A tissue is a combination or a group of cells that are mostly similar in nature. They work together closely to perform particular functions. They often form an organizational level group for performing these functions. These functions can vary from protection, transportation, reproduction, and more.
The Plant Tissue System looks at two types of tissues largely. They are Meristematic Tissue and Permanent Tissues. This division is on the basis of the function performed and the different types of cells they have. These tissues have various locations, features, organization, shapes, and more.
All these criteria decide their subdivision further. This is done to identify which part of the plants is performing what. And to make the structure of the plant more clear. The Meristematic Tissues and Permanent Tissue too have subgroups under them.
These groups again have a distinctive role to play in the body of a plant. Let us first understand the basic differences between the two major tissues i.e. Meristematic and Permanent. And then we can dive into the detailed information about each of them.
Difference Between Meristematic and Permanent Tissues
| Basis | Meristematic Tissues | Permanent Tissues |
| Division | possible | Not Possible |
| Cell Composition | Undifferentiated cells | Differentiated cells |
| Tissues | Simple Only | Can be Complex |
| Nature of cells | Living | Living and NonLiving |
| Size | Small | Large |
| Shape | Isodiametric | Varies |
| Cell Space | Compact | Compact and Loose |
| Metabolic Rate | High | Low |
| Nucleus | Present | Might be Absent |
Let’s look at each tissue in detail now –
Meristematic Tissue
Carl Wilhelm von Nägeli came up with this term. These tissues build a plant structure with undifferentiated cells. They have living cells of different shapes. They have a large-sized nucleus and the cells have no space between them.
The place or part where these cells live is meristem. These cells actively and simultaneously divide to form a special plant structure. They facilitate the increase in the length and breadth of the plant.
Characteristics of Meristematic Tissue
- Meristem is a common name for the cells of these tissues.
- These tissues possess self-renewal property. This allows every division of the cell to remain similar to the parent cell.
- The vacuoles are small and less in number.
- These tissues are alive and have thin walls.
- They have a dense protoplasm.
- They have healing power as well and can heal the wounds of injured plants.
- The cells of these tissues are young in age.
- These tissues do not store food but have high metabolic activity.
- They have a single and large-sized nucleus.
Types of Meristematic Tissue – Origin
Promeristem
- These tissues are the youngest meristematic tissue.
- They develop from the embryo.
- They are usually located in the root and the shoot tips.
Primary Meristem
- They develop from the Promeristem.
- The cells of these tissues divide actively.
- These tissues develop and form permanent tissue.
Secondary Meristem
- They develop out of primary meristem.
- They form the secondary meristem.
Types of Meristematic Tissue – Position
Apical Meristem
- They are located at the tips of the roots and shoots.
- They facilitate the increase in height of the plants
- This is by cell divisions which leads to cellular enlargement
- It has two zones – the Promeristem zone and the Meristematic zone.
- The first one actively divides the cells and the second contains protoderm, procambium, and ground meristem.
Intercalary Meristem
- They are located in the leaves and internodes.
- They facilitate the increase in the length of the internode.
- These are usually in grass, monocots, and pines.
- It is a part of the apical meristem.
Lateral Meristem
- They are located in the stems and roots of the plants.
- They facilitate the thickness of the plant.
- Vascular cambium and cork cambium come under it.
- They go through radial division and develop secondary permanent tissues.
Types of Meristematic Tissue – Function
Protoderm
- This is located at the outermost layer of the tissues and creates epidermis.
- It is responsible for protecting plants from mechanical shocks.
Procambium
- This is located in the innermost layer of the tissues.
- It gives a path to xylem and phloem.
- It facilitates the transportation of water and nutrients through the plant.
Ground Meristem
- The cells of this tissue are large in size with thick walls.
- They are responsible for forming the cortex, pericycle, and pith.
Permanent Tissues
The permanent tissues have the cells which can no longer divide themselves. But they are capable of offering elasticity, flexibility, and strength to the plant. They are further divided into two categories Simple Permanent Tissue and Complex Permanent Tissue. Let’s take a look at their features and functions.
Simple Permanent Tissue
These tissues are homogeneous. They usually have the same origin, structure, and function and come under a single cell type. They are further divided into three categories – sclerenchyma, collenchyma, and parenchyma. Let’s see how they are different from each other.
Parenchyma
- They are living cells with a large vacuole.
- They are oval or round in shape with no interstellar space.
- These have cellulose built cell walls which are quite thin.
- These cells are responsible for creating ground tissue and pith.
- They have chloroplasts which help in photosynthesis.
- They often act as a storeroom for starch in vegetables and fruits.
- These tissues are present in all parts of the plant.
- Aerenchyma is just parenchyma with large air cavities. They are mostly aquatic plants.
- And chlorenchyma is part of this too. They perform photosynthesis with the presence of chlorophyll. And thus parenchyma becomes chlorenchyma.
Collenchyma
- These cells are long or stretched out in shape.
- They have very little intercellular gaps.
- The cell walls are of pectin and cellulose.
- They offer flexibility with support to the plants.
- They have a very chloroplast as well.
- These are mainly located in marginal regions of leaves and stems.
Sclerenchyma
- These tissues are dead and very rigid.
- They have no space between the cells.
- They are mostly located in seeds and nuts covering.
- Their rigid nature provides strength to the plant.
- The cells have thick walls making it more rigid.
Difference Between Parenchyma, Collenchyma, and Sclerenchyma
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Difference between Parenchyma, Collenchyma, and Sclerenchyma |
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| Parenchyma | Collenchyma | Sclerenchyma |
| Thin-walled living cells | Thin-walled living cells | Dead Cells |
| Acts as food storage tissue | Mechanical Tissue | Mechanical Tissue |
| The cell wall is of cellulose | Cell wall is of pectin and hemicellulose | The cell wall of lignin |
| Located in all parts | Its Located in marginal regions of leaves and stems | Located in seeds and nuts covering |
| Round Shape | Stretched out Shape | Elongated Shape |
Complex Permanent Tissue
The complex tissues are most important as they are responsible for the transportation system in the plant. It includes phloem and xylem. They facilitate the transfer of water, nutrients, and food throughout the plant.
The xylem consists of parenchyma, fibres, vessels, and tracheids. While the phloem is made up of fibres, companion cells, sieve cells, and sieve tubes.
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Xylem
- This tissue transports the liquid matter to the entire plant.
- The transportation starts at the root and goes till every leaf.
- It supports the plant with lignin made components.
- The xylem consists of – vessels, tracheids, xylem fibres, and xylem parenchyma.
Phloem
- It is responsible for transporting food throughout the plant.
- Another name for it is bast.
- The Phloem consists of – fibres, sieve tubes, parenchyma, and companion cells.
Difference between Xylem and Phloem
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Difference between Xylem and Phloem |
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| Basis | Xylem | Phloem |
| Location | Centre of the vascular bundle | The outer side of the vascular bundle |
| Fibres | Smaller | Larger |
| Region | Roots, stems, and leaves | Stems and leaves |
| Movements | Unidirectional | Bidirectional |
| Tissues | More | Less |
| Components | vessels, tracheids, xylem fibres, and xylem parenchyma | fibres, sieve tubes, parenchyma, and companion cells |
| Functions | Transports water and liquids | Transports organic food |
| Feature | Lives with hollow dead cells | Lives with cytoplasm without the nucleus |
Other Important Plant Tissues
Protective Tissues
- They are the defending tissues of the plant.
- Cork and epidermis are part of this system.
- The epidermis is the outer layer of the plant structure.
- The stomata on the epidermis perform transpiration.
- The cork acts as an external defense tissue.
- It is lifeless and doesn’t have gaps between the cells.
- They act as a substitute to the epidermis in mature stems and roots.
Special Tissues
- The Laticiferous Tissues have latex.
- They develop from meristematic tissues.
- The cells are stretched out with multiple nuclei.
- Glandular Tissues have various glands that release liquids
- They are on the epidermis of the plant.
Epidermis
The epidermis is present in the outermost layers of cells. They are usually single and maybe thicker in plants of dry regions. The main function of it is to protect the plants. They are a bit waxy in aerial plants to minimize water loss and injury.
Because they are hard and rigid, there is no intercellular space between the cells. The cells are flat and have a thicker sidewall. Stomata are the pores on a leaf’s epidermis. They have a kidney-like shape and facilitate gas exchange with the atmosphere.
The transpiration also takes place here. The epidermis in roots is responsible for water absorption and has hairy like parts for this. In desert plants, these are thick and waxy cutin.
The age changes this tissue as the secondary meristem takes over it. A thick cork formation is present on tree barks. They are dead cells and with a compact arrangement.
Conclusion
It is important for a plant to have a well-maintained tissue system. It allows them to grow, develop, and function well. Each kind of tissue has some of the other important in the lifecycle of a plant. It is essential to understand them first then to understand the ecosystem.
This article will guide you on each and every aspect of the plant tissue system. It will look at their features, uses, location, composition, difference, and much more. This is important for competitive exams like UPSC, RRB, SSC, and more.
They can have a question from this in their GK section or the Science section. This is an important UPSC Biology Optional topic as well. Aspirants should give it a read before appearing for the exam.