CBSE Questions for Class 12 Medical Biology Sexual Reproduction In Flowering Plants Quiz 5 - MCQExams.com

In artificial hybridization, the process of removing stamens from the bisexual flowers without affecting female parts, so as to prevent self-pollination is known as emasculation. This process is carried out by plant breeders in order to cross-pollinate the required plant variety with the desired variety to get desired results.

So, the correct answer is 'Emasculation'

Solution

Correct answer is option B.

Explanation for correct option

• In plants, pollen grains are male gametophytes.
• Pollen is produced within the anthers (microsporangia or pollen sacs) of the flower.
• Pollen grains develop from sporogenous tissue in angiosperms.

• A zygote is formed by fertilization of egg and sperm (gametes) and further cell division leads to the development of an embryo. 
  
• A micropyle is a small opening in the ovule through which the pollen tube penetrates.
• Chalaza is the basal part of a plant ovule where the nucellus is fused to the surrounding integument and to which the funiculus is usually attached.
• Pollen grains are male gametes produced in the anthers.

• Adventive embryony, is also known as sporophytic apomixis, sporophytic budding, or nucellar embryony.
• In this process, megagametophyte in the ovule does not give rise to embryos rather they arise from cells of the nucellus of the integument. 
• It takes place without fertilization, therefore, egg cells are not involved.
  
  Thus, the correct answer is option A.

• Pollen grains contain the male gametophyte (microgametophyte) phase of the plant. Pollen grains are produced by meiosis of microspore mother cells that are located along the inner edge of the anther sacs (microsporangia). 
• The outer part of the pollen is the exine, which is composed of a complex polysaccharide, sporopollenin. Inside the pollen are two (or, at most, three) cells that comprise the male gametophyte. 
• The tube cell (also referred to as the tube nucleus) develops into the pollen tube. The germ cell divides by mitosis to produce two sperm cells. Division of the germ cell can occur before or after pollination.
• During development of male gametophyte from pollen mother cell, there occurs one meiotic and two mitotic division.
  
  

• Stamen is the male reproductive organ that consists of a long slender filament and broad knob like anther; each anther lobes of anther contains two long and cylindrical microsporangia. Since stamen bear microsporangia in anther lobes, they are also called microsporophylls. Option A is incorrect.
• Gynoecium represents the megasporophyll as it carries megasporangia, i.e., the ovule, at the basal part of the pistil. Option B is incorrect. 
• Megaspore represents the first cell of the embryo sac/female gametophyte. Option C is incorrect. 
• The pollen grain is the first cell of the male gametophyte that divides mitotically to form a small generative cell and a large tube/vegetative cells. Pollen with small generative and large vegetative or with one vegetative cell and two male gametes is known as a mature male gametophyte.

• Pollination is the transfer of pollen from the male anther to the female stigma. It is carried out with the help of animals, birds, insects, water, wind, etc. 
• The pollination carried out by insects is called entomophily. 
• Pollination carried out by water is called hydrophily. Pollination carried out by the wind is called anemophily.
•  Pollination carried out by the animals is called zoophily. 

1. Porogamy is the process of entry of pollen tube through micropyle end as in lily.
2. Mesogamy is the entry of pollen tube via integuments seen in Cucurbita.
3. When pollen tube develops to make entry of pollen grains into eggs is the process called siphonogamy.
4. Homogamy is the method in which stamens and pistils of the same flower reach maturity at the same time to execute autogamy.

• Blastophaga quadriceps, the legitimate pollinator of Ficus religiosa, possesses two thoracic pockets in which pollen is stored for subsequent introduction into the young figs.  
• Pocket loading takes place in the nearly ripe fig at the male phase. Impregnated female wasps leave the fig via narrow channels bored by the males. 
• Upon entering young receptive figs, the female wasps begin oviposition, during which pocket emptying and pollination takes place.