Unit VI Reproduction in flowering Plants (TNSCERT CLASS 12)

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Question 1.

Choose the correct statement from the following

(a) Gametes are involved in asexual reproduction

(b) Bacteria reproduce asexually by budding

(c) Conidia formation is a method of sexual reproduction

(d) Yeast reproduce by budding

Answer: (d) Yeast reproduce by budding

Question 2.

An eminent Indian embryologist is ____________

(a) S.R. Kashyap

(b) P. Maheswari

(c) M.S. Swaminathan

(d) K.C. Mehta

Answer: (b) P. Maheswari

Question 3.

Identity the correctly matched pair ____________

(a) Tuber – Allium cepa

(b) Sucker – Pistia

(c) Rhizome – Musa

(d) Stolon – Zingiber

Answer: (c) Rhizome – Musa

Question 4.

Pollen tube was discovered by ____________

(a) J.G. Kolreuter

(b) G.B. Amici

(c) E. Strasburger

(d) E. Hanning

Answer: (b) G.B. Amici

Question 5.

Size of pollen grain in Myosotis ____________

(a) 10 micrometer (b) 20 micrometer

(c) 200 micrometer (d) 2000 micrometer

Answer: (a) 10 micrometer

Question 6.

First cell of male gametophyte in angiosperm is ____________

(a) Microspore (b) Megaspore

(c) Nucleus (d) Primary Endosperm Nucleus

Answer: (a) Microspore

Question 7.

Match the following ____________

(I) External fertilization – (i) pollen grain

(II) Androecium – (ii) anther wall

(III) Male gametophyte – (iii) algae

(IV) Primary parietal layer – (iv) stamens

(a) I-(iv); II-(i); III-(ii); IV-(iii)

(b) I-(iii); II-(iv); III-(ii); IV-(i)

(c) l-(iii); II-(iv); III-(ii); IV-(i)

(d) I-(iii); II-(i); III-(iv); IV-(ii)

Answer: (b) I-(iii); II-(iv); III-(ii); IV-(i)

Question 8.

Arrange the layers of anther wall from locus to periphery

(a) Epidermis,middle layers, tapetum, endothecium

(b) Tapetum, middle layers, epidermis, endothecium

(c) Endothecium, epidermis, middle layers, tapetum

(d) Tapetum, middle layers endothecium epidermis

Answer: (d) Tapetum, middle layers endothecium epidermis

Question 9.

Identify the incorrect pair

(a) sporopollenin – exine of pollen grain

(b) tapetum – nutritive tissue for developing microspores

(c) Nucellus – nutritive tissue for developing embryo

(d) obturator – directs the pollen tube into micropyle

Answer: (c) Nucellus – nutritive tissue for developing embryo

Question 10.

Assertion : Sporopollenin preserves pollen in fossil deposits

Reason : Sporopollenin is resistant to physical and biological decomposition

(a) assertion is true; reason is false

(b) assertion is false; reason is true

(c) Both Assertion and reason are not true

(d) Both Assertion and reason are true.

Answer: (d) Both Assertion and reason are true.

Question 11.

Choose the correct statement(s) about tenuinucellate ovule

(a) Sporogenous cell is hypodermal

(b) Ovules have fairly large nucellus

(c) sporogenous cell is epidermal

(d) ovules have single layer of nucellus tissue

Answer: (a) Sporogenous cell is hypodermal

Question 12.

Which of the following represent megagametophyte ____________

(a) Ovule

(b) Embryo sac

(c) Nucellus

(d) Endosperm

Answer: (b) Embryo sac

Question 13.

In Haplopappus gracilis, number of chromosomes in cells of nucellus is 4.

What will be the chromosome number in Primary endosperm cell?

(a) 8

(b) 12

(c) 6

(d) 2

Answer: (b) 12

Question 14.

Transmitting tissue is found in

(a) Micropylar region of ovule

(b) Pollen tube wall

(c) Stylar region of gynoecium

(d) Integument

Answer: (c) Stylar region of gynoecium

Question 15.

The scar left by funiculus in the seed is ____________

(a) tegmen

(b) radicle

(c) epicotyl

(d) hilum

Answer: (d) hilum

Question 16.

A Plant called X possesses small flower with reduced perianth and versatile

anther. The probable agent for pollination would be ____________

(a) water

(b) air

(c) butterflies

(d) beetles

Answer: (b) air

Question 17.

Consider the following statement(s)

1. In Protandrous flowers pistil matures earlier

2. In Protogynous flowers pistil matures earlier

3. Herkogamy is noticed in unisexual flowers

4. Distyly is present in Primula

(a) i and ii are correct

(b) ii and iv are correct

(c) ii and Hi are correct

(d) i and iv are correct

Answer: (b) ii and iv are correct

Question 18.

Coelorhiza is found in ____________

(a) Paddy

(b) Bean

(c) Pea

(d) Tridax

Answer: (a) Paddy

Question 19.

Parthenocarpic fruits lack ____________

(a) Endocarp (b) Epicarp

(c) Mesocarp (d) seed

Answer: (d) seed

Question 20.

In majority of plants pollen is liberated at ____________

(a) 1 celled stage (b) 2 celled stage

(c) 3 celled stage (d) 4 celled stage

Answer: (b) 2 celled stage

Question 21. What is reproduction?

Answer:

Reproduction is the biological process of producing young ones of their own

kind. It is a vital process for the existence of a species and it also brings

suitable changes through variation in tlie offsprings for their survival on earth.

Question 22. Mention the contribution of Hofmeister towards Embryology.

Answer:

Hofmeister described the structure of pollen tetrad

Question 23. List out two sub-aerial stem modifications with example.

Answer:

1. Stolon – E.g.: Fragaria

2. Sucker – E.g.: Chrysanthemum

Question 24. What is layering?Answer:

Answer:

Layering is a conventional propagation method, where the stem of a parent

plant is allowed to develop roots while still intact. When the root develops, the

rooted part is cut and planted to grow as a raw individual. E.g.: Jasminum.

Question 25. What are clones?

Answer:

Individuals developed by asexual reproduction are morphologically and

genetically identical. Such individuals are called as clones.

Question 26. A detached leaf of Bryophyllum produces new plants. How?

Answer:

In Bryophyllum, the leaf is succulent and notched on its margin. Adventious

buds develop at these notches and are called epiphyllous buds. They develop

into new plants forming a root system and become independent plants when

the leaf gets decayed.

Question 27. Differentiate Grafting and Layering.

Answer:

Grafting:

1. In grafting, two different plants (stock & scion) are used to develop new

plant.

2. The new plant will support to possess the characters of both the parents

or new variation can be noticed.

Layering:

1. In layering, only one plant is used to develop new plant.

2. Variation cannot be expected. The new individual is exactly similar to

parent plant.

Question 28. Tissue culture is the best method for propagating rare and endangered plant species”- Discuss.

Answer:

Micropropagation of plants invitro through tissue culturing is a modem andalternative tool to conserve and safeguard rare plant species. Since the basic

principle behind PTC is totipotency. With the help of a single explant it is

possible to generate a huge population of plantlets within a short span of time.

Conservation through micropropagation offers the possibility to rescue

endangered and endemic species.

Question 29. Distinguish mound layering and air layering

Answer:

Mound Layering:

In mound layering, lower flexible branch with leaves is bent to ground and a

part of the stem is buried in the soil and the tip of branch is exposed above the

soil. After the roots emerge from the buried stem, a cut is made in parent plant

so that the buried plant grows into a new plant.

Air Layering:

In air layering, the stem is girdled at nodal part and hormones are applied and

covered with moist soil using polythene sheet. Roots emerge in these branches

after 2-4 months. Such branches are removed from parent plant and grown

separately.

Question 30. Explain the conventional methods adopted in vegetative propagation of higher plants.

Answer:

The common methods of conventional propagation are cutting, grafting and

layering.

a. Cutting: It is the method of producing a new plant by cutting the plant parts

such as root, stem and leaf from the parent plant. The cut part is placed in a

suitable medium for growth. It produces root and grows into a new plant.

Depending upon the part used it is called as root cutting (Malus), stem cutting

(Hibiscus, Bougainvillea and Moringa) and leaf cutting (Begonia, Bryophyllum).

Stem cutting is widely used for propagation.

b. Grafting: In this, parts of two different plants are joined so that they continue

to grow as one plant. Of the two plants, the plant which is in contact with the

soil is called stock and the plant used for grafting is called scion. Examples are

Citrus, Mango and Apple. There are different types of grafting based on the

method of uniting the scion and stock. They are bud grafting, approach

grafting, tongue grafting, crown grafting and wedge grafting.

(i) Bud grafting: A T- shaped incision is made in the stock and the bark is lifted.

The scion bud with little wood is placed in the incision beneath the bark and

properly bandaged with a tape.

(ii) Approach grafting: In this method both the scion and stock remain rooted.

The stock is grown in a pot and it is brought close to the scion. Both of them

should have the same thickness. A small slice is cut from both and the cut

surfaces are brought near and tied together and held by a tape. After 1-4 weeks

the tip of the stock and base of the scion are cut off and detached and grown

in a separate pot.

(iii) Tongue grafting: A scion and stock having the same thickness is cut

obliquely and the scion is fit into the stock and bound with a tape.

(iv) Crown grafting: When the stock is large in size scions are cut into wedge

shape and are

inserted on the slits or clefts of the stock and fixed in position using graft wax.

(v) Wedge grafting: In this method a slit is made in the stock or the bark is cut.

A twig of scion is inserted and tightly bound so that the cambium of the two is

joined.

c. Layering: In this method, the stem of a parent plant is allowed to develop

roots while still intact. When the root develops, the rooted part is cut and

planted to grow as a new plant.

Examples: Ixora Jasminum Mound layering and Air layering are few types of

layering.

(i) Mound layering: This method is applied for the plants having flexible

branches. The lower branch with leaves is bent to the ground and part of the

stem is buried in the soil and tip of (the branch is exposed above the soil. After

the roots emerge from the part of the stem buried in the soil, a cut is made in

parent plant so that the buried part grow into a new plant.

(ii) Air layering: In this method the stem is girdled at nodal region and

hormones are applied to this region which promotes rooting. This portion is

covered with damp or moist soil using a ; polythene sheet. Roots emerge in

these branches after 2-4 months. Such branches are removed-from the parent

plant and grown in a separate pot or ground.

Question 31. Highlight the milestones from the history of plant embryology.

Milestones in Plant Embryology

Answer:

1. 1682 – Nehemiah Grew mentioned stamens as the male organ of a

flower.

2. 1694 – R.J. Camerarius described the structure of a flower, anther,

pollen and ovule

3. 1761 – J.G. Kolreuter gave a detailed account on the importance of

insects in pollination.

4. 1824 – G.B. Amici discovered the pollen tube.

5. 1848 – Hofmeister described the structure of pollen tetrad.

6. 1870 – Hanstein described the development of embryo in Capsella and

Alisma.

7. 1878 – E. Strasburger reported polyembryony.

8. 1884 – E. Strasburger discovered the process of Syngamy.

9. 1899 – S.G. Nawaschin and L. Guignard independently discovered

Double fertilization.

10. 1904- E. Hanning initiated embryo culture. 11. 1950 – D.A. Johansen proposed classification for embryo development.

12. 1964 – S. Guha and S.C. Maheswari raised haploids from Datura pollen

grains

13. 1991 – E.S. Coen and E.M. Meyerowitz proposed the ABC model to

describe the genetics of initiation and development of floral parts

14. 2015 – K.V. Krishnamurthy summarized the molecular aspects of pre

and post fertilization reproductive development in flowering plants

Question 32. Discuss the importance of Modern methods in reproduction of plants.

Answer:

Advantages of modern methods

1. Plants with desired characteristics can be multiplied rapidly in a short

2. duration.

3. Plants produced are genetically identical.

4. Tissue culture can be carried out in any season to produce plants.

5. Plants which do not produce viable seeds and seeds that are difficult to

6. germinate can be propagated by tissue culture.

7. Rare and endangered plants can be propagated.

8. Disease free plants can be produced by meristem culture.

9. Cells can be genetically modified and transformed using tissue culture.

Question 33. What is Cantharophily?

Answer:

Pollination carried out by beetles is said to be cantharophily.

Question 34. List any two strategies adopted by bisexual flowers to prevent self-pollination.

Answer:

(a) Protandry or protogyny (b) Herkogamy

Question 35. What is endothelium?

Answer:

In Asteraceae species, the inner layer of integument get specialized for

nourishing the embryosac and this is called integumentary tapetum or

endothelium.

Question 36. “The endosperm of angiosperm is different from gymnosperm”. Do you agree. Justify your answer.

Answer:

Endosperm of Angiosperm:

1. Develops as a s result of double fertilization.

2. Endosperm is generally triploid (polyploid).

Endosperm of Gymnosperm:

1. Develops before the fertilization process.

2. Endosperm is haploid.

Question 37. Define the term Diplospory.

Answer:

Diplospory is a condition where a diploid embryosac is formed from

megaspore mother cells without a regular meiotic division.

E.g: Eupatorium.

Question 38. What is polyembryony. How it can commercially exploited.

Answer:

Occurrence of more than one embryo in a seed is called polyembryony.

1. Embryos developed through polyembryony are found virus free.

2. The seedlings formed from nuclear tissue in citrus are found on better

clones for orchards.

Question 39. Why does the zygote divides only after the division of Primary endosperm cell?

Answer:

The primary endosperm nuclear (PEN) divides prior to zygotic division and

form endosperm. Endosperm acts as a nutritive tissue and nourishes the

developing embryo.

Question 40. What is Mellitophily?

Answer:

Pollination carried out by Bees is said to be mellitophily.

Question 41. “Endothecium is associated with dehiscence of anther” Justify the statement.

Answer:

The inner tangential wall develops bands (sometimes radial walls also) of a

cellulose (sometimes also slightly lignified). The cells are hygroscopic. The

cells along the junction of the two sporangia of an anther lobe lack these

thickenings. This region is called stomium. This region along with the

hygroscopic nature of endothecium helps in the dehiscence of anther at

maturity.

Question 42. List out the functions of tapetum.

Answer:

1. It supplies nutrition to the developing microspores.

2. It contributes sporopollenin through ubisch bodies thus plays an

important role in pollen wall formation.

3. The pollenkitt material is contributed by tapetal cells and is later

transferred to the pollen surface.

4. Exine proteins responsible for ‘rejection reaction’ of the stigma are

present in the cavities of the exine. These proteins are derived from

tapetal cells.

Question 43. Write short note on Pollenkitt.

Answer:

Pollenkitt is contributed by the tapetum and coloured yellow or orange and is

chiefly made of carotenoids or flavonoids. It is an oily layer forming a thick

viscous coating over pollen surface. It attracts insects and protects damage

from UV radiation.

Question 44. Distinguish tenuinucellate and crassinucellate ovules.

Answer:

Tenuinucellate Ovule:

1. Ovules with hypodermal sporogerous cell with unilayerd nucellus tissue is called tenuinucellate type.

2. They have very small nucellus

Crassinucellate Ovule:

1. Ovule with subhypodermal sporogenous cell is called crassinucellate type.

2. They have large nucellus

Question 45. ‘Pollination in Gymnosperms is different from Angiosperms’ – Give reasons.

Answer:

In gymnosperms, the ovules are exposed and the pollens are deposited directly

on it. Hence the pollution is direct in gymnosperm. Whereas in angiosperms it

is said to be indirect, as the pollens are deposited on stigma or the pistil.

Question 46. Write short note on Heterostyly.

Answer:

Heterostyly: Some plants produce two or three different forms of flowers that

are different in their length of stamens and style. Pollination will take place only between organs of the same lepgth.

E.g: Primula.

Question 47. Enumerate the characteristic features of Entomophilous flowers.

Answer:

The characteristic features of entomophilous flowers are as follows:

1. Flowers are generally large or if small they are aggregated in dense

inflorescence. Example: Asteraceae flowers.

2. Flowers are brightly coloured. The adjacent parts of the flowers may

also be brightly coloured to attract insect. For example in Poinsettia and Bougainvillea the bracts become coloured.

3. Flowers are scented and produce nectar.

4. Flowers in which there is no secretion of nectar, the pollen is either

consumed as food or used in building up of its hive by the honeybees.

5. Pollen and nectar are the floral rewards for the visitors.

6. Flowers pollinated by flies and beetles produce foul odour to attract

pollinators.

7. In some flowers juicy cells are present which are pierced and the

contents are sucked by the insects.

Question 48. Discuss the steps involved in Microsporogenesis.

Microsporogenesis: The stages involved in the formation of haploid

microspores from diploid microspore mother cell through meiosis is called

Microsporogenesis. The primary sporogeneous cells directly, or may undergo a

few mitotic divisions to form sporogenous tissue. The last generation of

sporogenous tissue functions as microspore mother cells.

Each microspore mother cell divides meiotically to form a tetrad of four haploid

microspores (microspore tetrad). Microspores soon separate from one another

and remain free in the anther locule and develop into pollen grains.

Question 49. With a suitable diagram explain the structure of an ovule.

Answer:

Structure of ovule(Megasporangium):

Ovule is also called megasporangium and is protected by one or two covering

called integuments. A mature ovule consists of a Raphe stalk and a body. The

stalk or the funiculus (also called funicle) is present at the base and it attaches

the ovule to the placenta. The point of attachment of funicle to the body of the

ovule is known as hilum. It represents the junction ovule and funicle. In an

inverted ovule, the funicle is adnate to the body of the ovule forming a ridge

called raphe. The body of the ovule is made up of a central mass of

parenchymatous tissue called nucellus which has large reserve food materials.

The nucellus is enveloped by one or two protective coverings called

integuments. Integument encloses the nucellus completely except at the top

where it is free and forms a pore called micropyle.

The ovule with one or two integuments are said to be unitegmic or bitegmic

ovules respectively. The basal region of the body of the ovule where the

nucellus, the integument and the funicle meet or merge is called chalaza. There

is a large, oval, sac-like structure in the nucellus toward the micropylar end

called embryo sac or female gametophyte. It develops from the functional

megaspore formed within the nucellus. In some species(unitegmic

tenuinucellate) the inner layer of the integument may become specialized to

perform the nutritive function for the embryo sac and is called as endothelium

or integumentary tapetum (Example : Asteraceae).

Question 50. Give a concise account on steps involved in fertilization of an angiosperm plant.

Answer:

Steps involved in fertilization of angiospermic plant:

1. Germination of pollen grain on stigma.

2. Formation of pollen tube in stigma.

3. Growth of pollen tube inside the style.

4. Direction of pollen tube towards the micropyle of ovule.

5. Entry of pollen tube into the synergid of embryo sac.

6. Discharge of male gametes from the pollen tube.

7. Fusion of male gamete with egg cell (syngany)

8. Fusion of second male gamete with polar nuclei (triple fusion/double fertilisation)

Question 51. What is endosperm? Explain the types.

Answer:

1. Endosperm: The primary endosperm nucleus (PEN) divides immediately

after fertilization but before the zygote starts to divide, into an endosperm. The

primary endosperm nucleus is the result of triple fusion (two polar nuclei and

one sperm nucleus) and thus has 3n number of chromosomes. It is a nutritive

tissue and regulatory structure that nourishes the developing embryo.

Depending upon the mode of development three types of endosperm are

recognized in angiosperms. They are nuclear endosperm, cellular endosperm and helobial endosperm.

2. Nuclear endosperm: Primary Endosperm Nucleus undergoes several mitotic

divisions without cell As, wall formation thus a free nuclear condition exists in

the endosperm.

Examples: Coccinia, Capsella and Arachis.

3. Cellular endosperm: Primary endosperm nucleus divides into 2 nuclei and it

is immediately followed by wall formation. Subsequent divisions also follow

cell wall formation.

Examples: Adoxa, Helianthus and Scoparia.

4. Helobial endosperm: Primary Endosperm Nucleus moves towards base of

embryo sac and divides into two nuclei. Cell wall formation takes place leading

to the formation of a large micropylar and small chalazal chamber. The nucleus of the micropylar chamber undergoes several free nuclear division whereas

that of chalazal chamber may or may not divide.

Examples : Hydrilla and Vallisneria.

5. Ruminate endosperm: The endosperm with irregularity and unevenness in its

surface forms ruminate endosperm. Examples : Areca catechu, Passiflora and

Myristica

Question 52. Differentiate the structure of Dicot and Monocot seed

Answer:

Dicot Seed:

1. Possess two cotyledons

2. Absence of coleoptile and coleorhiza

3. Endosperm is scarce or absent

Monocot Seed:

1. Possess only one cotyledon

2. Presence of coleoptile and colerhiza surrounding plumule and radicle

respectively.

3. Endosperm from the major storage tissue.