epinasty

A *nastic movement in which the resultant bending of the plant part is downwards, due to increased growth on the upper side of an organ. This occurs in the opening of many flowers when the bracts and perianth parts curl downwards to expose the sexual organs. Epinasty can also occur in leaves where the petiole bends so that the leaf points to the ground rather than upwards. Compare hyponasty.