65 Questions with Answers and Explanations on “Plant Reproduction” for Botany Students.
1. Formation of gametophyte directly from sporophyte without meiosis is
(a) apospory
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Plant Reproduction For Kids”/>(b) apogamy
(c) parthenogenesis
(d) amphimixis.
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Answer and Explanation:
1. (a): Formation of gametophyte directly from sporophyte without meiosis and spore formation is apospory. The gametophyte has diploid number of chromosomes such gametophyte may form viable gametes which fuse to form tetraploid sporophyte. Apogamy is development of sporophyte directly from gametophytic tissue without fusion of gametes. Amphimixis is normal sexual reproduction. Parthenogenesis is development of embryo from egg without fertilization.
2. Parthenogenesis is
(a) development of embryo without fertilization
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(b) development of fruit without fertilization
(c) development of fruit without hormones
(d) development of embryo from egg without fertilization.
Answer and Explanation:
2. (d): Parthenogenesis is the phenomenon of development of embryo from egg without fertilization. It is of two types haploid and diploid parthenogenesis. It occurs usually due to defective meiosis that results in egg nucleus having unreduced number of chromosomes.
3. Male gametophyte of angiosperms is shed as
(a) four celled pollen grain
(b) three celled pollen grain
(c) microspore mother cell
(d) anther.
Answer and Explanation:
3. (b): The male gametophyte or microspore is shed at 3-nucleate stage. The microspore undergoes only two mitotic divisions.
4. Total number of meiotic division required for forming 100 zygotes/100 grains of wheat is
(a) 100
(b) 75
(c) 125
(d) 50.
Answer and Explanation:
4. (c): For formation of 100 zygotes, 100 male gametes and 100 female gametes (eggs) are required. 100 male gametes are developed from 100 microspores (from 25 meiotic divisions) and 100 eggs are developed from 100 megaspores (from 100 meiotic division).
Hence, number of meiotic divisions necessary for 100 zygotes formation = 25 + 100 = 125.
5. Double fertilization and triple fusion were discovered by
(a) Hofmeister
(b) Nawaschin and Guignard
(c) Leeuwenhoek
(d) Strasburger.
Answer and Explanation:
5. (b): Double fertilization and triple fusion were discovered by Nawaschin and Guignard in Fritillaria and Li Ham. In angiosperms one male gamete fuses with the two polar nuclei to form triploid primary endosperm nucleus. The process is called triple fusion. These two acts together are known as double fertilization.
6. Perisperm is
(a) remnant of endosperm
(b) persistent nuccllus
(c) peripheral part of endosperm
(d) disintegrated secondary nucleus.
Answer and Explanation:
6. (b): Perisperm is persistent nucellus. Endosperm formation is accompanied by degeneration of nucellus.
7. Development of an organism from female gamete/’ egg without involving fertilization is
(a) adventitive embryony
(b) polyembryony
(c) parthenocarpy
(d) parthenogenesis.
Answer and Explanation:
7. (d): Development of an organism from female gamete/egg without involving fertilization is parthenogenesis and when a fruit is developed by this technique it is called parthenocarpy.
8. Nucellar embryo is
(a) amphimictic haploid
(b) amphimictic diploid
(c) apomictic haploid
(d) apomictic diploid.
Answer and Explanation:
8. (d): Nucellar embryo is apomictic diploid. Substitution of usual sexual reproduction by a form of reproduction which does not include meiosis and syngamy is called apomixis. In this technique embryo is developed by some other tissue without fertilization e.g., nucellus or integuments or infertilized egg. Nucellus in a diploid tissue so nucellar embryo is apomictic diploid.
9. Generative cell was destroyed by laser but a normal pollen tube was still formed because
(a) vegetative cell is not damaged.
(b) contents of killed generative cell stimulate pollen growth
(c) laser beam stimulates growth of pollen tube
(d) the region of emergence of pollen tube is not harmed.
Answer and Explanation:
9. (a): Generative cell was destroyed by laser but a normal pollen tube was still formed because vegetative cell is not damaged. Each microspore divides by mitotic division making a smaller generative cell and a larger vegetative cell or tube cell. If generative cell is damaged then the normal pollen tube will be formed because pollen tube is formed by vegetative cell not by generative cell of microspore.
10. Which is correct?
(a) gametes are invariably haploid
(b) spores are invariably haploid
(c) gametes are generally haploid
(d) both spores and gametes are invariably haploid.
Answer and Explanation:
10. (a): Gametes are invariably haploid. Spores are formed in lower plants by mitotic division and they may be diploid but gametes are always be made by meiosis and they are always haploid.
11. A diploid female plant and a tetraploid male plant are crossed. The policy of endosperm shall be
(a) tetraploid
(b) triploid
(c) diploid
(d) pentaploid.
Answer and Explanation:
11. (a): A diploid female plant and a tetraploid male plant are crossed. The ploidy of endosperm shall be tetraploid. Diploid female plant will have 2 polar nuclei (each haploid) with which one male gamete from tetraploid male plant (male gamete of tetraploid plant will be diploid) fuses, making endosperm, so endosperm will be tetraploid.
12. Which ones produce androgenic haploids in anther cultures?
(a) anther wall
(b) tapetal layer of anther wall
(c) connective tissue
(d) young pollen grains.
Answer and Explanation:
12. (d): Young pollen grains produce androgenic haploids in anther cultures. Because rest all i.e., anther wall, tapetal layer of anther wall and connective tissue are the diploid tissue as they are part of anther pollen grains are produced by meiosis.
13. Male gametophyte of angiosperms/monocots is
(a) microsporangium
(b) nucellus
(c) microspore
(d) stamen.
Answer and Explanation:
13. (c): Male gametophyte of angiosperms is microspore. Microspore is haploid, uninucleate, minute spores produced in large numbers as a result of meiosis in microspore mother cell inside the microsporangia. These are the first cell of gametophytic generations in angiosperms.
14. Female gametophyte of angiosperms is represented by
(a) ovule
(b) megaspore mother cell
(c) embryo sac
(d) nucellus.
Answer and Explanation:
14. (c): Female gametophyte of angiosperms is represented by embryo sac. The polygonum type of embryo sac is eight nucleate and seven celled. It is found in more than 80% plant families. The nucleuses of megaspore undergo division and give rise to embryosac or female gametophyte by the process of megagametogenesis.
15. Sperm and egg nuclei fuse due to
(a) base pairing of their DNA and RNA
(b) formation of hydrogen bonds
(c) mutual attraction due to differences in electrical charges
(d) attraction of their protoplasts.
Answer and Explanation:
15. (d): The two gametes i.e., sperm released by pollen tube and egg move in opposite direction by an unknown mechanism but most probably by streaming currents of cytoplasm i.e., due to attraction of their protoplasts. The nucleus of one male gamete fuses with the egg nucleus and the phenomenon is called fertilization.
16. Entry of pollen tube through micropyle is
(a) chalazogamy
(b) mesogamy
(c) porogamy
(d) pseudogamy
Answer and Explanation:
16. (c): In most of the plants the pollen tube enters the ovule through the micropyle and the phenomenon is called as porogamy. Entry through chalaza is chalazogamy and through integuments or funiculus is mesogamy.
17. Cellular totipotency was demonstrated by
(a) Theodore Schwann
(b) A.V. Leeuwenhoek
(c) F.C. Steward
(d) Robert Hooke.
Answer and Explanation:
17. (c): Cellular totipotency was demonstrated by F.C. Steward. Cellular totipotency is the technique of regeneration or development of complete plant from explants or cell or tissue of the plant.
18. Pollination occurs in
(a) bryophytes and angiosperms
(b) pteridophytes and angiosperms
(c) angiosperms and gymnosperms
(d) angiosperms and fungi.
Answer and Explanation:
18. (c): The term pollination refers to the transfer of pollen from anther to stigma. Because pollens are found only in angiosperms and gymnosperms so this phenomenon relates to angiosperms and gymnosperms only.
19. Embryo sac occurs in
(a) embryo
(b) axis part of embryo
(c) ovule
(d) endosperm.
Answer and Explanation:
19. (c): Embryo sac occurs in ovule. Ovule is integumented megasporangium. It consists of nucleus covered by one or two integuments, mounted on a funicle, chalaza and micropyle. The ovule is vascularised.
20. Which of the following pair have haploid structures?
(a) nucellus and antipodal cells
(b) antipodal cells and egg cell
(c) antipodal cells and megaspore mother cell
(d) nucellus and primary endosperm nucleus
Answer and Explanation:
20. (b): Antipodal cells and egg cell are haploid structures as they are after meiosis while the others nucellus, megaspore mother cell and primary endosperm nucleus are diploid structures.
21. Point out the odd one
(a) nucellus
(b) embryo sac
(c) micropyle
(d) pollen grain
Answer and Explanation:
21. (d): Pollen grain is odd one among all the other three. Pollen grain in a male gametophytic structure. Whereas all the other three are found inside ovule, (nucellus, micropyle and embryo sac).
22. Syngamy means
(a) fusion of gametes
(b) fusion of cytoplasms
(c) fusion of two similar spores
(d) fusion of two dissimilar spores.
Answer and Explanation:
22. (a): Syngamy means fusion of gametes. Syngamy is the phenomenon in which male gametes fuses with the egg.
23. Double fertilization is fusion of
(a) two eggs
(b) two eggs and polar nuclei with pollen nuclei
(c) one male gamete with egg and other with synergid
(d) one male gamete with egg and other with secondary nucleus.
Answer:
(d) one male gamete with egg and other with secondary nucleus.
24. Meiosis is best observed in dividing
(a) cells of apical meristem
(b) cells of lateral meristem
(c) microspores and anther wall
(d) microsporocytes.
Answer and Explanation:
24. (d): Meiosis is best observed in dividing microsporocytes. Microsporocytes or microspore mother cell after meiosis give rise to microspore. Other cells do not divide by meiosis.
25. A population of genetically identical individuals, obtained from asexual reproduction is
(a) callus
(b) clone
(c) deme
(d) aggregate.
Answer and Explanation:
25. (b): A population of genetically identical individuals, obtained from asexual reproduction is clone. Cloning is a technique by which genetically same individuals can be produced without including any sexual reproduction, e.g. Dolly, the cloned sheep.
26. Study of formation, growth and development of new individual from an egg is
(a) apomixis
(b) embryology
(c) embryogeny
(d) cytology.
Answer and Explanation:
26. (b): Study of formation, growth and development of new individual from an egg is embryology. Study of an individual’s life cycle after the fertilization takes place till it develops into a new organism.
27. Ovule is straight with funiculus, embryo sac, chalaza and micropyle lying on one straight line. It is
(a) orthotropous
(b) anatropous
(c) campylotropous
(d) amphitropous.
Answer and Explanation:
27. (a): Orthotropous ovule is straight with funiculus, embryo sac, chalaza and micropyle lying on one straight line. It is an polygonum type ovule in which body of the ovule is straight. Funiculus, chalaza, embryo sac and micropyle lie in the same vertical axis.
28. Double fertilization is characteristic of
(a) angiosperms
(b) anatropous
(c) gymnosperms
(d) bryophytes.
Answer and Explanation:
28. (a): Double fertilization is the characteristic feature of angiosperms. This phenomenon first observed by Nawaschin, 1898 in Lilium and FriUllaria. In angiosperms one male gamete fuses with the two polar nuclei to form triploid primary endosperm nucleus. The process is called triple fusion. These two acts together are known as double fertilization.
29. Number of meiotic divisions required to produce 200/400 seeds of pea would be
(a) 200/400
(b) 400/800
(c) 300/600
(d) 250/500.
Answer and Explanation:
29. (d): Number of meiotic divisions required to produce 200/400 seeds of pea would be 250/500. 200 seeds of pea would be produced from 200 pollen grains and 200 eggs. 200 pollen grains will be formed by 50 microspore mother cell while 200 eggs will be formed by 200 megaspore mother cell so 250/500.
30. Embryo sac represents
(a) megaspore
(b) megagametophyte
(c) megasporophyll
(d) megagamete.
Answer and Explanation:
30. (b): Megaspore is the initial cell or beginning of female gametophyte or embryo sac. The nucleus of megaspore undergoes divisions and give rise to embryo sac or female gametophyte, the process is called megagametogenesis.
In polygonum type of embryosac, which is found in 70% of angiosperms, only the chalazal megaspore remains functional while the other three degenerate. The single nucleus of functional megaspore undergoes 3 mitotic divisions to form 8 nuclei. So the fully developed normal type of female gametophyte or embryo sac is 8-nucleated and 7-celled structure.
Number of nuclei in mature stage may have different patterns but most common pattern in eight-nucleate one with one egg nucleus in egg cell, two synergids at micropylar end, three antipodal cells at opposite pole and two polar nuclei in middle of sac. Fertilization of egg occurs within the embryo sac resulting in formation of zygote.
31. When pollen of a flower is transferred to the stigma of another flower of the same plant, the pollination is referred to as
(a) autogamy
(b) geitonogamy
(c) xenogamy
(d) allogamy.
Answer and Explanation:
31. (b): The phenomenon of transfer of pollens from anther to stigma of the same or different flower (on same or different plant) is known as pollination. Transfer of pollens from anthers to stigma of another flower on same plant is called geitonogamy. Genetically geitonogamy is equivalent to self pollination. Autogamy is the transfer of pollen grains from anther to stigma of the same flower.
It occurs in crops with bisexual flowers eg wheat, barley etc. Cross-pollination or allogamy is when the pollens are transferred from anther to stigma of different flower on different plant. It is also called xenogamy. It occurs in unisexual flowers and also in a large number of bisexual flowers.
32. The polyembryony commonly occurs in
(a) tomato
(b) potato
(c) Citrus
(d) turmeric.
Answer and Explanation:
32. (c): Presence of more than one embryo inside the seed is called polyembryony. It is more common in gymnosperms than angiosperms. In angiosperms, it is generally present as an unusual feature in few cases like Citrus, mango etc.
In Citrus many embryos are formed from the structures outside the embryo (like nucellus). This is commonly called adventive polyembryony. In Citrus upto 10 nucellar embryos are formed.
33. In an angiosperm, how many microspore mother cells are required to produce 100 pollen grains?
(a) 75
(b) 100
(c) 25
(d) 50.
Answer and Explanation:
33. (c): Pollen grains or microspores are formed inside anther, which is the fertile portion of stamen or microsporophyll. The formation of microspores or pollens is called microsporogenesis. The primary sporogenous cell gives rise to microspore mother cells or pollen mother cells. Each microspore mother cell on reduction division gives rise to 4 microspores or pollens. So for the formation of 100 pollen grains, 25 MMC are required. It inolves karyokinesis followed by cytokinesis.
34. The anthesis is a phenomenon, which refers to
(a) development of anthers
(b) opening of flower bud
(c) stigma receptors
(d) all of these.
Answer and Explanation:
34. (b): Anthesis refers to opening of a flower bud. It is the duration of life of a flower from the opening of the bud to setting of the fruit.
35. If there are 4 cells in anthers, what will be the number of pollen grains?
(a) 16
(b) 12
(c) 8
(d) 4.
Answer and Explanation:
35. (a): Pollen grains or microspores are formed inside anther, which is the fertile portion of stamen or microsporophyll. Inside the anther, primary sporogenous cell gives rise to microspore mother cells or pollen mother cells (MMC or PMC). Each MMC on reduction division gives rise to 4 microspores or pollens. So these four cells will give rise to 4 x 4 = 16 pollen grains.
The second male gamete fuses with 2 polar nuclei or secondary nucleus to form triploid primary endosperm nucleus and this is called triple fusion. This primary endosperm nucleus (3n) ultimately develops into a nutritive tissue for developing embryo called endosperm.
36. The role of double fertilization in angiosperms is to produce
(a) cotyledons
(b) endocarp
(c) endosperm
(d) hormones.
Answer:
(c) endosperm
37. If an angiospermic male plant is diploid and female plant tetraploid, the policy level of endosperm will be
(a) tetraploid
(b) pentaploid
(c) haploid
(d) triploid.
Answer and Explanation:
37. (b): If the female plant is tetraploid, then the central cell of embryo sac, which is a fused polar nuclei, will also be tetraploid. Fusion of the tetraploid central cell to the haploid male gamete forms a pentaploid endosperm in the given example.
38. The role of double fertilization in angiosperms is to produce
(a) cotyledons
(b) endocarp
(c) endosperm
(d) integuments.
Answer and Explanation:
38. (c): Refer answer 36.
39. The embryo in sunflower has
(a) two cotyledons
(b) many cotyledons
(c) no cotyledon
(d) one cotyledon.
Answer and Explanation:
39. (a): Sunflower (Helianthus) belongs to family asteraceae of dicotyledons. A dicot embryo has an embryonal axis and 2 cotyledons attached to it laterally. So the number of cotyledons in sunflower will be two.
40. An interesting modification of flower shape for insect pollination occurs in some orchids in which a male insect mistakes the pattern on the orchid flower for the female species anr1 tries to copulate with it, thereby pollinating the flower. This phenomenon is called
(a) pseudopollination
(b) pseudoparthenocarpy
(c) mimicry
(d) pseudocopulation.
Answer and Explanation:
40. (d): In an orchid Ophrys speculum, there is most interesting and unique mechanism of pollination. Here pollination occurs by a wasp called Culpa aurea. In this orchid, pollination occurs by act of pseudocopulation. The appearance and odour of Ophrys is similar to female wasp and are mistake by male wasps and they land on Ophrys flowers to perform act of pseudo-copulation and thus pollin takes place. This plant-insect relationship is useful only to plant.
41. Type of placentation in which ovary is syncarpous unilocular and ovules are on sutures is called
(a) marginal placentation
(b) superficial placentation
(c) apical placentation
(d) parietal placentation.
Answer and Explanation:
41. (a): Arrangement of ovules inside the ovary on placenta is called placentation. In marginal placentation ovary is unilocular and the placenta develops along the junction of the two margins of the carpel, called the ventral suture. It occurs in pea, wild pea, gram etc.
In superficial placentation ovary is multilocular and ovules are borne on inner surface or partition walls as in water lily. In parietal placentation the ovary is unilocular and the ovules are borne on periphery as in Brassica, Argemone etc.
42. The endosperm of gymnosperm is
(a) diploid
(b) polyploid
(c) triploid
(d) haploid.
Answer and Explanation:
42. (d): The endosperm of gymnosperms is haploid. It is a pre-fertilization tissue and is equivalent to female gametophyte, hence it is haploid in nature but in angiosperms it is post-fertilization tissue and is generally triploid in nature.
43. Eight nucleated embryo sac is
(a) only monosporic
(b) only bisporic
(c) only tetrasporic
(d) any of these formed during the double
Answer and Explanation:
43. (d): On the basis of number of megaspore nuclei taking part in development of female gametophyte or embryo sac, there are 3 types of embryo sacs –
(i) Monosporic type – In this type the single nucleus of functional megaspore undergoes 3 mitotic divisions to form 8 nuclei, 7 cells.
(ii) Bisporic type – Here embryo sac develops from 2 megaspore nuclei out of 4 nuclei formed after reduction division of MMC. It is also 8 nucleated.
(iii) Tetrasporic type – Here all the 4 megaspore nuclei formed after reduction division of megaspore mother cell are functional and take part in development of embryo sac. It is further of different types. Fritillaria type. Plumbago type and Adoxa type are 8 nucleated.
44. Endosperm is fertilization by
(a) two polar nuclei and one male gamete
(b) one polar nuclei and one male gamete
(c) ovum and male gamete
(d) two polar nuclei and two male gametes.
Answer and Explanation:
44. (a): In Angiosperms the endosperm is a post- fertilization tissue. The second male gamete fuses with 2 polar nuclei or secondary nucleus to form triploid primary endosperm nucleus and this is called triple fusion. The primary endosperm nucleus (3n) ultimately develops into a nutritive tissue for developing embryo called endosperm.
45. Anemophily type of pollination is found in
(a) Salvia
(b) bottle brush
(c) Valtisnaria
(d) coconut.
Answer and Explanation:
45. (d): Anemophily is the pollination by wind. Ancmophilous plants are characterized by small flowers, pollens present in large number which are small, dry and light in weight, number of ovules generally reduced in ovary, feathery or brushy stigma to recieve the pollen. All these features are shown by coconut flower.
In Vallisncria pollination occurs outside water called ephydrophily. Callistemon is pollinated by birds and is an example of ornithophily. Salvia is insect pollinated and is an example of entomophily.
46. In grasses what happens in microspore mother cell for the formatio” of inature pollen grains?
(a) one meiotic and two mitotic divisions
(b) or.c ineiotic and one mitotic divisions
(c) one meiotic division
(d) one mitotic division.
Answer and Explanation:
46. (b): Grass is a monocot plant. Primary sporogenous cell gives rise to microspore mother cells or pollen mother cells. Each MMC on reduction division gives rise to 4 microspores or pollens and this formation of microspores or pollens is called microsporogenesis. Karyokinesis is of successive type. The successive type of cytokinesis is common in monocots. Here both meiotic I and II nuclear divisions are followed by wall formation and it leads to isobilateral tetrad.
47. Adventive embryony in Citrus is due to
(a) nucellus
(b) integuments
(c) zygotic embryo
(d) fertilized egg.
Answer and Explanation:
47. (a): Refers answers 32.
48. In angiosperms pollen tube liberate their male gametes into the
(a) central cell
(b) antipodal cells
(c) egg cell
(d) synergids.
Answer and Explanation:
48. (d): On reaching of pollen tube inside the embryo sac, the two male gametes are discharged through a sub- texminal pore in pollen tube. The contents of the pollen tube are discharged in the synergid or between egg or synergid and the pollen tube does not grow beyond it in the embryo sac. Further the cytoplasm of the pollen tube is restricted to chalazal end of this synergidal cell.
49. What is the direction of micropyle in anatropous ovule?
(a) upward
(b) downward
(c) right
(d) left.
Answer:
(b) downward
50. In angiosperm all the four microspores of tetrad are covered by a layer which is formed by
(a) pectocellulose
(b) callose
(c) cellulose
(d) sporopollenin.
Answer and Explanation:
50. (a): Each microspore or pollen is having a two layered wall. Outer layer is thick tough cuticularized called exine, which is chiefly composed of a material called ‘sporopollenin’. Inner layer is thin, delicate and smooth called intine, which is made of pectocellulose.
Exine is not uniform but is thin at one or more places in the form of germ pores. Whereas intine made of pectocellulose cc-, wrs the entire stirfucv pollen grains.
51. In angiosperms pollen tube liberate their male gametes into the
(a) central cell
(b) antipodal cells
(c) egg cell
(d) synergids.
Answer and Explanation:
51. (a): In Angiosperms the embryosac is 8 nucleated and 7-celled structure. It includes an egg apparatus having 2 synergids and one egg cell, 3 antipodal cells at chalazal end and a central cell having two polar nuclei in center. The pollen tube always enters into the embryosac at the micropylar end. This entry may be between egg and one synergid or between wall of embryosac and synergid. So one synergid is always degenerated by pollen tube.
On reaching of pollen tube inside the embryo sac, the 2 male gametes are discharged through a sub-terminal pore in pollen tube. The contents of pollen tube are discharged in the synergid and the pollen tube does not grow beyond it in the embryo sac. Further the cytoplasm of pollen tube is restricted to chalazal end of this synergidal cell.
52. In a flowering plant, archesporium gives rise to
(a) only the wall of the sporangium
(b) both wall and the sporogenous cells
(c) wall and the tapetum
(d) only tapetum and sporogenous cells
Answer and Explanation:
52. (b): In flowering plants, archaesporial cells are vertical rows of hypodermal cells at four angles of anther. These undergo periclinal (transverse) division to form an outer primary parietal cell and inner sporogenous cell. Primary parietal wall after few more periclinal divisions forms anther wall and sporogenous cells give rise to sporogenous tissue.
53. An ovule which becomes curved so that the nucellus and embryo sac lie at right angles to the funicle is
(a) hemitropous
(b) campylotropous
(c) anatropous
(d) orthotropous.
Answer and Explanation:
53. (a): In hemianatropous or hemitropous ovule the nucellus and integument are at right angles to stalk or funicul us so that the ovule becomes curved. It is commonly found is primulaceae and Ranunculus. In campylotropous ovule the body of the ovule gets curved and micropyle is directed downwards.
Atropous ovule is erect and micropyle, chalaza and funiculus are in the same straight line. Anatropous ovule is the most common type of ovule in angiosperms. In this the body of the ovule gets inverted and the micropyle is on lower side. In campylotropous ovule the body of the ovule gets curved and the micropyle is directed downwards.
54. When a diploid female plant is crossed with a tetraploid male, the ploidy of endosperm cells in the resulting seed is
(a) tetraploidy
(b) pentaploidy
(c) diploidy
(d) triploidy.
Answer and Explanation:
54. (a): Endosperm is formed due to fusion of the haploid male gamete with the polar nucleus of the embryo sac. But in this case the male plant is tetraploid so that its gametes would be diploid. When these diploid gametes fuse with two polar nuclei of the embryo sac the resultant endosperm would be tetraploid.
55. Through which cell of the embryosac, does the pollen tube enter the embryo sac?
(a) egg cell
(b) persistant synergid
(c) degenerated synergids
(d) central cell.
Answer and Explanation:
55. (c): The pollen tube enters into the embryo sac at the micropylar end. This entry may be between egg and one synergid or between wall of embryo sac and synergid or through one synergid. So one synergid is always degenerated to allow the entry of the pollen tube.
56. Which one of the following represents an ovule, where the embryo sac becomes horse-shoe shaped and the funiculus and micropyle are close to each other?
(a) amphitropous
(b) circinotropous
(c) atropous
(d) antropous.
Answer:
(a) amphitropous
57. In a type of apomixis known as adventive embryony, embryos develop directly from the
(a) nucellus or integuments
(b) zygote
(c) synergids or antipodals in an embryo sac
(d) accessory embryo sacs in the ovule.
Answer and Explanation:
57. (a): Normal type of sexual reproduction having two regular features, i.e., meiosis and fertilization, is called amphimixis. But in some plants, this normal sexual reproduction (amphimixis) is replaced by some abnormal type of sexual reproduction called apomixis.
Apomixis may be defined as, ‘abnormal kind of sexual reproduction in which egg or other cells associated with egg (synergids, antipodals, etc.) develop into embryo without fertilization and with or without meiosis’. Adventive embryony is a type of apomixis in which development of embryos directly from sporophytic tissues like nucellus and integuments takes place, e.g., in Citrus, mango, etc.
58. In which one pair both the plants can be vegetatively propagated by leaf species?
(a) Agave and Kalanchoe
(b) Bryophyllum and Kalanchoe
(c) Asparagus and Bryophyllum
(d) Chrysanthemum and Agave.
Answer and Explanation:
58. (b): Leaves of a number of plants develop or possess adventitious buds for vegetative propagation e.g. Bryophyllum, Kalanchoe, Adiantum caudatum etc.
59. What type of placentation is seen in sweet pea?
(a) marginal
(b) basal
(c) axile
(d) free central
Answer and Explanation:
59. (a): The arrangement of ovules inside the ovary on placenta is called placentation. Sweet pea or Lathyrus odoratus belongs to family leguminosae or fabaceae and in all the members of this family the placentation is marginal in which ovary is unilocular and ovules are borne on margin.
60. The arrangement of the nuclei in a normal embryo sac in the dicot plants is
(a) 3 + 3 + 2
(b) 2 + 4 + 2
(c) 3+2 + 3
(d) 2 + 3 + 3
Answer and Explanation:
60. (c): Megaspore is the initial cell or beginning of female gametophyte or embryo sac. The nucleus of megaspore undergoes divisions and give rise to embryo sac or female gametophyte, which is called megagametogenesis.
During development, the single nucleus of functional megaspore (of chalazal end) undergoes 3 mitotic divisions to form 8 nuclei. Out of these 8 nuclei, 4 are present at micropylar end and 4 at chalazal end. One nucleus from each group conies in centre to form 2 polar nuclei. Remaining 3 nuclei at micropylar end constitute egg apparatus and remaining 3 nuclei at chalazal end constitute 3 antipodal cells or antipodals. So it is 3 + 2 + 3 arrangement.
So fully developed normal type of female gametophyte or embryo sac in 8-nucleated and 7-celled structure.
61. In a cereal grain the single cotyledon of embryo is represented by
(a) coleoptile
(b) coleorhiza
(c) scutellum
(d) prophyll
Answer:
(c) scutellum
62. Parthenocarpic tomato fruits can be produced by
(a) treating the plants with phenylmercuric acetate
(b) removing androecium of flowers before pollen grains are released
(c) treating the plants with low concentrations of gibberellic acid and auxins
(d) raising the plants from vernalized seeds
Answer and Explanation:
62. (c): Development of fruits without fertilization is called parthenocarpy and such fruits are called parthenocarpic fruits. Parthenocarpic fruits are seedless. A flower is emasculated and auxins are applied to the stigma of the flower, it forms a parthenocarpic fruit. For parthenocarpy induction by auxins, these should be applied after anthesis (first opening of flower) and by gibberellins, these should be applied earlier i.e., at anthesis.
63. Which one of the following is surrounded by a callose wall?
(a) male gamete
(b) egg
(c) pollen grain
(d) microspore mother cell.
Answer and Explanation:
63. (d): Anther consists of microsporangia or pollen sacs. The archesporium gives rise to parietal cells and primary sporogenous tissue. Sporogenous cells divide to form pollen grain or microspore mother cells. They are diploid and connected by plasmodesmata. The microspore, mother cells consists of a callose wall inner to the cell wall. The mother cell then undergoes meiosis and forms tetrads of microspores. Finally the wall of the mother cell degenerates and pollen grains are separated.
64. Two plants can be conclusively said to belong to the same species if they
(a) have more than 90 per cent similar genes
(b) look similar and possess identical secondary metabolites
(c) have same number of chromosomes
(d) can reproduce freely with each other and form seeds.
Answer and Explanation:
64. (d): If two plants can reproduce freely with each other and form seeds, they are concluded to belong to same species. Plants belonging to same species have mostly every character common and will be able to reproduce freely with each other to produce new generations.
65. Male gametes in angiosperms are formed by the division of
(a) generative cell
(b) vegetative cell
(c) microspore mother cell
(d) microspore.
Answer and Explanation:
65. (a): In the pollen sac (microsporangium) of the anther, haploid microspores are formed by mitosis. Mitosis then follows to produce a two-celled pollen grain with a small generative cell and a large vegetative cell. This generative cell will undergo further mitosis to form two male gametes (nuclei). The pollen tube grows through a spore in the pollen grain, with the tube (vegetative) nucleus at its tips and the male nuclei behind.