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Finish Line & Beyond

TISSUES

Plant Tissues

Meristematic TissuePermanent Tissue

Animal TissueConnective Tissue

MusclesEpithelial

Nerves

Tissue is a group of cells. The cells in a tissue can be similar or different. The groupof cells thus formed carry specific functions. A group of different tissues make an

organ.

Plant Tissues

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Plant tissue culture is a practice used to develop plant under sterile laboratory

conditions, often to produce clones of a plant. The production of exact copies ofplants that produce particularly good flowers, fruits, or have other desirable traits.

Advantages of Tissue Culture

To quickly produce mature plants.

The production of multiples of plants in the absence of seeds or necessary

pollinators to produce seeds.

The regeneration of whole plants from plant cells that have been genetically

modified.

The production of plants in sterile containers that allows them to be movedwith greatly reduced chances of transmitting diseases, pests, and pathogens.

The production of plants from seeds that otherwise have very low chances of

germinating and growing, i.e.: orchids and nepenthes.

To clean particular plant of viral and other infections and to quickly multiplythese plants as 'cleaned stock' for horticulture and agriculture.

Types of Plant Tissues

1) MERISTEMATIC TISSUE

Meristematic tissue is growth tissue and the location of most cell division. Itis known as undifferentiated tissue because cells in the meristematic tissue

will eventually become vascular, ground, or dermal tissue.


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Location of meristematic tissue in plant body

Plants generally grow where meristematic tissue is present. At the tips of roots

and stems, the meristematic tissue is called the apical meristem.

Primary Growth

The primary growth of the plant occurs in the apical meristem. The growth in

length of a plant part is due to primary growth.

Secondary Growth

Lateral growth or growth in thickness in a plant is called secondary growth,

which occurs in lateral meristem tissue. Woody trees and shrubs display

secondary growth when the plants become enlarged and thickened.

2) PERMANENT TISSUE


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When the cells formed by meristematic tissue take up a specific role and lose the

ability to divide. As a result, they form a permanent tissue. This process of taking upa permanent shape, size, and a function is called differentiation. Cells of

meristematic tissue differentiate to form different types of permanent tissue.

Simple permanent tissues

These tissues are called simple because they are composed of similar types of cells

which have common origin and function. They are further classified into:

(II)Parenchyma

(III) Collenchyma

(IV) Sclerenchyma

1. Parenchyma

Parenchyma is Greek word where "parn" means besides and "enchien" means to

pour. Parenchyma is the most specialized primitive tissue. It mainly consist of thin-walled cells which have intermolecular spaces between them. The cell wall is made

up of cellulose. Each parenchymatous cell is iso-diametric, spherical, or oval inshape. It is widely distributed in various plant organs like root, stem, leaf, flowers

and fruits. They mainly occur in cortex epidermis, piths and mesophyll of leaves.

Function of Parenchyma

The main function of parenchymatous tissue is assimilation and storage of reservefood materials like starch, fats and proteins. They also store waste products such as

gums, resins, and inorganic waste materials.

2. Collenchyma

Collenchyma is Greek word where "Collen" means gum and "enchyma" meansinfusion. It is a living tissue of primary body like Parenchyma. Cells are thin-walled

but possess thickening of cellulose and pectin substances at the corners wherenumber of cells join together. This tissue gives a tensile strength to the plant and the

cells are compactly arranged and do not have intermolecular spaces. It occurs chieflyin hypodermis of stems and leaves. It is absent in monocots and in roots.

Functions of Collenchyma

Collenchymatous tissue acts as a supporting tissue in stems of young plants. Itprovides mechanical support, elasticity, and tensile strength to the plant body. It

helps in manufacturing sugar and storing it as starch. It is present in margin of

leaves and resists tearing effect of the wind.


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3. Sclerenchyma

Sclerenchyma is Greek word where "Sclrenes" means hard and "enchyma" means

infusion. This tissue consists of thick-walled, dead cells. These cells have hard andextremely thick secondary walls due to uniform distribution of ligin. Lignin depositionis so thick that the cell walls become strong, rigid and impermeable to water.

Sclerenchymatous cells are closely packed without intra-cellular spaces betweenthem. Thus, they appear as hexagonal net in transverse section. The cells are

cemented with the help of lamella. The middle lamella is a wall that lies betweenadjacent cells. Sclerenchymatous cells mainly occur in hypodermis, pricycle,

secondary xylem and phloem. They also occur in endocorp of almond and coconut. Itis made of pectin, lignin, protein.

Types of Sclerenchyma

Fibres- Fibres are long, elongated sclerenchyamtous cells with pointed ends.

Sclerides- Sclerenchymatous cells which are short and possess extremely thick,

lamellated, lignified walls with long singular piths. They are called sclerides.

Function of Sclerenchyma

The main function of Sclerenchymatous tissues is to give support to the plant.

2. Complex permanent tissue

A complex permanent tissue may be classified as a group of more than one type of

tissue having a common origin and working together as a unit to perform a function.These tissues are concerned with transportation of water, mineral, nutrients and

organic substances. The important complex tissues in vascular plants are xylem,

phloem.

1. Xylem

Xylem is a chief, conducting tissue of vascular plants. It is responsible for conduction

of water and inorganic solutes.

1. Tracheids- Trachids are elongated, tube-like dead cells with elongated end-

walls. End walls remain intact and possess piths. In transverse section, theyusually occur as polygonal cells and lignified walls.

2. Vessels - Vessels are placed one upon another. Their end walls are

perforated. They form long tubes or channels for conduction of water and

minerals.


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3. XylemParenchyma - Xylem Parenchymatous cells are living cells present in

xylem. They help in lateral conduction of organic solutes and storagereserves.

4. Xylem Fibres - Xylem Fibres are lignified fibres present in xylem whichprovide mechanical strength to the plant body.

Xylem is a major conducting tissue of vascular plants. It serves in upward movement

of water and minerals from root to different parts of plant.

2. Phloem

Phloem is a chief conducting tissue of vascular plants. It is regarded as a living tissueresponsible for translocation of organic solutes.

1. Sieve tube - Sieve tubes are long tubular structures composed of elongated

sieve tube elements placed one above other forming a continuous tube.

2. Companion cell - Companion cells are living cells always associated with sieve

tubes. Sieve tube elements and companion cells arrive from the same, initialcell and therefore forms a single functional unit. Each companion cell shows

presence of fine piths with all the living components of the cell.

3. Phloem Parenchyma - These cells are living parenchymatous cells that are

present in phloem. These cells help in storage of food.

4. PhloemFibres - Phloem fibres are formed by dead, sclerenchymatous fibres.

The main function of phloem is translocation of organic solutes from the leaves tothe storage organ and later from the storage organ to the growing part. Sieve tube

allows free diffusion of soluble, organic substances across sieve plates due to thepresence of large number of sieve pores.


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Animal Tissues

Based on morphology, animal tissues can be grouped into four basic types. Multiple

tissue types comprise organs and body structures. While all animals can generally beconsidered to contain the four tissue types, the manifestation of these tissues can

differ depending on the type of organism.

The four basic Animal Tissues are:

2. a) Connective tissue

Connective tissue is comprised of cells separated by non-living material, which is

called extra cellular matrix. As the name suggests connective tissues are meant tomake connections. Connective tissue holds other tissues together such as in the

formation of organs, and has the ability to stretch and contract passively. Bone,often referred to as osseous tissue, and blood are examples of specialized connective

tissues

b) Muscle tissue

Muscle cells form the active contractile tissue of the body known as muscle tissue.Muscle tissue functions to produce force and cause motion, either locomotion or

movement within internal organs.

Types of Muscles

1.Smooth Muscle or Visceral Muscle found in inner linings of organs.

2.Skeletal Muscle is attached to bone to provide movement.

3.Cardiac Muscle is in heart and makes possible the pumping action of the heart.

3. c) Nervous tissue

Cells comprising the central nervous system and peripheral nervous system are

classified as neural tissue. In the central nervous system, neural tissue forms the

brain, cranial nerves and spinal cord and, in the peripheral nervous system,peripheral nerves inclusive of the motor neurons. You can imagine the nervous tissuelike an electrical wiring in which the brain is the power generator, the spinal cord is

the main line and peipheral nerves are lines going to different organs.


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4. d) Epithelial tissue

Epithelial tissues are formed by layers of cells that cover organ surfaces such as the

surface of the skin, the airways, and the inner lining of the digestive tract. The cellscomprising an epithelial layer are linked via semi-permeable, tight junctions.

Functions of Epithelial Tissues:

Protection of internal organs in case of intestine, kidney and heart and protection of

external organs also. In fact skin is an epithelial tissue covering the body. Skin is thefirst line of defence against foreign substances. A burn victim doesnt die because of

burn but because the whole defensive layer of skin is broken exposing the body tovarious infections.


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