Asexual Reproduction in Plants
Short Questions and Answers
One mark questions with answers
1. The form of vegetative reproduction of plants where seeds are formed without fusion of gametes is called
Answer: (a) agamospermy
2. Development of embryos directly from the cells of nucellus is known as
Answer: (c) polyembryony
3. Which one of the following may not be a modification of stem?
Answer: (d) bulbils
4. A method in which roots are induced on the stem while it is still attached to the parent plant is called
Answer: (b) layering
5. If the plants fail to develop viable seeds, these could best be grown by
(b) sexual methods
Answer: (d) micropropagation
6. A genetically uniform population of plants raised from a single plant constitutes
Answer: (b) clone
7. Plants identical to mother plant can be obtained from
(a) its seeds
(b) its fruits
(c) stem cuttings
Answer: (c) stem cuttings
8. Micropropagation is carried out by
(b) genetic recombination
(d) tissue culture
Answer: (d) tissue culture
9. One of the quick methods of obtaining large number of genetically identical plants is through
Answer: (c) micropropagation
10. Stem cuttings are commonly used for propagation in
Answer: (d) sugarcane
11. Banana plant develop from
Answer: (a) rhizome
12. Vegetative growth of potato is by
Answer: (d) tuber
Two marks questions with answers
1. What is asexual reproduction?
Answer: Asexual reproduction is the mode of formation of new individuals from the parts of the parent without the meiotic formation of gametes and their fusion. The method of reproduction which do not involve meiosis and fertilization are known as apomixis or asexual reproduction.
2. Differentiate between apogamy and apospory.
Answer: It also includes processes like apospory and apogamy. Apogamy is the formation of sporophyte directly from a gametophyte without involving the formation and fusion of gametes whereas apospory is the formation of gametophyte directly from sporophyte without meiotic formation of spores.
3. What do you mean by air layering? Give examples.
Answer: In this method, part of the stem is girdled (a ring of bark is removed). This part is covered with moist moss or cotton and enclosed in a polythene bag to prevent dessication. The root appears after sometime and at that stage, the branch is cut and planted. It grows into a new individual. Litchi, pomegranate, guava, orange, lemon etc are propagated by air layering method.
4. What do you mean by mound layering? Give examples.
Answer: Mound layering: In this method, the plant is pruned to stimulate the growth of new shoots, close to the ground. After several new branches have been produced, the base of the plant is covered with soil. The branch tip is kept outside the soil. Within few days, new shoots develop roots. These are separated from the parent and are planted. Grooseberry, apple, currant etc. are propagated by this method.
5. What is the difference between bulb and corm? Give examples.
Answer: Bulb is a modified shoot that has a very short stem and possesses apical and axillary buds. Some of these buds grow to form shoots, example, onion, tulip etc.
Corms such as that of saffron, Colocasia, gladiolus etc are the enlarged bases of herbaceous stems. They differ from bulbs in being solid rather than composed of scales.
6. How does root help in vegetative propagation?
Answer: The roots help in vegetative propagation. Some common examples of root tubers are sweet potato (Ipomoea batatas), Asparagaus, Dahlia etc. These roots develop adventitious buds, each of which forms plant. When placed in soil the buds present on the roots grow into leafy shoots called slips. Slips are separated and planted to form new plants. The roots of some woody plants produce shoots which grow into new plant. For example, Murraya, Albizzia, Dalbergia Sisso etc.
Three marks questions with answers
1. What is micropropagation?
Answer: Micropropagation is the propagation of plants by using plant cells, tissues and organs. Various plant parts used in micropropagation are known as explants and the technique of growing explants in artificial medium is known as tissue culture.
In micropropagation small pieces of plant organs or tissues are grown in container with suitable nutrient medium under sterilized and controlled conditions. The tissue grows into a mass of undifferentiated cells called callus, the callus later differentiates into plantlets which are separated and grown into full size normal plants in the nurseries or in the fields.
2. What do you understand by agamospermy?
It is a form of vegetative reproduction by plants in which seeds are formed but without fusion of gametes. It also includes processes like apospory and apogamy. In agamospermy, the seeds possess an embryo developed not from a diploid zygote but by an abnormally formed diploid egg. In such cases, not only the egg but the entire embryo sac is diploid because it develops without meiosis either from a megaspore mother cell or any cell of the nucellus. The diploid egg of an embryo sac, thus formed, directly develops into an embryo without fusion with the male gamete. The process of development of egg into an embryo without fertilization is called parthenogenesis. Besides this, embryos are also produced directly from the cells of the nucellus. This is called adventive polyembryony. It results in the formation of many embryos in each seed. The example is Citrus seed which contains 2 to 40 embryos.
3. Define vegetative propagation. Mention one advantage of vegetative propagation.
Vegetative propagation can be defined as regeneration or formation of new individual from any vegetative part of the plant body. The methods of vegetative propagation involve separation of a part of plant body which develops into a new plant.
It is the best known method of multiplication in seedless varieties and species. Plants like banana, grapes, pineapple, roses, gladioli, chrysanthemums, seedless orange, seedless grapes do not form viable seeds.
4. What are the demerits of vegetative propagation?
Answer: (1). Vegetative organs required for propagation cannot be preserved for long.
(2). Vegetative propagules are not so efficiently protected as the seeds are. They get easily decayed and are prone to various viral, fungal and bacterial diseases.
(3). Infected parents transfer disease to the daughters.
(4). Variability is absent. So adaptability to the changed environment decreases.
(5). The plants may show degeneration due to absence of variation.
(6). There is no mechanism for dispersal. Vegetative multiplication causes overcrowding and hence, severe competition which can damage most of the plants.
(7).Good qualities cannot be introduced nor bad characters eliminated in plants multiplied through vegetative propagation.
5. What is grafting?
Answer: It is the technique of joining parts of two plants so as to form a composite plant. A new variety is produced by joining parts of two different plants. The rooted shoot of one plant called stock is joined with the piece of another plant known as scion. The grafting ends of both, stock and scion, are cut obliquely and then placed over one and another in such a way that the cambia of two come in close contact. The two pieces are firmly held together by tape, rubber tubing, etc. This results in division of cambia and formation of a new vascular tissue. This method has been practised for many economically useful plants such as rose, mango, apple, pear, guava, citrus, rubber etc.