Differential growth of the upper or adaxial part of a plant organ. A well-known example is the growth of the upper side of the petiole causing the leaf to be bent downwards. Auxin and ethylene are involved in this response, which may also be induced by application of herbicides. It may be a symptom of disease, in which there is a pronounced and atypical bending downwards of the leaves.
Subjects: Ecology and Conservation — Plant Sciences and Forestry.