Dicot Stem

Dicot Stem is characterised by the presence of a well-defined epidermis with a cuticle and multicellular stem hairs. Collenchymatous hypodermis is found in the cortex on a regular or irregular basis. Endodermis is distinguished as the cortex’s deepest layer. Pericycle is made up of parenchyma and sclerenchyma that alternate as uneven patches (heterogenous). Vascular bundles are conjoint, collateral, endarch, open, and organised in a ring around the pith (eustele). The centre of pith is made up of thin-walled parenchyma cells with discrete intercellular gaps. Pith rays or medullary rays are discovered as a separation of two vascular bundles.

Anatomical Characteristics  of Dicot stem:

There are following parts of Dicot Stem showing anatomical features:

• The epidermis is the outermost layer of the (dicot) stem, including multicellular epidermal stem hairs. The cells are alive, barrel-shaped, and compactly packed, with no intercellular gaps or chloroplasts. They may have stomata for gas exchange. The epidermis is outwardly protected by a thick cuticle. The epidermal multicellular stem hairs aid in protection and heat loss.
• Cortex is present in multiple levels under the epidermis. It is classified as follows:
• The hypodermis is made up of 3-5 layers of collenchyma with no gaps between them. It comprises thickenings from the deposition of additional cellulose with pectin and provides mechanical support. It also aids in photosynthesis because of the presence of chloroplasts.
• The general cortex encloses intercellular spaces with resin ducts, which are bordered by a layer of small thin-walled spherical or oval cells. It is loosely organised parenchymatous. Cortical cells may contain chloroplasts and undergo photosynthesis. Some oil conduits are lined with epithelial cells. It also aids in gaseous exchange and the storage of food items.
• Endodermis is a unilayered innermost cortex composed of barrel-shaped, compactly packed parenchymatous tissues. It is often referred to as a starch sheath because it stores starch. Casparian stripes are plainly apparent in the endodermis. It is the deposition of lignin and suberin. Several dicot stems may lack separate endodermis.
• The pericycle is heterogeneous, with sclerenchyma and intervening masses of parenchyma. They have thick wall sclerenchymatous tissue located in patches above the phloem or bast, which is why they are also known as hard bast or bundle cap. The hard bast aids in mechanical support, whereas the parenchyma aids in the storage of food supplies.
• Medullary rays are parenchymatous, radially elongated or polygonal cells that exist between vascular bundles. It aids in the radial conduction of water and food items. Because it is an extension of pith, it is also known as pith rays.
• Vascular bundles are conjoint, collateral, open, and organised in a ring (eustele). Each bundle is made up of outer phloem and inner xylem on the same radius, with a strip of cambium in between (open type).

Outside of the vascular bundle, phloem is made up of sieve tubes, companion cells, phloem parenchyma (all of which are alive), and a few bast fibres. Companion cells are linked to sieve tubes.

• Xylem is found at the pith or centre of the plant and is made up of xylem vessels, tracheids, xylem fibres (wood fibres), and xylem parenchyma (wood parenchyma). The xylem is an endarch (i.e. protoxylem lie towards the pith, while metaxylem lies towards periphery). Protoxylem is narrower with annular, reticulate, or spiral thickenings, but metaxylem is wider with pitted vessels. The xylem parenchyma is usually located near the protoxylem.
• Cambium is a thin strip of dramatically organised two or three-layered cells. It is found between the xylem and the phloem. In a transverse section, the cells are nearly rectangular and have a thin wall. It is also known as intra fascicular cambium due to its location. Cambium is a form of lateral meristematic tissue that enhances plant thickness through secondary growth.
• The pith is well developed and takes up much of the ground tissue. It is composed of spherical or oval, thin-walled parenchymatous cells with a considerable number of intercellular gaps. Pith aids in the storage of food materials.

Conclusion:

Therefore, in this unit, we study about Dicot stem, it’s anatomical features and characteristics. We also learnt about the difference between dicot and monocot stem. Dicot stem is the type of stem with two number of cotyledons present in it’s seed.