Describe internal structure of monocot stem.

Explanation

Maize is a monocot plant. It.s stem is thin stained section when observed under microscope, following parts are seen. (1) Epidermis (2) Ground tissue (3) Vascular bundles.
(1) Epidermis : It is the outer most layer. It is a single layer made up of parenchymatous cells. Outer wall of cells are cuticularised.
No stem appendages are produced from this layer so its surface is soft. Stomata can be seen in this layer. This layer functions as protection and gas exchange.
(2) Ground Tissue : Unlike sunflower stem, cortex, endodermis and pericycle like structures are not found in ground tissue.
At the outer most side of ground tissue, hypodermis is located. It is made up of two or three layers of sclerenchyma tissue. These cells are non-living and lignified. They give mechanical support to stem.
Inside hypodermis thin walled parenchyma is located. Vascular bundles are present in this region. In ground tissue cells towards centre are comparatively large and have inter cellular spaces. (3) Vascular bundles : In maize stem numerous vascular bundles are scattered in ground tissue. Peripheral vascular bundles are generally smaller than the centrally located ones and are more in number and arranged quite near to each other. Sclerenchymatous bundle sheath surrounds them.
Centrally located vascular bundles are less in number and far from each other. Each vascular bundle is surrounded by sclerenchymatous bundle sheath. The vascular bundles having sclerenchymatous bundle sheath are called fibro vascular bundle.
Each vascular bundle is conjoint, collateral and closed vessels are developed as endorch.
In vascular bundles phloem tissue lies outside and xylem tissue lies inside vessels are arranged in shape vascular bundle lacks meristematic tissue.
Phloem tissue : Phloem tissue is located outside in .V. shape. There is no phloem parenchyma present in phloem tissue. Xylem tissue : Xylem tissue is arranged in the shape of an English alphabet .V.. Three to four vessels are present in it. Two big vessels are known as metaxylem. They are located on two separating ends of V while protoxylem are located inside based region of .V..
During development of vascular bundles, some cells around protoxylem break and a big cavity is produced. This cavity is known as Lysigenous cavity. This cavity is fulled with water.