Botany and Plant Science

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.

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 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.