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Reproduction in Plants - Sexual Reproduction in Flowering Plants

Questions - Answers

Very Short Answer type Questions (2 Marks)

1. Name the common functions that cotyledons and nucellus perform .

A: Both cotyledons and nucellus contain abundant food materials. The cotyledons provide food and energy to the germinating seed. The nucellus provides food for the growing embryo.

2. Name the parts of pistil which develop into fruit and seeds .

A: Ovary develops into fruit. Ovule develops into seed.

3. In case of polyembryony, if an embryo develops from the synergid and another from the nucellus which is haploid and which is diploid?

A: The embryo that develops from synergids is haploid and the embryo that develops from the nucellus is diploid.

4. Which are the three cells found in a pollen grain when it is shed at the three celled stage?

A: One vegetative cell and Two male gametes.

5. What is self-incompatibility ?

A: Inhibition of pollen germination or pollen tube growth on the pistil is called self incompatibility or self-sterility. e.g.: Abutilon.

6. Which is the triploid tissue in a fertilized ovule? How is the triploid condition achieved?

A: Endosperm. Triploid condition is achieved by fertilization of second male gamete with two polar nuclei of central cell to form a primary endosperm nucleus.

7. Mention two strategies evolved to prevent self-pollination in flowers .

A: Dichogamy 

     Herkogamy 

     Heterostyly 

     Self-sterility

8. Why do you think the zygote is dormant for some time in a fertilized ovule?

A: Zygote is dependent for its nourishment on the endosperm to form an embryo. Hence it is dormant for some time until some endosperm is formed.

9. If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?

A: Grapes and Guava. These fruits are selected because they are relished seedless and can be used directly for preparation of jams, jellies and squashes.

SHORT ANSWER TYPE QUESTIONS (4 MARKS)

1. List any three strategies that a bisexual chasmogamous flower can evolve to prevent self pollination (Autogamy).

A: Bisexual chasmogamous flowers prevent self pollination by the following out breeding devices:

a) Dichogamy: Maturation of Androecium and gynoecium at different times in a flower is called Dichogamy. If the pollen is released before the stigma becomes receptive it is called Protandry. e.g.: Sunflower. If the stigma becomes receptive before the release of pollen it is called Protogyny. e.g.: Datura.

b) Herkogamy: If the anthers and stigma are placed at different positions so that the pollen cannot come in stigma of the same flower it is called Herkogamy. e.g.: Gloriosa and Hibiscus.

c) Heterostyly: The styles of the flowers of the same species are in different heights.

e.g.: Primula.

d) Self-sterility: The germination of self-pollen on the stigma is prevented. e.g.: Abutilon.

2. Given below are the events that are observed in an artificial hybridization programme. Arrange them in the correct sequential order in which they are followed in the hybridization programme.

a) Re-bagging

b) Selection of parents

c) Bagging

d) Dusting the pollen on stigma

e) Emasculation

f) Collection of pollen from male parent

A: 1) Selection of parents

2) Emasculation

3) Bagging

4) Collection of pollen from male parent

5) Dusting the pollen on stigma

6) Re-bagging.

3. What is polyembryony and how can it be commercially exploited?

A: Occurrence of more than one embryo in a seed is called polyembryony. Embryos from seeds of Citrus and Mango varieties can be removed and cultured by embryo culture to produce large number of plants in a short span of time. If the embryos are developed from haploid cells like synergids they can be used to produce haploid plants which are used in genetic studies.

4. Are parthenocarpy and apomixis different phenomena? Discuss their benefits.

A: Yes parthenocarpy and apomixis are different phenomena. Parthenocarpy refers to production of fruits without fertilization of the ovary. As these seeds do not contain seeds they are relished by the consumer. Also seedless fruits are used in preparation of jams, jellies and squashes. Hence such fruits are produced commercially.

Apomixis refers to production of seeds without fertilization. Apomixis is used in production of hybrid seeds to avoid segregation of characters. This helps the farmer to use these apomictic hybrid seeds continuosly without buying them every year.

5. Why does the zygote begin to divide only after the division of primary endosperm cell (PEC)?

A: The zygote is dependent for its nourishment on the endosperm for further development into an embryo. Hence it starts dividing only after the primary endosperm cell divides sufficiently and produce sufficient amount of endosperm.

6. Discuss the various types of pollen tube entry into ovule with the help of diagrams. Pollen tube may enter the ovule by any of the following methods:

A: Porogamy: The pollen tube enters the ovule through the micropyle.

     Chalazogamy: The pollen tube enters the ovule through the chalaza.

     Mesogamy: The pollen tube enters the ovule through the integuments.

7. Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events?

A: Microsporogenesis is the formation of microspores from microspore mother cell inside the microsporangium of an anther. Megasporogenesis the formation of megaspore from megaspore mother cell inside the nucellus of embryo sac in a ovule.

Meiosis occurs in both these events.

Microspores are formed at the end of microsporogenesis.

Megaspores are formed at the end of megasporogenesis.

8. What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.

A: The fusion of three haploid nuclei inside the embryo sac is called triple fusion. It takes place inside the embryo sac. After one male gamete fuses with the egg cell, the second male gamete enters the central cell and fuses with the two polar nuclei. One male nucleus and two polar nuclei.

9. Differentiate between

a) Hypocotyl and epicotyl b) Coleoptile and coleorhiza

c) Integument and testa d) Perisperm and pericarp

A: * The portion below the level of cotyledons in a embryonal axis is called hypocotyl and the portion above the level of cotyledons in a embryonal axis is called epicotyl.

* The hollow foliar structure that covers the shoot apex in a monocot embryo is called coleoptile. The sheath like structure that covers the radical in a monocot embryo is called coleorhiza.

* Integument is the outer covering of a ovule. Testa is the outer covering of a seed coat in a seed.

* Perisperm is the remnant of nucellus in some seeds. Pericarp is the fruit wall.

LONG ANSWER TYPE QUESTIONS (8 MARKS)

1. Describe the process of fertilization in angiosperms .

A: After pollination the pollen grain germinates on the stigma and enters the ovary by producing a pollen tube.

* The pollen tube carries two male gametes formed from the generative cell in the pollen grain.

* Later the pollen tube enters the ovule by means of porogamy, mesogamy or chalazogamy.

* The pollen tube enters one of the synergids and bursts to release the two male gametes in the cytoplasm of the synergid.

* One of the male gametes fuses with the egg cell to form a diploid zygote. This is called syngamy or fertilization.

* The other male gamete fuses with the central cell with two polar nuclei to produce a primary endosperm nucleus (PEN). As this fusion involves fusion of three haploid nuclei it is called triple fusion.

* Since two types of fusions syngamy and triple fusion occur in the embryo sac, this phenomenon is called double fertilization.

* Later the zygote develops into an embryo and the central cell with primary endosperm nucleus develops into endosperm. 

Posted Date : 11-11-2021

గమనిక : ప్రతిభ.ఈనాడు.నెట్‌లో కనిపించే వ్యాపార ప్రకటనలు వివిధ దేశాల్లోని వ్యాపారులు, సంస్థల నుంచి వస్తాయి. మరి కొన్ని ప్రకటనలు పాఠకుల అభిరుచి మేరకు కృత్రిమ మేధస్సు సాంకేతికత సాయంతో ప్రదర్శితమవుతుంటాయి. ఆ ప్రకటనల్లోని ఉత్పత్తులను లేదా సేవలను పాఠకులు స్వయంగా విచారించుకొని, జాగ్రత్తగా పరిశీలించి కొనుక్కోవాలి లేదా వినియోగించుకోవాలి. వాటి నాణ్యత లేదా లోపాలతో ఈనాడు యాజమాన్యానికి ఎలాంటి సంబంధం లేదు. ఈ విషయంలో ఉత్తర ప్రత్యుత్తరాలకు, ఈ-మెయిల్స్ కి, ఇంకా ఇతర రూపాల్లో సమాచార మార్పిడికి తావు లేదు. ఫిర్యాదులు స్వీకరించడం కుదరదు. పాఠకులు గమనించి, సహకరించాలని మనవి.

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