Tubular leaf of a non-grassy monocot: Allium

Stem-like anatomy

Central parenchyma torn apart

Onion (Allium cepa), a tubular (or cylindrical) leaf. Only a segment of the cross-section is shown. The palisade mesophyll appears next to the epidermis around the complete cylinder. Below it is the non-photosynthetic spongy mesophyll in which vascular bundles are found. Note that the xylem of vascular bundles faces the center of the leaf as in the stem.

The central part of the leaf which is hollow, originally was composed of thin-walled parenchyma which was a stable tissue, and therefore torn apart as the outer part of the tubular leaf expanded. The adaxial side is to the inside of the leaf.