Monocot Stem: Zea
cross section: Zea stem
A single layered, cutinized epidermis overlies an interior composed entirely of cortical tissues. Within the cortex a few layers of sclerenchyma can be seen just beneath the epidermis. Below that lies a cortical region composed entirely of loosely packed thin walled parenchyma and intercellular spaces.
There is no apparent stele, rather the vascular bundles are scattered throughout the cortex with numerous small bundles crowded nearly the periphery of the stem and fewer larger bundles towards the center of the stem.
The vascular bundles are closed and collateral. Xylem is oriented towards the center of the stem and small amounts phloem to the outside. Cambium is lacking preventing secondary growth. In mature vascular bundles, the earliest protoxylem may break down to produce a large protoxylem cavity. The vascular bundles are wrapped in a bundle sheath of thick walled supportive sclerenchyma cells.
Unlike most grasses Zea stems are not hollow at the center.