How do auxins promote the growth of a tendril around a support?

When a tendril touches something it can wrap around, a plant hormone called auxin moves to the side away from the touch. The cells on that side grow faster, which makes the tendril bend toward the support and wrap around it.

Auxins are plant hormones synthesised at the shoot tip. When a tendril comes in contact with a support: 1. The touch (thigmotropism) causes auxin to diffuse away from the point of contact. 2. Auxin concentrates more on the side away from the support. 3. Higher auxin concentration on the side away from the support stimulates cells on that side to elongate faster. 4. Differential growth — faster elongation on one side than the other — causes the tendril to bend toward the support. 5. As the tendril encircles the support, auxin redistributes again, creating a spiral growth pattern. This is an example of thigmotropism — directional growth in response to touch.