The growth hormone auxin is produced at the tip of the shoot of the plant. It promotes the growth of longer cells at the shoot tips. Auxin induces faster growth of cells on the opposite side of a tendril when it encounters a support, resulting in unequal growth on both sides of the tendril. Due to this, the tendril coils around the support. As a result, the tendrils resemble a watch spring as they wrap around the support.