THE AUXIN HORMONE
*The auxin hormone:
→Auxin hormone is produced; in seeds, young leaves, shoots and root tips.
The functions of auxin:
→Auxin promotes stem elongation.
→Inhibits the growth of lateral buds that called apical dominance.
→Promotes the growth of root and cell differentiation.
→Promotes plant movement that known as tropism.
→Stimulates flowering in plants.
→Promotes fruit growth.
*Auxin experiments:
1. A cleoptile is placed under the light.
The result: The plant stem is elongated.
2. The cleoptile is placed in darkness.
The result: The plant stem is elongated.
3. Tip of the cleoptile is removed and then, the plant is placed under the light.
The result: The plant stem does not elongate.
4. Tip of the cleoptile is removed and then, the plant is placed in darkness.
The result: The plant stem does not elongate.
5. The light is placed on one side of the cleoptile.
→The auxin moves to the darker side of the plant and causing the cells there to grow larger than corresponding cells
on the lighter side of the plant.
The result: The tip of the plant stem is bended toward the light.
6. Tip of the cleoptile is removed and then, it replaced on one side of the cleoptile and after that, the plant is placed in
darkness.
The result: The tip of the plant stem is bended.
7. Tip of the cleoptile is removed and then, it replaced on one side of the cleoptile and after that, a light is
placed on one side of the cleoptile.
The result: The plant stem is elongated.
8. A mica sheet is half inserted into the cleoptile and then, a light is placed on one side of a cleoptile.
The result: The plant stem does not elongate.
9. A mica sheet is half inserted into the cleoptile and then, the plant is placed in darkness.
The result: The plant stem is bended.
10. A Mica sheet is full inserted into the cleoptile and then, a light is placed on one side of a cleoptile.
The result: The plant stem does not elongate or bend.
11. Seperated the tip of the cleoptile from the rest of the plant with an agar block and then, a light is placed
on one side of a cleoptile.
The result: The plant stem is bended.
12. Tip of the cleoptile is removed and then, an agar block with auxin is placed on one side of the cleoptile and
after that, the plant is placed in darkness.
The result: The plant stem is bended.
13. Tip of the cleoptile is removed and then, an agar block with auxin is placed on one side of the cleoptile and
after that, the plant is placed under the light.
The result: The plant stem is bended.
14. An opaque cap is covered on tip of the cleoptile and then, a light is placed on one side of a cleoptile.
The result: The plant stem is elongated.
###########################################################################################
