Growth

Plant growth is the process through which plants increase in size over time. This growth occurs through cell division and expansion in distinct areas called meristems. Meristems are specialized tissues where active cell division takes place. There are two main types of growth in plants:

• Primary Growth: This occurs at the tips of roots and shoots, allowing plants to grow in length. The apical meristems are responsible for primary growth.
• Secondary Growth: This involves the thickening of stems and roots, mainly in woody plants, and is facilitated by lateral meristems.

Understanding plant growth is essential because it determines the plant's ability to compete for resources like light, water, and nutrients. Effective growth strategies enable plants to survive and reproduce in their environments.

Apical Bud

The apical bud is located at the tip of a plant's stem, leading to the elongation of the plant in a vertical direction. The activity of the apical bud is crucial in determining the structure and overall shape of the plant. The apical bud contains a region known as the apical meristem, which includes cells that are constantly dividing. These cells contribute to the increase in length of the plant, a process known as elongation. One key feature of the apical bud is its ability to suppress the growth of lower lateral buds. This is due to the production of plant hormones, primarily auxins, which promote vertical growth and inhibit lateral growth. This strategic emphasis helps the plant reach optimal height to capture sunlight more effectively.

Lateral Bud Inhibition

Lateral buds are located along the sides of the plant stem and have the potential to form branches or flowering stems. However, their growth is often inhibited by the apical bud through a process known as lateral bud inhibition. This phenomenon is largely the result of hormonal control, specifically the action of auxins produced by the apical bud:

• Auxins travel downward from the apical bud, creating a concentration gradient that suppresses the activity of the lateral buds.
• This dominance of the apical bud is referred to as apical dominance, ensuring that the plant prioritizes vertical growth over branching.

Lateral bud inhibition is advantageous because it allows the plant to invest its resources in growing taller rather than wider, optimizing its access to sunlight and reducing competition with nearby plants.