Key Roles of Epidermis in Plant Protection and Water Regulation
The epidermis, ground tissue, and vascular tissue are three broad groups of plant tissues.
The epidermis is the layer of cells on the outside of plant shoots that protects them from moisture loss and physical damage. It's made up of a lot of different types of cells.
The epidermis of most plants has dorsoventral anatomy, with the top being adaxial and the lower being abaxial, and their architecture differs slightly, as well as their function.
The secondary covering known as periderm is produced by some of the woody stems and other sections of the potato tubers, and it replaces the epidermis as the protective covering.
The epidermis is the main part of the skin on the leaves, as well as the stems, roots, flowers, fruits, and seeds.
Epidermal cells are usually clear. They have fewer chloroplasts or don't have any at all, except for the guard cells.
There are four layers to the epidermis:
Stratum Basale
Stratum Corneum
Stratum Granulosum
Stratum spinosum
Pavement cells, guard cells, and their secondary cells that surround the stomata and trichomes, commonly known as leaf hairs, make up the plant epidermis.
Trichomes are controlled by two primary trichome specificity genes and develop at a separate stage during leaf development.
Stomata are pores in the epidermis of plants that are encircled by two guard cells that control the aperture's opening and closure.
These guard cells are encircled by subsidiary cells, which serve as a support system for the guard cells. The growth of stomata, particularly their density on the leaf surface, is influenced by environmental factors.
Epidermis Plant Tissue - Importance
The epidermis serves as a barrier against water loss and infection.
The epidermis is in charge of regulating the gas exchange mechanism.
The epidermis is responsible for the secretion of metabolic chemicals.
The epidermis is responsible for the absorption of water and vital minerals.
FAQs on Epidermis Tissue in Plants: Complete Biology Guide
1. What is the epidermis in a plant?
The epidermis is the outermost, single-cell thick layer of tissue that covers the entire body of a plant, including the leaves, stem, roots, and flowers. It is a type of protective tissue that acts as a barrier between the plant's internal systems and the external environment.
2. Describe the main functions of the plant epidermis.
The primary functions of the plant epidermis are:
- Protection: It shields the plant from mechanical injury, water loss, and invasion by pathogens like fungi and bacteria.
- Gas Exchange: It contains specialised pores called stomata (mainly in leaves) that regulate the exchange of carbon dioxide and oxygen.
- Water Absorption: In roots, epidermal cells form root hairs that significantly increase the surface area for absorbing water and minerals from the soil.
- Secretion: It secretes a waxy substance called cutin, which forms the protective cuticle layer.
3. What are the key structural features of epidermal cells?
Epidermal cells are typically flat and packed closely together without intercellular spaces, forming a continuous protective layer. The outer and side walls of these cells are generally thicker than the inner walls. In aerial parts of the plant, these cells are covered by a waxy, water-resistant layer called the cuticle. In roots, a cuticle is absent to allow for water absorption.
4. What is the role of the waxy cuticle on the epidermis?
The waxy cuticle is a waterproof layer secreted by the epidermal cells on the outer surface of a plant's leaves and young stems. Its primary role is to prevent water loss through evaporation, a process known as transpiration. It also provides an additional barrier against mechanical damage and microbial attack.
5. How do stomata, found in the epidermis, help the plant?
Stomata are tiny pores present in the epidermis of leaves, each enclosed by two kidney-shaped cells called guard cells. They are crucial for two main processes: gas exchange (taking in CO₂ for photosynthesis and releasing O₂) and transpiration (the release of water vapour), which helps pull water up from the roots.
6. Why is the epidermis of a plant root different from the epidermis of a leaf?
The epidermis of a root and a leaf are structurally different because of their distinct functions. The leaf epidermis is covered with a waxy cuticle to minimise water loss and has stomata for gas exchange. In contrast, the root epidermis lacks a cuticle to facilitate water absorption and has specialised extensions called root hairs to maximise the surface area for this purpose.
7. How does cork act as a protective tissue and replace the epidermis in older plants?
As a plant, particularly a tree, grows older and its stem increases in girth, the original epidermal layer stretches and breaks. It is replaced by a secondary protective tissue called cork or phellem. The cells of cork are dead and compactly arranged, and their walls are coated with a waxy substance called suberin. This makes them impermeable to gases and water, providing robust protection to the older parts of the plant.
8. What would happen to a plant if its epidermal layer was damaged or removed?
If the epidermal layer were removed, a plant would face severe threats. It would lose water rapidly through uncontrolled evaporation, leading to dehydration and wilting. The plant would also become highly vulnerable to infections from pathogens like bacteria and fungi, as its primary physical barrier would be gone. This would ultimately compromise its survival.
9. Why is the plant epidermis considered a simple permanent tissue?
The epidermis is classified as a simple permanent tissue because it is primarily composed of only one type of cell—the epidermal cell. Although it contains specialised structures like guard cells and root hairs, the fundamental, structural component is a single cell type. These cells are 'permanent' as they are fully differentiated and have lost the ability to divide, unlike meristematic tissues.
