The Tissue System

The Tissue System

There are three types of tissue systems based on their structure and location.

A. The epidermal tissue system

Epidermal cells, stomata, and epidermal appendages like trichomes and hairs make up the epidermal tissue system, which covers the entire plant body. The epidermis is the major plant body's outermost layer. It is made up of a continuous layer of elongated, compactly packed cells. The epidermis is normally one layer thick. Epidermal cells are parenchymatous, with a big vacuole and a little quantity of cytoplasm along the cell wall. The cuticle, a waxy thick covering on the outside of the epidermis that resists water loss, is commonly present. The roots have no cuticle. The epidermis of leaves has features called stomata. The process of transpiration and gas exchange is regulated by stomata.Guard cells enclose the stomatal pore in each stoma, which are two bean-shaped cells. The guard cells in grasses are formed like a dumbbell. Guard cells have thin outer walls that face away from the stomatal pore and robust interior walls that face the stomatal pore. Guard cells have chloroplasts and control stomata opening and closing. A few epidermal cells near the guard cells can become specialized in shape and size, and these cells are known as subsidiary cells. The Stomatal apparatus is made up of the stomatal orifice, guard cells, and surrounding subsidiary cells. Hairs are found on the epidermis cells.Root hairs are unicellular epidermal elongations that assist absorb water and minerals from the soil. Trichomes are epidermal hairs that grow on the stem. In the shoot system, trichomes are frequently multicellular. They might be soft or stiff, branching or unbranched. They could even be hidden. The trichomes aid in the prevention of water loss by transpiration.

B. The ground tissue system

It is also called the foundational tissue system.The ground tissue is made up of all tissues save the epidermis and vascular bundles. Simple tissues such as parenchyma, collenchyma, and sclerenchyma make up this layer. In the cortex, pericycle, pith, and medullary rays, as well as the primary stems and roots, parenchymatous cells are commonly seen. The mesophyll is the ground tissue in leaves that is made up of thin-walled chloroplast-containing cells. Ground tissue includes parenchyma (photosynthesis in the leaves and storage in the roots), collenchyma (shoot support in areas of active growth), and sclerenchyma (shoot support in areas where growth has ceased) and is the site of photosynthesis, provides a supporting matrix for the vascular tissue, provides structural support for the stem, and helps to store water and sugars, depending on the cell type and location in the plant.

C. The vascular tissue system:

Also called conducting tissue system. The vascular system is made up of two complicated tissues: phloem and xylem. Vascular bundles are made up of the xylem and phloem. Between the phloem and xylem in dicotyledonous stems, there is cambium. Because of the existence of cambium, such vascular bundles have the ability to produce secondary xylem and phloem tissues, and are hence referred to as open vascular bundles. The cambium is absent from the vascular bundles of monocotyledons. As a result, they are referred to as closed since they do not generate additional tissues. Radial arrangement occurs when xylem and phloem within a vascular bundle are placed in an alternative fashion along distinct radii, as in roots.The xylem and phloem are located along the same radius of vascular bundles in conjoint type vascular bundles. In stems and leaves, vascular bundles are common. Phloem is usually exclusively seen on the outer side of the xylem in conjoint vascular bundles.