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Sexual Reproduction in Flowering Plants NCERT Solutions

Last Updated : 19 Jun, 2023
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*As per the revised curriculum of CBSE Syllabus 2023-24, this chapter, previously known as Chapter 2, has now been renumbered as Chapter 1. Stay updated with the latest changes in the curriculum.

Sexual Reproduction in Flowering Plants Class 12 NCERT Solutions is all about the process of Sexual Reproduction in Plants. These NCERT Solutions are prepared by our Top Biology Experts in order to take care of all Important Topics that might be asked in the upcoming examination 2023. So, Students can also refer to these solutions for their final Examination preparation.

This Class 12 Biology Chapter 1 Solutions offered are carefully developed using easy-to-understand language while adhering to the guidelines for solving NCERT Solutions for Class 12. Working through these solutions can be highly beneficial for students in their board exams, as well as in preparing for future competitive Exams.

Sexual Reproduction in Flowering Plants Class 12 Question Answer

Q1: Name the parts of an angiosperm flower in which the development of male and female gametophytes takes place.

Answer:

The male gametophyte or pollen grain develops in the anther and the female gametophyte or embryo sac develops in the nucellus part of the ovule.

Q2: 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.

Answer: 

The differences between Microsporogenesis and Megasporogenesis are given below:

Microsporogenesis

Megasporogenesis

This is the meiotic formation of haploid (n) microspores from a diploid (2n) mother cell This is the meiotic formation of haploid (n) megaspores from a diploid (2n) megaspore mother cell
Four functional microspores (tetrad spores) are formed Of the four spores and tetrad spores, only one megaspore is functional
Occurs in the microsporangium (in the pollen sac of the anthers) Occurs in the megasporangium (ovum)
The arrangement of the microspores in the tetrad is tetrahedral. The arrangement of the megaspores in the tetrad is linear
 
This leads to the formation of pollen grains This leads to the formation of embryo sacs

The cell division that occurs during megasporogenesis and microsporogenesis is meiosis, meiotic cell division, or reduction cell division, resulting in haploid (n) gametes.

  • The structures formed as a result of these events are:
    • Pollen grains are formed as a result of microsporogenesis
    • The embryo sac is formed by megasporogenesis

Q3: Arrange the following terms in the correct developmental sequence: 

Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.

Answer:

Sporogenous tissue → pollen mother cell → microspore tetrad → pollen grain → male gametes

As the microsporangium develops, each spore-forming tissue cell functions as a pollen stem cell (PMC) and gives rise to the microspore tetrad containing four haploids (n) microspores. It occurs in the process of microsporogenesis. As the anther matures, the microspores separate and turn into pollen grains. As pollen grains mature, male gametes are formed.

Q4: With a neat, labeled diagram, describe the parts of a typical angiosperm ovule.

Answer:

Following are the various part of the angiosperm ovule is:

  • Funicle: This is a stalk-like structure that attaches the ovule to the placenta.
  • Integuments: These are the protective layers of cells that surround the ovule. These are two in number i.e. outer and inner.
  • Micropyle: It leads the pollen tube into the ovule.
  • Nucellus: It provides nourishment to the developing embryo.
  • Synergids: They allow the pollen tube to develop in the embryo sac.
  • Antipodal cells: These provide nutrients to the entire gametophyte. 
  • Egg cell: It attaches to one of the male gametes and performs fertilization.
  • Polar nuclei: They fuse with another male gamete and perform double fertilization.
Angiosperm Ovule

 

Q5: What is meant by the monosporic development of female gametophytes?

Answer:

In most flowering plants, a single megaspore mother cell (MMC) is present at the micropylar pole of the ovule, which undergoes meiosis to produce four haploid megaspores. Of these four megaspores, only one functional megaspore develops in the female gametophyte (embryo sac). This is referred to as the monosporic development of the female gametophyte.

Q6: With a neat diagram, explain the 7-celled, 8-nucleate nature of female gametophyte.

Answer:

The female gametophyte is formed by a mitotic division in the megaspore mother cell (MMC). Mitotic division occurs three times, giving rise to 8 nucleated embryo sacs. The events mentioned are:

Female Gametophyte

 

After the first mitotic division, two nuclei are formed. Of these two nuclei, one extends to the micropylar end and the other to the chalazal end. Subsequent divisions lead to the formation of the 8-nucleate stage. Now, there are four nuclei at both ends. At the end of the micropyle, three of the four nuclei develop into an ovule and synergids. At the chalazal pole, three of the four nuclei transform into antipodal cells. The cells that remain on both ends move toward the centre and are called the polar nuclei. Thus, when mature, the female gametophyte resembles a 7-celled structure.

Q7: What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.

Answer:

There are two types of flowers in plants, namely chasmogamous and cleistogamous flowers. In chasmogamous flowers, the anthers and stigmas are well exposed. Cross-pollination cannot occur in cleistogamous flowers because cleistogamous flowers do not open at all. In these flowers, the anthers and stigma are close together. Therefore, only self-pollination can occur in cleistogamous flowers.

Q8: Mention two strategies evolved to prevent self-pollination in flowers.

Answer:

Strategies to prevent self-pollination include:

  • Self-Incompatibility– In some plants, the stigma of the flower has the ability to prevent pollen tube germination. This is a genetic mechanism to prevent self-pollination known as self-incompatibility. Incompatibility can occur between individuals of the same species or between individuals of different species. This prevents inbreeding.
  • Protogyny and Protandria – In some plants, the gynoecium matures before the androecium. This phenomenon is called protogyny. The phenomenon in which androecium matures before gynoecium is called protandry. These conditions prevent the pollen from contacting the stigma of the same flower.

Q9: What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?

Answer:

Self-incompatibility is a genetic mechanism present in flowering plants (angiosperms) that prevents self-pollination. It can occur between individuals of the same species or between individuals of different species. Plants exhibiting this phenomenon have the ability to inhibit pollen tube germination and thus prevent pollen tube growth on the pistil. This is because it prevents the fusion of male and female germ cells or gametes during the development of the embryo. Therefore, it does not lead to the formation of seeds.

Q10: What is the bagging technique? How is it helpful in a plant breeding programme?

Answer:

Some artificial breeding techniques (as part of some crop improvement programmes) remove the anthers of bisexual flowers without affecting the female reproductive part i.e. pistil. This process is called emasculation. Emasculated flowers are wrapped to prevent pollination by unwanted pollen grains. This process is called bagging or wrapping. This technique is important in a breeding programme because it ensures that only pollen grains from the desired plants can be used to fertilize to produce only the desired variety of plants.

Q11: What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.

Answer:

Triple fusion occurs when the male gamete fuses with the two polar nuclei of the embryo sac of flowering plants/angiosperms. The events mentioned are:

The pollen grains settle on the stigma of the pistil and begin to germinate, forming a protruding pollen tube which enters the ovule. The pollen tube penetrates one of the synergids and releases two male gametes there. Of the two male gametes, one fuse with the nucleus of the ovum and forms a zygote. The second male gamete fuses with the two polar nuclei present in the central cell, forming a triploid endosperm nucleus (TEN). The nuclei involved in triple fusion are: the nucleus of the male gametes and two polar nuclei

Q12: Why do you think a zygote is dormant for some time in a fertilized ovule?

Answer:

The zygote is formed by the union of the male gametes with the nucleus of the egg cell. The zygote remains dormant in the fertilized egg cell for some time until the endosperm has formed. The endosperm is formed from the primary endosperm cell after triple fusion. It provides nourishment for the developing embryo, and once the endosperm has formed, the zygote divides to form the embryo.

Q13: Differentiate between:

(a) Epicotyl and hypocotyl

(b) Coleoptile and coleorrhiza

(c) Integument and testa

(d) Perisperm and pericarp

Answer:

a) Difference between Epicotyl and hypocotyl

Epicotyl

Hypocotyl

This is part of an embryo above the cotyledons This is part of an embryo beneath the cotyledons
This starts from the node of the cotyledon This starts from the radicle
This elongates in the hypogeal germination which keeps the cotyledon in the soil This elongates in the epigeal germination to take the cotyledons out of the soil
This develops into the upper part of the stem which has leaves, flowers, and fruits This develops into the first part of the stem from which roots develop

b) Difference between Coleoptile and Coleorrhiza

Coleoptile

Coleorrhiza

This is the protective covering for the seed plumule This is the protective covering for the seed radicle
This grows upward i.e. above the ground This grows downward i.e. towards the soil/below the ground
This protects the shoot tip/plumule This protects the root tip/radicle
This turns into green colour, once emerges This does not turn into green colour at any time

c) Difference between Integument and Testa

Integument

Testa

It is the covering of the ovule/embryo-sac it is the covering of the seed
It is thin and could be single or double layered It is thick and single layered
It is derived from the chalazal end of the ovule It is derived from the outer integument of the ovule
It is formed before fertilization i.e. pre-fertilized structure It is formed after fertilization i.e. post-fertilized structure

d) Difference between Perisperm and Pericarp

Perisperm

Pericarp

It is the unused or persistent remains of nucellus in the seed  It is the covering of fruit that develops from the ovary wall
It is a part of the seed It has reserved food material
It is non-functional It is the protective covering which plays other roles also like dispersal and nutrition
Example- black pepper Example- coconut water

Q14: Why is an apple called a false fruit? Which part of the flower forms the fruit?

Answer:

The fruits that emerge from the ovary and other accessories of the flower, such as the thalamus, are called pseudocarp or accessory fruit. The apple comes from the thalamus part and is therefore called a false fruit.

Q15: What is meant by emasculation? When and why does a plant breeder employ this technique?

Answer:

Emasculation is a technique in which the stamens of bisexual flowers are removed before the anthers mature to prevent the flowers from self-pollinating. This technique is used when the plant breeder wants to get the desired characteristics in a plant. The flowers are bagged before the anthers are mature, known as bagging. This is to prevent unwanted pollen from landing on the stigma of this flower. As the anther matures, pollen grains are scattered onto the enveloped stigma and left for pollination into flowers with the desired characteristics.

Q16: If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?

Answer:

Parthenocarpy is the process by which fruit develops without fertilization or seed formation. Therefore, this technique is used to produce seedless varieties of some fruits, such as lemon, orange, pear, etc. Certain plant hormones or phytohormones play an important role in this technique, for example, auxins.

Q17: Explain the role of tapetum in the formation of pollen grain walls.

Answer:

The tapetum is the inner layer of the microsporangium (anther), which plays an important role in forming the pollen grain layers. It provides nutrients for the development of pollen grains. In addition, the tapetum produces some important amino acids, enzymes, and hormones that are necessary for the ripening of the pollen grains.

Q18:  What is apomixis and what is its importance?

Answer:

Apomixis is the practice of producing seeds without going through the process of meiosis and syngamy. Apomixis prevents the loss of specific characteristics in hybrid varieties. It is also an economical method of seed production.

Key Features of NCERT Solutions Class 12 Biology Chapter 1 Reproduction in Organisms

  • They enhance the conceptual knowledge of the students.
  • Clear and Comprehensible Content.
  • Aid in Competitive Exam Preparation.
  • The answers are provided by Top subject experts.
  • Readily available and easily accessible.

FAQs on Sexual Reproduction in Flowering Plants NCERT Solutions

Q1: What is the name of chapter 1 of ncert class 12 Biology?

Answer:

The First Chapter Name is Sexual Reproduction in Flowering Plants which is all about the process of reproduction in plants.

Q2: Where can I find NCERT solutions for Class 12 Biology Chapter 1?

Answer:

NCERT solutions for Class 12 Biology Chapter 1 can be found on various online platforms such as the official NCERT website, GeeksForGeeks, and more.

Q3: What is the importance of studying Class 12 Biology Chapter 1?

Answer:

The importance of studying Class 12 Biology Chapter 1, is it covers the entire syllabus to gain a comprehensive understanding of the subject. and here is the key points

  1. Foundation of Biological Concepts
  2. Understanding Life Processes
  3. Significance of Reproduction
  4. Awareness of Human Reproduction
  5. Competitive Exams

Q4: What are the topics covered in NCERT Class 12 Biology Chapter 1?

Answer:

The NCERT Solution covered all the Topics from NCERT TextBook According to latest 2023 CBSE Guidlines and its including Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes and more.



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