Pollen Pistil Interaction Questions in English

(C) The $Stigma$ is the part of the gynoecium that determines the compatible nature of the pollen grain.
The pistil has the capacity to recognize suitable (right type) or unsuitable (wrong type) pollen grains.
If the pollen grain is of the right type, the pistil accepts it and promotes post-pollination events that lead to fertilization.
If the pollen is of the wrong type, the pistil rejects the pollen.
The ability of the pistil to recognize the pollen, followed by its acceptance or rejection, is the result of a continuous chemical dialogue between the pollen grain and the pistil.

(N/A) After successful pollination,the pollen grain germinates on the stigma. $A$ pollen tube emerges from one of the germ pores. The pollen tube grows through the tissues of the style and reaches the ovary.
Upon reaching the ovule,the pollen tube enters the embryo sac,typically through the micropyle. The filiform apparatus present at the micropylar end of the synergids guides the entry of the pollen tube.
Once inside the synergid,the pollen tube ruptures to release two male gametes. One male gamete fuses with the egg cell (syngamy) to form a zygote,while the other male gamete fuses with the two polar nuclei (triple fusion) to form the primary endosperm nucleus $(PEN)$.
The egg apparatus consists of two synergids and one egg cell.

(C) The pollen tube is a tubular structure produced by the pollen grain when it germinates on the stigma. Its primary function is to transport the male gametes from the pollen grain to the ovule,where fertilization occurs. Therefore,the pollen tube transports the male gametes.

(B) The viability of pollen grains is the duration for which they remain functional to germinate and produce a pollen tube.
This period is highly variable and depends primarily on the environmental conditions,specifically the prevailing temperature and humidity of the atmosphere.
While some pollen grains (like those of wheat and rice) lose viability within $30$ minutes of their release,others (like those of some members of Rosaceae,Leguminosae,and Solanaceae) can remain viable for months.
Therefore,the correct factor influencing this duration is the prevailing temperature and humidity.

(D) The $filiform$ $apparatus$ is a specialized cellular thickening located at the micropylar end of the synergids. Its primary function is to secrete chemical substances that guide the entry of the pollen tube into the synergids during the process of fertilization in angiosperms.

(A) The process of pollen-pistil interaction involves a chemical dialogue between the pollen grain and the pistil.
The $Stigma$ of the flower acts as the landing platform for pollen grains.
It possesses the ability to recognize the pollen grain, specifically whether it is of the right type (compatible) or the wrong type (incompatible).
If the pollen is compatible, the $Stigma$ accepts it and promotes post-pollination events like pollen tube germination.
Therefore, the correct answer is $A$.

(B) When a pollen grain is compatible,it lands on the stigma and absorbs water and nutrients.
This triggers the germination of the pollen grain,resulting in the formation of a pollen tube.
This process is a crucial part of the post-pollination events that lead to fertilization.
Therefore,the pistil accepts the compatible pollen and promotes post-pollination events.

(D) The pollen-pistil interaction is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen.
If the pollen grain is incompatible (i.e.,from a different species or self-incompatible),the pistil rejects the pollen by preventing pollen germination on the stigma or by inhibiting the growth of the pollen tube in the style.
Therefore,both $A$ and $B$ are correct mechanisms of rejection.

(C) Pollen-pistil interaction is a dynamic process involving the recognition of compatible pollen by the pistil.
This interaction is mediated by chemical components.
The pistil has the ability to recognize the pollen,whether it is of the right type (compatible) or of the wrong type (incompatible).
If the pollen is compatible,the pistil accepts it and promotes post-pollination events that lead to fertilization.
This recognition is achieved through a continuous dialogue between pollen grains and the pistil,which is mediated by chemical components released by the pollen and the pistil.

(B) In many angiosperms,pollen grains are shed at the $2$-celled stage. These two cells consist of a vegetative cell and a generative cell.
When these pollen grains land on the stigma,they germinate and produce a pollen tube.
The generative cell divides mitotically within the pollen tube to form two male gametes.
Therefore,the male gametes are formed inside the pollen tube.

(B) The filiform apparatus is a specialized cellular thickening present at the micropylar end of the synergid cells in the embryo sac of angiosperms.
Its primary function is to secrete chemical substances that guide the pollen tube into the synergid cell during the process of fertilization.
Therefore,it plays a crucial role in pollen-pistil interaction.

(D) The process starting from the landing of pollen grains on the stigma until the pollen tube enters the ovule is collectively known as $Pollen-Pistil$ interaction.
This is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen tube growth.
It is a dialogue between the pollen grain and the pistil mediated by chemical components of the pollen interacting with those of the pistil.

(A) In laboratory experiments,the germination of pollen grains can be observed by placing them in a nutrient medium. $A$ $10 \%$ sugar (sucrose) solution provides the necessary osmotic pressure and energy source to stimulate the pollen grain to germinate and produce a pollen tube. This process mimics the conditions found on the stigma of a flower.

(B) During the process of double fertilization in angiosperms,the pollen tube enters the ovule through the micropyle.
After entering the ovule,the pollen tube enters one of the two synergids through the filiform apparatus.
Once inside the synergid,the pollen tube ruptures and releases both male gametes into the cytoplasm of the synergid cell.
From there,one male gamete moves towards the egg cell to form the zygote,and the other moves towards the central cell to form the primary endosperm nucleus $(PEN)$.

(A) The pollen tube was first discovered by Giovanni Battista Amici in $1824$ while studying the process of fertilization in the orchid plant. He observed the growth of the pollen tube from the pollen grain towards the ovule.

(D) The growth of the pollen tube is significantly stimulated by the presence of $Boron$.
$Boron$ plays a crucial role in the germination of pollen grains and the elongation of the pollen tube by facilitating the uptake of sugar and its translocation.
It also helps in the synthesis of cell wall components required for the rapid growth of the pollen tube towards the ovule.

(B) In flowering plants,the gynoecium consists of the pistil or carpel. The pistil has three parts: the stigma,the style,and the ovary. The stigma serves as a landing platform for pollen grains during the process of pollination.

(C) When a pollen grain lands on the stigma,it absorbs moisture and nutrients. This process triggers the germination of the pollen grain,which results in the formation of a pollen tube. The pollen tube grows through the style to reach the ovary,carrying the male gametes to the embryo sac for fertilization.

(B) The pollen tube enters the embryo sac through one of the synergid cells.
This entry is guided by the filiform apparatus,which is a specialized cellular thickening present at the micropylar end of the synergid cells.
The synergid cells are located at the micropylar end of the ovule.

(A) Pollen grains are stored at $-196^{\circ} C$,which is the temperature of liquid nitrogen.
This process is known as cryopreservation.
At this extremely low temperature,the metabolic activities of the pollen grains are suspended,allowing them to remain viable for long periods.
Such stored pollen can be used in pollen banks,similar to seed banks,for crop breeding experiments and conservation purposes.

(B) The entry of the pollen tube into the ovule can occur through different routes:
$1$. $Porogamy$: The pollen tube enters through the micropyle. This is the most common method.
$2$. $Chalazogamy$: The pollen tube enters through the chalaza.
$3$. $Mesogamy$: The pollen tube enters through the integuments or the funiculus.
Since the question specifies entry through the micropyle,the correct term is $Porogamy$.

(D) The filiform apparatus consists of special cellular thickenings at the micropylar end of the synergids. Its primary function is to secrete chemical substances that guide the entry of the pollen tube into the synergid. Therefore,both statements $(a)$ and $(c)$ are correct.

(A) The movement of the pollen tube towards the embryo sac is known as chemotropism. This occurs because the pollen tube grows in response to chemical gradients,specifically substances like calcium ions,boron,and carbohydrates secreted by the synergids within the ovule.

(C) After entering the ovule, the pollen tube is attracted toward the micropylar end. The attractant is secreted by the filiform apparatus. The pollen tube pierces one of the two synergids and releases its gametes. Out of the two male gametes, one fuses with the egg to perform generative fertilization (syngamy), which gives rise to the diploid zygote. The nucleus of the second male gamete fuses with the two haploid polar nuclei to form the triploid endosperm nucleus. This second fertilization is called vegetative fertilization.

(A) Synergid cells are characterized by the presence of finger-like projections called the filiform apparatus,which are attached to their wall at the micropylar end. The primary function of this filiform apparatus is to secrete chemical substances that attract and guide the pollen tube into the synergid.

(D) The $filiform \text{ apparatus}$ is a specialized cellular thickening located at the micropylar end of the synergid cells in the embryo sac.
Its primary function is to secrete chemical substances that attract and guide the pollen tube into the synergid.
Therefore, the correct answer is $D$.

(D) Pollen-pistil interaction is a dynamic process that involves chemical signaling between the pollen grain and the stigma. It is also a genetically controlled process where the pistil recognizes the compatible pollen. Since both chemical mediation and genetic control are involved,the correct answer is that more than one option is correct.

(A) The filiform apparatus consists of finger-like projections of the synergid cell wall that extend into the cytoplasm of the synergid.
These structures are located at the micropylar end of the synergids.
Their primary function is to guide the entry of the pollen tube into the synergids by secreting chemical substances (chemotropic stimulus).
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for the Assertion.

(C) The initial growth of the pollen tube is supported by the food reserves present within the pollen grain itself.
As the pollen tube grows further through the stigma and style,it utilizes the nutrients available in the tissues of the pistil.
Therefore,the Assertion is correct.
The pollen tube grows through the style towards the ovary,guided by chemical signals (chemotaxis) released by the synergids in the ovule.
It typically travels through the intercellular spaces of the style,not intracellularly.
Thus,the Reason is incorrect because the movement is intercellular,not intracellular.

(A) The pollen-pistil interaction is a dynamic process involving chemical dialogue between the pollen grain and the stigma.
$A$: It is a well-established fact that specific proteins present on the surface of the pollen grain interact with the stigma to determine compatibility.
$R$: These compatibility proteins are indeed located in the outer layer of the pollen wall,known as the ektexine (part of the exine).
Since the interaction between the pollen and the stigma is mediated by these specific proteins located in the ektexine,the Reason correctly explains the Assertion.

(A) Boron is an essential micronutrient for plants. It plays a crucial role in pollen tube growth and the germination of pollen grains. Deficiency of boron leads to the failure of pollen germination and poor fruit or seed set.

(D) The viability of pollen grains depends on the prevailing temperature and humidity.
In some cereals like wheat and rice,pollen grains lose their viability within $30$ minutes of their release.
In contrast,members of some families like Rosaceae,Leguminosae,and Solanaceae maintain their viability for several months.
Therefore,the correct sequence is $30$ minutes for wheat/rice and months for the mentioned families.

(A) Pollen grains are stored in liquid nitrogen at a temperature of $-196^{\circ} C$ for long-term preservation.
This method is known as cryopreservation.
This technique allows pollen to remain viable for years,which is useful in crop breeding programs and gene banks.

(B) During the process of double fertilization in angiosperms,the pollen tube enters the ovule and reaches the embryo sac.
Upon reaching the embryo sac,the pollen tube enters one of the two synergids through the filiform apparatus.
The two male gametes are then released into the cytoplasm of this specific synergid.
From there,one male gamete moves towards the egg cell to form the zygote,and the other moves towards the central cell to form the primary endosperm nucleus $(PEN)$.

(D) The pollen-pistil interaction is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen. This recognition is mediated by chemical components of the pollen interacting with those of the pistil. Specifically,the pistil has the ability to recognize the pollen,whether it is of the right type (compatible) or of the wrong type (incompatible). This recognition is achieved through a continuous chemical dialogue between the pollen grain and the stigma,which involves the interaction of specific proteins present on the surface of the pollen and the stigma.

(B) In angiosperms,the pollen grain at the time of shedding is usually in a $2$-celled stage,consisting of a vegetative cell and a generative cell.
As the pollen tube grows through the style,the generative cell undergoes mitosis to form $2$ male gametes.
These $2$ male gametes are involved in the process of double fertilization,where one fuses with the egg cell and the other with the central cell.

(B) The process of pollen-pistil interaction follows a specific sequence:
$1$. First,the pollen grain lands on the stigma of the carpel $(b)$.
$2$. After landing,the pollen grain germinates to form a pollen tube $(c)$.
$3$. The pollen tube then grows through the tissues of the stigma and style to reach the ovule $(a)$.
$4$. Finally,the pollen tube,carrying $2$ male gametes,enters the ovule to facilitate fertilization $(d)$.
Therefore,the correct sequence is $b \rightarrow c \rightarrow a \rightarrow d$.

(A) The figure shows the germination of a pollen grain.
Statement $i$ is true: The figure depicts the germination of a pollen grain.
Statement $ii$ is false: Angiosperm male gametes are non-motile.
Statement $iii$ is false: The pollen tube contains two male gametes and one tube nucleus,not a female gamete.
Statement $iv$ is false: The pollen tube is an extension of the intine,but the exine remains on the pollen grain body.
Statement $v$ is true: The tube nucleus is typically located at the tip of the growing pollen tube.
Therefore,statements $i$ and $v$ are true.

(D) Pollen-pistil interaction is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen.
$1$. Pollen deposition on the stigma is the first step of this interaction.
$2$. Pollen germination and the growth of the pollen tube through the style are key events of this interaction.
$3$. The entry of the pollen tube into the ovule is the final stage of the pollen-pistil interaction.
$4$. Embryo development occurs after fertilization (syngamy and triple fusion) and is not a part of the pollen-pistil interaction.

(D) $Parthenium$,also known as carrot grass,is an invasive weed that was introduced into India as a contaminant with imported wheat. Its pollen grains are a major cause of respiratory allergies and hay fever in humans.

(C) The correct answer is $C$.
The filiform apparatus consists of specialized cellular thickenings at the micropylar end of the synergids.
Its primary function is to secrete chemical substances that guide the entry of the pollen tube into the synergids during the process of fertilization.

(C) The process of pollen-pistil interaction follows a specific sequence:
$1$. $II.$ Deposition of pollen grains on the stigma.
$2$. $IV.$ Development of the pollen tube through the style.
$3$. $V.$ Entry of the pollen tube into the ovule through the micropyle.
$4$. $III.$ Entry of the pollen tube into the embryo sac (synergids).
$5$. $I.$ Release of male gametes into the embryo sac for fertilization.
Therefore,the correct sequence is $II \to IV \to V \to III \to I$.