BIOLOGY CLASS IX ARTIFICIAL VEGETATIVE PROPAGATION

Transcription

1 BIOLOGY CLASS IX ARTIFICIAL VEGETATIVE PROPAGATION MICROPROPAGATION This a technique of propagating plants by removing tissues from a parent plant and culturing them in a chemical medium. 1. A sterilized vegetative bud or short apical bud is removed from the desired variety of plant and is used for initiating micro propagation. This is called an EXPLANT. 2. The explant is placed in a medium with nutrients. This enables the rapid multiplication of cells. The unorganized and undifferentiated mass of cells that develop from an explant is called CALLUS. 3. Portions of the callus are removed and placed in containers with growth hormones. The cells now begin to differentiate into cells of the root, stem and leaf. This is called an EMBRYOID. 4. Tiny plants begin to grow from the embryoid. These are now called PLANTLETS. Hence plantlets are defined as tiny plants produced by culturing the callus with growth hormones. ADVANTAGES Provides rapid propagation of identical individuals.

2 Disease free plantlets are usually obtained. This is useful where seeds are dormant. It can be done throughout the year. DISADVANTAGES It is an expensive and tedious process. It is not applicable in remote agricultural areas. HYBRIDIZATION Hybridization is the crossing of two genetically dissimilar plants to produce a new kind which is called a HYBRID. This method incorporates the good characteristics of both parents in the new variety. Cross pollination is a common method that is used to develop a hybrid. Scientists have developed techniques for ensuring cross pollination between two different varieties of plants, so as to get the combined good qualities of the two varieties. STEPS INVOLVED IN HYBRIDIZATION 1. SELECTION OF PLANTS- two parent plants of desired varieties is taken. 2. EMASCULATION- Anthers are removed from the flowers to prevent self pollination. 3. CROSS POLLINATION - pollen grains from the male flowers with desired characters are transferred to the stigma of the female flower. 4. BAGGING - the pollinated flowers are enclosed in bags to ensure that pollination occurs. 5. FORMATION OF HYBRIDS - pollination is followed by fertilization. The seeds thus formed are called hybrid seeds. SOMATIC CELL HYBRIDIZATION 1. In this technique,somatic cells or body cells of two varieties or species are taken and their cell walls are dissolved by a specific enzyme.these cells lacking a cell wall are called protoplasts. 2. The cellular contents of these protoplasts fuse and the resulting fused nucleus is called heterokaryon. 3. The heterokaryons are cultured in a special medium,they regenerate their cell walls and start producing tiny plants called plantlets. ADVANTAGES- Hybrid plants are stronger than the parent plants and give a higher yield and better quality of seeds. They are disease resistant and drought resistant. BIOTECHNOLOGY This is a method of using micro organisms to produce new substances. APPLICATIONS AND USE OF BIOTECHNOLOGY A. Age old practices using natural micro organisms - Cheese and yoghurt are obtained from milk by the action of lactic acid bacteria. Alcoholic beverages such as beer, wine and commercial ethyl alcohol are produced by the fermentation of yeast in the presence of sugars.

3 Vitamins B2and B12 are manufactured from certain micro organisms. Micro organisms are also used to produce different kinds of enzymes. Vinegar is also manufactured with the help of acetic acid bacteria. B. Using Genetically engineered micro organisms- For large scale production of insulin to treat Diabetes. Several antibiotics,vaccines,enzymes and vitamins are produced by this method. Transgenics are plants and animals that carry foreign genes formed by genetic engineering. They are more popularly called genetically modified organisms. Some examples of transgenic plants are- tomatoes with a longer shelf life,corn and soya bean which are tolerant to drought and Bt cotton which is resistant to pests. RECOMBINANT DNA TECHNOLOGY. ALSO CALLED GENETIC ENGINEERING The basic steps involved in Recombinant DNA technology : this is based on a cut and paste method. the DNA segment forming the insulin gene is cut from a healthy human cell this DNA segment is then inserted (pasted) into the plasmid of a bacterial cell.this is called recombinant DNA the R DNA is reintroduced into the bacteria. This genetically engineered bacteria is cultured on a large scale,each bacterium having the new DNA carrying the human gene for producing insulin.

4 BIOLOGY CLASS 1X ARTIFICIAL VEGETATIVE PROPAGATION MICROPROPAGATION This a technique of propagating plants by removing tissues from a parent plant and culturing them in a chemical medium. 5. A sterilized vegetative bud or short apical bud is removed from the desired variety of plant and is used for initiating micro propagation. This is called an EXPLANT. 6. The explant is placed in a medium with nutrients. This enables the rapid multiplication of cells. The unorganized and undifferentiated mass of cells that develop from an explant is called CALLUS. 7. Portions of the callus are removed and placed in containers with growth hormones. The cells now begin to differentiate into cells of the root, stem and leaf. This is called an EMBRYOID. 8. Tiny plants begin to grow from the embryoid. These are now called PLANTLETS. Hence plantlets are defined as tiny plants produced by culturing the callus with growth hormones. ADVANTAGES Provides rapid propagation of identical individuals. Disease free plantlets are usually obtained. This is useful where seeds are dormant. It can be done throughout the year.

5 DISADVANTAGES It is an expensive and tedious process. It is not applicable in remote agricultural areas. HYBRIDIZATION Hybridization is the crossing of two genetically dissimilar plants to produce a new kind which is called a HYBRID. This method incorporates the good characteristics of both parents in the new variety. Cross pollination is a common method that is used to develop a hybrid. Scientists have developed techniques for ensuring cross pollination between two different varieties of plants, so as to get the combined good qualities of the two varieties. STEPS INVOLVED IN HYBRIDIZATION 6. SELECTION OF PLANTS- two parent plants of desired varieties is taken. 7. EMASCULATION- Anthers are removed from the flowers to prevent self pollination. 8. CROSS POLLINATION - pollen grains from the male flowers with desired characters are transferred to the stigma of the female flower. 9. BAGGING - the pollinated flowers are enclosed in bags to ensure that pollination occurs. 10. FORMATION OF HYBRIDS - pollination is followed by fertilization. The seeds thus formed are called hybrid seeds. SOMATIC CELL HYBRIDIZATION 4. In this technique,somatic cells or body cells of two varieties or species are taken and their cell walls are dissolved by a specific enzyme.these cells lacking a cell wall are called protoplasts. 5. The cellular contents of these protoplasts fuse and the resulting fused nucleus is called heterokaryon. 6. The heterokaryons are cultured in a special medium,they regenerate their cell walls and start producing tiny plants called plantlets. ADVANTAGES- Hybrid plants are stronger than the parent plants and give a higher yield and better quality of seeds. They are disease resistant and drought resistant. BIOTECHNOLOGY This is a method of using micro organisms to produce new substances. APPLICATIONS AND USE OF BIOTECHNOLOGY A. Age old practices using natural micro organisms - Cheese and yoghurt are obtained from milk by the action of lactic acid bacteria. Alcoholic beverages such as beer, wine and commercial ethyl alcohol are produced by the fermentation of yeast in the presence of sugars. Vitamins B2and B12 are manufactured from certain micro organisms. Micro organisms are also used to produce different kinds of enzymes. Vinegar is also manufactured with the help of acetic acid bacteria.

6 B. Using Genetically engineered micro organisms- For large scale production of insulin to treat Diabetes. Several antibiotics,vaccines,enzymes and vitamins are produced by this method. Transgenics are plants and animals that carry foreign genes formed by genetic engineering. They are more popularly called genetically modified organisms. Some examples of transgenic plants are- tomatoes with a longer shelf life,corn and soya bean which are tolerant to drought and Bt cotton which is resistant to pests. RECOMBINANT DNA TECHNOLOGY. ALSO CALLED GENETIC ENGINEERING The basic steps involved in Recombinant DNA technology : this is based on a cut and paste method. the DNA segment forming the insulin gene is cut from a healthy human cell this DNA segment is then inserted (pasted) into the plasmid of a bacterial cell.this is called recombinant DNA the R DNA is reintroduced into the bacteria. This genetically engineered bacteria is cultured on a large scale,each bacterium having the new DNA carrying the human gene for producing insulin.

7 WORK SHEET QUESTION 1 Define the following terms: 1. Micropropagation 2. Hybridization 3. Transgenics 4. Biotechnology 5. Plasmid QUESTION 2 Differentiate between the following terms: 1. explant and plantlet 2. callus and embryoid 3. hybridization and hybrid 4. protoplasts and heterokaryon QUESTION 3 Answer the following: 1. Why should bagging be done during hybridization? 2. What do you understand by the term recombinant DNA? 3. Insulin is produced in large quantities by genetic engineering using bacteria. Give one reason why bacteria are used for this purpose. 4. State two advantages and two disadvantages of tissue culture. 5. State two advantages of hybridization. 6. Give 3 examples of age old applications of Biotechnology. 7. Name 3 transgenic plants and their importance. 8. State two applications of biotechnology in the pharmaceutical industry.