This flux is in response to movement of potassium ions between pulvinus and surrounding tissue. This is the largest pulvinus of any known plant. The specific name refers to the presence of a strongly developed pulvinus. Base of petiole swollen to form the pulvinus. Towards the base, the leaves narrow abruptly to a petiole set on a forward-angled pulvinus. Sunflowers do not have a pulvinus below their inflorescence. The petiole may be winged, and swollen into a pulvinus at the base. A pulvinus on a petiolule is called a pulvinulus. Petioles absent or short, sometimes resembling a pulvinus. A petiole is nearly always present, often with a pulvinus at its base. A pulvinus is also sometimes called a geniculum. The pulvinus is located at the base of each leaflet of the plant. The main structure mechanistically responsible for the drooping of the leaves is the pulvinus. The pulvinus is a motor structure consisting of a rod of sclerenchyma surrounded by collenchyma.