Problem 7 - Biology Concepts and Applications

Question

_____ stops lateral buds from branching out. a. Gibberellin b. Auxin c. Cytokinin d. Ethylene

Step-by-Step Solution

Answer

Auxin stops lateral buds from branching out.

Step 1: Understand Plant Hormones

Review the role of different plant hormones in plant growth and development. Auxin, gibberellin, cytokinins, and ethylene each play unique roles.

Step 2: Identify Hormone Functions

Determine the specific function of each hormone: - Auxins are involved in cell elongation and inhibition of lateral bud growth (apical dominance). - Gibberellins promote cell growth and elongation. - Cytokinins promote cell division in plant roots and shoots. - Ethylene influences fruit ripening and leaf abscission.

Step 3: Match Function to Question

The question asks about a hormone that stops lateral buds from branching out. Identify which hormone inhibits lateral bud growth.

Step 4: Conclude the Right Hormone

Since auxin is known to inhibit lateral bud growth by maintaining apical dominance, auxin is the hormone that stops lateral buds from branching out.

Key Concepts

Auxin

Auxin is a crucial plant hormone that plays a variety of roles in the growth and development of plants. Primarily, auxin is responsible for promoting cell elongation, which is essential for plant growth. It helps plants to grow upwards and outwards by elongating cells in the stems, allowing them to reach sunlight.

One of the fascinating aspects of auxin is its ability to regulate the direction and strength of a plant’s growth. By influencing cell growth at varying rates, auxin helps determine the shape and structure of the plant, enabling it to adapt to its environment.

• Encourages cell elongation, crucial for stem growth
• Influences plant bending toward light, known as phototropism
• Helps in developing roots, allowing better nutrient absorption

Auxin is produced in the shoot apical meristems (the growing tips of plants) and is transported downward through the plant. This downward transport of auxin plays an important role in many developmental processes and helps regulate the plant’s overall morphology.

Apical Dominance

Apical dominance is a phenomenon where the main, central stem of the plant grows more strongly than the lateral buds. This is primarily due to the action of the hormone auxin.

In simple terms, apical dominance ensures that the plant expends most of its energy growing upwards. This allows it to access better light and resources. The shoot apex (tip) produces auxin, which travels down the stem and inhibits the growth of lateral buds.

• Ensures vertical growth over horizontal
• Maximizes exposure to sunlight and resources
• Controlled by the concentration of auxin

Apical dominance serves an evolutionary purpose by allowing plants to outgrow their neighbors and avoid competition for light. Should the main stem be damaged or cut, the inhibition is removed, and lateral buds may start to grow more dominantly, leading to bushier plants.

Lateral Bud Growth Inhibition

Lateral bud growth inhibition is a key function of the hormone auxin. By preventing the growth of lateral buds, auxin maintains apical dominance, focusing the plant's resources on vertical growth.

This inhibition occurs because auxin, produced at the shoot tip, actively suppresses the growth of buds further down the plant. This process ensures that the plant grows taller rather than wider, which can be advantageous in accessing light and stimulating photosynthesis.

• Concentrated auxin at shoot tips suppresses lateral growth
• Inhibits bushy plant structure, maintaining tall growth
• Can be overcome by removing the shoot tip

Understanding lateral bud growth inhibition is important for practices such as pruning, where gardeners manipulate plant shape by removing certain parts of a plant to promote or inhibit growth according to their objectives. When the primary source of auxin (the shoot tip) is removed, lateral buds can activate and grow, influencing plant structure significantly.