He vegetable epidermal tissue is the one that forms the outermost covering of the body of the plant and includes epidermal cells, stomata and epidermal appendages (trichomes and hairs).
The epidermal system of plants consists of the outer skin or epidermis of all plant organs, starting from the roots, to the fruits and seeds. This layer represents the point of contact between the plants and the outside environment, and exhibits various structures.
Mainly a protective fabric, which protects the internal tissues from excessive water loss through perspiration and mechanical injuries.
Additionally, this tissue may have subsidiary functions, such as water storage, mucus, protection against infection, secretion, and rarely even photosynthesis.
The plants have three types of tissues, and the epidermal tissue is the one that covers the external surface of the herbaceous plants. This tissue is composed of epidermal cells, which are clustered cells that secrete a waxy cuticle, which plays a role in preventing water loss.
Components of plant epidermal tissue
Epidermis
The epidermis is the outermost layer of the plant's primary body. It is made of long cells, compactly arranged to form a continuous layer.
The epidermis usually has a single layer. Epidermal cells are parenchyma, with a small amount of cytoplasm lining the cell wall, and a large vacuole.
The epidermis cover is often wrapped with a thick layer of wax, called cuticle, which prevents water loss. The cuticle does not exist in the roots.
Stomas
The continuity of the epidermis is interrupted by the presence of some minute pores or apertures. These pores are called stomas, through which gas exchange takes place between the internal tissues and the external atmosphere.
Although gas exchange occurs within the pore (process called stomatal opening), the term stoma includes the entire structure; this includes the pore, guard cells and subsidiary cells, when present.
Each stoma is composed of two bean-shaped cells, which are known as guardian cells. In the grass, these cells are bell shaped.
The outer walls of the guardian cells (away from the stomatal pore) are thin, and the inner walls (within the stomatal pore) are of a high thickness. Guardian cells have chloroplasts and regulate both the opening and closing of the stomata.
Sometimes, some epidermal cells in the vicinity of the guardian cells become subsidiary cells. The whole of the opening of the stomata, the guardian cells and the subsidiary cells located around it is called the stomatal apparatus.
Hairs
The cells of the epidermis have a number of hairs. Root hairs are unicellular elongations of epidermal cells and help to absorb water and minerals from the soil.
On the stem, epidermal hairs are called trichomes. The trichomes in the stem system are usually multicellular. They may have branches or not have branches, and be soft or stiff. Sometimes they can be secretory. Trichomes help in preventing water loss due to perspiration.
Cuticle
The cuticle is a protective layer that covers the epidermis of the leaves, young stems and other organs of aerial plants. It contains lipid and hydrocarbon polymers impregnated with wax, as it is synthesized exclusively by epidermal cells.
The main function of a plant's cuticle is to create a permeable water barrier that prevents evaporation of water from the epidermal surface, and also prevents external water and solutes from entering the tissue.
Epidermal cells
Epidermal cells live with a thin layer of protoplast, around a large central vacuole.
Chloroplasts are present only in stomatal guard cells, in the case of organs exposed to sunlight, but occur in the epidermal cells of aquatic plants and in plants growing in humid and shady situations.
Epidermal cells have the potential to divide. These cells exhibit great diversity in size, shape and clustering. However, they are essentially compactly grouped so that a continuous layer is formed without cell spaces.
Function of the plant epidermis
The epidermis has several functions: it protects against loss of water, regulates the exchange of gases, secretes metabolic compounds and, especially in the roots, absorbs water and mineral nutrients.
The epidermis serves as the skin of the plant, epidermal cells protect the inner tissues of the outside world by creating a barrier.
When the pores of the stomata open for gas exchange during photosynthesis, water is also lost through these small openings as a result of evaporation.
Plants do not like to lose water, and the waxy cuticle of the epidermis helps them to minimize this loss; prevents the plants from drying out and dying.
The epidermis also helps to protect plants from being eaten by animals and parasites. Many plants have thick hairs or spines that leave the epidermis, which makes them unattractive for a hungry animal.
An example of this are cacti with their large spines. The danger associated with trying to access what lies behind these thorns makes plants unattractive to predators.
References
- The tissue system. Recovered from kshitij-pmt.com
- Plant epidermis: function and structure. Recovered from study.com
- Plant cuticle. Retrieved from wikipedia.org
- The epidermal tissue system of plans. Retrieved from biologydiscussion.com
- Epidermis (botany). Retrieved from wikipedia.org