Introduction
The epidermis forms the outermost layer of cells on the primary plant body. it is present over stems, roots, leaves, flowers, and fruits. In most plants, the epidermis is composed of a single layer of cells.
Different plants, sometimes have two or more than two layers of epidermis. The single-layer epidermis is called the hypodermis. When it is composed of many layers it is called the multiseriate epidermis.
The root epidermis is called rhizodermis or epiblema. The main function of the epidermis is to check transpiration. It also protects the plant parts. It also has stomata for gaseous exchange.
Origin of epidermis
The skin of all organs originates from the outermost layer of the apical meristem. This surface layer of meristem is called a protoderm. In cryptogams, the epidermis stems from a single initial cell that additionally creates cortex and stele.
The skin of the gymnosperm root comes from, in association with the root cap, from periblem. In the dicotyledonous root, the skin develops from initials of dermatogen, which are not distinct from those of root cap.
The skin of monocotyledonous root owes its beginning from the periblem in addition to the cortex.
Structure of Epidermis
The skin of aerial parts of a plant includes living parenchyma cells whose shape, dimension, and setup might differ. The skin cells are more or less tabular (horizontally flattened) in cross-sectional view.
The skin cells are without chloroplasts. The guard cells of stomata that are specialized epidermal cells consist of chloroplasts. Various other pigments like anthocyanin might happen in skin cells.
In some plants, silicon might be transferred in the epidermal cell’s cither in the lumen or wall. The wall of the trichome may be silicified.
Typically, the walls of skin cells are thin. Thick-walled lignified epidermal cells take place in some gymnosperms. Cutin, a fatty compound, is commonly deposited on the external surface of the skin cell wall to develop cuticle over which wax might also be deposited.
The cuticle is immune to decay and is well maintained in fossils.
Cells of Epidermis
The epidermis of plants consist of the following cells:
1. Pavement cells
Pavement cells are the most usual cells of the plant’s epidermis. As such, they can be found covering all plant organs in any kind of plant. As compared to the various other kinds of cells, sidewalk cells are not completely specialized.
Firmly packed together, pavement cells offer to prevent excess water loss. On top of that, they compose a safety layer that protects other more customized cells located below.
They perform the following functions:
- Assist maintain the internal temperature
- Maintain the inner layers of cells in position
2. Stomatal Guard Cells
Stomatal guard cells become part of the epidermal cells that perform several functions in plants. Relying on the sort of plant, the spatial setup of these cells is not just based on dimension, however also on the shape of air-space below them. Guard cells also contain chloroplasts that allow for photosynthesis.
3. Trichomes
Trichomes (epidermal hairs) are little hairs situated on the skin tissue. Like stomatal guard cells, trichomes are likewise extra customized and therefore have well-defined forms that add to their functions.
Various kinds of trichomes have been shown to play a protective role in plants where they protect plants from insects in addition to organisms that cause diseases like pathogens.
4. Cuticle
In plants, skin cells are located on the top and lower part of the leave where they form the upper and lower epidermis. The cuticle, however, lies on the upper skin for the most part.
In plants, this is the outermost component that is produced by the epidermis. Right here, it includes a compound known as the cutin (polymerized esters of fats).
Function of Epidermis
- Prevents the loss of water from the surface of the plant
- Reduces transpiration
- Acts as a protective layer. Protects internal tissues from mechanical injuries
- Acts as a barrier against the attack by insects and other parasites.
- In some xerophytic plants, it stores water
- In some hydrophytes, they prepare food.
- Roots hairs are elongation of the epidermis which helps in water and mineral absorption from the soil.