key term - Auxin

Definition

Auxin is a plant hormone that plays a crucial role in regulating growth and responses to environmental stimuli. It influences various physiological processes, including cell elongation, root formation, and tropisms, allowing plants to adapt to their surroundings and optimize resource use. By promoting growth on the side of the plant that is away from light, auxin helps direct growth towards favorable conditions.

5 Must Know Facts For Your Next Test

1. Auxin is primarily produced in the shoot tips and is transported downwards to promote cell elongation in stems.
2. It plays a vital role in apical dominance by suppressing the growth of lateral buds, allowing the plant to focus resources on upward growth.
3. Auxin also influences root development by promoting cell division and elongation in root cells, especially in response to gravity.
4. In addition to tropisms, auxin is involved in processes like fruit development and the formation of flowers, emphasizing its importance in overall plant health.
5. Synthetic auxins are used in agriculture to promote rooting in cuttings and regulate fruit drop, showcasing its practical applications.

Review Questions

• How does auxin contribute to phototropism in plants?
  • Auxin contributes to phototropism by redistributing itself towards the shaded side of the plant when light is detected. This uneven distribution leads to greater cell elongation on the shaded side, causing the plant to bend towards the light source. This response ensures that the plant maximizes its exposure to sunlight, which is essential for photosynthesis.
• Discuss the relationship between auxin and apical dominance in plants.
  • Auxin plays a key role in maintaining apical dominance by inhibiting the growth of lateral buds while promoting the growth of the main shoot. The auxin produced at the shoot apex travels down the stem and suppresses lateral bud development through a feedback mechanism. This ensures that energy is focused on vertical growth, which can be advantageous for competing for sunlight and resources.
• Evaluate how auxin's interactions with other hormones like ethylene affect plant responses to environmental changes.
  • Auxin's interactions with ethylene significantly influence how plants respond to environmental changes, such as stress or developmental cues. For instance, while auxin promotes cell elongation and growth, ethylene can induce responses like fruit ripening or leaf abscission. The balance between these hormones allows plants to adapt effectively; for example, when stressed, increased ethylene can signal a shift away from growth promoted by auxin, leading to changes that prioritize survival over growth.

Related terms

Phototropism:

The directional growth of a plant in response to light, often facilitated by the action of auxin.

Apical Dominance: A phenomenon in plants where the main central stem grows more strongly than other side stems, often regulated by auxin produced at the shoot apex.

Ethylene:

A plant hormone that regulates fruit ripening and can interact with auxin to influence growth and development.