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Plant Hormones (Phytohormones)
Definition and Overview
- Definition: Chemical substances produced naturally in plants that regulate growth and development.
- Common Examples:
- Auxin
- Gibberellin
- Cytokinin
- Abscisic Acid (ABA)
- Ethylene
- Note on Non-Plant Hormones: Insulin, Thyroxine, and Estrogen are human/animal hormones and are not classified as plant hormones.
Functions of Specific Hormones
| Hormone | Primary Function(s) |
|---|---|
| Auxin | – Responsible for cell elongation. – Promotes apical dominance (inhibition of lateral bud growth). |
| Gibberellin | – Promotes cell elongation. |
| Cytokinin | – Stimulates cell division. |
| Abscisic Acid (ABA) | – Acts as a growth inhibitor. – Associated with drought tolerance (stress hormone). |
| Ethylene | – Primarily responsible for fruit ripening. |
Unique Properties and Practical Applications
- Ethylene’s Unique State: It is the only major plant hormone that exists in a gaseous form.
- Artificial Ripening:
- Ethylene gas is used for the artificial ripening of green fruits.
- A common commercial gas used for this purpose is Acetylene (which can release ethylene).
- Production of Seedless Fruits:
- Seedless fruits (e.g., seedless tomatoes) can be produced by spraying hormones onto flowers.
- This process is known as induced parthenocarpy.
Know More About Plant Hormones: