Auxins are growth hormones regulators produced by apical terminals of roots and stems. They are present at the tip of the tendril. The growth is slowed down when the tendrils are attached around any support because auxins are sensitive to touch and they move to the tip on the side away from the support. Due to presence of auxins on the other side (away from the support), the other side grows faster than the side of tendril in contact with the support and the tendril bends towards the support.