Apomixis and Polyembryony Questions in English

(B) $1$. The production of seeds without fertilization is indeed called apomixis. This is a form of asexual reproduction that mimics sexual reproduction.
$2$. The occurrence of more than one embryo in a seed is correctly referred to as polyembryony. This is commonly observed in species like Citrus and Mango.
$3$. Pollen grains represent the male gametophytes in angiosperms,as they contain the male gametes.
Since all three statements are scientifically correct,the total number of correct statements is $3$.

(A) The formation of a gametophyte directly from a sporophyte without undergoing meiosis is known as $Apospory$. In this process,the diploid cells of the sporophyte develop into a gametophyte without the reduction division. Conversely,$Apogamy$ is the development of a sporophyte directly from a gametophyte without fertilization. $Apomixis$ is a general term for asexual reproduction that mimics sexual reproduction,and $Amphimixis$ refers to normal sexual reproduction involving the fusion of gametes.

(D) The development of an organism from an unfertilized female gamete or egg is known as $Parthenogenesis$.
$Apogamy$ refers to the development of an embryo from cells other than the egg cell (like synergids or antipodals).
$Polyembryony$ is the occurrence of more than one embryo in a seed.
$Parthenocarpy$ is the development of fruit without fertilization.

(A) Adventive embryony is a type of polyembryony where embryos develop directly from the diploid cells of the nucellus or integuments.
In citrus,the cells of the nucellus surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos.
Since these cells are diploid and originate from the maternal tissue (nucellus),the resulting embryos are genetically identical to the parent plant.
Therefore,the correct answer is $A$ (Nucellus).

(A) Adventive embryony is a form of apomixis where the embryo arises directly from diploid sporophytic cells such as the nucellus or integuments,bypassing the process of fertilization. These cells protrude into the embryo sac and develop into embryos. This is commonly observed in species like Citrus and Mango.

(B) Adventive embryony is a type of polyembryony where embryos develop directly from the diploid sporophytic cells of the ovule,such as the nucellus or integuments,without fertilization.
In citrus,the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos.
Therefore,adventive embryos in citrus arise from the nucellar cells.

(D) Adventive polyembryony is a type of polyembryony where embryos develop directly from the diploid cells of the nucellus or integuments,bypassing the fertilization process.
This phenomenon is commonly observed in species like $Citrus$ and $Mangifera$ (Mango).
In these plants,the nucellar cells surrounding the embryo sac start dividing and protrude into the embryo sac,eventually developing into embryos.
Therefore,among the given options,$Citrus$ is the correct species where adventive polyembryony is reported.

(C) Apomixis is a form of asexual reproduction that mimics sexual reproduction,where seeds are formed without fertilization. In this process,the embryo develops directly from the diploid egg cell or other cells of the embryo sac without undergoing meiosis or syngamy. This is a common phenomenon in species of Asteraceae and grasses.

(D) Vegetatively propagated crops are ideal for maintaining hybrid varieties because vegetative propagation is a form of asexual reproduction.
In asexual reproduction,the offspring are genetically identical to the parent plant (clones).
Therefore,once a desirable hybrid genotype is obtained,it can be maintained indefinitely through vegetative propagation without the risk of segregation or recombination of traits that occurs during sexual reproduction (meiosis).
This ensures that the specific characteristics of the hybrid are preserved across generations.

(D) The phenomenon where the female gamete develops into an embryo without fertilization is known as $Parthenogenesis$.
In the context of plants,this is often associated with $Apomixis$.
$Autogamy$ refers to self-pollination.
$Parthenocarpy$ refers to the development of fruit without fertilization.
$Syngamy$ is the fusion of male and female gametes (fertilization).

(B) In plants,normal sexual reproduction includes meiosis and fertilization. It is called amphimixis.
But in some plants,an abnormal form of reproduction called apomixis has been observed.
Apomixis is a form of asexual reproduction that mimics sexual reproduction,where seeds are formed without the processes of syngamy (fertilization) and meiosis.
In this process,the egg or other cells like synergids or antipodals develop into an embryo without fertilization.
The term apomixis was coined by Winkler $(1908)$.
Examples include $Citrus$ and $Ranunculus$.

(D) Vegetative reproduction and apomixis are both forms of asexual reproduction.
In both processes,the offspring produced are genetically identical to the parent plant because no meiosis or fertilization occurs to create genetic variation.
Therefore,both methods result in the production of clones.

(N/A) Apomixis is a form of asexual reproduction that mimics sexual reproduction,where seeds are produced without the processes of meiosis and syngamy.
Its importance lies in the following points:
$1$. It plays a crucial role in hybrid seed production.
$2$. Cultivating hybrid seeds is expensive for farmers,and the hybrid characters do not remain stable over generations due to segregation during meiosis.
$3$. Apomixis prevents the loss of specific hybrid characters in the progeny.
$4$. It is a cost-effective method for large-scale seed production.

(N/A) Apomixis is a special mechanism evolved by some flowering plants,such as species of $Asteraceae$ and grasses,to produce seeds without fertilization.
It is a form of asexual reproduction that mimics sexual reproduction.
In some species,a diploid egg cell is formed without reduction division (meiosis) and develops into an embryo without fertilization.
In other cases,such as in $Citrus$ and $Mango$,nucellar cells surrounding the embryo sac start dividing and develop into embryos. This leads to polyembryony,where each ovule contains multiple embryos.
Importance of Apomixis:
$1$. Hybrid varieties of food and vegetable crops significantly increase productivity.
$2$. However,hybrid seeds must be purchased every year because seeds collected from hybrid plants segregate and do not maintain hybrid characteristics in the next generation.
$3$. If hybrids are made into apomicts,there is no segregation of characters in the progeny.
$4$. This allows farmers to use seeds from their own harvest to raise new crops every year without having to buy expensive hybrid seeds annually.
$5$. Active research is ongoing to transfer apomictic genes into hybrid varieties to reduce costs for farmers.

(A) $(i)$ All single-celled eukaryotes are placed under the kingdom Protista.
$(ii)$ The process of seed formation without fertilization is known as Apomixis.

(N/A) Hybrid varieties of several food and vegetable crops are being extensively cultivated,which has tremendously increased productivity.
One of the major problems with hybrids is that hybrid seeds must be produced every year.
If seeds collected from hybrid plants are sown,the progeny will segregate,and the hybrid characters will not be maintained.
Production of hybrid seeds is costly,making them expensive for farmers.
If these hybrids are made into apomicts,there is no segregation of characters in the hybrid progeny.
Consequently,farmers can use the seeds from their own harvest to raise new crops year after year without needing to purchase new hybrid seeds annually.

(N/A) $1.$ Apomixis: The process of producing seeds without fertilization is known as apomixis.
$2.$ Polyembryony: The occurrence of more than one embryo in a single seed is referred to as polyembryony.

(A) $1$. The synergid is a cell of the embryo sac,which is formed after meiosis and is therefore haploid $(n)$. An embryo developing from a synergid (apogamy) will be haploid $(n)$.
$2$. The nucellus consists of maternal sporophytic tissue,which is diploid $(2n)$. An embryo developing from the nucellus (adventive polyembryony) will be diploid $(2n)$.

(A) Yes,an unfertilised,apomictic embryo sac can give rise to a diploid embryo.
This occurs through a process called diplospory or apospory.
In diplospory,the megaspore mother cell undergoes mitosis instead of meiosis,resulting in a diploid embryo sac.
Consequently,the egg cell within this embryo sac is diploid $(2n)$.
This diploid egg cell then develops directly into an embryo through mitotic divisions without undergoing fertilisation,a process known as parthenogenesis.

(N/A) No,pollination and fertilisation are not necessary in apomixis. The reasons are as follows:
$(i)$ In many cases of apomixis,the embryo is formed without meiosis from the megaspore mother cell or other diploid cells. The ovules remain diploid and are converted directly into embryos.
$(ii)$ In adventive embryony,the embryo is formed from the cells of the diploid nucellus. Since the egg cell or the surrounding cells are already diploid,they develop into embryos without the need for fertilisation or syngamy.

(N/A) The occurrence of more than one embryo in a seed is referred to as polyembryony.
In many citrus and mango varieties,some of the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos. In such species,each ovule contains many embryos.
Polyembryony plays a major role in plant breeding and horticulture.
The plants obtained from these embryos are typically virus-free and exhibit vigorous growth.
Many fruit and vegetable crops are propagated using this method,as these nucellar embryos produce clones that maintain the desirable traits of the parent plant,leading to higher productivity and uniformity in hybrid crops.

(N/A) Yes,parthenocarpy and apomixis are distinct biological phenomena.
$\Rightarrow$ Benefits of Parthenocarpy:
$(i)$ Parthenocarpy is the development of fruit without fertilisation of the ovule. It is commercially used to produce seedless fruits such as $Banana$ and $Grapes$.
(ii) It is highly beneficial in the fruit juice and food processing industries as it eliminates the need for seed removal.
Benefits of Apomixis:
$(i)$ During apomixis,there is no meiosis or syngamy,so the genetic characteristics of the parent are maintained across many generations without segregation.
(ii) It facilitates the production of hybrid seeds. Since hybrid seeds do not segregate in the progeny,farmers do not need to buy new hybrid seeds every year.
(iii) Adventive embryony is used to produce virus-free plant varieties and to maintain specific rootstock characteristics.

(A) Apomixis is a form of asexual reproduction that mimics sexual reproduction but occurs without fertilization. In many apomictic species,the embryo sac develops from a diploid megaspore mother cell $(MMC)$ that undergoes mitosis instead of meiosis.
$1$. In some species,the $MMC$ does not undergo meiosis,resulting in a diploid embryo sac. Consequently,the egg cell within this sac is also diploid.
$2$. This diploid egg cell develops directly into an embryo without the need for fertilization (parthenogenesis).
$3$. In other cases,such as in $Citrus$,cells of the nucellus surrounding the embryo sac start dividing and protrude into the embryo sac to develop into embryos (adventive embryony).
Because the process bypasses meiosis,the resulting embryo sac and the embryo remain genetically identical to the parent plant,maintaining a diploid state despite appearing morphologically normal.

(B) Apomixis is a form of asexual reproduction that mimics sexual reproduction.
In this process,seeds are produced without the occurrence of fertilization (syngamy) and meiosis.
Therefore,it is defined as the formation of seeds without fertilization.

(D) Apomixis is a form of asexual reproduction that mimics sexual reproduction. It is commonly observed in the family $Asteraceae$ and in many species of grasses. In these plants,seeds are produced without fertilization. Therefore,both $A$ and $B$ are correct.

(D) Polyembryony is the occurrence of more than one embryo in a seed.
It is a common phenomenon in many species of the genus $Citrus$ (e.g.,lemon,orange) and $Mangifera$ (mango).
In these plants,some of the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos.
Therefore,the correct option is $D$.

(A) $Polyembryony$ is defined as the occurrence of more than one embryo in a seed. This phenomenon is commonly observed in species like $Citrus$ and $Mango$. During this process,additional embryos may arise from the synergids,antipodal cells,or the nucellus,leading to the development of multiple embryos within a single ovule that matures into a seed.

(A) $Apomixis$ is a form of asexual reproduction that mimics sexual reproduction.
In this process,seeds are formed without fertilization.
Since there is no fusion of gametes and no meiosis involved in the formation of the embryo,the offspring produced are genetically identical to the parent plant.
Therefore,they are considered genetic clones.

(C) The incorrect statement is that all plants of the Asteraceae family form fruits through sexual reproduction. In many plants of the Asteraceae family and grasses,seeds are produced without fertilization through a process called apomixis. Apomixis is a form of asexual reproduction that mimics sexual reproduction. The other statements are correct: Orobanche and Striga are parasitic plants known for producing a massive number of tiny seeds. Polyembryony is a well-documented phenomenon in mango ($Mangifera$ $indica$) and citrus. Hybrid seeds lose their hybrid vigor in subsequent generations,necessitating the production of fresh hybrid seeds every year.

(A) The process in which an embryo develops from an unfertilized egg is known as $Parthenogenesis$.
$Parthenocarpy$ refers to the development of fruit without fertilization.
$Apomixis$ is a form of asexual reproduction that mimics sexual reproduction,often used in plants.
Therefore,the correct term for the development of an embryo from an egg without fertilization in animals is $Parthenogenesis$.

(B) Apomixis is a form of asexual reproduction that mimics sexual reproduction. In this process,seeds are produced without fertilization. Because apomictic seeds are genetically identical to the parent plant,they do not segregate traits in the offspring. This is highly beneficial in hybrid seed production because it prevents the loss of hybrid vigor in subsequent generations,eliminating the need for farmers to purchase new hybrid seeds every year.

(A) Apomixis is a form of asexual reproduction that mimics sexual reproduction. In this process,seeds are produced without fertilization. Specifically,a diploid embryo is formed from the diploid egg cell or other diploid cells of the embryo sac without undergoing meiosis or fertilization.

(D) Apomixis is a form of asexual reproduction that mimics sexual reproduction,where seeds are produced without fertilization. It does not involve meiosis or syngamy.
Amphimixis is the normal sexual reproduction involving meiosis and fertilization (syngamy).
Therefore,the rate and mechanism of multiplication differ significantly between the two.
Assertion is incorrect because multiplication rates and mechanisms are not the same.
Reason is incorrect because apomixis does not involve meiotic division.
Thus,both Assertion and Reason are incorrect.

(B) Apomixis is defined as the development of seeds without fertilization.
Although seeds are generally the product of fertilization,a few flowering plants,such as some species of $Asteraceae$ and grasses,have evolved a special mechanism to produce seeds without fertilization,which is known as apomixis.

(D) In $Citrus$ and $Mango$ plants,some of the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into many embryos.
In such species,each ovule contains many embryos.
The occurrence of more than one embryo in an ovule is referred to as $Polyembryony$.

(C) Although seeds are generally the product of fertilization,a few flowering plants,such as some species of $Asteraceae$ and grasses,have evolved a special mechanism to produce seeds without fertilization,which is called apomixis.

(C) The process in which a haploid embryo develops directly from a haploid egg cell without the process of fertilization is known as $Apogamy$.
$Apogamy$ is a type of $Apomixis$ where the embryo arises from cells other than the zygote (specifically from the egg cell or other gametophytic cells) without syngamy.
$Apospory$ refers to the development of a diploid gametophyte from a vegetative cell of the sporophyte.
$Agamospermy$ is the formation of seeds without fertilization.
Therefore,the correct term for the formation of an embryo from a haploid egg without fertilization is $Apogamy$.

(C) Apomixis is a form of asexual reproduction that mimics sexual reproduction,where seeds are produced without fertilization.
Specifically,the formation of seeds without fertilization is known as agamospermy,which is a type of apomixis.
Parthenocarpy refers to the development of fruit without fertilization.
Parthenogenesis refers to the development of an embryo from an unfertilized egg.
Apogamy refers to the development of an embryo from cells other than the egg cell (e.g.,synergids or antipodals) without fertilization.

(C) Adventive polyembryony is a type of polyembryony where embryos develop directly from the diploid cells of the nucellus or integuments of the ovule, bypassing the normal sexual process. This phenomenon is commonly observed in species like $Mango$ $(Mangifera \text{ } indica)$ and $Citrus$.

(C) The correct statement is that there are many embryos of different sizes and shapes in the seeds of orange. This phenomenon is known as polyembryony.
$A$. The hanging drop method is used for in-vitro (not in-vivo) germination of pollen grains to study pollen tube growth.
$B$. The obturator is a structure that guides the pollen tube,but it is not a universal feature for all seeds.
$C$. Polyembryony is common in citrus fruits like orange,where multiple embryos develop within a single seed.
$D$. In adventive embryony,embryos arise from diploid sporophytic cells (like nucellus or integuments),not from the egg cell.

(C) Statement $I$ is correct: Apomixis is a form of asexual reproduction that mimics sexual reproduction by producing seeds without fertilization.
Statement $II$ is correct: In apomictic plants,the embryo can develop from a diploid egg cell (diplospory) or from the diploid cells of the nucellus (adventive embryony).
Statement $III$ is incorrect: Seeds collected from hybrid plants do not maintain hybrid characters for a long time because segregation and independent assortment during meiosis lead to the loss of hybrid vigor in subsequent generations.
Statement $IV$ is incorrect: Apomixis is a form of asexual reproduction; therefore,there is no meiosis and no segregation of characters.
Thus,only statements $I$ and $II$ are correct.

(D) Apogamy is the development of a sporophyte directly from the gametophyte cells without the fusion of gametes (fertilization).
Since the sporophyte is formed directly from the gametophyte tissue,it retains the ploidy level of the gametophyte.
Therefore,a tetraploid gametophyte would produce a tetraploid sporophyte,not the other way around.
Thus,the Assertion is incorrect.
Reasoning: Apogamy is a type of apomixis where the sporophyte develops without fertilization.
Since fertilization is absent,the Reason statement is also incorrect because it implies apogamy involves fertilization.

(A) Apomixis is a form of asexual reproduction that mimics sexual reproduction.
In apomixis,seeds are produced without fertilization.
Since there is no meiosis or fusion of gametes involved,the offspring are genetically identical to the parent plant.
Because the offspring are clones of the parent,the segregation of traits (which occurs during sexual reproduction due to meiosis and recombination) is prevented.
Therefore,both the Assertion and the Reason are correct,and the Reason correctly explains why apomixis is considered an asexual mode of reproduction that maintains genetic stability.

(A) Polyploids with an odd number of chromosomes (e.g.,triploids,$3n$) often face difficulties during meiosis because homologous chromosomes cannot pair correctly.
This leads to the production of unbalanced gametes,which results in sterility and the absence of seed formation.
Since these plants cannot reproduce sexually through seeds,they must be propagated vegetatively to maintain the population.
Therefore,both the Assertion and the Reason are correct,and the Reason explains why vegetative propagation is necessary.

(C) Polyembryony is the phenomenon of having more than one embryo in a single seed.
It is a characteristic feature of $Gymnosperms$ (e.g.,$Pinus$).
While it can occur in some $Angiosperms$ (like $Citrus$ or $Mango$),it is a defining and common characteristic feature of the $Gymnosperm$ group.

(B) $1$. Parthenocarpy is the process of fruit development without fertilization,resulting in seedless fruits (e.g.,banana).
$2$. Apomixis is a form of asexual reproduction that mimics sexual reproduction,where seeds are formed without fertilization (e.g.,some species of Asteraceae and grasses).
$3$. Therefore,$P$ is Parthenocarpy and $Q$ is Apomixis.

(C) The phenomenon of the occurrence of more than one embryo in a seed is called $Polyembryony$.
$Apomixis$ is the production of seeds without fertilization.
$Parthenocarpy$ is the development of fruit without fertilization.
Therefore,the correct answer is $Polyembryony$.

(D) Polyembryony is the occurrence of more than one embryo in a seed.
In many species of $Citrus$ and $Mango$,some of the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos.
Gymnosperms also frequently exhibit polyembryony.
Therefore,all the given options are correct examples of plants that exhibit polyembryony.

(A) Apogamy refers to the development of an embryo or a plant from cells other than the zygote. When this process occurs from haploid cells within the embryo sac (excluding the egg cell,such as synergids or antipodal cells),it is termed as haploid apogamy. Since these cells are haploid $(n)$,the resulting plant is also haploid. Therefore,the formation of a plant from haploid cells of the embryo sac other than the egg cell is the correct definition.