The internal structure of the stem is more complex. The stem is differentiated into nodes and internodes. The vascular bundles are irregularly scattered in monocot stem. There is no distinction between cortex and pith.
Identifications of a monocot stem (from the internal structure):
- The epidermis is composed of one-layered parenchymatous cells and it is surrounded by a thick layer of cuticle. Have thick cuticle, single-layered epidermis and epidermal hairs are absent. It contains stomata with guard cells.
- Interstellar and extrasolar regions cannot be separated. There is no distinction between pith and pith rays
- The hypodermis is usually composed of sclerenchymatous cells. Intercellular space is absent in this layer. It has no distinct endodermis and pericycle
- The whole area, from the lower part of hypodermis up to the center, consisting of parenchymatous cells is called ground tissue. Intercellular space is present in this region. Ground tissues are not differentiated into cortex and pith
- Vascular bundles are more in number and are scattered throughout the ground tissue. It is the outermost layer made up of a single layer of tightly packed parenchymatous cells with a thick cuticle.
- Each vascular bundle is covered with bundle sheath made of sclerenchyma. Each vascular bundle is oval, conjoint, collateral and closed.
- Vascular bundle — conjoint, collateral and closed type. Scattered vascular bundles are surrounded by sclerenchymatous bundle sheath cells and called atactostele
- The circular stem may have depressed structures due to the presence of lateral branches.
- Xylem is endarch, phloem is represented only by companion cells, sieve tubes, and little phloem fibers.
- The ground tissue is mainly composed of parenchyma cells. These parenchyma cells may be absent in the central region. It makes the stem hollow. The ground tissue is represented by several layers of loosely arranged parenchyma cells enclosing prominent intercellular spaces. It is meant for the storage of food.