Epidermal Tissue System in Plants

Study Notes

Epidermal Tissue System

The outermost layer of the plant body is called the epidermis.
Epidermis is made up of epidermal cells, stomata, trichomes, and hairs.
Epidermal cells are usually parenchymatous with a small amount of cytoplasm lining the cell wall and a large outside layer of epidermis is a waxy thick layer called cuticle which prevents loss of water.
Stomata are present in the epidermis of leaves to regulate transpiration and gaseous exchange.
Each stoma is made up of two guard cells which enclose a stomatal pore.
In grasses, the guard cells are dumb-bell shaped.
The outer cells of the guard cells are thin and the inner cells are thick.
Guard cells possess chloroplasts, and regulate the opening and closing of stomata.
Few epidermal cells in the vicinity of the guard cells become specialized, in size and shape, and are known as subsidiary cells.
The guard cell and subsidiary cell are together called the stomatal apparatus.
The cells of the epidermis bear a number of hairs.
Root hairs are unicellular and help absorb water and minerals from the soil.
On the stem, epidermal hairs called trichomes, which are usually multicellular, may be branched or unbranched, and help in preventing water loss due to transpiration.

Ground Tissue System

All tissues except the epidermis and vascular bundles constitute the ground tissue.
It consists of simple tissues: parenchyma, collenchyma, and sclerenchyma.
Parenchyma cells are usually present in the cortex, pith, and medullary rays, also in the roots and primary stems.
In leaves, the ground tissue consists of thin-walled cells called mesophyll cells.

Vascular Tissue System

In dicot stems, vascular bundles are conjoint and open type.
In monocot stems, vascular bundles are conjoint and closed type.
Xylem and phloem are present between the cambium.
The ability to form secondary tissue called cambium is called open vascular.
In monocots, there is no vascular cambium, hence called closed.
Xylem and phloem are arranged and within in a vascular bundle alternately in roots, stems, and leaves

Dicot Root

The outermost layer of the Sunflower root in transverse section is the epiblema.
The cortex consists of several layers of thin-walled parenchymal cells with intercellular spaces.
The innermost layer of the cortex is the endodermis.
The endodermis comprises a single layer of barrel-shaped cells without any intercellular spaces.
The tangential and radial walls of the endodermal cells have a deposition of water-impermeable, waxy material called the casparian strips.
Next to the endodermis lies a few layers of thick-walled parenchymatous cells called the pericycle.
Vascular cambium in the initiation of lateral roots may take place in the pericycle cells.

Description

This quiz tests your knowledge on the epidermal tissue system in plants, focusing on its structure, functions, and components such as stomata and guard cells. Understand how these elements work together to regulate water loss and gaseous exchange in plant biology.