strips is not developed. with intercellular spaces. The pith extends between the vascular bundles. are called primary pith rays or primary medullary rays.
Function of the pith is storage of food. A sector enlarged Ground plan Epidermis Hypodermis Cortex Endodermis Epidermal hair Vascular bundle Pith Pericycle Epidermal hair Cuticle Chlorenchyma Resin duct Parenchyma Starch sheath Bundle cap Primary phloem Cambium Metaxylem Epidermis Collenchyma Protoxylem Pith Primary medullary ray Figure . : T. S of Dicot Stem (Sunflower stem) Primary Structure of Monocot Stem-maize Stem Epidermis It is the outermost layer of the stem.
It is made up of single layer of tightly packed parenchymatous cells. Their outer walls are covered with thick cuticle. The continuity of this layer may be broken here and there by the presence of a few stomata. There are no epidermal outgrowths.
Hypodermis A few layer of sclerenchymatous cells lying below the epidermis constitute the hypodermis. This layer gives mechanical strength to the plant. It is interrupted here and there by chlorenchyma cells. Ground Tissue There is no distinction into cortex, endodermis, pericycle and pith.
The entire mass of parenchyma cells lying inner to the hypodermis forms the ground tissue. Epidermis Hypodermis Ground tissue Vascular bundles Cuticle Epidermis Hypodermis Chlorenchyma Vascular bundle Ground tissue Crushed protophloem Metaphloem Metaxylem Protoxylem Protoxylem lacuna Sclerenchymatous bundle sheath A sector enlarged Ground plan Figure . : T.S. of Monocot stem (Maize stem) The cell wall is made up of cellulose .
The cells contain reserve food material like starch . The cells of the ground tissue next to the hypodermis are smaller in size, polygonal in shape and compactly arranged. Towards the centre, the cells are loosely arranged, rounded in shape and bigger in size. The vascular bundles lie embedded in this tissue.
The ground tissue stores food and performs gaseous exchange. Vascular Bundles Vascular bundles are scattered (atactostele) in the parenchymatous ground tissue. Each vascular bundle is surrounded by a sheath of sclerenchymatous fibres called bundle sheath . The vascular bundles are conjoint, collateral, endarch and closed .Vascular bundles