Plant Development and Morphogenesis Questions and Answers

Q: Arabidopsis plants have 10 chromosomes (5 pairs) in their somatic cells. How many chromosomes are present in each of the following ?(i) egg cell nucleus in the female gametophyte(ii) generative cell nucleus in a pollen grain(iii) endosperm nucleus(iv) fertilized egg nucleus

The counts are 5, 5, 15, 10.The somatic number is 2n = 10, so n = 5.The egg cell of the female gametophyte is haploid: 5.The generative cell of the pollen grain is haploid: 5.The endosperm nucleus forms when a sperm fuses with the two polar nuclei, so it is triploid: 15.The fertilised egg (zygote) is diploid: 10.The option 5, 5, 10, 15 swaps the endosperm and the zygote, and the other two treat the gametophyte cells as diploid or triploid, which they are not.

Q: The unit of pollen dispersal in Calotropis is :

The unit of pollen dispersal in Calotropis is the pollinium.In Calotropis and other milkweeds, all the pollen grains of an anther lobe are held together in a waxy sac, the pollinium. Pollinia from adjacent anthers are joined by a translator into a pollinarium, which clings to the leg of a visiting insect and is carried off as one unit.Most plants disperse single grains (monads). Tetrads, four grains kept together after meiosis, occur in plants such as Typha and ericads, and dyads are rarer still; none is the unit in Calotropis.

Q: Which of the following statements about LEAFY (LFY), a regulatory gene in Arabidopsis thaliana is correct ?

The correct statement is that LFY is involved in floral meristem identity.LEAFY encodes a plant-specific transcription factor that, together with APETALA1, converts the flanks of the inflorescence meristem into floral meristems. In lfy mutants of Arabidopsis, flowers are replaced by shoot-like structures, and over-expression of LFY makes shoots flower early. LFY then activates the floral organ identity genes such as APETALA3 and AGAMOUS.Despite its name, it does not control leaf expansion, and it has no role in root meristem identity or in general shoot differentiation.

Q: Which of the following statements about embryo sac development in plants is NOT CORRECT ?

The statement that is not correct is Polygonum type of embryo sac is derived from the micropylar megaspore of the tetrad and is eight nucleate.In the Polygonum (monosporic) type, which occurs in most flowering plants, the three megaspores towards the micropyle degenerate and the chalazal megaspore develops. Three mitotic divisions give eight nuclei, which organise into seven cells. So 'eight nucleate' is right, but the functional megaspore is the chalazal one, not the micropylar one.The other statements are correct. A mature embryo sac is usually seven-celled and eight-nucleate (three antipodals, two synergids, the egg and the binucleate central cell). The Plumbago type is tetrasporic: all four megaspore nuclei take part. The two synergids sit beside the egg at the micropylar end and are elongated cells with a filiform apparatus.

Q: In plants, when the apical cell of the 2-celled pro-embryo divides longitudinally and further the basal cell plays only a minor role or none in the development of the embryo proper then the embryo is ............ type.

The embryo is of the Onagrad type.In Johansen's classification of angiosperm embryo development, the first point is how the apical (terminal) cell of the two-celled proembryo divides. A longitudinal division places the embryo in the Crucifer group, which is split by the role of the basal cell. In the Onagrad (Crucifer) type, the basal cell contributes little or nothing to the embryo proper; in the Asterad type, the basal cell also contributes to it.In the Solanad and Chenopodiad types, the apical cell divides transversely, so they are excluded by the first condition.

Q: Floral development associated AGAMOVS, PISTILLATA and APETALA3 genes of Arabidopsis encodes proteins with ..................... domain.

These genes encode proteins with a MADS domain.AGAMOUS (printed AGAMOVS), PISTILLATA and APETALA3 are floral organ identity genes of the ABC model in Arabidopsis. All three encode MADS-box transcription factors, named after MCM1, AGAMOUS, DEFICIENS and SRF, which bind DNA as dimers and specify petals, stamens and carpels.GRAS (printed GRASS), WRKY and NAC are other plant transcription factor families, involved in processes such as gibberellin signalling, defence and stress responses, and development of secondary walls. They are not the domain shared by these floral genes.

21.

Arabidopsis plants have 10 chromosomes (5 pairs) in their somatic cells. How many chromosomes are present in each of the following ?

(i) egg cell nucleus in the female gametophyte
(ii) generative cell nucleus in a pollen grain
(iii) endosperm nucleus
(iv) fertilized egg nucleus

A.5, 5, 15, 10
B.5, 5, 10, 15
C.15, 10, 5, 5
D.10, 15, 5, 5

Exam Year(s)

MH SET - 2020, SET Exam - 2020,

Answer: A

The counts are 5, 5, 15, 10.

The somatic number is 2n = 10, so n = 5.

The egg cell of the female gametophyte is haploid: 5.
The generative cell of the pollen grain is haploid: 5.
The endosperm nucleus forms when a sperm fuses with the two polar nuclei, so it is triploid: 15.
The fertilised egg (zygote) is diploid: 10.

The option 5, 5, 10, 15 swaps the endosperm and the zygote, and the other two treat the gametophyte cells as diploid or triploid, which they are not.

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22.

Androgenesis in plants refers to :

A.development of androecium
B.development of anthers
C.development of haploid embryo from microspores or pollen in vitro
D.Initiation of androecium

Exam Year(s)

MH SET - 2020, SET Exam - 2020,

Answer: C

Androgenesis is the development of haploid embryo from microspores or pollen in vitro.

In anther or pollen culture, immature pollen grains are switched from their normal path to pollen development and divide to form embryos or callus, giving haploid plants from the male gametophyte. Guha and Maheshwari first produced such plants from Datura anthers in 1964; doubling the chromosomes then gives homozygous lines.

Development or initiation of the androecium and the anthers is ordinary flower development, not androgenesis.

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23.

The unit of pollen dispersal in Calotropis is :

A.dyad
B.tetrad
C.monad
D.pollinium

Exam Year(s)

MH SET - 2020, SET Exam - 2020,

Answer: D

The unit of pollen dispersal in Calotropis is the pollinium.

In Calotropis and other milkweeds, all the pollen grains of an anther lobe are held together in a waxy sac, the pollinium. Pollinia from adjacent anthers are joined by a translator into a pollinarium, which clings to the leg of a visiting insect and is carried off as one unit.

Most plants disperse single grains (monads). Tetrads, four grains kept together after meiosis, occur in plants such as Typha and ericads, and dyads are rarer still; none is the unit in Calotropis.

Discuss in Forum

24.

Which of the following statements about LEAFY (LFY), a regulatory gene in Arabidopsis thaliana is correct ?

A.LFY is involved in floral meristem identity
B.LFY is involved in leaf expansion
C.LFY is involved in root meristem identity
D.LFY is involved in shoot differentiation

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: A

The correct statement is that LFY is involved in floral meristem identity.

LEAFY encodes a plant-specific transcription factor that, together with APETALA1, converts the flanks of the inflorescence meristem into floral meristems. In lfy mutants of Arabidopsis, flowers are replaced by shoot-like structures, and over-expression of LFY makes shoots flower early. LFY then activates the floral organ identity genes such as APETALA3 and AGAMOUS.

Despite its name, it does not control leaf expansion, and it has no role in root meristem identity or in general shoot differentiation.

Discuss in Forum

25.

With reference to plants, gynogenesis refers to :

A.Initiation of gynoecium
B.Development of gynoecium
C.Development of haploid plants from the egg cell of unfertilized female gametophyte in vitro
D.Development of an ovary

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: C

Gynogenesis is the development of haploid plants from the egg cell of unfertilized female gametophyte in vitro.

In plant tissue culture, haploids can be raised from either gametophyte. Androgenesis uses anthers or pollen; gynogenesis uses unpollinated ovaries or ovules, inducing the egg (or another embryo sac cell) to develop without fertilisation. It is used in crops such as onion, sugar beet and gerbera where anther culture works poorly, and the haploids are doubled to give homozygous lines for breeding.

Initiation and development of the gynoecium, or of an ovary, are normal flower development, and the word is not used for them.

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26.

When somatic cells of ovule directly form embryos, the phenomenon is called as ......................

A.Adventive embryony
B.Diplospory
C.Apospory
D.Parthenogenesis

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: A

Embryos formed directly from somatic cells of the ovule are called adventive embryony.

In adventive embryony, a form of sporophytic apomixis, embryos arise directly from diploid cells of the nucellus or integument, without forming an embryo sac or gametophyte. It is common in Citrus and mango, where a seed may contain several nucellar embryos alongside the zygotic one (polyembryony).

Diplospory and apospory are gametophytic apomixis: an unreduced embryo sac forms, from the megaspore mother cell in diplospory or from a somatic nucellar cell in apospory, and its egg develops without fertilisation. Parthenogenesis is that development of an unfertilised egg, not the direct formation of embryos from somatic cells.

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27.

Which of the following statements about embryo sac development in plants is NOT CORRECT ?

A.Embryo sac is mostly a 7-celled structure
B.Plumbago type of embryo sac is derived from four megaspore nuclei
C.Synergids are elongated cells present at the micropylar end of the embryo sac
D.Polygonum type of embryo sac is derived from the micropylar megaspore of the tetrad and is eight nucleate

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: D

The statement that is not correct is Polygonum type of embryo sac is derived from the micropylar megaspore of the tetrad and is eight nucleate.

In the Polygonum (monosporic) type, which occurs in most flowering plants, the three megaspores towards the micropyle degenerate and the chalazal megaspore develops. Three mitotic divisions give eight nuclei, which organise into seven cells. So 'eight nucleate' is right, but the functional megaspore is the chalazal one, not the micropylar one.

The other statements are correct. A mature embryo sac is usually seven-celled and eight-nucleate (three antipodals, two synergids, the egg and the binucleate central cell). The Plumbago type is tetrasporic: all four megaspore nuclei take part. The two synergids sit beside the egg at the micropylar end and are elongated cells with a filiform apparatus.

Discuss in Forum

28.

In plants, when the apical cell of the 2-celled pro-embryo divides longitudinally and further the basal cell plays only a minor role or none in the development of the embryo proper then the embryo is ............ type.

A.Asterad
B.Onagrad
C.Solanad
D.Chenopodial

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: B

The embryo is of the Onagrad type.

In Johansen's classification of angiosperm embryo development, the first point is how the apical (terminal) cell of the two-celled proembryo divides. A longitudinal division places the embryo in the Crucifer group, which is split by the role of the basal cell. In the Onagrad (Crucifer) type, the basal cell contributes little or nothing to the embryo proper; in the Asterad type, the basal cell also contributes to it.

In the Solanad and Chenopodiad types, the apical cell divides transversely, so they are excluded by the first condition.

Discuss in Forum

29.

Floral development associated AGAMOVS, PISTILLATA and APETALA3 genes of Arabidopsis encodes proteins with ..................... domain.

A.GRASS
B.WRKY
C.MADS
D.NAC

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: C

These genes encode proteins with a MADS domain.

AGAMOUS (printed AGAMOVS), PISTILLATA and APETALA3 are floral organ identity genes of the ABC model in Arabidopsis. All three encode MADS-box transcription factors, named after MCM1, AGAMOUS, DEFICIENS and SRF, which bind DNA as dimers and specify petals, stamens and carpels.

GRAS (printed GRASS), WRKY and NAC are other plant transcription factor families, involved in processes such as gibberellin signalling, defence and stress responses, and development of secondary walls. They are not the domain shared by these floral genes.

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