Pulvinus

A pulvinus (pl. pulvini) may refer to a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. Pulvinus is also a botanical term for the persistent peg-like bases of the leaves in the coniferous genera Picea and Tsuga. Pulvinar movement is common, for example, in members of the bean family Fabaceae (Leguminosae) and the prayer plant family Marantaceae.

Pulvini may be present at the base of the leaf stalk or on its other end (apex), where the leaf is attached, or in a compound leaf at the place where the leaflets are joined to its middle stem. They consist of a core of vascular tissue within a flexible, bulky cylinder of thin-walled parenchyma cells. A pulvinus is also sometimes called a geniculum (meaning a knee-like structure in Latin).