NIOS Class 12 Biology Chapter 19 Reproduction in Plants

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NIOS Class 12 Biology Chapter 19 Reproduction in Plants

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Reproduction in Plants

Chapter: 19

MODULE – III: REPRODUCTION AND HEREDITY

NIOS TEXTBOOK QUESTIONS ANSWERS

INTEXT QUESTIONS 19.1

1. Define reproduction.

Ans: Process by which living organisms produced their offsprings for the continuity of the species is called reproduction.

2. How is asexual reproduction different from sexual reproduction?

Ans: Offsprings reproduce from a vegetative unit produces by a parent without fusion of gamete. In case of sexual reproduction fusion of male and female reproductive cells from male and female reproductive organs.

3. What is a gamete?

Ans: Male and female reproductive cells are called gametes.

4. Name two types of asexual reproduction.

Ans: (i) Fission.

(ii) budding.

5. Choose the correct option: Apomixis is:

(a) Development of plants in darkness.

(b) Development of plants without fusion of gametes.

(c) Inability to perceive stimulus for flowering. 

(d) Effect of Low Temperature on Plant Growth. 

Ans: (b) Development of plants without fusion of gametes.

INTEXT QUESTIONS 19.2

1. Define the term isogamy. Which species of Chalmydomonas exhibit it?

Ans: Male and female gametes are identical in structure, their fusion is called isogamy. C.engametos.

2. What does meiosis occur in Chlamydomonas?

Ans: Zygote.

3. Give the method of asexual reproduction in Chlamydomonas. What is the function of zoospores in Chlamydomonas?

Ans: Asexual reproduction zoospore grows into an adult cell. 

4. Name the species of Chlamydomonas that reproduces by Anisogamy and the species that reproduce by Oogamy.

Ans: Anisogamy: Chlamydomonas braunii. Oogamy: C. Coccifera.

5. Define the term Zoospore and Aplanospore.

Ans: Zoospore: It refers to “a flagellate but thin walled asexual reproductive unit in plants”

Aplanospore: When a Zoospore loses its flagella and then becomes non-motile, this defined as an aplanospore.

INTEXT QUESTIONS 19.3

1. Vegetative reproduction in Spirogyra takes place by means of.

Ans: Fragmentation.

2. Name the kind of sexual reproduction that occurs in Spirogyra.

Ans: Scalariform Conjugation.

3. When does meiosis occur in Spirogyra?

Ans: Diploid nucleus in zygote on return of the favourable circumstances.

4. How many filaments are involved in lateral conjugation?

Ans: Only one filament is involved in lateral conjugation.

INTEXT QUESTIONS 19.4

1. Define the terms:

(i) Annual.

Ans: Annuals: The plants that produce flowers and seeds within one season.

(ii) Biennial.

Ans: Biennials: The plants that complete their life-cycle in two seasons. In first year, they are in vegetative state and in second year reproductive state.

(iii) Perennial.

Ans: Perennials: The plants that live for several years. For first few years, they are vegetative state and later in reproductive state. in influence

2. List the factors which influence flowering.

Ans: Temperature, light-day length.

3. Give one example where application of hormone can reverse the sex of a flower. 

Ans: Cannabis or Cucumis.

4. Name the essential whorls in a flower.

Ans: Stamens and the carpels

INTEXT QUESTIONS 19.5

1. What is the innermost wall layer of microsporangium called? 

Ans: Tapetum.

2. Name the organ where pollen grains are formed.

Ans: Pollen sac.

3. Name the two layers of pollen grain. 

Ans: (i) Exine. and 

(ii) Intine.

4. Name two parts of a mature ovule. 

Ans: (i) Nucellus. and 

(ii) Integuments.

INTEXT QUESTIONS 19.6

1. What is pollination?

Ans: Pollination is “the transfer of pollen grains from the anther to stigma of a flower.” 

2. Mention suitable terms for the following:

(i) Flowers do not open and gets self pollinated.

 Ans: Cleistogamy.

(ii) Male and female reproductive organs mature at different times.

Ans: Dichogamy. 

3. Give two features of insect pollinated flowers.

Ans: (a) Some flowers secret nector.

(b) The flowers are showy, colored as well as large in size. 

INTEXT QUESTIONS 19.7

1. Which part of the ovule forms the seed coat?

Ans: Integuments.

2. Define a seed. 

Ans: Ripened or mature ovule.

 3. Give one example of a dicot seed and one of a monocot seed.

Ans: (a) Pea/Gram.

(b) Maize grain. 

4. Define a fruit.

Ans: It is a “mature ovary”.

5. List the parts of a mature seed.

Ans: (a) Seed coat.

(b) Embyo.

(c) Cotyledon.

(d) Endosperm.

6. Development of an embryo from a cell of embryo sac other than egg an example of _________.

Ans: Adventive Polyonbryony.

7. Formation of more than one embryo from a single zygote is called ________.

INTEXT QUESTIONS 19.8

1. Define vegetative reproduction.

Ans: It is “the process of multiplication in which a portion of the plant body becomes detached and develops into new plants.”

2. Give an example of each of the following:

(a) rhizome.

(b) tuber.

(c) bulb.

(d) runner.

(e) sucker.

Ans: (a) Ginger, (b) Potato, (c) Onion, (d) Lawn grass, (e) Mint.

3. Give an example of vegetative reproduction which is carried out by leaves. 

Ans: Bryophyllum.

4. Name two ways by which vegetative reproduction occurs in plants. 

Ans: (i) Bulbs.

(ii) Rhizomes.

INTEXT QUESTIONS 19.9

1. What are the various methods which man uses for propagating plants artificially?

Ans: (a) Cutting.

(b) Grafting.

(c) Layering. 

2. Name at least four specialised plant parts which help in vegetative, propagation.

Ans: (a) Runner.

(b) Tuber.

(c) Bulb.

(d) Sucker. 

3. Write one advantage of vegetative reproduction?

Ans: Desirable varieties of ornamental plants and fruit trees can be multiplied easily.

INTEXT QUESTIONS 19.10

1. Give two examples each of plants which are propagated by the following methods:

(a) Cutting: (i) _________ (ii) _________.

Ans: (i) Croton.

(ii) Money plant.

(b) Layering: (i) _________ (ii) _________.

Ans: (i) Jasmin.

(ii) Grapevine.

(c) Grafting: (i) _________ (ii) _________.

Ans:(i) Rose.

(ii) Mango.

2. Name the artificial means of vegetative propagation commonly used in the laboratory.

Ans: Micropropagation technique.

3. Give two examples of plants which are propagated by micropropagation technique.

Ans: (a) Asparagus.

(b) Chrysanthemum.

TERMINAL EXERCISES

1. Explain the term isogamy taking Chlamydomonas as an example. 

Ans: Isogamy with reference to Chlamydomonas. During isogamy two similar gametes unites. The cell of Chlamydomonas has flagella. It loses it and becomes non-motile. Division of the protoplasm occurs mitotically repeatedly and thirty-two daughter cells are formed. Each develops flagella and forms a gamete. Biflagellate gametes are all similar. They are known as isogametes. They liberate by the rupture of gametanial wall. Then two gametes unite each other in water. Zygote is formed after the fusion of the gametes. A thick wall is developed around it. It becomes a zygospore.

During favourable circumstances zygote nucleus undergoes meiosis division to form four haploid zoomeisopores.

2. Describe scalariform conjugation in Spirogyra.

Ans: Scalariform Conjugation in Spirogyra: Two filaments of Spirogyra lie close to each other. Cells of the two develop contacts with each other by a conjugation tube.

contents of each cell of a filament round off and form the gametes in each cell. They enter into the other filament known as female filament. The contents of the two filament fuse to each other inside the female filament and zygote is produced. The cell of males are now empty. Zygote becomes zygospore by producing a cell wall around it. Nucleus of zygospore undergoes meiosis division to produce four haploid nuclei. Thereafter, these disintegrate. The thick wall breaks out as germ tube and a filament is developed after repeated division

Fig. 19.10. Scalariform Conjugation in Spirogyra. (A) Contents of one cell (Male gamete migrate of the other through the tube and fuse to form the zygote. (B) Zygote thick wall and form a Zygospore (c) The Zygospore germinates.

Fig. 19.11. Stages in the Germination of Zygospore in Spirogyra, ABC, Zygotic meiosis; (D) Development of a germ tube and a new filament.

3. Differentiate between annuals, biennials and perennial plants.

Ans: Difference Between Annuals, Biennials and Perennials.

Annuals	Biennials	Perennials
1. The plants which complete their life-cycle in one season are called annuals.	The plants which complete their life-cycle in two seas-ion are called biennial.	The plants which produces flowers year after year, if they starts flower-ing.
2. Example: Maize rose and sun- flower, etc.	Example: Radish, cabbage and carrot, etc.	Example: Neem, mango and jamun, etc.

4. Give significance of pollination.

Ans: Significance of Pollination:

(i) It is essential for fertilisation. It is essential for the formation of viable seeds.

(ii) Now varieties may be produced. Pollination initiates the level of hormones in the ovary and help in fruit ripening.

5. Draw a labelled sketch of a mature ovule.

Ans:

Fig. 19.12. L.S. of an Angiospermic mature ovule.

6. Give a labelled diagram of a mature pollen grain.

Ans: See Fig. 18.13:

Fig. 19.13. Mature Pollen Grain.

7. Mention the important characteristies of:

(i) Anemophilous. and 

(ii) Hydrophilous plants.

Ans: Important characteristics of:

(i) Anemophilous Plants:

(a) Pollen grains are formed in large number. Stigma is usually large feather and protruding feathers.

(b) Pollens may be winged.

(c) The stigma is large and feathery.

(d) Pollen grains are light, smooth and dry. e.g., maize, bamboo.

(ii) Hydrophilus Plants:

(a) Pollen grains are produced in large quantity. 

(b) They float on water until they meet female flowers. 

(c) Examples are Vallisneria and Hydrilla.

8. Give the significance of fertilisation.

Ans: Significance of Fertilisation:

(i) It is essential for formation of viable seeds.

(ii) It gives stimulus for ripening of ovary and formation of fruit. Fertilisation helps in recombination of characters because genes of two different indivi- duals unite in zygote.

9. Mention the changes that take place when the fruit ripens.

Ans: Changes that take place when the fruit ripens are following:

1. The starch is transformed into the sugar (chemical changes in stored food).

2. The break down of chlorophyll leads to some changes in colour of the covering of the fruit.

3. Production of various organic sub-stances gives taste and flavour

10. Define the following terms: 

(a) Corm.

Ans: Corm: It is rounded, oval, fleshy, underground, atem, having an apical bud out its one end which develops into aerial shoot. Scale leaves are found on the surface of the com eg. Colocasia, Amorphophallus. It is called gimikand or elephant foot yam.

Fig. 19.14. Corm of Amorphophallus.

(b) Scion.

Ans: Scion: Small stem branch of a desired plant is inserted in a stem or stalk of old plant but this is not sufficient plant. New shoot developed is of scion type.

(c) Callus.

Ans: Callus: In micropropagation, small piece of a plant/ a tissue/ a cell is isolated and transferred into aseptic nutrient medium. This develops and grows into an unorganised mass known as callus.

(d) Micropropagation.

Ans: Micropropagation: It is a technique to induce artificial vegetative propagation in plants. A single cell or a small part of a plant is isolated and transferred into a container having nutrient medium.

(e) Vegetative reproduction.

Ans: Vegetative Reproduction: New individual is produced from parts of plants (somatic cells) other than flowers and seeds. In many aquatic and terrestrial species of angiospermic plants structures like runners, suckers, tubers, offsets and rhizomes are capable of giving rise to new offsprings. This method of asexual reproduction is mostly called as vegetative propagation.

11. In what ways do plants reproduce vegetatively without human assistance?

Ans: Plants reproduce vegetatively by stems, roots and leaves, etc., without human assistance.

(i) By Leaves: Leaves of Bryophyllum produce adventitious buds on the margins. They help in multiplication of the plant.

Fig. 19.15. Leaf of Bryophyllum.

(ii) By Bulbils: Floral buds of Asparagus grow into full plants.

(iii) By stems: Runner, sucker, corm, rhizome, tuber are the plant parts which produce whole plants.

12. In what ways do plants reproduce vegetatively with human assistance?

Ans: Plants reproduce vegetatively with human assistance by the following methods:

(i) Micropropagation: The tissue culture is an artificial method for propagation of plants. Part of tissue of the plant developed into asep-tate nutrient medium.

(ii) Grafting: The old plant is cut above the ground level. A small piece of the desired plant is surgically inserted into the stock plant. The scion sprouts after sometime. Example: Rose, pear, etc.

(iii) Layering It is applied on a tender branch of a plant. Its bark is removed and lowered. It is kept in the soil by covering it. When roots develop it is cut from the parent plant and then planted other place. It forms a new plant.

Fig. 19.16. Aerial Layering.

(iv) Cutting: It is other method of propagation. The stem is cut into pieces having internodes and nodes. Roots and branches develop from the nodes. Example: Rose, Croton, gurhal, etc.

Fig. 19.17. Cutting.

13. Define and give an example of each of the following: