The production of new plants from special tissues in the synthetic nutritive medium containing plant nutrients and plant hormones is called tissue culture or micro propagation.

In this technique some plant cells or plant tissues are taken from the meristamatic regions of the plants and put into the culture solution taken in a beaker under favourable and controlled conditions. Culture solution is a special solution containing essential nutrients and plant hormones, in which the tissues are grown. The plant cells grow rapidly in the culture medium and get converted into a group of cells called ‘callus’. The callus thus produced is shifted in other beakers containing suitable hormones. These hormones induce the growth of root and shoot system in the callus. In this way the callus is converted into a tiny plantlet. This plantlet is then shifted in the soil where it grows into a full plant.

Test Your Understanding and Answer These Questions:

1. What is callus?
2. What is tissue culture technique?
3. Explain the process of tissue culture.

Artificial vegetative propagation is the deliberate production of new plants from parts of old plants by humans. This can be done by following three methods:

    1. Cutting
    2. Layering
    3. Grafting

Cutting
The part of the plant which is removed by cutting it from the parent plant is called a ‘cutting’. In this method one year old stem of root is cut from a distance of 20 to 30 cm. and is buried in the moist soil in natural position. After sometime, roots develop from this cutting and it grows into a new plant. This method is commonly used in rose and sugar cane.

Layering
This method of vegetative propagation is used in those plants whose soft branches occur near the ground such as jasmine plant. In this method, a branch of the plant which is near to the ground is pulled towards the ground and a part of this branch is covered with moist soil leaving the tip of this branch above the ground.

 After sometime, roots develop from that part of the branch which was buried in the soil. This branch is then cut of along with the roots from the parent plant and develops into a new plant. This method of asexual reproduction is also used in the production of plants such as Bougainvillea, jasmine, guava, strawberries, lemon, China rose etc.

Grafting
 In this method of vegetative propagation the stems of two different plants are joined together so as to produce a new plant containing the characters of both plants. Out of the two plants one plant has a strong root system while the other has a better flower or fruit yield. The plant of which the root system is taken is called ‘stock’, while the other plant of which the shoot is selected is known as ‘scion’ or ‘graft’.. These two stems i.e. the stock and the scion are fitted together by making slanting cuts in them and bound tightly with a piece of cloth and is covered with a polythene sheet.

While joining the scion with the stock care should be taken that the diameter of the stock and scion chosen for grafting should be equal. Scion gets the mineral and water from the soil through the stock and develops branches and produce fruits.

This method of propagation is used in mango, apple, rose, banana, pear, grape, pineapple and peach.

Test Your Understanding and Answer These Questions:

1. What is grafting?
2. How will you show that vegetative propagation takes place in potatoes and ginger?
3. Explain the method by which the sugarcane and rose are grown.
4. Give the names the different methods of artificial vegetative reproduction.
5. Name the plants which are grown by grafting method.
6. Name the plants which are grown by layering method.
7. Name the plants which are grown by cutting method

Vegetative reproduction is the method of obtaining new plants from the parts (such as stems, roots and leaves) of an old plant, without any type of involvement of sex organs. Thus this method of reproduction is used in the production of higher plants from the vegetative parts of an old plant. This method of asexual reproduction is found in sweet potatoes, onion, guava, bryophyllum, potatoes and in banana.

The production of new plants from the parts of old plant can take place naturally or artificially. So we can classify vegetative propagation in two types.

    1. Natural vegetative propagation
    2. Artificial vegetative propagation

Natural vegetative propagation
Natural vegetative propagation can take place from the following parts of a plant.

    1. Roots
    2. Stem
    3. Leaves

1. Vegetative propagation by roots
In some plants vegetative propagation can take place from roots. For example, in sweet potatoes the roots bear adventitious buds from which new plants can develop when it is buried in the moist soil. Such roots are called reproductive roots.

2. Vegetative propagation by stem
Vegetative propagation can take place from the stem in ginger and potatoes. In these plants the stem bear small outgrowths called buds. When a cutting of such a stem along with the bud is buried in the moist soil then a new plant develops from these buds.

3. Vegetative propagation by leaves
 Vegetative propagation can also take place from the leaves. This method is found in plants such as Bryophyllum and Begonia.

Vegetative propagation by leaves in Bryophyllum
 In the leaves of Bryophyllum meristamatic marginal notches are present. From these meristamatic tissues new plants can develop after coming in contact of soil. The new plants can detach from the leaves and develop into a full plant after falling on the ground.

Advantages of vegetative propagation
 Following are the advantages of vegetative propagation.

1. The new plants produced by vegetative propagation are exactly like the parent plant i.e. the new plants possess all characteristics of the parent plant.
2. The plants produced by vegetative propagation grow rapidly.
3. Desired varieties and qualities of fruits and plants can be produced by vegetative propagation.
4. Those plants can also be produced by vegetative propagation which do not produce seeds or which cannot produce viable seeds.
5. The desirable characters of a variety can be preserved indefinitely through vegetative reproduction.

Test Your Understanding and Answer These Questions:

1. What do you mean by vegetative reproduction? Give its types.
2. Explain vegetative propagation by leaves in bryophyllum.
3. Name the plants which are grown by using their stems.
4. Give the names of the different methods of natural vegetative reproduction.
5. Name the plants which are grown by using roots.
6. List two advantages of vegetative propagation.
7. What are the various methods of vegetative propagation?

Fragmentation
 Fragmentation may be defined as the process of breaking up of parent animal into small parts, each of which can grow into a new complete individual. This process of asexual reproduction is found in planaria and hydra.

Regeneration
Regeneration may be defined as the ability of an organism to grow its lost parts. This method of asexual reproduction is found in protozoa, sponges, hydra, earthworms and starfish.

Regeneration in star fish
In this method if any part or arm of starfish cuts from the main body then this fragment can develop into a complete animal by growing its missing parts.

Test Your Understanding and Answer These Questions:

1. Explain spore formation method of asexual reproduction in nonflowering plants.
2. Write a short note on sporangia and hyphae.
3. What are aplanospores?
4. What are zoospores?

Spore formation is a method of asexual reproduction which is found in non flowering plants such as fungi (Rhizopus) and bacteria. In this method of reproduction, the parent plant produces hundreds of tiny spores which can grow into new plants. The spores are the microscopic, tough and resistant bodies which are round in shape and can grow into a new plant under suitable conditions. We shall now discuss the formation of new plants by spores by taking the example of fungi called as bread mould or Rhizopus.

In Rhizopus numerous spores are produced within sacs called sporangia as shown in the figure. The sporangia are knob like structures which are present at the top of the thread like structures called hyphae. When these sporangia bursts, the spores are scattered by rain, wind or insects and under suitable conditions develop into a new Rhizopus plant, when they fall on a suitable substance like bread.

Types of Spores

The spores are of two types:

1. Aplanospores
2. Zoospores

Aplanospores
 These are non-motile spores. These spores are non-motile due to the absence of flagella in them.

Zoospores
The motile spores are called zoospores. These spores are motile due to the presence of flagella in them.

Test Your Understanding and Answer These Questions:

1. Explain spore formation method of asexual reproduction in nonflowering plants.
2. Write a short note on sporangia and hyphae.
3. What are aplanospores?
4. What are zoospores?

Budding may be defined as the process in which a small part of the body of the parent organism grows out as a small projection called ‘bud’ which when detaches becomes a new organism.

This method of asexual reproduction is found in hydra, sponges, flatworms and yeast.

Budding in hydra
In hydra a small outgrowth which is called ‘bud’ is produced from the parent hydra. This bud drives nourishment from the parent hydra and grows. Ultimately it detaches from parent hydra and becomes an independent animal.

Budding in yeast
 Yeast is a unicellular, non green fungus which reproduces by budding. In yeast first of all a small bud appears as an outgrowth from the body of the parent. Then the nucleus of the parent yeast divides into two parts and one nucleus shifts into the bud. In the end, the newly formed bud separates and grows into a new yeast cell.

The process of budding is fast in yeast, and often the first bud starts forming new buds before getting detached from parent yeast cell. In this way a small chain of buds is formed on parent yeast cell, which ultimately breaks and all the buds form new yeast cells.

Test Your Understanding and Answer These Questions:

1. What is budding?
2. Explain various steps of budding in yeast.
3. Explain various steps of budding in hydra?

Fission Fission means ‘to break’. Thus in this method an organism can divide into two or more organisms. So it can be of two types:

    1. Binary fission
    2. Multiple fission

Binary Fission
The term ‘binary fission’ consists of two words ‘binary’ and ‘fission’. The word ‘binary’ means ‘two’ and the term ‘fission’ means ‘to break’. It may be defined as the division of an organism into two offsprings or daughter organisms.

This method of reproduction is found in protozoans like amoeba, paramecium and bacteria. In this method under favourable conditions the parent organisms grows to its full extent and then divides into two parts. Each part of the parent then separates and grows into a new organism. This process is repeated further by the new organisms to produce a large number of organisms.

Multiple Fission
The term ‘multiple fission’ consists of two words ‘multi’ and ‘fission’. The word ‘multi’ means ‘many’ and the term ‘fission’ means ‘to break’. It may be defined as the division of a parent into many small offsprings or daughter organisms, at the same time.

This method of reproduction is also shown by protozoans such as amoeba, paramecium and plasmodium.

Multiple Fission in Amoeba
In this method, sometime under unfavourable or drastic conditions a very tough layer which is called as cyst is formed around the parent amoeba. Inside the cyst, the nucleus of the parent divides many times to form many nuclei. Later on, the cytoplasm of the cyst also divides

and each part of the cytoplasm encloses one nucleus. In this way many small amoebae are produced inside the cyst. On the return of favourable conditions, the cyst breaks and all the amoebae are released. These amoebae then grow into adults.

Multiple fission in Plasmodium
 Plasmodium is the malarial parasite which produces malaria disease in human beings. The method of multiple fission in plasmodium is same as that of the amoeba.

Test Your Understanding and Answer These Questions:

1. What is binary fission? Give example of binary fission.
2. Explain binary fission in amoeba.
3. What is multiple fission? Give example of multiple fission.
4. Explain multiple fission in amoeba.
5. Explain multiple fission in plasmodium.

We know that all the plants and animals die after completing their life cycle. Thus, new organisms must be produced to take their place. The process of formation of new organisms of a species from pre existing ones is called reproduction. Reproduction is the most important biological activity of living organisms. It ensures the continuity of a particular species of organisms on earth by producing more and more individuals of that particular species.

Types of Reproduction

Reproduction is of two types:

1. Asexual reproduction
2. Sexual reproduction

ASEXUAL REPRODUCTION
The production of offspring by a single parent without the formation and fusion of gametes is called asexual reproduction. Thus in asexual reproduction only one parent is needed to produce a new organism i.e. in the asexual reproduction the involvement of male and female gamete is not necessary. This is the simplest method of reproduction and brings about very fast increase in the population of an organism.

Characteristics of asexual reproduction

Following are the important characteristics of asexual reproduction:

1. Asexual reproduction helps in production of a large number of individuals from a single parent.
2. Asexual reproduction involves only one parent i.e. a large number of individual can be produced from a single parent.
3. The new individuals formed by asexual reproduction are usually genetically similar to their parent.
4. The chance of mutations or variations is very less.
5. Asexual reproduction takes place without involvement of male and female gametes.

 Methods of Asexual Reproduction

Asexual reproduction can take place in an organism by following methods:

1. Fission
2. Budding
3. Spore formation
4. Fragmentation
5. Regeneration
6. Vegetative reproduction

Test Your Understanding and Answer These Questions:

1. Define reproduction.
2. What are types of reproduction?
3. What is asexual reproduction?
4. What are characteristic of asexual reproduction?
5. Write names of different methods of asexual reproduction.
6. What is the common method of reproduction in unicellular organisms?