Apomixis and Polyembryony Questions in English

(A) The correct answer is $Apospory$.
$1$. $Apospory$ is the development of a gametophyte directly from a sporophytic cell (such as a spore mother cell) without undergoing $meiosis$.
$2$. In this process, the resulting gametophyte remains $diploid$ $(2n)$ because no reduction division occurs.
$3$. This phenomenon was first observed by $Druery$ $(1884)$ in the fern $Athyrium$ $filix-femina$.
$4$. In contrast, $Apogamy$ is the development of a sporophyte directly from a gametophytic cell without fertilization.

(A) Apogamy is a type of apomixis where the sporophyte develops directly from the gametophytic cells without the fusion of gametes.
Since these cells originate from the gametophyte,which is inherently haploid $(n)$,the resulting apogamous cells are also haploid $(n)$.

(C) Pinus exhibits both simple and cleavage polyembryony.
In simple polyembryony,multiple embryos develop due to the fertilization of different archegonia within the same ovule.
In cleavage polyembryony,the zygote undergoes cleavage to form multiple embryos from a single fertilized egg.

(A) In $Cycas$,multiple embryos are formed within a single seed,a condition known as polyembryony.
Specifically,it exhibits 'potential true polyembryony',where multiple embryos develop initially,but only one embryo survives and reaches maturity,while the others degenerate.

(C) Apospory is the development of a gametophyte directly from the vegetative cells of the sporophyte without the involvement of meiosis or the formation of spores. This process bypasses the typical alternation of generations where spores are required to produce the gametophyte.

(D) Arrhenotoky is a form of parthenogenesis where unfertilized eggs develop into haploid males. This process is commonly observed in Hymenopteran insects such as honey bees,wasps,and ants. In these organisms,the queen lays unfertilized eggs that develop into males (drones),while fertilized eggs develop into females (workers or queens).

(B) Apomixis is a form of asexual reproduction that mimics sexual reproduction.
In this process,seeds are produced without the fusion of gametes (fertilization) and without meiosis.
Therefore,the resulting offspring are genetically identical to the parent plant.

(D) The development of a sporophyte directly from the vegetative cells of the gametophyte without the fusion of gametes (fertilization) is known as $Apogamy$.
In contrast,$Apospory$ is the development of a gametophyte directly from the vegetative cells of the sporophyte without meiosis.
Therefore,the correct term for the given definition is $Apogamy$.

(C) The development of an embryo directly from the diploid sporophytic cells of the nucellus or integuments is known as adventive embryony.
This process is a type of apomixis where the embryo is formed without fertilization.
Examples include species of $Citrus$ and $Mangifera$.

(A) Adventive embryony is a form of apomixis where the embryo develops directly from diploid sporophytic cells,such as the $Nucellus$ or $Integuments$,without undergoing fertilization.
These cells protrude into the embryo sac and develop into embryos.
This process is common in plants like $Citrus$ and $Mango$.

(A) The formation of a gametophyte directly from the sporophyte tissue without undergoing meiosis is known as Apospory.
In this process,the diploid cells of the sporophyte develop into a haploid gametophyte without the reduction division (meiosis).
Conversely,Apogamy is the development of a sporophyte from a gametophyte without fertilization.

(B) In $Non-recurrent$ $apomixis$,the megaspore mother cell undergoes normal meiosis to form a haploid embryo sac.
Since the embryo sac is haploid,the embryo formed from it (if fertilization does not occur) is also haploid.
Such haploid plants are generally sterile because they cannot undergo normal meiosis during gametogenesis due to the lack of homologous chromosome pairs.
Therefore,the correct answer is $Non-recurrent$ $apomixis$.

(C) The formation of a sporophyte or embryo from a gametophytic cell without the process of fertilization (fusion of gametes) is known as apogamy.
$Apospory$ refers to the development of a gametophyte from a sporophyte without meiosis.
$Isogamy$ is the fusion of morphologically similar gametes.
$Syngamy$ is the actual fusion of male and female gametes to form a zygote.

(C) The development of a seed from an unfertilised egg or other cells of the embryo sac without fertilization is known as $Apomixis$.
$Vivipary$ refers to the germination of seeds while still attached to the parent plant.
$Parthenocarpy$ is the development of fruit without fertilization.
$Apospory$ is the development of a diploid gametophyte from a vegetative cell of the sporophyte without meiosis.

(D) Polyembryony is the phenomenon of having more than one embryo in a single seed.
In $Pinus$,both cleavage polyembryony and simple polyembryony are observed.
Cleavage polyembryony occurs when the zygote divides into multiple embryos,while simple polyembryony occurs due to the fertilization of multiple eggs within the same ovule.
Therefore,$Pinus$ is considered a classic example of polyembryony.

(C) Nucellar embryony is a type of apomixis where the embryo develops directly from the diploid nucellar cells surrounding the embryo sac.
Since the nucellar cells are diploid $(2n)$ and they develop into an embryo without fertilization,this process is known as adventitive embryony.
Therefore,nucellar embryo is an example of adventitive embryony.

(A) In agamospermy,the process of meiosis is bypassed during the formation of the embryo sac.
Specifically,in diplospory (a type of agamospermy),the megaspore mother cell $(MMC)$ undergoes mitosis instead of meiosis.
As a result,the $MMC$ directly develops into a diploid embryo sac without the reduction of chromosome number.
Therefore,the correct origin of such a diploid embryo sac is the megaspore mother cell.

(D) The correct answer is $D$. Adventive polyembryony is a phenomenon where embryos develop directly from diploid sporophytic cells such as the nucellus or integuments,rather than from the zygote. $A$ classic example of this is found in $Mango$ and $Citrus$.

(A) Polyembryony is defined as the occurrence of more than one embryo in a single seed.
In many species of $Citrus$,the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos.
Thus,each ovule contains many embryos,making it a characteristic feature of $Citrus$.

(A) Nuclear polyembryony is a phenomenon where multiple embryos develop from the nucellar cells surrounding the embryo sac.
In the genus $Citrus$,the nucellar cells start dividing,protrude into the embryo sac,and develop into embryos.
This results in the presence of more than one embryo within a single seed,which is a characteristic feature of $Citrus$ and some varieties of $Mango$ (though $Citrus$ is the most classic example cited in textbooks for nucellar polyembryony).

(B) The correct answer is $B$. Apomixis is a form of asexual reproduction that mimics sexual reproduction. In this process,the embryo develops directly from the egg cell or other diploid cells of the ovule without fertilization (syngamy) and meiosis. Since no fusion of gametes occurs,the genetic makeup of the offspring remains identical to the parent plant,resulting in uniform progeny despite the parent being highly heterozygous.

(D) $Apomixis$ is a form of asexual reproduction that mimics sexual reproduction. In this process,seeds are formed without the fusion of male and female gametes (fertilization). Therefore,it is an asexual process that replaces the sexual method of reproduction.

(D) Hybrid vigour (heterosis) is the phenomenon where the progeny of a cross between two genetically diverse parents shows superior traits compared to the parents. In sexually reproducing plants,hybrid vigour is lost in subsequent generations due to segregation and recombination during meiosis. Vegetative propagation is an asexual method of reproduction where the offspring are genetically identical clones of the parent plant. Therefore,if a desirable hybrid is produced,vegetative propagation ensures that the hybrid vigour is maintained indefinitely without any genetic change or loss of traits in the progeny.

(C) $Apomixis$ is the formation of new individuals directly through asexual reproduction without the involvement of gamete formation and fusion. Therefore,populations whose members reproduce by the process of $apomixis$ are called $apomictic$.

(A) The formation of a gametophyte directly from a sporophyte without the involvement of meiosis and spore formation is known as $Apospory$.
In this process,the diploid cells of the sporophyte develop into a haploid or diploid gametophyte.
$Apogamy$ is the opposite process,where a sporophyte develops directly from a gametophyte without fertilization.
$Apomixis$ is a form of asexual reproduction that mimics sexual reproduction,and $Parthenocarpy$ is the development of fruit without fertilization.

(C) Haploid parthenogenesis is a form of reproduction where an unfertilized haploid egg develops into a new individual.
In many insects,such as honeybees,this process is specifically known as $Arrhenotoky$,where unfertilized haploid eggs develop into males (drones).
$Thelytoky$ refers to the production of females from unfertilized eggs.
$Amphimixis$ involves the fusion of male and female gametes.
$Diplospory$ is a type of apomixis where the embryo sac develops from a diploid megaspore mother cell.

(A) Adventive polyembryony is a type of polyembryony where additional embryos develop from the diploid cells of the nucellus or integuments. In $Citrus$,these embryos typically arise from the nucellar cells surrounding the embryo sac. These cells protrude into the embryo sac and develop into embryos,which are genetically identical to the parent plant. Therefore,the correct answer is the nucellus.

(C) In normal meiosis,a spore mother cell $(SMC)$ undergoes one meiotic division to produce four haploid spores (tetrad). However,in some cases,the spore mother cell undergoes additional divisions,resulting in the formation of more than four spores. This phenomenon is known as $Polyspory$.

(A) Polyembryony is defined as the occurrence of more than one embryo in a seed.
In many species of $Citrus$ and $Mangifera$,some of the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos.
Thus,each ovule contains many embryos.
Therefore,$Citrus$ is the correct answer.

(A) The development of an embryo from an egg without fertilization is known as $Parthenogenesis$.
In the context of plants,when seeds are produced without fertilization,it is referred to as $Apomixis$.
However,specifically referring to the development of an embryo from an unfertilized egg,the term is $Parthenogenesis$.

(D) In plants, when an embryo develops directly from the vegetative cells of the sporophyte (such as nucellus or integuments) without fertilization, it is known as $Adventive \text{ } embryony$. This is a type of $Apomixis$ where the embryo bypasses the sexual cycle. Therefore, the correct option is $D$.

(B) The term 'apomixis' was introduced by the German botanist Hans Winkler in $1908$. Apomixis is a form of asexual reproduction that mimics sexual reproduction,where seeds are produced without fertilization.

(C) Polyembryony is the phenomenon of having more than one embryo in a seed.
It was first discovered by Antonie van Leeuwenhoek in $1719$ in the seeds of orange (Citrus).
Therefore,the correct answer is Leeuwenhoek.

(C) Apomixis is a form of asexual reproduction that mimics sexual reproduction. In this process,embryos are formed without the fusion of male and female gametes (fertilization). This phenomenon is commonly observed in some species of Asteraceae and grasses.

(A) Vegetative propagation is a form of asexual reproduction where new plants are formed from vegetative parts of the parent plant.
Apomixis is a form of asexual reproduction that mimics sexual reproduction but produces seeds without fertilization.
In both processes,the offspring produced are genetically identical to the parent plant,as they do not involve meiosis or syngamy.
Therefore,both result in the production of clones or progeny identical to the parent.

(A) Parthenogenesis is a form of asexual reproduction in which an embryo develops from an unfertilized egg cell. In this process,the female gamete (egg) undergoes development into a new individual without fertilization by a male gamete (sperm). This is a common phenomenon in various organisms,including some insects,reptiles,and plants (often associated with apomixis).

(A) Adventive embryony is a type of apomixis where the embryo develops directly from the diploid cells of the nucellus or integuments,bypassing the normal process of fertilization. In this process,these diploid cells start dividing and form an embryo that protrudes into the embryo sac. Therefore,the correct answer is the nucellus and integuments.

(B) The development of an embryo from any cell of the embryo sac other than the egg cell (such as synergids or antipodal cells) is known as $Apogamy$.
In $Apogamy$, the embryo develops without fertilization from haploid cells of the gametophyte.
$Apospory$ refers to the development of a gametophyte from vegetative cells of the sporophyte.
$Adventive$ $\text{embryony}$ involves the development of an embryo directly from diploid sporophytic cells like the nucellus or integuments.
$Apomixis$ is a general term for asexual reproduction that mimics sexual reproduction.

(C) Apomixis is a form of asexual reproduction that mimics sexual reproduction. In this process,seeds are produced without fertilization (fusion of gametes). Since there is no meiosis or syngamy involved,the offspring are genetically identical to the parent plant. This phenomenon is commonly observed in species of $Asteraceae$ and grasses.

(A) The development of an embryo from any cell of the embryo sac other than the egg cell (such as synergids or antipodal cells) is known as $Apogamy$.
In this process, the haploid cells of the embryo sac give rise to the embryo without fertilization.
$Apospory$ refers to the development of a diploid embryo sac from a vegetative cell of the nucellus.
$Adventive$ $\text{embryony}$ involves the development of an embryo directly from diploid sporophytic cells like the nucellus or integuments.
$Diplospory$ is a type of apomixis where the embryo sac develops from a diploid megaspore mother cell.

(C) 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.
Therefore,both Citrus and Mango exhibit polyembryony.
Thus,the correct option is $C$.

(B) Apomixis is a form of asexual reproduction that mimics sexual reproduction. In flowering plants,it is a mechanism to produce seeds without fertilization. It involves the development of an embryo without the fusion of male and female gametes. Therefore,it represents the failure or avoidance of the fusion of gametes to produce a seed.

(C) Adventive embryony is a type of polyembryony where embryos develop directly from the diploid cells of the nucellus or integuments. In $Citrus$ and $Mango$,the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos. This process is a form of apomixis where the embryo is genetically identical to the parent plant.

(A) 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. This phenomenon is known as nucellar polyembryony. Therefore,$Citrus$ is the correct answer.

(B) In citrus,apomixis is a common phenomenon where embryos develop without fertilization.
Specifically,in citrus,the nucellar cells surrounding the embryo sac start dividing,protrude into the embryo sac,and develop into embryos.
This process is known as adventive polyembryony.
Since these cells are part of the maternal sporophytic tissue (nucellus),they are diploid and genetically identical to the parent plant.
Therefore,the correct option is $B$.

(B) : Apomixis is a form of asexual reproduction that mimics sexual reproduction. In apomictic flowering plants,seeds are formed without the process of fertilisation. The embryos develop directly from the cells of the ovule without the fusion of male and female gametes.

(A) : In nucellar polyembryony,some of the nucellar cells surrounding the embryo sac start dividing.
These cells then protrude into the embryo sac and develop into embryos.
In such species,each ovule contains many embryos.
The occurrence of more than one embryo in a seed is referred to as polyembryony.
Nucellar polyembryony is commonly found in many species of $Citrus$ and $Mangifera$ (mango).

(B) : Apomixis is a form of asexual reproduction that mimics sexual reproduction. In $Citrus$,apomictic embryos are formed through adventive embryony.
Adventive embryony is a type of apomixis where embryos develop directly from the diploid maternal sporophytic tissues of the ovule,such as the nucellus or integuments,without fertilization.
Since these cells are diploid and part of the parent plant,the resulting embryos are genetically identical to the parent plant.

(A) Parthenogenesis is a form of asexual reproduction where an embryo develops from an unfertilized egg.
In $Honeybees$,the queen bee produces eggs that can develop into males $(Drones)$ without fertilization through parthenogenesis.
This process is a common phenomenon in certain insects,rotifers,and some lizards.