Why do tendrils circle around a support provided?
There are two reasons for this tendency: tropism and hormone .
When tendrils comes in contact with its support,it shows a positive tropism i.e,the support act as stimulus and tendrils response to that by circling around it.This tropism is known as thigmotropism.
This action is controlled by the plant hormone called auxin. Auxins are growth regulator hormone which is present at the tip of tendrils.