Describe the T.S. of the dicot stem with well-labeled diagrams and compare it with the monocot stem also.

Following are the features of a typical dicot stem:

1. Epidermis: it is the uppermost single layer of the stem made up of compactly arranged, thin-walled parenchymatous cells. The epidermis is externally covered by a thin or thick cuticle. The epidermis of the sunflower contains several unbranched multicellular hairs and few stomata. The various functions of the epidermis are the protection of internal tissues, exchange of gases through stomata, etc.
   
   
2. Hypodermis: it is present below the epidermis and consists of 3-5 layers of collenchymataous tissues with lamella ion thickening. The cells are living and may contain some chloroplasts which may function as photosynthetic cells.
   
   
3. Cortex: it is a few to several cells in thickness. The cortex is made up of thin-walled parenchymatous cells. They enclose intercellular space. Its cells may contain some chloroplasts which may function as assimilatory cells.
   
   
4. Endodermis: it is a way layer of one cell is thicker. The endodermis lies at the innermost boundary of the cortex. It is made up of barrel-shaped cells which do not enclose intercellular spaces. The endodermis cells contain starch grains as reserve food. Therefore, the endodermis is also called the starch sheath.
   
   
5. Pericycle: it is a few layered regions that lie inner to the endodermis and outside the vascular bundle. The pericycle is made up of both parenchyma and sclerenchyma. Lies above the phloem in the form of semicircular patches hence also called bundle cap. Parenchyma pericycle is present outside medullary rays. The sclerenchyma pericycle provides mechanical strength to the young stem while the parenchymatous pericycle stored food.
   
   
6. Vascular bundle: the vascular strand is in the form of a vascular bundle present around the central pith and inner to the pericycle. The vascular bundle is wedge-shaped. Each vascular consists of primary phloem on the outside, primary xylem towards the inside, and a strip of cambium in between the two. Phloem and xylem tissues lie on the same radius. Such vascular bundles are called conjoint ­­­(with both xylem and phloem), collateral (with phloem and xylem on the same radius), and open (with a strip of cambium in between phloem and xylem), xylem consists of two parts, smaller protoxylem, and larger metaxylem. Protoxylem lies at the tip of the metaxylem towards the pith. Therefore, the xylem is endarch.
   
   
7. Medullary or pith rays: they are the radial strips of parenchyma which are present between adjacent vascular bundles. The medullary rays connect the pith with the pericycle and cortex.
   
   
8. Pith or medulla: it forms the center of the stem. It is made up of oval or rounded parenchyma cells which enclose intercellular spaces. The pith cells store food.

 The comparision of Dicot stem with Monocot stem are as follows: