Tag: cross pollination

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.