Parenchyma

Parenchyma (Gk. para = beside, enchein = to pour) is the plant's default, all-purpose ground tissue - present in almost every organ, living, thin-walled and built of cellulose, with cells that can be oval, polyhedral, cylindrical, irregular, elongated or even armed with projections. Its defining visual feature is the prominent intercellular space typically left where several cells meet, which is what lets parenchyma double as a storage compartment (for water, air or 'ergastic' reserve substances) and still allow gas or fluid to move between cells; occasional cells that specialise in storing resin, tannins or calcium crystals are given the special name idioblasts. Because parenchyma is so functionally flexible, the book names five named sub-types built around a single job each: aerenchyma, whose huge intercellular air cavities give buoyancy and aeration to aquatic plants like Hydrilla and Nymphaea; storage parenchyma, packed with reserve food such as the starch of a root or stem tuber; stellate parenchyma, star-shaped with arms radiating outward to leave large air spaces, as in banana or Canna petioles; chlorenchyma, chloroplast-bearing parenchyma specialised for photosynthesis, a …