Auxins are the plant hormones produces at the tip of a shoot and root. Auxins are present at the tip of tendrils. When tendrils are attached around any support their growth is slowed down as auxins are sensitive to touch. This make them move to the other side of the tip to get support this makes the other side grow faster than the side of tendril in contact with the support and the tendril bends towards the support.

Auxins and Tendril Growth

Auxins are plant hormones that play a crucial role in various aspects of plant growth and development. One of their important functions is promoting the growth of tendrils around a support. Tendrils are slender, coiling structures that plants use for climbing and support.

1. Initial Contact
When a tendril comes into contact with a support, it undergoes a series of physiological changes. The initial contact stimulates the release of auxins, primarily indole-3-acetic acid (IAA), from the cells at the point of contact.

2. Unequal Distribution of Auxins
Upon contact, auxins accumulate on the side of the tendril that is away from the support. This uneven distribution of auxins leads to a difference in growth rates on the two sides of the tendril.

3. Cell Elongation
Auxins promote cell elongation by stimulating the uptake of water into the cells on the side of the tendril facing away from the support. This causes those cells to elongate more rapidly than the cells on the side facing the support.

4. Coiling Movement
As the cells on one side of the tendril elongate more rapidly, the tendril begins to bend and coil around the support. The coiling movement is a result of the differential growth rates induced by auxins.

5. Differential Growth
The differential growth caused by auxins is a result of their ability to stimulate the synthesis of specific proteins involved in cell elongation. These proteins are responsible for loosening the cell wall, allowing for expansion and elongation.

6. Phototropism
Additionally, auxins can also promote phototropism in tendrils. Phototropism is the growth response of plants towards light. When a tendril is exposed to light, auxins accumulate on the shaded side, causing the tendril to grow towards the light source.

Conclusion
In conclusion, auxins play a crucial role in promoting the growth of tendrils around a support. They induce differential growth rates, leading to cell elongation and coiling movement. This response is essential for the tendril to anchor itself to a support and facilitate the climbing behavior of plants.