Comparative anatomy of Dicotyledons stem and monocotyledons stem

• Transverse section of Dicotyledons and monocotyledons stem  shows that  various tissue systems are almost similar except some basic difference. 

Epidermal tissue system: 

• The anatomy of both monocotyledons and Dicotyledons stem have epidermis as outermost protective layer. 

• Epidermis is covered by thin layer of cuticle. 

• Epidermis may bear trichome and few stomata.

Ground tissue system 

• In both monocotyledons and  Dicotyledons stem, the cells are arranged in multiple layers between epidermis and pericycle. This region is called cortex.

• Cortex is divided into three subozone  - Hypodermis, cortical layer and endodermis. 

• In Dicotyledons, hypodermis is made up of collenchyma which provide mechanical strength to young stem. 

• In monocotyledons, Hypodermis is made up of sclerenchyma. 

• Cortical layer below hypodermis is made up of parenchyma with well marked intercellular space. 

• The innermost layer of cortex  is endodermis. The cells of endodermis is rich in starch grain therefore it also referred as Starch sheath.

• Pericycle is located on inner side of endodermis and above the phloem in form of semi lumar patches of sclerenchyma. 

• Medullary ray is also present between the vascular bundle. These Rays are made up of parenchyma.
• Vascular tissue system- A large  number of vascular bundle are arranged in ring. 

• The ring arrangement of vascular bundle is characteristic feature of dicot stem.

•  In monocotyledon a large number of vascular bundle are scattered and enclosed by a sclrenchymatous bundle sheath.

• In Dicotyledons stem,  vascular bundle is conjoint open and endarch whereas in monocotyledons, vascular bundles are conjoint and closed. 

• Peripheral vascular bundle are generally smaller than the centrally located  in monocotyledon stem. 

• In monocotyledons, water containing cavities are present in vascular bundle.

Remember 👌👌 phloem parenchyma is absent in monocotyledons stem.

• A Large number of rounded parenchymatous cell with large intercellular spaces in central portion of stem is called pith.