Auxin is plant hormone which is synthesized at the tip of the shoot. It helps the cell grow longer. When a tendril comes in contact with a support, auxin stimulates faster growth of the cells on the opposite side that's why the tendril forms a coil around the support.

Understanding Auxins
Auxins are a class of plant hormones that play a crucial role in various growth processes, including the growth of tendrils around supports. They are primarily produced in the growing tips of stems and roots.
Mechanism of Tendril Growth
- Differential Growth: Auxins promote elongation in plant cells. When a tendril comes into contact with a support, auxins are distributed unevenly, causing the cells on the side of the tendril that is away from the support to elongate more than those on the side that is in contact with the support.
- Tropic Response: This differential growth leads to a phenomenon known as thigmotropism, where tendrils curl around the support. The tendril bends towards the support due to the enhanced growth on the outer side, creating a loop that secures the plant.
Role of Auxins in Tendril Movement
- Auxin Redistribution: Upon contact with a support, auxins are redistributed towards the side of the tendril that is further from the support, promoting greater cell elongation on that side.
- Reinforcement of Structure: As tendrils wrap around supports, auxins continue to promote growth, reinforcing the structure and allowing the plant to stabilize itself and access light more effectively.
Significance of Auxins in Plant Survival
- Support and Stability: By facilitating the curling of tendrils, auxins enable climbing plants to reach for sunlight and enhance their survival in competitive environments.
- Adaptation to Environment: This growth pattern allows plants to efficiently adapt and thrive in diverse habitats by utilizing vertical spaces.
In summary, auxins are integral to the growth and support mechanisms in climbing plants, enabling them to secure themselves and optimize their growth towards light.