Pollination and its types - class-XII

• Transfer of pollen grains from the male reproductive organ (anther) of one plant to the female reproductive organ (stigma) of another plant. 
• Insects and wind are the main agents of cross-pollination.
  
• Thus, it creates genetic variations in the plants making it more resistant to diseases and other conditions than the parent plants.

Allogamy is also called as cross pollination. In the case of allogamy, the pollen from a flower falls on the flower of a different plant. This causes the genetic recombinations to take place. This is not possible in any other type of pollinations. Thus it produces the superior progeny.

Emasculation involves the removal of stamens from bisexual flowers of the female parents in order to avoid self-pollination in these flowers. It is done before the anthers mature. If in a condition the female parent bears bisexual flowers, then elimination of anthers from the flower bud before the anther dehisces by means of a pair of forceps is necessary. This step is called as emasculation.

Cross-pollination is advantageous because it results in formation of better progeny. The transfer of pollen from the male reproductive organ (an anther or a male cone) of one plant to the female reproductive organ (a stigma or a female cone) of another plant. Insects and wind are agents of cross-pollination.

• Emasculation is the removal of anthers in a bisexual flower to prevent self-pollination. 
• The female reproductive part is not involved in this process. It is a technique used by plant breeders to obtain the desired variety by crossing a plant with the desired pollen grain obtained by emasculation. 

Cross-pollination is the transfer of pollen from the male reproductive organ (an anther or a male cone) of one plant to the female reproductive organ (a stigma or a female cone) of another plant. Insects and the wind are the main agents of cross-pollination. 

Cross pollination: The transfer of pollen from the anthers of one flower to the stigma of another flower by the action of wind, insects, etc. It requires production of large number of pollen grains. Progeny shows enhanced vigor.
Offsprings are more viable and resistant. There is a possibility to get new desirable characters. Yield of crop can be maintained. It helps in evolution.
Undesirable characters of the plant can be eliminated.

Emasculation involves the removal of anthers of a flower in order to prevent self-pollination or the undesirable pollination of neighbouring plants. After emasculation the female reproductive part of the plant should be covered to prevent unwanted fertilisation.
Thus, the correct answer is option (B), 'Removal of anthers'.

• Emasculation is the removal of anthers in a bisexual flower to prevent self-pollination. 
• The female reproductive part is not involved in this process. It is a technique used by plant breeders to obtain the desired variety by crossing a plant with the desired pollen grain obtained by emasculation. 

Cross pollination occur when pollen grains are transferred to a flower from a different plant. The plants that undergo cross pollination often have taller stamens than their carpels. They use mechanisms to ensure that the pollen grains are spread to other plants' flowers. The process of cross pollination requires the help of abiotic or biotic agents like wind, water, insects, birds, bats, snails and other animals as pollinators. 

Herkogamy - common strategy employed by hermaphroditic angiosperms to reduce sexual interference between male and female function. Herkogamy differs from other such strategies by supplying a spatial separation of the anthers and stigma.
Dichogamy - having pistils and stamens that mature at different times, thus promoting cross - pollination rather than self - pollination.
Self sterility - sterile to its own pollen or sperm.

Pollination is a process in which pollen is transferred to the female reproductive organs of seed plants, thereby enabling fertilization and reproduction through growth of the pollen tube and eventual release of sperm. Both gymnosperms and angiosperms undergo pollination, although the mechanism for angiosperms is much faster and more complex. A successful angiosperm pollen grain (gametophyte) containing the male gametes is transported to the stigma, where it germinates and its pollen tube grows down the style to the ovary. Pteridophytes and bryophytes pollination does not occur. 

Cleistogmay is also called as automatic self - pollination. It describes the trait of certain plants to propagate using non - opening, self - pollinating flowers.

Mass selection is a simplest , common and oldest method of crop improvement, in which large number of plants of similar phenotype are selected and their seeds are harvested and mixed together to constitute the new variety. This method is practised in both self and cross – pollinated crops and plants are selected on the basis of their phenotype of appearance. Therefore, selection is done for easily observable characteristics such as plant height, ear/type, grain colour, grain size, etc.

• Cross-pollination is important for the production of new varieties of plants. Plants are having better growth and the creation of more viable seeds.  
• Cross-pollination is the process where the plants of different variety can breed with another to create a unique plant. 
• The resultant plant shows the characteristics of both the parent generation and therefore it is used to create new varieties of plants. 
• Cross-pollination is also performed to create more viable seeds of plants and also to generate plants having a better scope of growth.
• The correct option is D. 

Zostera is a seagrass that undergoes hydrophily (pollination by water). These plants typically have small, inconspicuous flowers without bright colors or nectar, as they do not need to attract insects.

If it produces a pink flower in the next generation then cross-pollination might have occurred.

Incomplete dominance or blending dominance is a type of inheritance where the hybrid is not related to either of the parents but exhibit a blending of characters of the two parents.

• Cross-pollination is the transfer of pollen from the anthers of one flower to the stigma of another flower by the action of wind, insects, etc. 
• The two plants genetic material combines and the resulting seeds from that pollination will have characteristics of both varieties and is a new variety. 
• Sometimes cross-pollinating is used intentionally in the garden to create new varieties. So option A is correct.

In pea, anthers and stigma are present close to each other therefore pollination is easy while in cross pollinating plants pollination takes place with the help of an external agency.

Heterostyly is the presence of $2-3$ types of flower with different heights of styles and stamens. In diheterostyly (dimorphic heterostyly), there are two types of flower, pin eyed (long style and short stamens) and thrum eyed(short style and long stamens), e.g., Primula vulgaris (primrose), jasmine.

• Emasculation is the removal of stamens or anthers or killing the pollen of a flower without the female reproductive organ is known as emasculation. In bisexual flowers, emasculation is essential to prevent self-pollination. In monoecious plants, male flowers are removed or male inflorescence is removed. 
• In species with large flowers e.g., (cotton, pulses) hand emasculation is accurate and it is adequate. In species with large flowers, removal of anthers is possible with the help of forceps. It is done before anther dehiscence. 
• The corolla of the selected flower is opened with the help of forceps and the anthers are carefully removed with the help of forceps. 
• An efficient emasculation technique should prevent self-pollination and produce a high percentage of seed set on cross-pollination.

In tobacco, due to the continuous self-pollination, homozygosity increases. It results in the occurrence of inbreeding depression, and the plants are called Inbred lines. When these inbred lines are subjected to hybridization, fertile hybrids are obtained. This is called Hybrid vigour or heterosis. This was developed by Kolreuter.

So, the correct option is ‘Kolreuter’.

Commelina produces two types of flower chasmogamous flowers which are similar to the flower of other species with exposed anthers and stigma, and cleistogamous flowers which do not open at all. In such flowers, the anthers and stigma lie 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-pollen landing on the stigma. Cleistogamous flowers assure seed-setting even in the absence of pollinators. 

Plants prevent self-pollination by following methods:-

Cleistogamous flowers are intersexual. They remain closed causing self-pollination. Cleistogamy occurs late in the flowering season in some plants. e.g., Commelina, balsam, Oxalis, Viola. These plants possess both chasmogamous and cleistogamous flowers. In cleistogamous flowers, the anthers dehisce inside closed flowers. The growth of style brings the pollen grains in contact with stigma. Cleistogamy ensures self-pollination. So, the correct answer is 'Cleistogamy'.

Cleistogamy procedure do not depend on pollinators. It is because, cleistogamy is automatic self-pollination which describes the trait of certain plants to propagate by using non-opening, self-pollinating flowers. Especially well known in peanuts, peas and beans, this behaviour is most widespread in the grass family.

Cleistogamy or automatic self-pollination describes the trait of certain plants to propagate by using non-opening, self-pollinating flowers. Especially well known in peanuts, peas and beans, this behaviour is most widespread in the grass family. The principal advantage of cleistogamy is that it requires less plant resources to produce seeds than does chasogamy because development of petals, nectar and large amounts of pollen are not required. This efficiency makes cleistogamy particularly useful for seed production on unfavourable sites or adverse conditions.

Cleistogamy is a type of self-pollination occurs in closed flower in which transfer of pollen grain from an anther to stigma when they lie close to each other in a flower e.g., Balsam, Arachis and Commelina. 

Self pollination is a form of pollination that can occur when a flower has both stamen and a carpel in which the sultivar or species is self fertile and the stamens and the sticky stigma of the carpel contact each other in order to accomplish pollination. It is prevented by: dichogamy, self-sterility and hekrogamy. Dichogamy - having pistils and stamens that mature at different times, thus promoting cross-pollination rather than self pollination. Herkogamy - common strategy employed by angiosperms to reduce sexual interference between male (anthers) and female (stigma) function.

Self pollination is the transfer of pollen from the anther to the stigma of the same flower. This is called Type I self pollination.
In Type II self-pollination, pollen is transferred from the anther of one flower to the stigma off another flower from the same plant.
Thus, the correct answer is option (C), 'Same or genetically similar flower of the same or other plant'.

• Heterostyly is the anther and stigma are present at different levels of the flower which prevents the self-pollination and fertilization. 
• The decline in the presence of only one kind of reproductive whorl in a flower. The decline is thus called unisexuality. 
• The plant may be unisexual means this may exhibit either male or female gametes.

So the correct answer is none of these.

The correct option is D.

• Self-pollination is when pollen from the same plant arrives at the stigma of a flower or at the ovule.
• Examples of self-pollinating plants include wheat, barley, oats, rice, tomatoes, potatoes, apricots, and peaches.
• Hence Self-pollination means transference of pollen from anthers to the stigma within the same flower.
• So, the correct answer is 'Transference of pollen from anthers to the stigma within the same flower'.

When a flower has both the essential whorls, i.e., androecium and gynoecium (male and female reproductive units), including stamens, carpels and an ovary, it is called as bisexual or perfect flower. In bisexual flowers, the stamens are generally numerous.
Thus, the correct answer is option D.

Self-pollination is when pollen from the same plant arrives at the stigma of a flower or at the ovule (in gymnosperms). There are two types of self-pollination. In autogamy, pollen is transferred to the stigma of the same flower. In geitonogamy, pollen is transferred from the anther of one flower to the stigma of another flower on the same flowering plant, or from microsporangium to ovule within a single (monoecious) gymnosperm. Some plants have mechanisms that ensure autogamy, such as flowers that do not open, or stamens that move to come into contact with the stigma. 

Flowers by nature are mostly cross pollinated. There are various adaptations for this process. In unisexual and bisexual flowers, certain devices are present for the effective self pollination and avoiding cross pollination, which are called as contrivances of self pollination. They are: bisexuality- both male and female sex organs in single flower, homogamy- inbreeding and cleistogamy- propagation using non-opening, self pollinating flowers.

Very less number of seeds were seen in the flower which undergoes self-pollination.

A mechanism to prevent cross-pollination is called cleistogamy. It is a condition in which flower does not open. In such flowers, the anthers and sigma lie close to each other. When anther dehisces in the flower buds, pollen grains come in contact with stigma to effect pollination, e.g., Arachis hypogea. It ensures seed formation even in the absences of any pollination agent. It is cheaper for the plant as there is no costly nectar or fragrance which the plant has to produce for pollination.

A bisexual flower which never opens is cleistogamous. It is a condition in which flower does not open. It is an adaptation seen in plants to ensure self-pollination. In such flowers, the anthers and stigma lie close to each other. When anther dehisces in the flower buds, pollen grains come in contact with stigma to effect pollination, e.g., Arachis hypogaea. 

Cleistogamy is a type of automatic self-pollination of certain plants that can propagate by using non-opening, self-pollinating flowers. The largest genus of cleistogamous plants is Viola.

The anthers and stigmas of chasmogamous or the open flowers are brought together by the growth, bending as well as by folding. In Catharanthus, the growth of style brings the stigma in contact of ripe anthers present on the mouth of corolla tube When cross-pollination fails in Sunflower, the bifid bent style stigma curls back so as to pick the pollen sticking to the surface of style. It is a fail-safe mechanism of self-pollination.

So the correct option is A.

Tape grass is a submerged hydrophyte. It is a dioecious plant with the flowers borne underwater. The male flowers detach on maturity and float on the surface of the water while the female flowers grow underwater and they come up to the surface with the help of their thin long stalk.

So the correct option is C.

In Salvia, pollination is entomophilous, which means it occurs by insects. Pollination occurs by the lever or turns pipe mechanism. The petals of the Salvia are bifurcated. When the insect visits some flower and sits on the petals, then the stamens are brought down to the touch the back of insect and pollen are laden on it.

When the insect visits another flower, cross-pollination occurs.

 Thus, the correct answer is A.

Continued self-pollination over many generations leads to the accumulation of recessive deleterious alleles, a phenomenon known as inbreeding depression.

Self-pollinated flowers remain closed and don't open allowing maximum time for the mature stamens and pistils to exchange and receive the gametes. 

The inconspicuous flower is a flower that is small, not showy and difficult to see. They are observed in self-pollinating flowers.

Pollen grains of other species are not compactable and do not germinate on the stigma of the flower of different species.

Xenogamy or cross pollination is the transfer of pollen grains from the anther of one flower to the stigma of a genetically different flower. Cross pollination is performed with the help of an external agency.

Commelina bears aerial, chasmogamous (stigma and anthers exposed to pollinating agents), insect pollinated flowers and underground cleistogamous flowers. Cleistogamous flowers are bisexual flowers which never open. In such flowers, the anther and stigma lie very close to each other. When anther dehisce in the flower buds, pollen grains come in contact with the stigma of the same flower i.e, autogamy occurs. So, these flowers produce assured seed set, even in the absence of pollinators.

• There are several methods to prevent self-pollination in plants. Bisexual flowers show self-pollination. 
• Chances of self-pollination increases when pistil has increased receptivity for pollen from the same plant. Self-pollination occurs in flowers where the stamen and carpel mature at the same time. 
• Hence, to prevent self-pollination, stamen and pistil must mature at different times.