Plant Tissues: Definition, Types & Characteristics

We know that photosynthesis allows green plant components to produce their own nourishment. So, how does this ready-to-eat food get to all areas of the plant? How does the water absorbed by the roots go to all areas of the plant? How come plants, which are anchored in place by their roots, are not blown away by tremendous wind velocity? Plant Tissues is the answer. Plant tissues come in a variety of shapes and sizes, each with its own set of functions.

The epidermis, the ground tissue, and the vascular tissue are the three tissue systems in plant anatomy. Cells that form the outer surface of the leaves and the young plant body are known as the epidermis. The xylem and phloem make up the majority of vascular tissue.

Continue reading this article to know more about Plant Tissues, definition, types, characteristics, etc.

What are Plant Tissues?

A group of cells that perform or help to perform a common function and have a common origin in plants is called a plant tissue.
All the plant organs, i.e., leaves, roots, flowers, fruits and stems, are made of different types of tissues. These different tissues have different functions.

What are the Types of Tissue in a Plant?

Plant tissues are of two types:
1. Meristematic tissues- Cells are capable of cell division.
2. Permanent tissues- Cells are incapable of cell division.

Meristematic Tissues- Characteristics

1. Cells of meristematic tissue divide continuously and are found at the tips of the plant-like root tips, tips of stems, etc.
2. Its cells can be rounded, oval, polygonal or rectangular.
3. These cells are compactly arranged, i.e., have no intercellular space between them.
4. Its cells have thin cellulose cell walls.
5. Cells of meristematic tissue have a nucleus and dense cytoplasm.
6. Vacuoles are small or absent.

Meristematic Tissues- Types

On the basis of position in the plant body, meristematic tissue is divided into the following types:

a. Apical Meristem

1. This meristem is located at the growing tips of main and lateral roots and shoots. These cells are responsible for the linear growth of an organ.
2. They are mostly primary meristems.
3. E.g., Shoot apex and root apex.

b. Intercalary Meristem

These meristems are responsible for the growth of the plant in length and present mostly at the base of the node, internode and leaf.

c. Lateral Meristem

1. It is found beneath the bark called cork cambium and in vascular bundles called vascular cambium. These meristems help in increasing the diameter of an organ. (Shown in the figure)
2. They are primary as well as secondary in origin.
3. E.g., vascular cambium, cork cambium and marginal meristem of some leaves.

Fig: Meristematic Tissues

On the basis of origin and method of development, meristems are of the following three types:-

a. Promeristem

1. It originates from embryos and the so-called primordial or embryonic meristem.
2. Promeristem is the group of initial cells that forms the base or foundation of an organ of the plant.
3. It consists of limited cells which rapidly divide and then form the primary meristem.
4. Present at the extreme tip of a young stem consisting of only a few cells.

b. Primary Meristem

1. It originates from promeristem.
2. Protoderm, procambium and the ground meristems are the kinds of the primary meristem.

c. Secondary Meristem

1. It originates from the permanent tissue which has already undergone differentiation.
2. Secondary meristem, for example, originates as vascular cambium when secondary growth is needed.
3. It can arise as cork cambium when the formation of periderm and healing of wounds is needed.

Permanent Tissues- Characteristics

1. Permanent tissues are made up of mature cells that have undergone growth and differentiation.
2. It originates from meristematic tissues and becomes permanent, i.e., lost its power of division.
3. It possesses a definite shape, size and function.
4. They may be living or dead.

These tissues are further divided into
1. Simple Permanent Tissues– It is composed of similar types of cells.
2. Complex Permanent Tissues– It is composed of more than one type of cell.

1. Simple Permanent Tissues

a. Simple permanent tissue is composed of similar types of cells. Those cells have a common origin and perform common functions.
b. It is of two types- Protective tissue and supporting tissue.

Protective tissue is further divided into:

a. Epidermis

1. It is the outermost covering of the plant body.
2. A waterproof layer called cuticle covers the epidermis, which is thick in desert plants.
3. It is protective in nature and helps in the prevention of water loss from its surface.
4. For water loss, a special structure is present in the epidermis called stomata, whose primary function is gaseous exchange.

b. Cork

1. Protective in nature.
2. It is formed in older roots and stems.
3. It is made of dead cells.
4. Do not have intercellular spaces.
5. Its cell wall is deposited with suberin, so impermeable to water and gases.

Supporting tissue is further divided into:

a. Parenchyma- (Greek, para=beside; enchyma= in filling)

1. Cells are living and have the power of division.
2. Have intercellular spaces between them.
3. The cell wall is thin, enclosing the cytoplasm containing a small nucleus and a large vacuole.
4. May store food.
5. Provide temporary support to the plant.
6. Parenchyma serves as packing tissue
7. Parenchymatous cells in leaves that contain chloroplasts form a tissue called chlorenchyma, which helps the plants to make their food.
8. Parenchymatous cells having large spaces in between them, called aerenchyma tissue.

b. Collenchyma- (Greek, Colla= glue)

1. Cells of this tissue are elongated and thick at the corners due to the deposition of pectin, hemicellulose and cellulose.
2. Intercellular space may or may not be present.
3. Support the parts of the plant.
4. Gives tensile strength to the plant body.
5. It provides easy bending of parts of the plant.
6. Present on the leaf margins of some leaves and resist tearing due to the wind.
7. Some of its cells have chloroplast and can perform photosynthesis.

c. Sclerenchyma- (Greek, sclerous= hard)

1. Consists of long, narrow thick-walled dead cells.
2. Thick cell walls due to deposition of lignin.
3. Due to excessive thickening of the cell wall, its lumen or cell cavity becomes nearly absent.
4. Found in stems and veins of the leaves.
5. It provides strength to plant parts.
6. It is of two types-

1. Fibres

a. Sclerenchymatous tissue consists of long elongated cells with tapering ends called fibres.
b. Its wall is thick due to the deposition of lignin.
c. The wall possesses simple and oblique pits.
d. Fibres originate from meristematic cells.
e. Provides mechanical strength.
f. Plant fibres such as hemp and linen are used to form ropes, mats, etc.

2. Sclereids

a. Sclerenchymatous tissue consists of short cells having thick lignified walls called sclereids.
b. The walls have long, tubular, simple pits.
c. They form a hard covering of nuts and seeds.
d. They provide stiffness.

Fig: Simple Permanent Tissues

2. Complex  Permanent Tissues

Tissues having more than one type of cells working together as a unit are called complex permanent tissues. It is of two types-

a. Xylem– (Greek, xylos = wood)

1. It is the chief conducting tissue of vascular plants responsible for water conduction with inorganic solutes from roots to all parts of the plant.
2. The older xylem forms wood and does not participate in transport.
3. The age of the tree can be counted by counting the xylem rings.
4. Components of xylem are-

A. Tracheids-

I. These are elongated tube-like dead cells having tapering ends.
II. Wall is hard, thick and lignified and encloses an empty lumen.
III. Provide mechanical support.
IV. Conducts water.
V. These do not have open ends, so water passes from cell to cell through pits.

B. Vessels

I. Vessels are shorter, wider, and form a long tube by attaching end to end.
II. They have open ends as horizontal walls get dissolved and make a continuous water pipe.
III. These are meant for transporting water and minerals.

C. Xylem parenchyma

I. It Stores food and helps in lateral conduction of water.
II. It is living.

b. Phloem

1. It is the chief food conducting tissue of vascular plants.
2. Components of phloem are

A. Sieve tubes

I. It forms a continuous tube, placed one above the other.
II. These are thin living cells without nucleus.
III. Dependent on adjacent companion cells for food.
IV. Walls are perforated.

B. Companion cells

I. Associated with the sieve tubes, so these cells are called companion cells.
II. Contains active cytoplasm, nucleus, mitochondria and ribosomes.

C. Phloem parenchyma

I. These are living cells of parenchyma having thin walls.
II. Its function is translocation and storage of food reserves.

D. Phloem fibres

I. These are also called bast fibres.
II. Non-living cells
III. Provide mechanical support and give strength and rigidity to the organ.

Fig: Xylem and Phloem

Special Tissues

Laticiferous Tissues

1. Plant tissues having latex (milky or yellowish colour fluid) are called Laticiferous Tissues.
2. Its cells are elongated, thick-walled.
3. Its cell consists of multiple nuclei.
4. Its function is not yet confirmed. Might be involved in the storage of food or waste products.

Glandular Tissues

1. It refers to the tissues having glands.
2. Glands may secrete oil, gum, resin, tannin, etc.

Summary

From the above discussion, we came to know that higher plants have highly complex structures made up of various kinds of cells. These cells unite to perform specific functions. Plant tissue is a group of cells that perform or help to perform a common function and have a common origin. Broadly plant tissue is divided into two groups, i.e. Meristematic tissue and Permanent tissue. Meristematic tissues are actively dividing tissue while permanent tissues have lost the ability to divide.

In meristematic tissues, cells are compactly arranged, i.e., have no intercellular space between them. These are found at the tips of the plant-like root tips, tips of stems, etc. Permanent tissues are made up of mature cells that have undergone growth and differentiation. It is further divided into simple and complex permanent tissues.

Frequently Asked Questions

We have provided some frequently asked questions about Plant Tissues here:

Q.1. What is an example of plant tissue?
Ans: An example of plant tissue is Parenchyma tissue.

Q.2. Is phloem a plant tissue?
Ans: Yes, phloem is a plant complex permanent tissue that helps in the translocation of food.

Q.3. Which tissue is responsible for the growth of plants?
Ans: Meristematic tissue is responsible for the growth of plants.

Q.4. What are the two types of tissues in plants?
Ans: 1. Meristematic tissue
2. Permanent tissue

Q.5. What are plant tissues?
Ans: A group of cells in a plant that perform or help to perform a common function and have a common origin is called a plant tissue.