epinasty
noun
epi·nas·ty ˈe-pə-ˌna-stē 
: a nastic movement in which a plant part (such as a flower petal) is bent outward and often downward
Word History
Etymology
International Scientific Vocabulary epi- + Greek nastos close-pressed (from nassein to press) + International Scientific Vocabulary -y entry 2
First Known Use
1880, in the meaning defined above