Pollen Pistil Interaction Questions in English

(B) The cytoplasm of pollen grains has a high concentration of solutes compared to water or a dilute sugar solution.
When placed in these hypotonic environments,water enters the pollen grains due to the process of endosmosis.
As a result,the internal turgor pressure increases significantly,causing the pollen grains to swell and eventually burst.

(D) The pollen tube enters the embryo sac through the synergids. Specifically,the pollen tube enters the embryo sac through the degenerated synergid. The filiform apparatus present in the synergids guides the entry of the pollen tube into the embryo sac.

(B) Intra-species incompatibility (self-incompatibility) is a genetic mechanism that prevents self-pollination.
Bud-pollination is a technique used to overcome this incompatibility.
In this method,pollination is performed when the flower is still in the bud stage,before the stigma becomes fully mature and develops the chemical barriers that reject self-pollen.
By applying pollen to the immature stigma,the pollen tube can germinate and fertilize the ovule before the incompatibility reaction is triggered.

(C) The entry of the pollen tube into the ovule can occur through different routes:
$1$. Porogamy: When the pollen tube enters through the micropyle.
$2$. Chalazogamy: When the pollen tube enters through the chalaza.
$3$. Mesogamy: When the pollen tube enters through the integuments or funiculus.
Porogamy is the most common method of pollen tube entry in angiosperms,for example,in $Lily$.

(A) The entry of the pollen tube into the ovule can occur through different pathways:
$1$. $Porogamy$: The pollen tube enters through the micropyle.
$2$. $Mesogamy$: The pollen tube enters through the integuments (e.g.,$Cucurbita$) or the funiculus (e.g.,$Pistacia$).
$3$. $Chalazogamy$: The pollen tube enters through the chalaza (e.g.,$Casuarina$).
Therefore,when the pollen tube enters through the integuments,the process is known as $Mesogamy$.

(C) When the pollen tube enters the embryo sac,it contains two male gametes,a degenerating tube nucleus,and some cytoplasm. These two male gametes are essential for double fertilization,where one fuses with the egg cell to form a zygote and the other fuses with the central cell to form the primary endosperm nucleus $(PEN)$.

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

(D) The growth of the pollen tube through the style is a result of chemotropism.
Specifically,the filiform apparatus present in the synergids secretes chemical substances (primarily polysaccharides and other signaling molecules) that guide the pollen tube toward the ovule.
This phenomenon is known as chemical attraction or chemotropic movement.

(B) The germination of pollen grains on the stigma occurs within the natural environment of the flower,which is referred to as $In$ $vivo$ germination.
$In$ $vivo$ refers to processes that take place within a living organism,whereas $In$ $vitro$ refers to processes performed outside a living organism (e.g.,in a laboratory setting).

(C) The growth of the pollen tube towards the embryo sac is an example of chemotaxis.
This movement is induced by chemical substances,such as calcium,boron,and inositol,which are secreted by the synergids within the embryo sac.
These chemicals create a gradient that guides the pollen tube towards the micropyle,ensuring successful fertilization.

(A) The pollen tube enters the ovule,typically through the micropyle,and reaches one of the two synergids.
Upon reaching the synergid,the tip of the pollen tube ruptures,and it releases its two male gametes into the cytoplasm of the synergid cell.
From there,one male gamete moves towards the egg cell for syngamy,and the other moves towards the central cell for triple fusion.

(C) After reaching the ovary,the pollen tube enters the ovule through the micropyle.
Inside the embryo sac,the pollen tube releases the two male gametes into the cytoplasm of one of the synergids.
Therefore,the pollen tube typically enters the embryo sac by passing through one of the synergids,guided by the filiform apparatus present in them.

(A) The growth of the pollen tube towards the embryo sac through the style is a classic example of chemotactic movement. This movement is directed by chemical signals (chemotropism) released by the synergids in the ovule. The pollen tube secretes pectinases and other hydrolytic enzymes to digest the tissues of the style,creating a passage for its growth.

(B) The correct answer is $B$. In angiosperms,the process of pollen tube guidance is mediated by chemical signals. The filiform apparatus present in the synergid cells secretes chemotropic substances that attract the pollen tube towards the micropyle of the ovule,ensuring successful fertilization.

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

(B) In angiosperms,the pollen tube typically enters the embryo sac through one of the two synergids.
This process is facilitated by the filiform apparatus present in the synergids,which guides the entry of the pollen tube.
Therefore,the correct answer is $B$.

(B) The pollen tube exhibits $Apical$ $growth$ (tip growth).
During the process of pollen germination,the pollen tube emerges from the germ pore of the pollen grain.
The growth of the pollen tube is restricted to its tip,where the cell wall is thin and the cytoplasm is rich in vesicles containing cell wall materials.
This localized growth at the apex allows the pollen tube to penetrate the stigma and style efficiently to reach the ovule.

(B) In plants, the length of the pollen tube is directly related to the length of the style.
Maize $(Zea \, mays)$ is a monocot plant where the style and stigma are very long, collectively known as the 'silk'.
To reach the ovary for fertilization, the pollen grain must grow a very long pollen tube through this elongated style.
Therefore, a long pollen tube is characteristic of maize.

(A) The entry of the pollen tube into the ovule can occur in three ways:
$1$. $Porogamy$: When the pollen tube enters the ovule through the micropyle.
$2$. $Chalazogamy$: When the pollen tube enters the ovule through the chalaza.
$3$. $Mesogamy$: When the pollen tube enters the ovule through the integuments or funiculus.
Therefore,the entry through the micropyle is known as $Porogamy$.

(D) The pollen tube enters the embryo sac through the filiform apparatus present in the synergids. As the pollen tube approaches the synergids,one of the synergids begins to degenerate. The pollen tube then enters the embryo sac through the degenerated synergid. Therefore,the correct answer is $D$.

(C) The transmitting tissue is a specialized tissue found in the style of flowers with a hollow style or a solid style. It facilitates the growth of the pollen tube from the stigma towards the ovary. In plants with a solid style,such as $Lilium$ or $Calotropis$ (Aak),the pollen tube grows through this specialized transmitting tissue,which is rich in nutrients and provides a pathway for the pollen tube to reach the ovule.

(A) Upon reaching the embryo sac,the pollen tube enters through the micropyle or other regions. The cytoplasm of the synergids contains a high concentration of solutes compared to the pollen tube tip. This creates a water potential gradient,causing water to move from the synergids into the pollen tube tip via $Endosmosis$. This influx of water increases the turgor pressure within the pollen tube tip,causing it to swell and eventually burst,thereby releasing the male gametes into the embryo sac.

(D) The micropyle is a small opening in the ovule through which the pollen tube enters the embryo sac during the process of fertilization.
Therefore,the micropyle facilitates the entry of the pollen tube into the ovule.

(C) In flowering plants,the pollen tube can enter the ovule through different routes.
$1$. Porogamy: Entry through the micropyle.
$2$. Mesogamy: Entry through the integuments or funiculus.
$3$. Chalazogamy: Entry through the chalaza.
Therefore,Mesogamy is defined as the entry of the pollen tube into the ovule through the integuments.

(C) The filiform apparatus is a specialized cellular thickening present at the micropylar end of the synergids.
Its primary function is to secrete chemical substances that guide the pollen tube into the synergids.
Once the pollen tube reaches the synergids,it releases the male gametes,which then participate in fertilization.
Therefore,the filiform apparatus specifically guides the pollen tube into the synergids.

(D) The pollen tube enters the ovule most commonly through the micropyle,a process known as porogamy.
While it can also enter through the chalaza (chalazogamy) or the integuments (mesogamy),the micropylar entry is the most frequent and standard pathway in angiosperms.
Therefore,the correct option is $D$.

(B) Pollen germination and the growth of the pollen tube are significantly influenced by the presence of specific elements in the stigma.
Boron,in the form of borate ions,plays a crucial role in the translocation of sugars and is essential for the germination of pollen grains and the elongation of the pollen tube.
It facilitates the uptake of water and the synthesis of cell wall components required for the rapid growth of the pollen tube through the style.

(C) The pollen tube enters the embryo sac through the micropyle. Once it reaches the synergids,the tip of the pollen tube absorbs water and nutrients from the surrounding cells. This leads to an increase in turgor pressure within the pollen tube. Simultaneously,the synergids release specific enzymes that weaken the cell wall at the tip of the pollen tube. Due to the high turgor pressure and the enzymatic degradation of the wall,the tip of the pollen tube ruptures,releasing the two male gametes into the embryo sac.

(C) The pollen tube was discovered by Giovanni Battista Amici in $1824$ while studying the process of fertilization in the orchid $Portulaca$ $oleracea$. He observed the pollen tube growing from the pollen grain and entering the ovule.

(B) The growth of the pollen tube towards the ovule is directed by chemical substances secreted by the synergids. This phenomenon is known as chemotropism. Since it is a directional growth movement in response to a chemical stimulus,it is classified as a tropic movement (chemotropism).

(A) In angiosperms,when the pollen tube enters the ovule,it typically enters the embryo sac through one of the synergids. The 'filiform apparatus' present in the synergids guides the entry of the pollen tube into the synergid cell.

(D) In angiosperms,the pollen tube enters the embryo sac through the micropylar end.
Upon reaching the embryo sac,the pollen tube discharges its two male gametes into the cytoplasm of one of the synergids.
This process is facilitated by the filiform apparatus present in the synergids,which guides the entry of the pollen tube.
Therefore,the correct answer is synergids.

(C) The pollen tube enters the embryo sac through the filiform apparatus present in the synergids. As the pollen tube approaches the synergids,one of the two synergids degenerates to facilitate the entry of the pollen tube into the embryo sac. Therefore,the pollen tube enters through the degenerated synergid.

(C) is the incorrect statement. Pollen-pistil interaction is a dynamic process involving chemical dialogue between the pollen grain and the stigma. Only compatible pollen grains are allowed to germinate and grow their pollen tubes through the style to reach the ovule. Incompatible pollen grains are rejected and their growth is inhibited at the stigmatic surface or within the style. The statement in option $C$ is incorrect because pollen grains of many species cannot germinate on the stigma of a flower; only compatible pollen grains of the same species (or specific related species) can germinate.

(D) The correct answer is $D$.
In flowering plants,the style is the part of the carpel that the pollen tube must traverse to reach the ovule.
Styles are categorized into two types: hollow and solid.
In hollow styles,the stylar canal is lined by glandular cells.
In contrast,a solid style contains a central core of specialized cells known as transmitting tissue.
This transmitting tissue is composed of thin-walled cells that provide nutrition and a pathway for the pollen tube to grow through the style towards the ovary.

(D) The correct answer is $D$.
In the ovule,the pollen tube is attracted by secretions from the synergids.
Typically,the pollen tube enters the embryo sac by passing into one of the two synergids.
The filiform apparatus,which consists of finger-like projections in the synergids,plays a crucial role in guiding the pollen tube towards the egg cell.
Once the pollen tube reaches the synergid,it ruptures and releases its male gametes into the embryo sac for fertilization.

(B) The correct answer is $B$.
Within the embryo sac,three cells are grouped together at the micropylar end and constitute the egg apparatus.
The egg apparatus consists of two synergids and one egg cell.
The synergids have special cellular thickenings at the micropylar tip called the filiform apparatus.
This structure plays an important role in guiding the pollen tubes into the synergid.

(B) Fertilization in flowering plants is a precise process that requires the synchronization of the male and female gametophytes. For successful fertilization to occur,the pollen grains must land on the stigma while they are still viable (capable of germination). If the pollen grains lose their viability before reaching the stigma,or if the stigma is not receptive at the time of pollination,fertilization cannot take place. Therefore,the correct condition is that pollen grains must land on the stigma before they lose their viability.

(D) Pollen grains of many species can be stored for years in liquid nitrogen at $-196^{\circ}C$. This process is known as cryopreservation. Such stored pollen can be used as pollen banks, similar to seed banks, in crop breeding programmes.

(B) The viability of pollen grains varies significantly among different plant species.
In some families like $Poaceae$ (which includes cereals like wheat and rice),the pollen grains lose their viability within $30$ minutes of their release.
Therefore,wheat and rice are the correct examples of plants whose pollen grains lose viability within $30$ minutes.

(D) Pollen-Pistil interaction is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen.
This interaction is mediated by chemical components released by the pollen grain and the stigma.
These chemical components interact with the stigma surface to facilitate the recognition process.
Additionally,the stigma provides necessary nutrients and water to support the germination of the pollen tube.
Physical components,such as the surface texture of the stigma,also play a role in the initial landing and adhesion of the pollen grain.
Therefore,all these factors contribute to the successful interaction between the pollen and the pistil.

(C) The process of pollination involves the transfer of pollen grains from the anther to the stigma of a flower.
Once the pollen grain lands on the compatible stigma,it absorbs moisture and nutrients.
This triggers the germination of the pollen grain,leading to the development of the pollen tube.
Therefore,the pollen tube develops on the stigma.

(C) When the pollen tube enters the ovule through the micropyle,it is called $Porogamy$.
$Chalazogamy$ refers to the entry of the pollen tube through the chalaza.
$Mesogamy$ refers to the entry of the pollen tube through the integuments.
$Pseudogamy$ is a type of apomixis where pollination is required for fruit development but fertilization does not occur.

(D) In angiosperms,the pollen tube enters the ovule,usually through the micropyle,and then enters one of the two synergids through the filiform apparatus.
Once inside the synergid,the pollen tube releases the two male gametes into the cytoplasm of the synergid.
From there,one male gamete moves towards the egg cell for syngamy,and the other moves towards the central cell for triple fusion.

(D) The filiform apparatus is a specialized cellular thickening present in the synergid cells of the embryo sac in angiosperms.
Its primary function is to secrete chemical substances that guide the entry of the pollen tube into the synergids.
Therefore,it acts as a chemo-tropic guide for the pollen tube.

(D) The correct answer is $D$.
In flowering plants,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 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 by preventing pollen germination on the stigma or the pollen tube growth in the style.
Therefore,the statement that pollen grains can germinate on the stigma of any flower but only the right species grows through the style is incorrect,as the rejection mechanism often occurs at the stigma level itself.

(C) Pollen grains are stored in liquid nitrogen to maintain their viability for long periods.
This process is known as cryopreservation.
The temperature of liquid nitrogen is $-196^oC$.
At this extremely low temperature,the metabolic activities of the pollen grains are suspended,allowing them to be stored for several years.

(N/A) Once the pollen grains are shed,they must land on the stigma before they lose viability to bring about fertilization.
The period for which pollen grains remain viable is highly variable and depends on the prevailing temperature and humidity.
In some cereals such as rice and wheat,pollen grains lose viability within $30$ minutes of their release.
In some members of families like Rosaceae,Leguminosae,and Solanaceae,they maintain viability for months.
It is possible to store pollen grains of a large number of species for years in liquid nitrogen at $-196^{\circ}C$. Such stored pollen can be used in pollen banks,similar to seed banks,for crop breeding programs.

(N/A) Pollen-pistil interaction is a dynamic process involving a chemical dialogue between the pollen grain and the stigma.
$1$. Recognition: The pistil has the ability to recognize whether the pollen is of the compatible (right) type or incompatible (wrong) type.
$2$. Acceptance: If the pollen is compatible,the pistil accepts it and promotes post-pollination events,such as pollen germination on the stigma,leading to fertilization.
$3$. Rejection: If the pollen is incompatible (from other species or self-incompatible),the pistil rejects it by preventing pollen germination or pollen tube growth.
$4$. Chemical Dialogue: This interaction is mediated by chemical components and proteins present on the surface of the pollen grain and the stigma. These components facilitate the recognition process.
$5$. Pollen Tube Growth: Upon successful acceptance,the pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores,and the contents of the pollen grain move into the pollen tube.

(N/A) In nature,pollination does not guarantee the transfer of the compatible or right type of pollen. Often,pollen of the wrong type,either from other species or from the same plant (if it is self-incompatible),also lands on the stigma.
The pistil has the ability to recognize the pollen,whether it is of the right type or of the wrong type.
If the pollen is of the right type (compatible),the pistil accepts the pollen and promotes post-pollination events that lead to fertilization.
If the pollen is of the wrong type (incompatible),the pistil rejects the pollen by preventing pollen germination. The ability of the pistil to recognize the pollen followed by its acceptance or rejection is the result of a continuous dialogue between the pollen grain and the pistil. This dialogue is mediated by chemical components and protein elements present in both.
It is only in recent years that botanists have been able to identify some of the pollen and pistil components and the interactions leading to recognition,followed by acceptance or rejection. In compatible pollination,the pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores,and the contents of the pollen grain move into the pollen tube.