Maharashtra Board Class 12 Solutions for Biology Chapter 1 Reproduction in Lower and Higher Plants

Multiple Choice Questions

1. Insect pollinated flowers usually possess:

1. Sticky pollens with rough surface 

2. Large quantities of pollens

3. Dry pollens with a smooth surface

4. Light colored pollens

Ans: Correct Option : (a) Sticky pollens with rough surface 

• Insect pollinated flowers usually possess sticky pollen with a rough surface.

• The pollination carried out through the insects is called Entomophily.

• The pollen grains are usually spiny and mucilaginous due to the presence of a pollen kit.

2. In the ovule, meiosis occurs in ..........

1. Integument 

2. Nucellus

3. Megaspore 

4. Megaspore mother cell

Ans: Correct Option : (d) Megaspore mother cell

• In the ovule, meiosis occurs in the megaspore mother cell.

• Integument, nucellus is the accessory part found in the ovule(female gametophyte).

• Megaspore(haploid) is formed as the result of meiosis undergone by the megaspore mother cell(diploid).

3. The ploidy level is NOT the same in ......

1. Integuments and nucellus

2. Root tip and shoot tip

3. Secondary nucleus and endosperm

4. Antipodals and synergids

Ans:   Correct Option : (c) secondary nucleus and endosperm.

• The ploidy level is NOT the same in the secondary nucleus and endosperm.

• The ploidy is the set of chromosomes present in a particular group of cells in a ovule.

• Root tip and shoot tip, integument and nucellus, antipodal, and synergids hold the same level of ploidy.

• Secondary nucleus is of diploid nature as it gets formed as a result of a fusion of two haploid polar nuclei.

• Endosperm is of triploid nature as it gets formed by the fusion of two polar nuclei and one of the two male nuclei.

4. Which of the following types require pollination but the result is genetically similar to autogamy?

1. Geitonogamy 

2. Xenogamy

3. Apogamy 

4. Cleistogamy

Ans: Correct Option : (a) Geitonogamy

• Geitonogamy is the type that requires a pollinator but the result is genetically similar to autogamy.

• Transfer of pollen grains of one plant to the stigma of the same plant. It is a way autogamy is carried out by avoiding cross-pollination.

• Pollinators are required in the completion process of geitonogamy.

5. If the diploid chromosome number in a flowering plant is 12, then which one of the following will have 6 chromosomes?

1. Endosperm

2. Leaf cells

3. Cotyledons

4. Synergids

Ans: Correct Option: (d) Synergids

• The one having a haploid number of chromosomes is synergid.

• The number of haploid cells are found in sexual reproduction carrying out cells, which means synergids, polar nuclei, and egg cells.

• Synergids are the intricate part of the female gametophyte that shows filiform projections known as filiform apparatus.

6. In angiosperms, the endosperm is formed by/ due to ..........

1. Free nuclear divisions of megaspore

2. polar nuclei

3. polar nuclei and male gamete

4. synergids and male gamete

Ans: Correct Option : (c) Polar Nuclei and male gamete

• In angiosperm, the endosperm is formed by the fusion of one of the male gametes with the two polar nuclei present at the center of the female gametophyte.

• The four cells present at each pole, out of them one each from both the sides, migrate in the center and these allocated nuclei are termed polar nuclei.

• They possess a haploid number of chromosomes each.

7. Point out the odd one ..........

1. Nucellus

2. Embryo sac

3. Micropyle

4. Pollen grain

Ans: Correct Option: (d) Pollen Grain

• The odd one out is pollen grain.

• It is the oddest of all because it belongs to the male gamete-associated structure.

• Rest of the options, which include nucellus, embryo sac, and micropyle belong to the ovule of the female gametophyte.

Very Short Answer Type Questions

1. Name the part of gynoecium that determines the compatible nature of pollen grain.

Ans: Stigma is the part of gynoecium(pistil) that determines the compatible nature of pollen grain. Stigma ensures the intraspecific pollen germinates only, other than that the pollen having intraspecific differences should be prevented from getting germinated.

2. How many haploid cells are present in a mature embryo sac?

Ans: The number of haploid cells present in the mature embryo sac is 8 in number.

• The haploid cells found are present at two different ends respectively the chalazal end and micropylar end.

• At the micropylar end two synergids and one egg cell possess a haploid set of chromosomes.

• At the chalazal end, three antipodal cells present are haploid.

• At the center of the female gametophyte two cells are present called polar nuclei(N) each.

3. Even though each pollen grain has 2 male gametes, why are at least 20 pollen grains required to fertilize 20 ovules in a particular carpel?

Ans: 

• Once we look into the pattern of fusion of gametes after germination occurs, we notice that out of two male gametes only one fuses with the egg cell present at the micropylar end.

• The second male gamete fuses with the pair of polar nuclei present in the center, forming endosperm, viz. used to provide nourishment to the female gametophyte or ovule.

• Thus, from the process we get a clear picture, that only one gamete of the pollen grain is used for fertilizing the respective female gamete(egg cell)  at a time.

• This is why 20 pollen grains are required to fertilize 20 female ovules, in the particular carpel.

4. Define Megasporogenesis. 

Ans: The process of formation of haploid cells from the diploid cells is called meiotic division. The megaspore mother cell has a diploid number of chromosomes when it undergoes successive cell division and forms a haploid megaspore cell. This process is termed Megasporogenesis. Megasporogenesis takes place in the female gametophyte.

5. What is hydrophily?

Ans: The pollination carried/facilitated by the water is termed hydrophily. Example-  Vallisneria, Ceratophyllum. The adaptation they hold are as follows-

• They possess small inconspicuous flowers.

• They lack nectar and fragrance.

• Pollen grains are long and hydrophobic.

6. Name the layer which supplies nourishment to the developing pollen grains.

Ans: The layer that supplies nourishment to the developing pollen grains is the tapetum layer found inside the anther.

• Tapetum is deeply embedded in the anther.

• It is the innermost layer of the anther.

7. Define parthenocarpy.

Ans:  The development of fruit without fertilization is termed parthenocarpy. As a result of parthenocarpy, seedless fruits could be acquired. The term parthenocarpy was given by Noll in 1902.

8. Are pollination and fertilization necessary in apomixis?

Ans:  The development of an embryo without fertilization is termed apomixis.

• It is a kind of asexual reproduction and the formation of gamete does not take place in it.

• For example- orange and mango.

9. Name the parts of the pistil which develop into fruits and seeds.

Ans:

• The part of the pistil i.e gynoecium that develops in fruit is the ovary.

• The part of the pistil that develops into seeds is the ovule.

• The development takes place commonly after successful pollination, germination, and fertilization.

10. What is the function of a filiform apparatus?

Ans:

• The function of the filiform apparatus present in the synergids is to guide the pollen grain (male gamete ) to the egg of the ovule.

• Filiform apparatus is the feature of synergid cells, present at the micropylar end of the ovule.

• Out of eight nuclei present in the ovule two synergids, haploid in nature are present along with the egg cell where the actual fusion of gametes takes place.

Short Answer Questions

1. How can polyembryony be commercially exploited?

Ans:

• Polyembryony is a process in which the formation of multiple embryos takes place at a time, from a single ovule.

• The formation of another embryo may take place with the help of nucellus and integument.

• They result in the formation of similar embryos as obtained from the fusion of gametes.

• It can be commercially exploited by the means that rather than obtaining a single plant, the commercials acquire numerous plants at a time without any extra effort.

2. Pollination and seed formation are very crucial for fruit formation. Justify the statement.

Ans: 

• The term pollination refers to the transfer of pollen grain to the stigma of either the same plant or the different plant.

• Pollination is a medium through which non-motile male gametes may reach their respective stigma so as to fertilize and produce new plants respectively.

• Seed formation takes place as a result of the fusion of the two gametes, after which the embryo further develops to form the seed and its intricate parts such as the seed coat (integument)

• The goal of seed formation is universally the only way to obtain offspring for the next generation.

• Thus, yes pollination and seed formation are crucial for seed formation.

3. Incompatibility is a natural barrier in the fusion of gametes. How will you explain this statement?

Ans:

• Incompatibility refers to the incapabilities that the gametes face while carrying out the pollination because the fusion takes place only when the pollen is of intraspecific species.

• The reason behind it may be the maturation stage gap between the male and female gamete along with that the physical, and physiological barriers play a crucial role.

• Natural barriers can be explained using the examples of protogyny, protandry, herkogamy, heterostyly, etc.

• All of the self-incompatibility processes are a way to obtain bred species, and demote the inbreeding depression.

4. Describe three devices by which cross-pollination is encouraged in Angiosperms by avoiding self-pollination.

Ans:

• The devices through which cross-pollination is encouraged are as follows- 

1. Diocese

2. Dichogamy

3. Herkogamy

• In the first method dioecism refers to the plantation of dioecious plants i.e., male and female gametes on two different plants.

• Dichogamy refers to the protandry and protogyny where the male gamete and female gamete mature prior to the other respectively.

• Herkogamy is a form of mechanical barrier introduced so as to avoid self-pollination by methods such as bagging etc.

Long Answer Questions

1. Describe the process of double fertilization.

Ans: 

• The process of double fertilization is observed in the angiosperms(flowering plants; phanerogams)

• When two male gametes produced from the generative cell pass the pistil pollen interaction successfully, they get to fertilize the egg cell by entering the ovule.

• The ovule when unfertilized consists of 8 haploid nuclei arranged accordingly at their respective positions.

• When the male gamete enters the ovule, one of the fuses with the egg cell, which further forms the embryo by undergoing syngamy.

• The second male gamete fuses the secondary nucleus, viz, formed by the fusion of two polar nuclei. As a result of this fusion, the formation of endosperm takes place which provides nourishment to the embryo.

• The formation of triploid endosperm and diploid syngamy zygote at a time is referred to as double fertilization.

2. Explain the stages involved in the maturation of microspores into male gametophytes.

Ans:

• The stages of development of microspore into male gametophyte are as follows-

• At the first stage each microspore or pollen grain undergoes unequal mitotic division wherein they form a thin-walled generative nucleus and a bigger, naked irregular nucleus possessing a vegetative nucleus.

• The generative nuclei divide(mitotically) further to form two male gametes that owing to the fertilization process enter the ovule via synergids.

3. Explain the development of the dicot embryo.

Ans: The development of the dicot embryo can be classified in the following levels-

• The zygote formed as a result of syngamy forms the bicelled proembryo.

• The two called proembryo divides to form basal or micropylar end associated cells called suspensor cells initials and apical cells(at the chalazal end) form the embryonal initials.

• The basal cells divide to form 6-10 film entous suspensor cells.

• The cells formed through the basal filamentous suspensor cells result in the formation of haustoria and hypophysis.

• The apical embryonic initial cells give rise to the octant stage(obtained from successive divisions at a right angle) after it undergoes three successive mitotic divisions.

• The upper four cells form the plumule and cotyledons respectively whereas the lower tetrad cells lead to the formation of hypocotyl and radicle.

• The hypophyseal region of the suspensor cell contributes to making the radicle and forms the root cap simultaneously.

• Cells of the upper tier divide and form a heart-shaped structure and on its further enlargement contribute to the formation of the cotyledons.

• This is how the ovule gets converted to form seed and ovary into fruit on the further development of scutellum, coleoptile, and coleorhiza.

4. Draw a labeled diagram of the L.S. of the anatropous ovule and list the components of the embryo sac and mention their fate after fertilization.

Ans: Components of embryo sac are as follows -pair of synergids, pair of polar nuclei, egg cells, and three antipodal cells.

• Synergids - disintegrate after the fertilization takes place and during fertilization it holds a water-absorbing surface by the male gamete.

• Polar nuclei-fuses with male gamete to form an endosperm that provides nourishment to the embryo.

• Egg cell - fertilize to form the zygote.

• Antipodal cells -likewise they also disintegrate along with synergids right after fertilization takes place.

L.S. of The Anatropous Ovule

Fill in the Blanks

1. The ..................... collects the pollen grains. 

Ans:  The stigma  collects the pollen grain.

• It is the receptive part where pollen pistil interaction is being checked.

• The stigma checks for the intraspecific species.

2. The male whorl, called the ..................... produces ..................... .

Ans: The male whorl, called the Androecium produces male gametes.

• The male gametes are produced by the pollen grain that undergoes unequal mitotic division to form vegetative and generative nuclei simultaneously.

• The generative nucleus is responsible for forming two male gametes.

• The vegetative nucleus contributes to the formation of tube cells.

3. The pollen grains represent the ........................

Ans:  The pollen grain represents the male gametophyte.

It consists of tapetum, endothecium, sporogenous tissue, connective tissue, etc.

4. The .................... contains the egg or ovum. 

Ans: The embryo sac contains the egg or ovum in angiosperm. The embryo sac is an 8-celled structure.

5.  ....................     takes place when one male gamete and the egg fuse together. The 

a fertilized egg grows into a seed from which the new plants can grow.

Ans: Syngamy takes place when one male gamete and egg fuse together.

6.  ......................... is the transfer of pollen grains from the anther of the flower to the stigma of the same or a different flower.

Ans:  Pollination is the transfer of pollen grains from the anther of the flower to the stigma of the same or a different flower.

It is carried out by using different agents such as water, air animals, and birds.

7. Once the pollen reaches the stigma, the pollen tube traverses down the ................... to the ovary where fertilization occurs.

Ans:  Once the pollen reaches the stigma, the pollen tube traverses down the stigma to the ovary where fertilization occurs.

8. The ................................ is the base of the flower to which other floral parts are attached.

Ans: The thalamus is the base of the flower to which other floral parts are attached.

9. The whorl ...................... is green that protects the flower until it opens.

Ans: The whorl calyx is green which protects the flower until it opens.

The calyx is a leafy structure that surrounds the flower' corolla', androecium, and gynoecium present within it.

Match the Column

Ans:

Explanation

• Funiculus is the stalk of seeds, it is termed the umbilical cord of the embryo through which the seeds are attached. When it detaches from the seed it leaves a scar behind.

• The scar of the ovule is the point of attachment of the hilum with the funicle. 

• The zygote divides further to form embryos.

• Inner integument forms the tegmen. It acts as a barrier between the inner environment and outer respectively.

Importance of Maharashtra Board Class 12 Biology Chapter 1 Reproduction in Lower and Higher Plants

As mentioned earlier, every organism reproduces. There are different methods of reproduction that a species has developed over the years. It is an essential process that ensures the continuity of life. In fact, it is a characteristic that defines life. A living organism will surely follow a way to reproduce and give birth to the next generation.

Lower plants follow two different types of reproductive measures. These two major types are sexual and asexual reproduction. As the name suggests, sexual reproduction involves two different sexes or gametes. The union of two different gametes will result in the formation of another generation.

On the other hand, asexual reproduction is something different. In this method of reproduction, there is no involvement of gametes. Gametes are not produced or fertilized to create offspring. In this aspect, plants follow spore formation, budding, fission, fragmentation, and other asexual methods to produce young ones.

Most asexual methods are vegetative in nature. The process follows where the parent plant gives birth to an identical plant from any of its parts. Various such methods have also been developed artificially to promote vegetative reproduction in agriculture.

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Download Reproduction in Lower and Higher Plants Class 12 Solutions PDF

You can now download and get the free PDF version of the solutions along with the notes for the chapter Reproduction in Lower and Higher Plants. Find out a detailed explanation of the concepts related to reproduction in plants with examples in these solutions. Resolve your queries, make your preparation better and score well in the board exams.