Understanding the Plant Tissue System
Meristematic tissue consists of cells that retain the ability to divide continuously. These cells are typically small, with dense cytoplasm and a prominent nucleus. They have thin cell walls and very little to no intercellular spaces. When someone asks, “What is meristematic tissue?”, the simplest answer is that it is the tissue responsible for primary (lengthwise) and secondary (widthwise) growth.
Meristematic tissues can be categorised based on their position in the plant:
Apical Meristem: Present at the tips (apex) of roots and shoots, causing the plant to grow longer.
Lateral Meristem: Found along the sides of stems and roots, enabling the plant to grow wider or thicker.
Intercalary Meristem: Located at the internodes or the base of leaves, facilitating lengthening between mature tissues (especially in grasses).
Over time, meristematic cells differentiate and become part of permanent tissues—this is a process called “differentiation.”
For more insights on these actively dividing tissues, explore Meristematic Tissues in detail.
Permanent Tissues
Permanent tissues arise when meristematic cells lose the capacity to divide and instead specialise for various functions such as support, storage, and transport. They are broadly divided into simple permanent tissues and complex permanent tissues.
Simple Permanent Tissues
Parenchyma
Usually composed of living, thin-walled cells.
Often polygonal in shape with large intercellular spaces.
Special types include:
Chlorenchyma: Contains chloroplasts; vital for photosynthesis.
Aerenchyma: Contains large air spaces, providing buoyancy (often found in aquatic plants).
Collenchyma
Consists of elongated living cells with thickened corners due to pectin and cellulose deposits.
Offers flexibility and mechanical support, particularly in the stems and leaf stalks.
Sclerenchyma
Composed of long, dead cells with lignified cell walls and negligible intercellular spaces.
Provides significant strength and rigidity (seen in the shells of nuts and the gritty texture in pears).
Complex Permanent Tissues
Complex permanent tissues are made up of more than one type of cell, working together to perform a common function—primarily conduction.
Xylem
Transports water and minerals from the roots to other plant parts.
Comprises tracheids, vessels, xylem parenchyma, and xylem fibres.
Lignin in xylem elements adds strength, helping the plant stay upright.
Phloem
Conducts prepared food from leaves (or storage tissues) to all other parts.
Consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibres.
For a more focused comparison, refer to Difference Between Xylem and Phloem.
Protective Tissues
Protective tissues shield the plant’s outer surfaces from water loss, mechanical injury, and infection.
Epidermis
The single outer layer covers leaves, stems, and roots.
May be punctuated by stomata that facilitate gas exchange and transpiration.
Cork (Phellem)
Substitutes the epidermis in mature roots and stems.
Composed of tightly packed, dead cells.
Walls contain suberin, making them impervious to water and gases.
Quick Mnemonic for Plant Tissues
Here’s a fun mnemonic for the main tissues: “My Plants Grow Pretty Constantly.”
My – Meristematic
Plants – Parenchyma
Grow – Ground tissues (Collenchyma, Sclerenchyma)
Pretty – Phloem
Constantly – Complex tissue (Xylem and others)
This mnemonic reminds you that meristematic tissues are responsible for growth, and permanent tissues come in various types (simple and complex).
Short Quiz for Practice
Here’s a quick quiz you can use for plant tissue class 9 mcq practice:
1. Which tissue is responsible for the increase in the thickness of the stem?
A. Apical meristem
B. Lateral meristem
C. Intercalary meristem
D. Epidermis
2. What type of tissue is present in the husk of a coconut?
A. Parenchyma
B. Collenchyma
C. Sclerenchyma
D. Phloem
3. Which tissue in plants helps in the transport of food?
A. Xylem
B. Phloem
C. Sclerenchyma
D. Parenchyma
Quiz Answers
B – Lateral meristem
C – Sclerenchyma
B – Phloem
Plant Tissue Class 9 Questions and Answers
1. Explain the main features of meristematic tissue.
Students should highlight that meristematic tissue has actively dividing cells, thin cell walls, dense cytoplasm, and large nuclei.
2. Why is the xylem called a complex permanent tissue?
Expected answer: Xylem is composed of different types of cells—tracheids, vessels, xylem fibres, and xylem parenchyma—all collaborating for water transport and support.
3. Differentiate between parenchyma and sclerenchyma.
Parenchyma cells generally live with thin walls and intercellular spaces, whereas sclerenchyma cells are dead, heavily lignified, and provide structural strength.
For further clarity on specific plant tissue elements, check out Difference Between Tracheids and Vessels
FAQs on Plant Tissue System Explained: Types, Functions and Diagrams
1. What are the two main categories of plant tissues as per the Class 9 syllabus?
Plant tissues are broadly divided into two main categories based on their ability to divide: Meristematic Tissues, which consist of actively dividing cells responsible for growth, and Permanent Tissues, which are derived from meristematic tissues and have lost the ability to divide, becoming specialised for functions like support, storage, and transport.
2. What is the primary role of meristematic tissue in a plant?
The primary role of meristematic tissue is to facilitate plant growth. These tissues are made of actively dividing cells. They are found in the growing regions of the plant, such as the tips of roots and shoots (apical meristem), and are responsible for increasing the plant's length and girth (lateral meristem).
3. How do simple and complex permanent tissues differ in their composition and function?
The main difference lies in their cellular structure and collaborative function.
- Simple permanent tissues, like parenchyma, collenchyma, and sclerenchyma, are made up of only one type of cell performing a uniform function.
- Complex permanent tissues, such as xylem and phloem, are composed of multiple types of cells that work together as a single unit to perform a more specialised task, primarily the transport of substances throughout the plant.
4. What are the key differences between the functions of xylem and phloem?
While both are complex conducting tissues, their functions are distinct:
- Xylem is responsible for the unidirectional transport of water and dissolved minerals from the roots up to the rest of the plant.
- Phloem is responsible for the bidirectional transport of prepared food (sucrose) from the leaves to all other parts of the plant, including storage organs like roots and fruits.
5. Why is sclerenchyma tissue, which is composed of dead cells, so important for a plant's survival?
Sclerenchyma tissue is crucial because it provides significant mechanical strength and rigidity to the plant. Even though its cells are dead at maturity, their cell walls are heavily thickened with a substance called lignin. This makes plant parts hard and stiff, offering protection against mechanical stress, which is evident in the husk of a coconut or the gritty texture of a pear.
6. What is the significance of protective tissues like the epidermis and cork for a plant?
Protective tissues are vital as they form the outermost layer of the plant body. The epidermis on leaves and young stems prevents water loss, protects against mechanical injury, and regulates gas exchange through pores called stomata. In older stems and roots, cork provides a tough, waterproof barrier against pathogens and environmental damage.
7. Why do aquatic plants like the lotus have specialised parenchyma tissue called aerenchyma?
Aerenchyma is a specialised type of parenchyma tissue containing large air cavities. In aquatic plants like the lotus, this tissue is essential for two reasons:
- It provides buoyancy, helping the leaves and flowers float on the water's surface to access sunlight for photosynthesis.
- It facilitates the circulation and storage of gases like oxygen, ensuring that submerged parts like the roots receive an adequate supply.
8. What would be the impact on a tree's growth if its lateral meristem stopped functioning?
If a tree's lateral meristem (also known as cambium) stopped functioning, the tree would lose its ability to grow in diameter or thickness. While it might continue to grow taller due to the apical meristem, it would not develop a sturdy, thick trunk and branches. This would make it structurally weak and unable to support its own weight or withstand environmental pressures like wind over time.
