Bending of tendrils after coming in contact of support is called thigmonasty. Opening and closing of flowers in response to light and darkness is called photonasty, e.g. Calendula. Greater growth on one side causes the organ to bend to the opposite side, e.g. circinate coiling and opening of fern leaf are called nyctinasty. Hydronasty is the nastic movement in which the stimulus is water.