The hyponastic response is an upward bending of leaves or other plant parts, resulting from accelerated growth of the lower side of the petiole in comparison to its upper part. This can be observed in many terrestrial plants and is linked to the plant hormone ethylene.The plant’s root senses the water excess and produces 1-Aminocyclopropane-1-carboxylic acid which then is converted into ethylene, regulating this process. Plants that are exposed to elevated ethylene levels in experimental set-ups also show the hyponastic response.