Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 10 Improvement in Food Production Textbook Questions and Answers.
CHSE Odisha 12th Class Biology Chapter 10 Question Answer Improvement in Food Production
Improvement in Food Production Class 12 Questions and Answers CHSE Odisha
Very Short Answer Type Questions
Fill in the blanks with correct answers from the choices given in the brackets of each bit
1. Physical removal of anthers is done by …………… process.
(introduction, mutation, hybridisation, emasculation)
Answer:
emasculation
2. The cross between two varieties of same crop is called ………… hybridisation. (intervarietal, intravarietal, intrageneric, intergeneric)
Answer:
intervarietal
3. In the process of breeding, genetic makeup of ……….. the concerned organism may be changed, (mutation, interspecific, selection, intraspecific)
Answer:
mutation
4. The plant part used in tissue culture is called …………… .(cells, zygote, explant, gamete)
Answer:
explant
5. To produce haploid plants ………… culture can be made.
(anther, embryo, endosperm, zygote)
Answer:
anther
6. The autotroph ………… is cultured to obtain single cell protein.
(Saccharomyces, Pseudomonas, Spirulina, Chaetomicem)
Answer:
Spirulina
Multiple choice questions
Question 1.
The cross breed milch breed is
(a) Red Sindhi
(b) Tharparkar
(c) Frieswal
(d) Sahiwal
Answer:
(c) Frieswal
Question 2.
The exotic breed of cattle is
Or Which is an exotic breed of cattle?
(a) Jersey
(b) Sahiwal
(c) Gir
(d) Red Sindhi
Answer:
(a) Jersey
Question 3.
An indigenous breed of cattle is
(a) Red Dane
(b) Jersey
(c) Karan Swiss
(d) Rathi
Answer:
(d) Rathi
Question 4.
Sunandini, a cross breed cattle is produced by crossing.
(a) Brown-Swiss bull with Sahiwal cow
(b) Jersey bull with Red Sindhi cow
(c) Red Dane bull with Sahiwal cow
(d) Holstein-Friesian bull with Rathi cow
Answer:
(a) Brown-Swiss bull with Sahiwal cow
Question 5.
An indigenous milch breed of buffalo is
(a) Haryana
(b) Jaffarabadi
(c) Kankrej
(d) Jamunapuri
Answer:
(b) Jaffarabadi
Question 6.
The indigenous breed of poultry is
(a) Nicobari
(b) Rhode Island Red
(b) Barred Plymouth Rock
(d) New Hampshire .
Answer:
(a) Nicobari
Question 7.
Commercial poultry production is done under
(a) free range system
(b) intensive system
(c) semi-intensive system
(d) folding unit system,
Answer:
(b) intensive system
Question 8.
Which of the following is a disease of cattle
(a) Ranikhet disease
(b) Marek’s disease
(c) bacillary white diarrhoea
(d) All of the above
Answer:
(d) All of the above
Express in one or two word(s)
1. What is the nutrient source not required for obtaining single cell protein from autotrophs ?
Answer:
Carbon source
2. What is called to the amorphous mass of loosely arranged thin-walled parenchymatous cells developed in the process of tissue culture?
Answer:
Callus
3. What is called to the remaining part of plant cells when its wall is mechanically or enzymatically removed?
Answer:
Protoplast
4. What is called to the sum total of all the alleles of gene present in a particular species and its allied wild and cultivated varieties?
Answer:
Gene pool
5. What is the process called, where flower buds are artificially enclosed to avoid undesired pollination?
Answer:
Bagging
6. In which process can genetic makeup of concerned organism changed ?
Answer:
Mutation
7. The preservation of semen at ultra low temperature.
Answer:
Cryopreservation
8. The substance the queen bee is fed with.
Answer:
Royal jelly
9. Development of haploid eggs without fertilisation.
Answer:
Parthenogenesis
10. The important monosaccharide present in honey.
Answer:
Levulose
11. The repeated breeding between closely related individuals.
Answer:
Upgrading
12. Breeding between unrelated individuals.
Answer:
Cross-breeding
Correct the sentences, if required by changing the underlined word only
1. The process of aseptic transfer of explant from nutrient medium to culture vessels is called micropropagation.
Answer:
inoculation
2. When cytoplasms are fused and one of the two nuclei lost in formation of new organism, it is called a hybrid.
Answer:
cybrid
3. For nuclear fusion, PEG is used.
Answer:
protoplast fusion
4. Cross between different genotypes of same variety is called intrageneric hybridisation.
Answer:
intravarietal
5. When pollens from selected male parents are transferred to stigma, it is called natural pollination.
Answer:
cross
Fill in the blanks
1. The cross between two species of a genus is called …………. hybridisation.
Answer:
intrageneric
2. In selection and testing of superior recombinants, F1-generation offsprings are …………… pollinated.
Answer:
self
3. Biofortification is done to enrich crops with micronutrients like minerals and ………. .
Answer:
vitamins
4. Explants sterilised by mercuric chloride or hydrogen peroxide, etc. are known as ………….. sterilisation.
Answer:
surface
5. Through the process of tissue culture, large number of plants raised in a small area and called micropropagation or ……. propagation.
Answer:
clonal
6. Triploids can be raised by ……….. culture.
Answer:
endosperm
7. Milk yielding cattle breeds are known as ………… breeds.
Answer:
milch
8. Foot and mouth disease is a common disease of ………
Answer:
cattle
9. Traditional method of breeding is substituted by artificial ………. .
Answer:
insemination
10. The housing system employed in the commercial poultry farming is known as ……….. farming.
Answer:
intensive system
11. Ranikhet disease is a common disease of …………..
Answer:
poultry
12. Culture of honeybee on a commercial basis is known as ……………
Answer:
apiculture
13. The drones develop from haploid eggs, which are not fertilised. This development is termed as …………….
Answer:
parthenogenesis
14. The deserting of the queen bee is known as ……………… .
Answer:
swarming
15. The characteristic flight of the queen bee during fertilisation is known as …………..
Answer:
nuptial flight
16. The juvenile bees are reared in …………. chamber of the honey comb.
Answer:
brood
17. The worker bees develop from fertilised eggs and hence are diploid ………….. .
Answer:
sterile females
Short Answer Type Questions
Answer the following within 50 words each
Question 1.
Name five indigenous breeds of cattle.
Answer:
Indigenous Milch Breeds of Cattle
The indigenous breeds of cattle are classified into
- Milch breeds These are high milk producers.
- Dual purpose breeds In these breeds, cow yield average quantity of milk, while males are good working bullocks.
- Draught breeds These include poor milkers but superior quality bullocks.
These breeds are the highest milk producing catde. These include Sahiwal, Red Sindhi, Gir, Tharparkar and Rathi.
Question 2.
Name three cross-breeds of cattle.
Answer:
Cross-Breed Strains of Cattle:
Some of the cross-breed cows are as follows
(a) Karan Swiss This breed was developed at National Dairy Research Institute ‘Karnal, by the breeding of Sahiwal cows with Brown Swiss bulls imported from USA.
(b) Karan Fries This breed has got its origin at the National Dairy Research Institute, Karnal by the crossing between Tharparkar and Holstein-Friesian.
(c) Sunandini This breed originated in Kerala by crossing the local non-descript cattle with Jersey, Brown Swiss and Holstein-Friesin breeds.
(d) Frieswal This breed is developed by crossing Holstein-Friesian bulls with Sahiwal cows.
Question 3.
Name three exotic breeds of cattle.
Answer:
Exotic Milch Breeds of Cattle
This breed includes high milk producing cattle breeds of other countries which have been cross breed with indigenous breeds for producing high yielding hybrids which can easily adopt to Indian conditions.
The common exotic breeds which are used in such programme include Holstein-Friesian of Netherlands, Brown-Swiss of Switzerland, Jersey of Europe and America and Red Dane of Denmark.
Img 2
Question 4.
What is cryopreservation?
Answer:
Cryopreservation is the preservation of tissues, embryos gametes, etc., at -196°C (liquid nitrogen), the preserved material is revived through special technique when required. Cryopreservation methods seek to reach low temperatures without causing additional damage caused by the formation of ice during freezing. Traditional cryopreservation has relied on coating the material with cryoprotectants.
Question 5.
Describe organic dairy farming
Answer:
Organic Dairy Farming
Though the milk production has increased by leaps and bounds by the use of synthetic chemicals on cattle and buffaloes, there is a chance of contamination of the harvested milk. It has been found that milk and milk products are contaminated by residue components of harmful chemicals.
Question 6.
What is free-range poultry farming?
Answer:
The term ‘poultry’ means rearing of domesticated fowl (birds) for food (meat) or their eggs, i.e. chicken, ducks, , geese, turkeys and some varieties of pigeons. Poultry farming upto 1960 was considered under free-range condition.
Free-range system In this system, the birds are allowed to move freely to outside. The farmer provides them with food supplements as requird moving outside.
Question 7.
What is intensive housing system in poultry?
Answer:
Intensive system
This system is practiced where there is a need of a large scale production of meat and eggs. The birds do not have access to outside and are kept in a walled house. There are two types of housing system. Cage system is the system, where birds are kept in cages and it also helps in preventing the spread of diseases. In litter system however, birds are kept on a floor covered with rice husk, saw dust, dried leaf, etc.
Question 8.
Describe the protein source in poultry nutrition.
Answer:
These are required for growth and repair of the body tissues. For protein, the feed is supplemented with soyabean meal, groundnut cake, sunflower cake.
The fish meal prepared from the wastes of fish processing industry and meat meal from the wastes of meat processing industry are also used to feed poultry birds. The skimmed milk is highly nutritive for young chicks and should be given in clean vessels. The green foods such as fresh tender grass, garlic lettuce, onions, etc. are important part of the feed.
Fats Only unsaturated fats could be digested by poultry. This requirement is met by providing groundnut, cake, sunflower cake, etc.
Minerals Some minerals are required in large quantity such as calcium, sodium, etc. Minerals such as zinc, iron, copper, are required in lesser quantities and so, are called as trace minerals.
Vitamins fat soluble (A, D, E, K) and water soluble (B,C) all are essential for normal growth of chickens.
Question 9.
Why is inbreeding harmful?
Answer:
Breeding between the animals of the same breed for 4-6 generation is called inbreeding. It increases homozygosity. Thus, inbreeding is necessary to develop pureline. It also helps in accumulation of superior genes and elimination of less desirable genes. But continued inbreeding reduces fertility and even productivity so, it is harmful also.
Question 10.
What is artificial insemination?
Answer:
Artificial Insemination
It is a method in which the semen collected from a superior male parent is injected into the reproductive tract of the selected female parent by the breeder. This results in development of progeny with superior traits like better growth and increased milk production.
The success rate of artificial insemination is fairly low, even then it is carried out because of the following advantages
- The semen collected can be used immediately or stored in frozen form for later use.
- The semen from a desired breed can be easily transported in the frozen form to distant places, where the selected females are present and thus can be used for impregnating the females on a large scale.
- It helps to overcome several problems of normal mating.
Question 11.
What is in vitro fertilisation?
Answer:
In Vitro Fertilisation and Embryo Transfer
In this modern method of animal breeding, eggs of an ovulating livestock animal, e.g. cattle are isolated. Then they are fertilised in- vitro by semen of a bull which possesses desired characters.
This fertilised egg is kept in a suitable medium and is then stimulated to undergo cleavage to a 8-16 called stage embryo which is known as a blastocyst, also in-vitro. This embryo is then finally transferred or implanted into uterus of a surrogate cow and made pseudopregnant.
The cow completes the term and then give birth to calf with the required characters.
Question 12.
What is a transgenic animal?
Answer:
Transgenic Animals:
It involves the transfer of genes intti special cells or embryos. In this method, the unfertilised egg is enucleated by treating with cytochalasin-B and the blastula stage nuclei are obtained from embryo donor. These two are incubated together in’the presence of Polyethylene Glycol (PEG) and transferred into surrogate mother for fusion. The foetus develops into a transgenic animal. Various products like a-antitrypsin, haemoglobin, lacteferrin, iron binding protein, etc., are obtained from transgenic animals. In Japan, gynogenesis is being used to improve fish size.
Question 13.
Describe swarming.
Answer:
Swarming It is the process by which a new honeybee colony is formed when the queen bee leaves the colony with a large group of worker bees.
Swarming is mainly a spring phenomenon, usually within a two or three weeks period depending on the locality but occasional swarms can happen throughout the producing season.
Write notes on with 2/3 valid points
Question 1.
Germplasm collection
Answer:
Collection of Germplasm:
This is the major step acting as the root of any breeding programme. In this step, the pre-existing genetic variability available in purelines, wild varieties, species no longer cultivated and relatives of many crop species are collected and preserved.
Evaluation of their characteristics is a pre-requisite for the effective exploitation of natural genes available in the populations. The entire collection of plants/seeds having all diverse alleles for all genes in a given crop is called germplasm collection. A good germplasm collection is essential for a successful breeding programme.
Question 2.
Emasculation
Answer:
Emasculation
It is the process of removal of stamens of a flower, without affecting the female reproductive organs. Emasculation is usually done in bisexual flowers before the anthers mature and stigma has become receptive. It can be done by various methods, such as, hand emasculation, suction method, hot water emasculation, alcohol treatment, cold treatment and genetic emasculation. Among these methods, hand and suction method are mostly used.
For example, in Triticum (wheat) flowers may be exposed to some chemical like 2,4-dichloro phenoxyacetic acid, maleic hydrozide or a panicle of Sorghum is dipped in lukewarm (50°C) water for 10 minutes, etc. These methods are applied on those cases where the methods of physical nature could not be applied.
Question 3.
Bagging
Answer:
Bagging In this method, the emasculated flower or inflorescence is immediately bagged to avoid . pollination by any foreign pollen. Emasculation bags made up of butter paper, fine cloth or polythene, etc., may be used depending upon the crop.
Question 4.
Artificial pollination
Answer:
Artificial pollination In order to bring about artificial pollination, the collected pollen grains from selected male parents are dusted on the stigma of female plant. The properly labelled flowers are then allowed to cross-pollinate. The crossed flowers are then tagged again.
Question 5.
Breeding for disease resistance
Answer:
Resistance of the host plant is the ability to prevent the pathogen from causing disease and is determined by the genetic constitution of host plant. Crops are required to be disease resistant, as there are a wide range of fungal, bacterial and viral pathogens that affect the yield of cultivated crop species, especially in tropical climates.
Question 6.
Biofortification
Answer:
It is a method of breeding crops with higher levels of vitamins, minerals, healthier fats to improve public health. The objective of breeding for improved nutritional quality is to enhance
(i) Protein, oil content and quality.
(ii) Vitamin content.
(iii) Micronutrients and mineral content
Question 7.
Explant
Answer:
It is the technique of maintaining and growing plant cells, tissues or organs in nutrient media under controlled environmental conditions. The plant part taken out to be grown in a test tube in special nutrient media is called explant.
Explant Selection:
It is the tissue obtained from the plant for the purpose of tissue culture. The most commonly used explant tissues are the meristematic ends of the plants. These include stem tip, auxiliary bud tip and root tip. Meristematic tissues have high rate of cell division. Before the procedure starts, explants are cleaned and surface sterilised with the help of disinfectants and detergents to remove germs.
Question 8.
Tissue culture medium
Answer:
Tissue Culture Techniques and Steps
Plant tissue culture involves producing entire plants from a few plant cells or tissues by growing them in an artificial medium.
1. Explant Selection
2. Sterilisation
3. Preparation of Nutrient or Culture Medium
4. Inoculation
5. Callus Formation and its Culture
6. Organogenesis
7. Somatic Embryogenesis
Question 9.
Totipotency .
Answer:
Totipotency The capacity to generate a whole plant from any cell/ explant is called cellular totipotency in fact, the whole plant can be regenerated from any plant part or cells.
Question 10.
Micropropagation
Answer:
Micropropagation or Clonal Propagation
By the process of plant tissue culture which requires lesser space and lesser time, a large population of plants could be raised. Also since the plants produced are genetically identical, this process is also called as clonal propagation. Examples of plants cutlivated micropropagation include grapes, bamboo, coffee, banana, cardamoms, etc.
Question 11.
Anther culture
Answer:
This technique was developed by Guha and Maheshwari (1946) in Datura innoxia. In this technique, floral buds are opened to remove anthers. These anthers are then cultured for the production of haploid embryoids. The plants produced by haploid culture are sterile. These haploids could be subjected to colchicine treatment in order to double their chromosome number.
Question 12.
Somaclonal variation
Answer:
Somaclonal variation Genetic variation present among plant cells of a culture is called somaclonal variation.
The term somaclonal variation is also used for the genetic variation present in plants regenerated from a single culture.
Question 13.
Synthetic seeds
Answer:
Synthetic Seeds/Artificial Seeds:
Artificial seeds are those seeds in which somatic embryos or plantlets are encapsulated by calcium alginates. This can put a stop to desiccation and they could be used by farmers like normal seeds and are also used for rapid propagation of crop plants.
Question 14.
Secondary metabolites
Answer:
Secondary Metabolites Production:
Cell suspension culture has been employed for commercial production of secondary metabolites like tannin, latex, resin. These cost of secondary metabolites production would be very high if manufactured chemically. So, the plant tissue culture comprising of large scale cell suspension culture has been used.
For example, taxol which is an anticancer drug is obtained from Taxus. The cells of Taxus are cultured which produce a similar chemical which is later chemically modified to taxol. Another example includes Digitalis lantana which is being employed to modify digoxin, to digitoxin, a drug used in cardiac treatment.
Question 15.
Embryo rescue
Answer:
Endosperm Culture:
It is used to produce triploids. Endosperm culture is helpful in producing seedless apple, Citrus which are of better commercial values.
Differentiate between the following
Question 1.
Bagging and Tagging.
Answer:
Differences between bagging and tagging are as follows
| Bagging | Tagging |
| It is the step involved in hybridisation. | It is also a step of hybridisation. |
| Emasculated flowers are immediately covered by paper, plastic or polythene bags. | Bapqed flowers tagged by writing date, time, male and female, parents. |
Question 2.
Chemical pest control and Biological pest control.
Answer:
Differences between chemical pest control and biological pest control are as follows
| Chemical pest control | Biological pest control |
| In this method chemicals are used for pest control. | In this method biological organisms, i.e predator, parasitoids are used for pest control. |
| Various types of chemicals are used, i.e herbicides, insecticides, pesticides, etc. | Various predators, i.e Trichoderma, B. thuringiensis, etc. are used. |
| These are expensive. | These are cost effective methods. |
Question 3.
Callus and Protoplast.
Answer:
Differences between callus and protoplast are as follows
| Callus | Protoplast |
| It is a growing mass of unorganised plant parenchyma cells. | It refers to entire cell excluding cell wall. |
| Explants are supplemented with auxin, cytokinin, etc to initiate callus. | It is used to study membrane biology, protoplast fusion, etc. |
Question 4.
Synthetic seeds and Embryo.
Answer:
Differences between synthetic seeds and embryo are as follows
| Synthetic seeds | Embryo |
| These are encapsulated somatic embryo, shoot buds or aggregates of cell or any tissues which has the ability to form a plant in in vitro. | It is the part of seed, consisting of precursor tissues for the leaves, stem and roots. |
| Hybrid plants can be easily propagated using synthetic seeds. | Embryo culture is used for the culturing of embryo. |
Question 5.
Endosperm culture and Anther culture
Answer:
Differences between endosperm culture and anther culture are as follows
| Endosperm culture | Anther culture |
| Endosperm is used for culturing. | Anther is used for culturing. |
| Triploid plants are formed. | Haploid plants are formed. |
| Used in production of seedless fruits. | It is useful for the improvement of crop plants. |
Question 6.
Hybrid and Cybrid.
Answer:
Differences between hybrid and cybrid are as follows
| Hybrid | Cybrid |
| It is the result of combining the qualities of two organisms of different breeds, varieties, species through hybridisation. | It is a eukaryotic cell produced by the fusion of two protoplast. |
| Hybrids are produced through hybridisation. | These are produced through somatic hybridisation. |
Long Answer Type Questions
Question 1.
Describe the main steps of breeding to develop genetic variability in crop plants.
Answer:
Steps in Plant Breeding:
The major steps in breeding a new genetic variety of a crop are
(i) Collection of Germplasm:
This is the major step acting as the root of any breeding programme. In this step, the pre-existing genetic variability available in purelines, wild varieties, species no longer cultivated and relatives of many crop species are collected and preserved.
Evaluation of their characteristics is a pre-requisite for the effective exploitation of natural genes available in the populations. The entire collection of plants/seeds having all diverse alleles for all genes in a given crop is called germplasm collection. A good germplasm collection is essential for a successful breeding programme.
(ii) Evaluation and Selection of Parents:
It is carried out by evaluating germplasm, to identify plants with desirable combination of characters.
The selected plants are multiplied and hybridised by self-pollination. Purelines are created, whenever desired and possible.
(iii) Cross Hybridisation among Selected Parents
It is possible by cross hybridising the two parents to produce hybrids that genetically combine the desired characters in a single plant. It is known to be a time consuming and tedious process as it involves collection of pollen grains from the desired plants (male parent) and have to be placed on the stigma of the selected flower (female parent) to incorporate desired traits.
It is also not necessary that the hybrids do combine desired characters. The chances of desirable combination is usually only one in few hundred to a thousand crosses carried out.
Some of the objectives of hybridisation are as follows
(a) To produce variations in progeny which are useful. It is achieved by recombination of characters.
(b) To make the use of hybrid vigour which is the superiority of progeny over its parents.
(c) To develop high yielding varieties which are also resistant to diseases.
Depending on the nature of plants involved in the cross, there may be different types of hybridisation such as
(a) Inter-varietal Cross between two varieties of same crop.
(b) Intra-varietal Cross between different genotypes of the same variety.
(c) Intra-generic Cross between two species of a genus.
(d) Inter-generic Cross between two genera.
Techniques of Hybridisation:
The first step in hybridisation is to ensure that pollination can not occur before the intended artificial process. This can be achieved by
(a) Emasculation It is the process of removal of stamens of a flower, without affecting the female reproductive organs. Emasculation is usually done in bisexual flowers before the anthers mature and stigma has become receptive. It can be done by various methods, such as, hand emasculation, suction method, hot water emasculation, alcohol treatment, cold treatment and genetic emasculation. Among these methods, hand and suction method are mostly used. For example, in Triticum (wheat) flowers may be exposed to some chemical like 2,4-dichloro phenoxyacetic acid, maleic hydrozide or a panicle of Sorghum is dipped in lukewarm (50°C) water for 10 minutes, etc. These methods are applied on those cases where the methods of physical nature could not be applied.
(b) Bagging In this method, the emasculated flower or inflorescence is immediately bagged to avoid pollination by any foreign pollen. Emasculation bags made up of butter paper, fine cloth or polythene, etc., may be used depending upon the crop.
(c) Tagging In this process, the emasculated and bagged inflorescence or flowers are tagged and properly labelled.
The labels contain following information
1 Date of emasculation
2 Date of pollination
3 Name of female and male plants. The name of the female parent plant is written first and that of the male parent plant is written later.
(d) Artificial pollination In order to bring about artificial pollination, the collected pollen grains from selected male parents are dusted on the stigma of female plant. The properly labelled flowers are then allowed to cross-pollinate. The crossed flowers are then tagged again.
(e) Selection and testing of superior recombinants:
This step consists of selection of plants among the progeny of the hybrids with desired combination of characters. It yields plants that are superior than both the parents. This is known as hybrid vigour/heterosis. These are self-pollinated for several generations, till they reach a state of uniformity or homozygosity, so that the characters will not segregate in the progeny.
(f) Testing, release and commercialisation of new varieties Evaluation is done for newly selected lines for their yield and other agronomic traits of quality, disease resistance, etc. Selected plants are grown in research fields and their performance is recorded under ideal fertiliser applications, irrigation and other crop management practices.
Testing of hybrid line is done in farmer’s field after evaluation. After testing, the crop is grown at different locations in the country with different agroclimatic zones for atleast three growing seasons. The tested material is evaluated in comparison to the best available local crop cultivar used as reference cultivar. Release of tested material is finally done in bulk after selection and certification.
Examples of Some Improved Varieties
(i) Wheat Kalyan Sona and Sonalika are semi-dwarf, high yielding and resistant to root disease, introduced to wheat growing belt of India.
(ii) Rice Along with the above wheat varieties, rice varieties such as IR – 8 and Taichung and their derivatives Jaya and Ratna varieties were introduced around the same time in India. All these varieties contributed to the quantum jump in food production which is called green revolution.
Question 2.
Describe the techniques of hybridisation.
Answer:
Techniques of Hybridisation:
The first step in hybridisation is to ensure that pollination can not occur before the intended artificial process. This can be achieved by
(a) Emasculation It is the process of removal of stamens of a flower, without affecting the female reproductive organs. Emasculation is usually done in bisexual flowers before the anthers mature and stigma has become receptive. It can be done by various methods, such as, hand emasculation, suction method, hot water emasculation, alcohol treatment, cold treatment and genetic emasculation. Among these methods, hand and suction method are mostly used. For example, in Triticum (wheat) flowers may be exposed to some chemical like 2,4-dichloro phenoxyacetic acid, maleic hydrozide or a panicle of Sorghum is dipped in lukewarm (50°C) water for 10 minutes, etc. These methods are applied on those cases where the methods of physical nature could not be applied.
(b) Bagging In this method, the emasculated flower or inflorescence is immediately bagged to avoid pollination by any foreign pollen. Emasculation bags made up of butter paper, fine cloth or polythene, etc., may be used depending upon the crop.
(c) Tagging In this process, the emasculated and bagged inflorescence or flowers are tagged and properly labelled.
The labels contain following information
1 Date of emasculation
2 Date of pollination
3 Name of female and male plants. The name of the female parent plant is written first and that of the male parent plant is written later.
(d) Artificial pollination In order to bring about artificial pollination, the collected pollen grains from selected male parents are dusted on the stigma of female plant. The properly labelled flowers are then allowed to cross-pollinate. The crossed flowers are then tagged again.
(e) Selection and testing of superior recombinants:
This step consists of selection of plants among the progeny of the hybrids with desired combination of characters. It yields plants that are superior than both the parents. This is known as hybrid vigour/heterosis. These are self-pollinated for several generations, till they reach a state of uniformity or homozygosity, so that the characters will not segregate in the progeny.
(f) Testing, release and commercialisation of new varieties Evaluation is done for newly selected lines for their yield and other agronomic traits of quality, disease resistance, etc. Selected plants are grown in research fields and their performance is recorded under ideal fertiliser applications, irrigation and other crop management practices.
Testing of hybrid line is done in farmer’s field after evaluation. After testing, the crop is grown at different locations in the country with different agroclimatic zones for atleast three growing seasons. The tested material is evaluated in comparison to the best available local crop cultivar used as reference cultivar. Release of tested material is finally done in bulk after selection and certification.
Question 3.
Give an account of techniques and steps of plant tissue culture.
Answer:
Tissue Culture:
It is the technique of maintaining and growing plant cells, tissues or organs in nutrient media under controlled environmental conditions. The plant part taken out to be grown in a test tube in special nutrient media is called explant.
The capacity of producing a whole plant from this explant is called totipotency.
It was Gottilieb Haberlandt (1902) who discovered totipotency. Haberlandt also attempted to cultivate plant leaf cells for the first time in simple nutrient medium. Plant tissue culture technique is a major tool in various areas of crop improvement, experimental biology and fundamental or applied research.
Tissue Culture Techniques and Steps:
Plant tissue culture involves producing entire plants from a few plant cells or tissues by growing them in an artificial medium.
1. Explant Selection
It is the tissue obtained from the plant for the purpose of tissue culture. The most commonly used explant tissues are the meristematic ends of the plants. These include stem tip, auxiliary bud tip and root tip. Meristematic tissues have high rate of cell division. Before the procedure starts, explants are cleaned and surface sterilised with the help of disinfectants and detergents to remove germs.
2. Sterilisation
For plant tissue culture, it is essential that the explants, culture vessel, media and instruments, etc. are free from microbes. For this purpose, explants are treated with specific antimicrobial chemicals like mercury chloride, hydrogen peroxide, etc.
This procedure is called surface sterilisation. The vessels, media and instruments, are suitably treated with steam (in autoclave), dry heat or alcohol or subjected to filtration to make them free from microbes. This is complete sterilisation.
3. Preparation of Nutrient or Culture Medium
The medium on which explants are cultured is known nutrient medium or culture medium or simply medium. The culture media may be solid or liquid. The optimum pFl of the media should be 5.7.
The basic components of culture media are
(i) Inorgnic nutrients These include salts, providing all essential macro and microelements. Macronutrients include salts of calcium, magnesium, nitrogen, phosphorus and potassium. Micronutrients include iron, chloride, copper, zinc, boron and molybdenum.
(ii) Source of carbon These are the sources of energy in the form of sucrose, glucose, fructose or carbohydrates, amino acids, etc.
(iii) Growth hormones and vitamins Auxin (2, 4 -D) and cytokinins (benzyl amino purine), vitamins (Pyridoxine HCL) are commonly used in tissue culture. A media without growth hormones is known as base media. High auxins result in root formation while high cytokinins may yield shoots. After the preparation of medium, agar-agar is added in order to obtain a solid medium. In some cases liquid medium is required, for example in root culture where no agar-agar is added.
4. Inoculation
The process of transfer of explant to suitable nutrient medium contained in culture vessels is called inoculation. It is done under sterile conditions, achieved in an inoculation chamber or under laminar air flow. After the process, temperature and light of vessels is kept at controlled range. The temperature ranges between 18-25°C.
5. Callus Formation and its Culture
In callus culture, cell division in the explant forms a callus. It is an amorphous mass of’loosely arranged thin-walled parenchymatous cells developing frome proliferating cells of the parent tissue (Dodos and Roberts; 1985). This is usually maintained on a medium gelled with agar. If nutrient medium contains auxins cell division occurs and the upper surface of explant gets covered by callus. This callus later develops into normal roots, shoots and finally lead to the formation of plant. The development of callus occurs through three stages, i. e. induction, cell division and differentiation.
The callus formation is affected by the composition of medium, the source from which explant has been taken and the surrounding environmental factors. The first stage (induction) involves stimulation of metabolic rate of cells. With the increase in the metabolic rate, these cells enter the cell division stage. Finally in differentiation stage, the cells produce secondary products by the expression of certain metabolic pathways. It is necessary to subculture the callus in fresh media when the callus is being grbwn for a long time on the nutrient media.
6. Organogenesis
It involves the formation of plant organs, i.e. roots and shoots directly from cultured tissues. Organogenesis begins from the stimulation provided by the chemicals of medium, endogenous compounds produced by the culture and substances that have been carried over from the original explants. The process of formation of roots is known as rhizogenesis while that of shoots is caulogenesis. Organogenesis is highly controlled by the ‘ melatin concentrations of auxin and cytokinin in medium.
It was Skoog and Miller (1957) who demonstrated that a high concentration of auxin promotes rhizogenesis while high concentration of cytokinin promotes caulogenesis.
7. Somatic Embryogenesis
A Somatic Embryo (SE) is an embryo derived from a somatic cell, other than zygote. SEs are obtained usually on culture of the somatic cells in vitro. So, this process is called somatic embryogenesis. The embryo formed is known as embryoids. SEs are bipolar structures, i.e. they have a radicle and a plumule.
It is induced by a relatively high concentration of an auxin, like 2, 4-D. There are two different media for the formation of embryoids. The first medium comprises of auxin that initiates embryogenic cells.
The second medium either lacks or has decreased level of auxins. For the further development of embryonic cells into embryoids and plantlets the embryogenic cells undergo three developmental stages such as globular, heart-shaped and torpedo stage. Examples of plants undergoing embryogenesis in vitro include Nicotiana tabaccum, Loffea arabica, Atropa belladona, Brassica oleracea, etc.
The method used for tissue culture is as given below
Major Methodology of plant Tissue Culture
Events of somatic embryogenesis
Question 4.
Elaborate the application of plant tissue culture.
Answer:
Applications of Plant Tissue Culture
(i) Micropropagation or Clonal Propagation:
By the process of plant tissue culture which requires lesser space and lesser time, a large population of plants could be raised. Also since the plants produced are genetically identical, this process is also called as clonal propagation. Examples of plants cutlivated micropropagation include grapes, bamboo, coffee, banana, cardamoms, etc.
(ii) Production of Virus-Free Plants:
Crop plants that reproduce asexually are susceptible to viral infections which advances through the vegetative organs for propagation like stem, tuber, rhizome, etc. The cambium culture in some plants produces virus-free plants.
(iii) Synthetic Seeds/Artificial Seeds:
Artificial seeds are those seeds in which somatic embryos or plantlets are encapsulated by calcium alginates. This can put a stop to desiccation and they could be used by farmers like normal seeds and are also used for rapid propagation of crop plants.
(iv) Embryo Rescue:
It is a technique in which immature embryos are dissected out from the fruit (seeds). They are then grown in nutrient medium which lead to the formation of plantlets. Embryo rescue technique is done in conditions where the embryo does not develop after initial divisions though the pollination and fertilisation had been successfully completed.
This technique is being used to improve chick-pea, groundnut, etc. at International Crop Research Institute for Semi Arid Tropics (ICRISAT), Hyderabad.
(v) Endosperm Culture:
It is used to produce triploids. Endosperm culture is helpful in producing seedless apple, Citrus which are of better commercial values.
(vi) Secondary Metabolites Production:
Cell suspension culture has been employed for commercial production of secondary metabolites like tannin, latex, resin. These cost of secondary metabolites production would be very high if manufactured chemically. So, the plant tissue culture comprising of large scale cell suspension culture has been used.
For example, taxol which is an anticancer drug is obtained from Taxus. The cells of Taxus are cultured which produce a similar chemical which is later chemically modified to taxol. Another example includes Digitalis lantana which is being employed to modify digoxin, to digitoxin, a drug used in cardiac treatment.