Chapter – 6A : Plant Tissues and its distribution | Chapter Solution Class 9

(a) A group of similar or dissimilar cells having a common origin and similar function.

Explanation:

Tissues are groups of cells that share a common origin and function. These cells may be structurally similar or different but always work together to perform a specific function.

(a) Meristematic tissue

Explanation:

Meristematic tissues are composed of actively dividing cells. These cells are responsible for plant growth and are found in the apical (tip), lateral (sides), and intercalary (middle) regions of plants.

(a) Simple tissue

Explanation:

Parenchyma is a simple permanent tissue composed of thin-walled, living cells with large vacuoles. It functions in storage, photosynthesis, and support.

(b) Sclereids

Explanation:

Sclereids are short, irregularly shaped, thick-walled sclerenchyma cells that provide mechanical support. They are found in seed coats, nutshells, and the pulp of fruits like pears.

(c) Complex tissue

Explanation:

Xylem and phloem are complex permanent tissues because they consist of different types of cells working together to perform the functions of transporting water, minerals, and food.

(a) Lignified cell wall

Explanation:

Sclerenchyma cells have thick, lignified (hardened) cell walls, making them rigid and providing mechanical support to plants.

(c) Sieve tube

Explanation:

Sieve tubes are specialized phloem cells responsible for transporting food. They lack a nucleus to facilitate easier flow of nutrients but are supported by companion cells, which regulate their functions.

(a) Tissue

Explanation:

A tissue is defined as a group of cells working together to perform a specific function. It can be simple (one type of cell) or complex (multiple types of cells).

(b) Living and contains protoplasm

Explanation:

Collenchyma is a living tissue with thickened cell walls, providing mechanical support to young stems and petioles.

(d) Xylem

Explanation:

Xylem is a complex permanent tissue composed of tracheids, vessels, xylem fibers, and xylem parenchyma. It is responsible for water conduction in plants.

(b) Sieve tubes

Explanation:

Companion cells are specialized phloem cells that provide nourishment and support to sieve tubes, which lack a nucleus.

(a) Phloem

Explanation:

Sieve tubes and companion cells are key components of phloem, which is responsible for transporting food (sugars) throughout the plant.

Permanent

Explanation:

Sclerenchyma is a permanent tissue because its cells lose the ability to divide and develop thick, lignified walls for mechanical support.

Sieve tube

Explanation:

Sieve tubes, which are part of the phloem, lack a nucleus. They rely on companion cells for their function of transporting food in plants.

Phloem

Explanation:

Bast fibers are long, thick-walled fibers found in phloem tissue. They provide mechanical strength and are used for making ropes and textiles.

Sclerenchyma

Explanation:

Jute fibers are made of sclerenchyma cells that have thick, lignified walls. These fibers are strong and durable, making them useful for textiles and ropes.

Sieve tubes

Explanation:

Companion cells are specialized phloem cells that help sieve tubes in food conduction by providing energy and regulating their functions.

Chlorenchyma

Explanation:

Chlorenchyma is a special type of parenchyma tissue that contains chlorophyll and is involved in photosynthesis.

Chlorenchyma

Explanation:

Chlorenchyma is a special type of parenchyma tissue that contains chlorophyll and is involved in photosynthesis.

Complex

Explanation:

Xylem is a complex permanent tissue because it consists of multiple cell types (tracheids, vessels, xylem fibers, and xylem parenchyma) that work together to transport water and minerals.

True

Explanation:

A tissue is defined as a group of cells that have a common origin and function. These cells can be either structurally similar or different, but they always work together.

False

Explanation:

Tissues that are always dividing are called meristematic tissues. Permanent tissues have matured and lost their ability to divide.

False

Explanation:

Meristematic tissue consists of actively dividing cells, whereas permanent tissue consists of matured, non-dividing cells.

True

Explanation:

Apical meristem is found at the tips (apices) of roots and shoots, where it promotes primary (lengthwise) growth.

True

Explanation:

Sclerenchyma fibers are long, narrow, and tapering at both ends. They provide mechanical strength to plants.

True

Explanation:

Sclereids are short, thick-walled sclerenchyma cells found in seed coats, nutshells, and fruit pulp (e.g., pear).

True

Explanation:

Xylem is a complex permanent tissue that transports water and minerals from roots to the rest of the plant.

False

Explanation:

Sieve tubes in phloem are living cells (although they lack a nucleus). They help in transporting food in plants.

False

Explanation:

Phloem fibers are also called bast fibers, whereas wood fibers are actually xylem fibers.

• Meristematic Tissue
• Permanent Tissue

Apical Meristem.

• Parenchyma
• Collenchyma

Aerenchyma

Chlorenchyma.

Collenchyma.

Sclerenchyma.

• Collenchyma
• Sclerenchyma

Sieve Tube Cell.

• Xylem
• Phloem

Sieve Tubes

A tissue is a group of similar or dissimilar cells that work together to perform a specific function. These cells originate from the same source and may be structurally identical (simple tissue) or composed of different cell types (complex tissue). Tissues are the building blocks of organs in both plants and animals.

Tissues are classified into two main types: Meristematic tissue and Permanent tissue.

• Meristematic tissue consists of actively dividing cells responsible for plant growth.
• Permanent tissue consists of matured cells that no longer divide and perform specialized functions like transport and support.

A meristem is a group of actively dividing cells found in growing regions of plants. It is responsible for plant growth by continuously producing new cells. Meristematic tissue can be found in the root tip, shoot tip, and vascular cambium.

The apical meristem is a type of meristematic tissue found at the tips of roots and shoots. It is responsible for the primary growth of plants, increasing their length. This tissue ensures the elongation of stems and roots, helping the plant grow taller and deeper into the soil.

Lateral meristem is found along the sides of stems and roots and is responsible for secondary growth in plants. It increases the girth (thickness) of stems and roots, making them stronger. Examples of lateral meristem include the vascular cambium and cork cambium.

Intercalary meristem is present at the base of leaves and internodes (stem regions between two nodes). It helps in the elongation of plant parts, especially in grasses and monocots. This meristem allows plants to regrow quickly after being cut, as seen in lawn grasses.

Aerenchyma is a specialized parenchyma tissue with large air spaces between cells. It helps aquatic plants, like water hyacinths and lotus, float by providing buoyancy. This adaptation is crucial for plants growing in waterlogged conditions.

A complex tissue consists of more than one type of cell working together to perform a common function. It is mainly involved in transportation in plants. Xylem (conducts water) and phloem (conducts food) are the two types of complex permanent tissues.

A simple tissue consists of only one type of cell that performs a specific function. It is mainly responsible for support, storage, and photosynthesis in plants. Examples of simple tissues include parenchyma, collenchyma, and sclerenchyma.

Parenchyma is a living simple permanent tissue with thin cell walls and large vacuoles. It functions in storage, photosynthesis, and secretion. Some specialized types include chlorenchyma (photosynthetic) and aerenchyma (provides buoyancy in aquatic plants).

Collenchyma is a living simple permanent tissue that provides mechanical support and flexibility to growing plant parts. Its cells have thickened corners due to cellulose and pectin deposits. It is commonly found in leaf veins, petioles, and young stems.

Sclerenchyma is a dead simple permanent tissue with thick, lignified cell walls that provide mechanical strength and rigidity. It is found in hard plant parts like seed coats, nut shells, and fibers (e.g., jute and coconut husk). Its two types are sclerenchyma fibers and sclereids.

Sclerenchyma tissue consists of dead cells with thick, lignified walls that provide rigidity and support to plants. It helps in protection and mechanical strength, making plant structures tough and durable. Examples include bark, seed coats, and vascular tissues.

Complex tissues are composed of different types of cells that work together for a specific function. They are mainly responsible for transporting substances in plants. The two types of complex tissue are xylem (water transport) and phloem (food transport).

Xylem is a complex permanent tissue responsible for transporting water and minerals from roots to leaves. It consists of tracheids, vessels, xylem fibers, and xylem parenchyma. Xylem also provides mechanical support to the plant.

Phloem is a complex permanent tissue that transports food (sugars) from leaves to all parts of the plant. It consists of sieve tubes, companion cells, phloem fibers, and phloem parenchyma. Unlike xylem, most phloem cells are living.

Sclereids are short, thick-walled sclerenchyma cells that provide hardness to plant structures. They are found in seed coats, nutshells, and fruit pulp (e.g., pears). Sclereids help in protection and mechanical strength.

Sclerenchyma fibers are long, narrow, dead cells with thick lignified walls that provide mechanical strength. They are found in jute, flax, and coconut husk and are used in making ropes and textiles.

• Xylem transports water and minerals from roots to leaves and provides structural support.
• Phloem transports food (sucrose and nutrients) from leaves to different parts of the plant.

The two main conducting tissues in plants are:

1. Xylem – Conducts water and minerals.
2. Phloem – Conducts food (sugars and nutrients).

A sieve tube is a long, tubular phloem cell responsible for transporting food throughout the plant. It has sieve plates at the ends and lacks a nucleus, depending on companion cells for support.

A sieve plate is a perforated end wall found in sieve tubes of phloem. It allows the movement of food materials from one sieve tube cell to another.

A companion cell is a living phloem cell attached to sieve tubes. It regulates the food transport process and provides nourishment and support.

Jute fiber is a natural fiber obtained from the stem of jute plants. It consists of sclerenchyma fibers and is used in making ropes, bags, and textiles.

The characteristics of sclerenchyma fibre are:

• Dead cells with lignified walls.
• Provides mechanical support.
• Elongated and narrow structure.
• Used in textile industries (e.g., jute, hemp).

A tracheid is a long, dead xylem cell that transports water and minerals in plants. It has thick, lignified walls and is found in gymnosperms and ferns.

Meristematic tissue consists of actively dividing cells that help in plant growth, whereas permanent tissue consists of mature, non-dividing cells that perform specific functions like support, transport, and storage.

Meristematic tissue is a type of plant tissue made up of actively dividing cells responsible for plant growth. These cells have thin walls, dense cytoplasm, and a large nucleus. They lack intercellular spaces and contain small vacuoles or none at all.

Structure of Meristem:

• Cell Shape: Mostly round, oval, or polygonal.
• Nucleus: Large and prominent.
• Cytoplasm: Dense and active.
• Cell Wall: Thin and flexible (made of cellulose).
• Vacuoles: Either absent or very small.

Types of Meristem Based on Location:

1. Apical Meristem – Found at root and shoot tips (helps in primary growth).
2. Lateral Meristem – Found along the sides of stems and roots (helps in secondary growth).
3. Intercalary Meristem – Located at the base of leaves and internodes (found in grasses).

Permanent tissue consists of matured cells that have lost their ability to divide and perform specialized functions in plants. They originate from meristematic tissues after differentiation.

Types of Permanent Tissue:

1. Simple Permanent Tissue – Made up of one type of cells (e.g., parenchyma, collenchyma, sclerenchyma).
2. Complex Permanent Tissue – Made up of different types of cells working together (e.g., xylem, phloem).

Two Characteristics of Permanent Tissue:

1. Cells are specialized for a particular function (e.g., storage, support, transport).
2. Cell division stops after maturation, and the structure remains stable.

Parenchyma is a simple permanent tissue composed of thin-walled living cells. It plays a major role in storage, photosynthesis, and secretion.

Structure of Parenchyma:

• Cell Shape: Isodiametric, oval, or polygonal.
• Cell Wall: Thin and made of cellulose.
• Cytoplasm: Present with a nucleus.
• Vacuole: Large and prominent.
• Intercellular Spaces: Present to facilitate gas exchange.

Functions:

• It stores food and water (e.g., potato tubers).
• It helps in photosynthesis (when chlorophyll is present—called chlorenchyma).
• It provides buoyancy in aquatic plants (when air spaces are present—called aerenchyma).

Collenchyma is a simple permanent tissue composed of living cells with unevenly thickened cell walls. It provides mechanical support and flexibility to young plant parts.

Structure of Collenchyma:

• Cell Shape: Elongated with thickened corners.
• Cell Wall: Thick at corners (due to cellulose, pectin, and hemicellulose).
• Cytoplasm: Present with a nucleus.
• Intercellular Spaces: Absent or very small.

Functions:

• It Provides mechanical strength.
• It Helps in flexibility and bending of plant parts.
• It Can perform photosynthesis (when chlorophyll is present).

A tracheid is a long, dead, tube-like xylem cell that helps in the transportation of water and minerals. It is present in gymnosperms, ferns, and lower vascular plants.

Structure of Tracheid:

• Cell Shape: Long and tapering at both ends.
• Cell Wall: Thick and lignified.
• Pits: Small pores present for water conduction.
• Cytoplasm: Absent, as the cell is dead.

A sieve tube is a long, cylindrical phloem cell responsible for food conduction in plants. It lacks a nucleus and depends on companion cells for survival.

Structure of Sieve Tube:

• Cell Shape: Elongated tube-like.
• Cell Wall: Made of cellulose.
• Sieve Plates: Perforated end walls for food transport.
• Cytoplasm: Present but lacks a nucleus.

Differences Between Parenchyma and Collenchyma

Differences Between Collenchyma and Sclerenchyma

Differences Between Xylem and Phloem