Internal Structure of Monocot Stem (Maize)
A transverse section of monocot stem reveals the following structures.
1. Epidermis: It is the outermost layer. It is made up of single layer of parenchyma cells. It is covered with thick cuticle. Multicellular hairs are absent and stomata are also less in number.
2. Hypodermis: It is made up of few layers of sclerenchyma cells interrupted by chlorenchyma. Sclerenchyma provides mechanical support to plant.
3. Ground tissue: The entire mass of parenchyma cells next to hypodermis and extending to the centre is called ground tissue. It is not differentiated into endodermis, cortex, pericycle and pith.
4. Vascular Bundle: Vascular bundles are skull shaped and scattered in the ground tissue. Vascular bundles are conjoint, collateral, endarch and closed. Each vascular bundle is surrounded by few layer of sclerenchyma cells called bundle sheath.
(a) Xylem: It consists of metaxylem and protoxylem. Xylem vessels are arranged in V or Y shape. In mature vascular bundle, the lower most protoxylem disintegrates and form a cavity. This is called protoxylem lacuna.
(b) Phloem: It consists of sieve tube elements and companion cells. Phloem parenchyma, and phloem fibers are absent.
5. Pith: Pith is not differentiated in monocot stems.