Mix Examples-Sexual Reproduction in Flowering Plants Questions in English

(A) In $Paramecium$,both autogamy and conjugation are classified as sexual processes primarily because they involve the process of genetic recombination.
During these processes,the micronuclei undergo meiosis,followed by the exchange or fusion of haploid nuclei,which results in the formation of a new diploid nucleus with a unique genetic combination.
This genetic recombination leads to variation,which is a hallmark of sexual reproduction,even though conjugation involves two individuals and autogamy involves only one.

(D) In organisms with a haplontic life cycle,the zygote undergoes meiosis to produce haploid spores,which then develop into the gametophyte. The gametes are subsequently produced by mitosis. However,in organisms where meiosis directly produces gametes (like in many animals or specific algae),these are simply referred to as gametes. None of the terms $Coenogametes$,$Meiogametes$,or $Mitogametes$ are standard biological terminology for gametes produced by meiosis. Therefore,the correct answer is $D$.

(A) plant that bears both male (staminate) and female (pistillate) flowers on the same individual is known as monoecious.
Examples include $Ricinus$,$Zea$ $mays$ (maize),and various Cucurbits.

(D) Gynodioecious: This condition occurs when female flowers and bisexual (hermaphrodite) flowers are found on different plants of the same species.
In $Thymus$,some plants bear only female flowers,while others bear only bisexual flowers. This specific breeding system is known as gynodioecy.

(A) The condition where bisexual flowers do not open at all is known as $Cleistogamy$.
In $Cleistogamous$ flowers,the anthers and stigma lie very close to each other. When anthers dehisce in the flower buds,pollen grains come in contact with the stigma to effect pollination.
Thus,$Cleistogamous$ flowers are invariably $Autogamous$ as there is no chance of cross-pollination. Examples include $Commelina$ $benghalensis$,$Oxalis$,and $Viola$.

(A) Wheat is an angiosperm plant. In this plant,$80$ grains (seeds) are produced by the fertilization between $80$ male and $80$ female gametes.
To produce $80$ male gametes (pollen grains),$20$ meiotic divisions are required in microspore mother cells,as each meiosis produces $4$ microspores.
To produce $80$ female gametes (egg cells),$80$ meiotic divisions are required in megaspore mother cells,because in angiosperms,after meiosis in a single megaspore mother cell,$4$ megaspores are formed,but only $1$ survives while the other $3$ degenerate.
Thus,the total number of meiotic divisions is $20 + 80 = 100$.

(A) To form $200$ grains of wheat,we require $200$ pollen grains (male gametes) and $200$ functional megaspores (female gametes).
$1$. For male gametes: Each microspore mother cell $(MMC)$ undergoes one reduction division (meiosis) to produce $4$ microspores. Therefore,to produce $200$ microspores,we need $\frac{200}{4} = 50$ reduction divisions.
$2$. For female gametes: Each megaspore mother cell $(MMC)$ undergoes one reduction division to produce $4$ megaspores,out of which only one is functional. Therefore,to produce $200$ functional megaspores,we need $200$ reduction divisions.
Total reduction divisions = $50 + 200 = 250$.

(A) In angiosperms,the development of the female gametophyte (embryo sac) involves the formation of a megaspore mother cell $(MMC)$.
Each $MMC$ undergoes a single meiotic division to produce $4$ megaspores.
Out of these $4$ megaspores,$3$ degenerate and only $1$ functional megaspore develops into a female gametophyte (embryo sac).
Therefore,to produce $1$ female gametophyte,$1$ meiotic division is required.
To produce $101$ female gametophytes,$101$ meiotic divisions are required.

(C) Parthenocarpy is the development of fruit without fertilization,resulting in seedless fruits.
Auxins are plant hormones that play a crucial role in fruit development.
High levels of auxin in the ovary stimulate the development of the fruit wall (pericarp) even in the absence of fertilization.
In bananas,natural parthenocarpy occurs due to high levels of auxin in the ovary,which leads to the formation of seedless fruits.

(A) The development of fruit without fertilization is known as $Parthenocarpy$. Pollen grains are rich in growth hormones,particularly $Auxins$. When pollen extract is applied to unpollinated carpels,the $Auxin$ present in the extract mimics the effect of natural pollination,thereby stimulating the ovary to develop into a fruit. Therefore,the correct option is $A$.

(C) Nitsch conducted experiments on strawberries to study the role of seeds in fruit development. He observed that the growth of the strawberry receptacle is dependent on the presence of achenes (seeds). By selectively removing some achenes (carpels) from the surface of the developing strawberry,he was able to produce fruits with irregular or curious shapes,as the receptacle tissue failed to grow in the areas where the achenes were removed.

(B) In anther culture,haploid plants are typically produced from the microspores (pollen grains). However,if diploid plants are observed,they usually arise from the somatic cells of the anther wall (such as the tapetum,middle layers,or endothecium). These cells are diploid $(2n)$ in nature and can undergo callus formation and subsequent organogenesis to produce diploid plants,unlike the haploid microspores which produce haploid plants.

(A) In certain plant species,the pollen tube can exhibit branching during its growth towards the ovule.
$Cucurbita$ (pumpkin/squash family) is a well-known example where branched pollen tubes are observed.
This phenomenon is often associated with the presence of multiple ovules or specific chemotropic guidance mechanisms within the style.

(B) In typical meiosis,a single spore mother cell (microspore mother cell or megaspore mother cell) undergoes division to produce a tetrad,which consists of four spores.
When more than four spores are produced from a single spore mother cell,the phenomenon is known as Polyspory.
Polyspermy refers to the fertilization of an egg by more than one sperm.
Polyembryony is the development of more than one embryo in a single seed.
Polysiphony is a term related to the thallus structure in certain algae.

(D) ,$B$,and $C$ are parts of the ovule (megasporangium).
$D$ (Pollen grain) is the male gametophyte produced in the anther (microsporangium).
Therefore,the pollen grain is the odd one out.

(C) In anther culture,the primary goal is to produce haploid plants from microspores (pollen grains).
However,it is often observed that some diploid plants also develop alongside the haploids.
These diploid plants originate from the somatic cells of the anther wall (such as the tapetum,middle layers,or endothecium) rather than the germinal cells.
Since these somatic cells are diploid $(2n)$,they undergo callus formation and subsequent regeneration to produce diploid plants.

(C) The influence of pollen grains on the development and characteristics of the endosperm is known as $Xenia$. This phenomenon occurs because the male gamete contributes genetic material that affects the phenotype of the endosperm tissue,which is a product of double fertilization.

(A) In an angiosperm embryo sac,the antipodal cells and the egg cell are both haploid $(n)$ structures.
$1$. Antipodal cells are part of the embryo sac and are formed after mitotic divisions of the functional megaspore.
$2$. The egg cell is the female gamete,also formed from the functional megaspore.
$3$. Nucellus and megaspore mother cells are diploid $(2n)$ structures.
$4$. The primary endosperm nucleus is triploid $(3n)$ as it is formed by the fusion of two polar nuclei and one male gamete.

(D) Self-pollination (autogamy) is facilitated by several mechanisms in plants:
$1$. Bisexuality: The presence of both male (stamen) and female (pistil) reproductive organs in the same flower.
$2$. Homogamy: The maturation of both anthers and stigma at the same time,which ensures that pollen can fertilize the stigma of the same flower.
$3$. Cleistogamy: $A$ condition where flowers remain closed,forcing self-pollination to occur within the closed bud.
Since all these mechanisms promote self-pollination,the correct answer is $D$.

(C) Chalazogamy is the process where the pollen tube enters the ovule through the chalaza region instead of the micropyle.
Examples of plants exhibiting chalazogamy include $Casuarina$ and $Juglans$.
In contrast,when the pollen tube enters through the micropyle,it is known as porogamy,which is the most common type of fertilization in angiosperms.

(D) The pollen tube can enter the ovule through three different routes:
$1$. Porogamy: The pollen tube enters through the micropyle.
$2$. Chalazogamy: The pollen tube enters through the chalaza.
$3$. Mesogamy: The pollen tube enters through the integuments or the funiculus.
Therefore,all three routes are possible for the entry of the pollen tube into the ovule.

(D) Professor $P. Maheshwari$ is widely recognized as a pioneer in the field of plant embryology in India.
He established the Department of Botany at the University of Delhi and made significant contributions to the study of plant embryology,particularly in the development of test-tube fertilization of angiosperms.
His work laid the foundation for modern plant embryology research in India.

(D) $Xenia$ refers to the direct effect of pollen grains on the tissues of the seed,specifically the endosperm,outside the embryo.
$Metaxenia$ refers to the effect of pollen grains on the maternal tissues of the fruit,such as the $testa$ and fruit wall.
$Maize$ is a classic example of $Xenia$,while $Date$ $palm$ is a well-known example of $Metaxenia$.

(C) Bananas are seedless because they are parthenocarpic.
Parthenocarpy is the development of fruit without fertilization.
In bananas,the fruits develop without the formation of seeds,which is a natural process.
Therefore,the correct option is $(c)$.

(A) In angiosperms,the male gametes (sperm cells) are non-motile and are delivered to the embryo sac via a pollen tube.
In contrast,many lower plant groups (like algae,bryophytes,and pteridophytes) produce motile,flagellated sperm cells that require water for fertilization.
However,gymnosperms also possess non-motile male gametes.
Therefore,the statement that angiosperms differ from 'the rest of the plant groups' (which includes lower plants) is best explained by the fact that angiosperm sperm cells are non-motile,whereas in many other primitive plant groups,they are flagellated.

(B) The life cycle of angiosperms follows a specific sequence of reproductive events.
$1$. Pollination: The transfer of pollen grains from the anther to the stigma.
$2$. Fertilization: The fusion of male and female gametes (double fertilization) to form a zygote and primary endosperm nucleus.
$3$. Seed formation: The development of the ovule into a seed and the ovary into a fruit.
$4$. Germination: The process by which the seed develops into a new plant under favorable conditions.
Therefore,the correct sequence is Pollination $\rightarrow$ Fertilization $\rightarrow$ Seed formation $\rightarrow$ Germination.

(D) The diploid number $(2n)$ of the plant is $24$.
$1$. Pollen grain: These are haploid $(n)$ structures formed after meiosis. Therefore,the number of chromosomes is $24 / 2 = 12$.
$2$. Endosperm: In angiosperms,the endosperm is formed by triple fusion,making it triploid $(3n)$. Therefore,the number of chromosomes is $3 \times 12 = 36$.
$3$. Integument: These are part of the ovule and are diploid $(2n)$ in nature. Therefore,the number of chromosomes is $24$.
Thus,the correct sequence is $12, 36, 24$.

(C) In sexually reproducing organisms,fertilization involves the fusion of two haploid gametes (a male gamete and a female gamete).
Each gamete contains a haploid set of chromosomes,denoted as $n$.
Since both the male and female gametes contribute an equal haploid set of chromosomes to form the diploid zygote $(2n)$,the number of chromosomes in the nuclei of the fusing gametes is similar (i.e.,both are haploid).

(D) Variation in offspring is primarily caused by genetic recombination during sexual reproduction.
$1$. Self-pollination leads to homozygosity and reduces variation.
$2$. Cross-pollination between a pureline and a hybrid results in limited genetic diversity.
$3$. Cross-pollination between two hybrids involves the segregation and independent assortment of multiple heterozygous alleles,leading to a high degree of genetic recombination and phenotypic variation in the progeny.
$4$. Cross-pollination between different species (interspecific hybridization) is often difficult due to reproductive isolation and frequently results in sterile offspring,making it less effective for producing viable,varied populations compared to intraspecific hybridization between two hybrids.

(C) The chromosomal number in a flowering plant cell can vary depending on the type of cell:
$1$. Haploid $(n)$: Found in germinal cells (gametes) such as pollen grains and egg cells.
$2$. Diploid $(2n)$: Found in somatic cells (vegetative cells) that make up the plant body.
$3$. Triploid $(3n)$: Found in the endosperm cells,which are formed after double fertilization.
Therefore,the correct answer is that there are many types of ploidy levels in a flowering plant.

(D) . Vernalization was extensively studied and the term was coined by $T.D. Lysenko$ $(3)$.
$B$. Double fertilization in angiosperms was discovered by $S.G. Nawaschin$ $(4)$.
$C$. Pollination was first described by $Rudolph$ $Camerarius$ $(1)$.
$D$. Alternation of generations in plants was described by $Wilhelm$ $Hofmeister$ $(2)$.
Therefore,the correct matching is $A-3, B-4, C-1, D-2$.

(D) $Triticum$ $aestivum$ is a common bread wheat.
It is a hexaploid species with a chromosome number of $2n = 6x = 42$.
This means it contains six sets of chromosomes,where the basic chromosome number $(x)$ is $7$.

(D) Colchicine is an alkaloid extracted from the plant $Colchicum$ $\text{autumnale}$.
It acts as a mitotic poison by inhibiting the formation of spindle fibers during cell division.
By preventing the separation of chromosomes during anaphase, it leads to the doubling of the chromosome number in the cell, a condition known as polyploidy.
Therefore, it is widely used in plant breeding to induce polyploidy.

(A) In the context of embryo transfer technology and assisted reproductive technologies,embryos are typically preserved via cryopreservation (deep freezing) at the blastocyst stage or earlier stages of cleavage. Among the given options,the $1$-day old stage (which corresponds to the zygote or early cleavage stage) is the standard stage at which embryos are successfully cryopreserved for future use in animal breeding programs.

(B) The Century plant, scientifically known as $Agave$, is famous for its massive inflorescence.
It produces a tall flowering stalk that can reach a height of approximately $6$ meters.
This is a classic example of a monocarpic plant that flowers once in its lifetime and then dies.

(A) The gametophytic phase is characterized by the presence of a haploid $(n)$ plant body.
In this phase,the cells are haploid $(n)$.
Since the gametophyte produces gametes through mitosis,the haploid cells undergo mitotic division to form gametes.
Therefore,in the gametophytic phase,haploid cells undergo mitosis.

(A) Statement $X$ is true: In gymnosperms,the endosperm is a haploid tissue formed from the female gametophyte before fertilization.
Statement $Y$ is true: In angiosperms,double fertilization (syngamy and triple fusion) is a unique characteristic feature.
However,the formation of endosperm in gymnosperms is independent of the process of double fertilization in angiosperms. Therefore,statement $Y$ does not explain statement $X$.

(A) $1$. In angiosperms (like roses),the endosperm is formed as a result of the fusion of one male gamete with two polar nuclei (or a secondary nucleus),a process known as triple fusion.
$2$. Triple fusion is a part of the double fertilization process,which occurs only after the pollen tube enters the embryo sac.
$3$. Therefore,the formation of the endosperm in angiosperms is a post-fertilization event.
$4$. Both statements $A$ and $R$ are correct,and $R$ (the occurrence of double fertilization) is the reason why the endosperm (a product of triple fusion) is formed after fertilization.

(D) The correct answer is $D$.
$A$. $Thuja$ is a gymnosperm commonly used as an ornamental plant.
$B$. In angiosperms,endosperm is formed after fertilization (double fertilization),and $Catharanthus$ (Vinca) is an angiosperm.
$C$. $Araucaria$ is a gymnosperm,which exhibits single fertilization.
$D$. The largest flower is $Rafflesia$,not $Agave$. $Agave$ is known for its tall inflorescence,but not for having the largest flower.

(B) External fertilization involves the fusion of gametes outside the body of the female organism. This process requires a medium,typically water,to facilitate the movement of male gametes towards the female gametes. Therefore,organisms that exhibit external fertilization,such as many bony fishes and amphibians,release their gametes into the surrounding water where fertilization occurs. Consequently,these organisms lay their eggs in water.

(C) Sexual reproduction involves the fusion of gametes from two different parents,which leads to genetic recombination during meiosis (crossing over).
This process creates new combinations of genes in the offspring,leading to genetic variation.
These variations are the raw material for evolution and are essential for adaptation to changing environments.
In contrast,asexual reproduction,fission,and apomixis produce clones that are genetically identical to the parent,offering very little scope for evolutionary change.

(B) In angiosperms,a single megaspore mother cell $(MMC)$ undergoes meiosis to produce $4$ megaspores.
Out of these $4$ megaspores,usually only $1$ remains functional (functional megaspore),while the other $3$ degenerate.
Therefore,to produce $1$ functional megaspore,$1$ meiotic division is required.
To produce $100$ functional megaspores,$100$ meiotic divisions are required.

(A) In plants,a single spore mother cell undergoes meiosis to produce $4$ haploid spores.
To calculate the number of spore mother cells required for $64$ spores,we divide the total number of spores by $4$.
Number of spore mother cells = $\frac{64}{4} = 16$.
Therefore,$16$ spore mother cells are required to produce $64$ spores.

(B) In flowering plants, one microspore mother cell $(MMC)$ undergoes meiosis to produce $4$ microspores (pollen grains).
Therefore, the number of meiotic divisions required to produce $n$ pollen grains is given by the formula: $\text{Number of meiotic divisions} = \frac{n}{4}$.
For $200$ pollen grains, the number of meiotic divisions required is $\frac{200}{4} = 50$.

(D) In flowering plants,one meiotic division (meiosis) of a microspore mother cell produces $4$ microspores or pollen grains.
To calculate the number of meiotic divisions required to produce $n$ pollen grains,the formula is $n/4$.
Here,$n = 64$.
Therefore,the number of meiotic divisions required = $64 / 4 = 16$.
Thus,$16$ meiotic divisions are needed to produce $64$ pollen grains.

(C) Plants that flower and fruit only once in their lifetime and then die are known as $Monocarpic$ plants. Examples include bamboo species and $Strobilanthes$ $kunthiana$ (Neelakuranji). In contrast,$Polycarpic$ plants flower and fruit repeatedly throughout their life.

(D) The analysis of the given statements is as follows:
$1$. The stigma receives pollen grains,which is correct.
$2$. The pollen tube was discovered by $G.B. Amici$ $(1824)$,which is correct.
$3$. Pollen kit is absent in the pollen grains of $Capsella$ (a dicot plant),as pollen kit is typically found in insect-pollinated plants,which is correct.
$4$. Tigellum is not the main axis of the embryo; the main axis of the embryo is called the 'embryonal axis' or 'tigellum' is often used as a synonym for the axis,but in specific botanical contexts,the term 'embryonal axis' is the standard nomenclature. However,in many contexts,the tigellum is considered the axis itself. Re-evaluating the options,the statement 'Tigellum is the main axis of the embryo' is technically correct in botanical terminology,but if we look for the most incorrect statement,we must verify the definitions. Actually,the term 'Tigellum' is indeed the axis of the embryo. Upon closer inspection,all statements $A$,$B$,$C$,and $D$ are factually correct in standard botany. Given the options,if one must be incorrect,there might be a nuance. However,based on standard biology,all these statements are generally accepted as true. If this is a multiple-choice question where one must be false,the question or options may be flawed. Assuming the provided solution logic,statement $D$ is often cited as the incorrect one in specific curriculum contexts where 'embryonal axis' is preferred over 'tigellum'.

(C) The life cycle of angiosperms follows a specific sequence of reproductive events:
$1$. $\text{Pollination}$: Transfer of pollen grains from the anther to the stigma.
$2$. $\text{Fertilization}$: Fusion of male and female gametes (double fertilization) to form a zygote and primary endosperm nucleus.
$3$. $\text{Seed formation}$: The ovule develops into a seed, and the ovary develops into a fruit.
$4$. $\text{Germination}$: The seed germinates under favorable conditions to produce a new plant.
Therefore, the correct sequence is $\text{Pollination} \rightarrow \text{Fertilization} \rightarrow \text{Seed formation} \rightarrow \text{Germination}$.

(C) Polysiphonous pollen grains are those that produce more than one pollen tube during germination. This condition is characteristic of the family $Malvaceae$ (e.g.,$Hibiscus$) and the family $Cucurbitaceae$. Therefore,both families exhibit this trait.

(B) The nucellar cells are diploid $(2n)$. Given $2n = 24$,the haploid number $(n)$ is $12$.
$1$. Pollen grains are haploid $(n)$,so they contain $12$ chromosomes.
$2$. The endosperm in angiosperms is formed by triple fusion and is triploid $(3n)$. Thus,$3 \times 12 = 36$ chromosomes.
$3$. The embryo is formed by the fusion of a male gamete and an egg cell,making it diploid $(2n)$. Thus,$2 \times 12 = 24$ chromosomes.
Therefore,the sequence is $12, 36, 24$.