A tendril is a plant structure whose function is to help the plant climb (up to reach more sunlight). A tendril will actually wrap itself around anything that it comes into contact with and then it provides support to the plant as the plant continues to grow upward. Some tendrils even have a device that helps it stick to an object... you see this when you try to pull English Ivy off of a building or fence.
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.
