Parenchyma is the most common plant tissue. It is relatively unspecialized and makes up a substantial part of the volume of a herbaceous plant and of the leaves, flowers and the fruits of woody plants. The thin-walled parenchyma cells have large vacuoles and distinct intercellular spaces. The most important function of the parenchyma cells of roots and stem is the storage of food and water, the intercellular air spaces permit gaseous exchange.