Solution- Sexual Reproduction in Flowering Plants Test Class 12 Notes | EduRev

Class 12 : Solution- Sexual Reproduction in Flowering Plants Test Class 12 Notes | EduRev

 Page 1


      CBSE TEST PAPER-02 
CLASS - XII BIOLOGY (Sexual Reproduction in Flowering Plants) 
(Answer Key) 
1. Microsporogenesis results into formation of four haploid pollen grains arranged
generally in a tetrahedral tetrad while Megasporogenesis forms four megaspores
arranged in linear tetrad.
2. The stalk of the ovule is called funiculus.
3. Production and development of seedless fruit is called parthenocarpy.
4. The process that leads to the formation of microspores from pollen mother cell through
meiosis is referred to as microsporogenesis.
5. Emasculation that is the stamens are removed prior to artificial hybridization to ensure
no undesirable pollens fall on the stigma and the flower can be pollinated with the
desired pollen grains.
6. The structure of the microsporangium is as follows:
- It is almost circular with four wall layers.
- The outer three layers: epidermis, endothecium and middle layers are protective in
function and help in dehiscence of anther to release pollen grains.
- The inner tapetum nourishes the developing embryo. Sporogenous tissue occupies the
central position.
Page 2


      CBSE TEST PAPER-02 
CLASS - XII BIOLOGY (Sexual Reproduction in Flowering Plants) 
(Answer Key) 
1. Microsporogenesis results into formation of four haploid pollen grains arranged
generally in a tetrahedral tetrad while Megasporogenesis forms four megaspores
arranged in linear tetrad.
2. The stalk of the ovule is called funiculus.
3. Production and development of seedless fruit is called parthenocarpy.
4. The process that leads to the formation of microspores from pollen mother cell through
meiosis is referred to as microsporogenesis.
5. Emasculation that is the stamens are removed prior to artificial hybridization to ensure
no undesirable pollens fall on the stigma and the flower can be pollinated with the
desired pollen grains.
6. The structure of the microsporangium is as follows:
- It is almost circular with four wall layers.
- The outer three layers: epidermis, endothecium and middle layers are protective in
function and help in dehiscence of anther to release pollen grains.
- The inner tapetum nourishes the developing embryo. Sporogenous tissue occupies the
central position.
7. Pollen grains are well preserved as fossils because the exine of the pollens is composed of
a chemical, sporopollenin which can withstand high temperature, strong acids and
alkalies and strong enzymes
8. An embryo sac is a 7 celled and 8 nucleated structure. At the micropylar end is present a
group of three cells; two synergids and one egg cell. The chalazal end consists of three
cells called antipodals. There is a central cell with two polar nuclei.
9. In a cleistogamous flower, the flower never opens and when the anther dehisce in the bud
the pollen grains fall on the stigma of the same flower and thus it is strictly autogamous.
10. Advantage: Pollen grains are rich in nutrients and therefore in the western world pollen
tablets are used as food supplements.
Disadvantage: Pollens of many species cause severe allergies and bronchial afflictions
leading to chronicle respiratory disorder.
11. 
 Microsporogenesis  Megasporogenesis 
1. It is the formation of haploid
microspores or pollen grains from the 
diploid microspore mother cell. 
1. it is the formation of megaspores from
the diploid megaspore mother cell. 
2. The pollen grains are arranged in
tetrahedral tetrad. 
2. The megaspores are arranged in linear
tetrad. 
3. All the microspores are functional. 3. Only one megaspore is functional.
Others degenerate. 
12. The microspore has a dense cytoplasm and a prominent nucleus in the centre. As the
microspore matures the nucleus is pushed towards the periphery due the formation of
vacuoles in the upper end of the cytoplasm. The nucleus divides mitotically to form two
nuclei which separate out into two cells; the upper bigger vegetative cell and the lower
generative cell. A mature pollen grain normally has two cells.
13. The nucleus of the vegetative cell of the pollen grain fuse with the two polar nuclei of the
central cell of the female gametophyte fuse to form the primary endosperm. This fusion is
known as vegetative fusion or triple fusion as it involves three nuclei.
It occurs in the central cell of the egg apparatus.
14. An anatropous ovule consists of:
Page 3


      CBSE TEST PAPER-02 
CLASS - XII BIOLOGY (Sexual Reproduction in Flowering Plants) 
(Answer Key) 
1. Microsporogenesis results into formation of four haploid pollen grains arranged
generally in a tetrahedral tetrad while Megasporogenesis forms four megaspores
arranged in linear tetrad.
2. The stalk of the ovule is called funiculus.
3. Production and development of seedless fruit is called parthenocarpy.
4. The process that leads to the formation of microspores from pollen mother cell through
meiosis is referred to as microsporogenesis.
5. Emasculation that is the stamens are removed prior to artificial hybridization to ensure
no undesirable pollens fall on the stigma and the flower can be pollinated with the
desired pollen grains.
6. The structure of the microsporangium is as follows:
- It is almost circular with four wall layers.
- The outer three layers: epidermis, endothecium and middle layers are protective in
function and help in dehiscence of anther to release pollen grains.
- The inner tapetum nourishes the developing embryo. Sporogenous tissue occupies the
central position.
7. Pollen grains are well preserved as fossils because the exine of the pollens is composed of
a chemical, sporopollenin which can withstand high temperature, strong acids and
alkalies and strong enzymes
8. An embryo sac is a 7 celled and 8 nucleated structure. At the micropylar end is present a
group of three cells; two synergids and one egg cell. The chalazal end consists of three
cells called antipodals. There is a central cell with two polar nuclei.
9. In a cleistogamous flower, the flower never opens and when the anther dehisce in the bud
the pollen grains fall on the stigma of the same flower and thus it is strictly autogamous.
10. Advantage: Pollen grains are rich in nutrients and therefore in the western world pollen
tablets are used as food supplements.
Disadvantage: Pollens of many species cause severe allergies and bronchial afflictions
leading to chronicle respiratory disorder.
11. 
 Microsporogenesis  Megasporogenesis 
1. It is the formation of haploid
microspores or pollen grains from the 
diploid microspore mother cell. 
1. it is the formation of megaspores from
the diploid megaspore mother cell. 
2. The pollen grains are arranged in
tetrahedral tetrad. 
2. The megaspores are arranged in linear
tetrad. 
3. All the microspores are functional. 3. Only one megaspore is functional.
Others degenerate. 
12. The microspore has a dense cytoplasm and a prominent nucleus in the centre. As the
microspore matures the nucleus is pushed towards the periphery due the formation of
vacuoles in the upper end of the cytoplasm. The nucleus divides mitotically to form two
nuclei which separate out into two cells; the upper bigger vegetative cell and the lower
generative cell. A mature pollen grain normally has two cells.
13. The nucleus of the vegetative cell of the pollen grain fuse with the two polar nuclei of the
central cell of the female gametophyte fuse to form the primary endosperm. This fusion is
known as vegetative fusion or triple fusion as it involves three nuclei.
It occurs in the central cell of the egg apparatus.
14. An anatropous ovule consists of:
- a stalk called funicle attached to the placenta. 
- the junction between the funicle and the ovule is called helium. 
- The ovule may be surrounded by one or more integuments with an opening at the tip. 
The opening is called the micropyle. 
- the opposite end of the micropyle is referred to as chalazal end, the basal part of the 
ovule. 
- mass of cells known as nucellus is present within the integuments that contain normally 
single embryo sac. 
15. -The functional megaspore grows in size.
- The nucleus divides mitotically to form two nuclei which move to opposite poles.
- Each nucleus at the poles undergoes two mitotic divisions to form four nuclei in each
pole or a total of 8 nuclei.
- two nuclei from each pole move to the centre to form the polar nuclei.
-the other nuclei, three at each pole get surrounded by bit of cytoplasm to form cells.
- the female gametophyte or the embryo sac thus has 7 cells and eight nuclei.
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