The Tissue System Homework Help
The Tissue System
Based on the structure, function and location, there are three tissue systems in plants, namely, epidermal tissue system, the ground or fundamental tissue system and the vascular or conducting tissue system. Get Expert help on The Tissue System Homework Help by Tutorspoint
Epidermal tissue system: This tissue system forms the outermost covering of the whole plant body and comprises epidermal cells, stomata and epidermal appendages namely, trichomes and hairs. The epidermis is composed of elongated cells compactly arranged to form a continuous layer throughout the plant body.
Epidermal cells are parenchymatous consisting of large vacuoles and their cell walls lined with little cytoplasm. The outer layer of the cells is covered with waxy thick layer called the cuticle. This cuticle is present in leaves and stem and is absent in roots. The cuticle helps in preventing the loss of water.
Stomata: In the epidermis of leaves, small pore-like structures called stomata are present. These stomata help in regulating the process of transpiration and gaseous exchange. Each stomata is made up of two bean-shaped cells called guard cells, the outer walls of which are thin and the inner walls of which are thick. The guard cells possess chloroplasts and regulate the opening and closing of stomata. Sometimes, the epidermal cells present in the near proximity of stoma, change their shape and structure, thus specializing in transpiration process. These cells are called as subsidiary cells. The stomata aperture, guard cells and subsidiary cells together are called as stomatal apparatus.
Epidermal appendages: The epidermal cells elongate into unicellular structures called root hairs, which help in absorbing minerals from the soil. In the shoot system, these hair-like structures are multicellular and are known as trichomes. They may be branched or unbranched and soft or stiff. The main function of trichomes is to prevent water loss due to transpiration.
The ground tissue system: The ground tissue system comprises of all tissues present in plant body except epidermis and vascular bundles. It includes simple tissues like parenchyma, collenchyma and sclerenchyma. In primary stem and roots, the parenchymatous cells are present in cortex, pericycle, pith and medullary rays. In leaves, the ground tissue is composed of thin-walled chloroplast containing cells and is known as mesophyll.