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Introduction

Plant hormones, also known as phytohormones, are chemical messengers that control various growth and developmental processes in plants. Understanding these hormones is crucial for GCSE Biology students as they play a key role in plant growth, reproduction, and responses to environmental stimuli.

Key Concepts and Definitions

• Auxins: Promote cell elongation and apical dominance.
• Cytokinins: Stimulate cell division and shoot growth.
• Gibberellins: Induce stem elongation and fruit development.
• Abscisic acid (ABA): Inhibits growth and prepares plants for stress.
• Ethylene: Promotes fruit ripening and leaf senescence.

Biological Processes and Systems

• Seed germination: Gibberellins promote seed germination by breaking seed dormancy.
• Root growth: Auxins stimulate root hair growth and elongation.
• Flowering: Cytokinins and gibberellins are involved in flower initiation and development.
• Fruit ripening: Ethylene triggers fruit ripening and softening.
• Response to stress: ABA and ethylene help plants adapt to environmental stresses such as drought and high temperatures.

Step-by-Step Explanations

• Auxin's role in apical dominance: Auxin produced in the shoot tip inhibits the growth of lateral buds, resulting in a single main stem.
• Cytokinin's effect on cell division: Cytokinins promote cell division in meristems, leading to new tissue growth.
• Gibberellin's induction of stem elongation: Gibberellins stimulate stem elongation by increasing the length of internodal cells.
• ABA's inhibition of growth: ABA triggers stomatal closure and reduces water loss during drought conditions.
• Ethylene's role in fruit ripening: Ethylene promotes the production of enzymes that break down starch into sugars, resulting in fruit softening.

Common Mistakes to Avoid

• Confusing different hormones and their functions.
• Oversimplifying hormone interactions and pathways.
• Ignoring the role of environmental factors in hormone responses.

Practice Problems with Solutions

• Problem: Which hormone stimulates cell division in root tips?
• Solution: Cytokinin
• Problem: How does ethylene affect plants during drought stress?
• Solution: Ethylene triggers stomatal closure, reducing water loss.

Conclusion

Plant hormones are essential for regulating a wide range of processes in plants. By understanding the key concepts and biological systems involved, GCSE Biology students can enhance their exam success and gain a deeper understanding of plant biology.

Tips for Exam Success

• Revise definitions and biological processes thoroughly.
• Practice identifying hormones involved in specific plant responses.
• Use diagrams and examples to illustrate hormone actions.
• Study the role of environmental factors in hormone responses.

FAQ

• What is the difference between auxin and cytokinin?

Auxin promotes cell elongation while cytokinin stimulates cell division.

• How do plant hormones interact with each other?

Hormones can work synergistically or antagonistically to regulate plant processes.

• Why is plant hormone study important?

Understanding plant hormones is crucial for crop production and environmental management.