When tendrils come in contact with an object, they encircle it and wind around it. Why?
The part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object.
Tendrils are sensitive to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus cling to it.