CBSE Questions for Class 12 Medical Biology Sexual Reproduction In Flowering Plants Quiz 7 - MCQExams.com

1. An ovary is the part of the pistil that produces ovum.
2. Anthers are the part of stamens that produce pollen grains (male gametophytes)
3. Microsporangium in anthers gives rise to microspore mother cell.
4. The sporophyte is the condition in an alternation of generation in plants in which spore develops the gametophyte of a plant as in ferns.
5. The generative nucleus is one of the two nuclei in angiosperms that divide to produce two male gamete nuclei (male gametes) for double fertilization.

• The pollen grains are the male gametophytes. The pollen grains have two protective layers. 
• The inner is the thin layer which is called as intine. The outer is a tough and hard layer called as exine. 
• There is a presence of the compound sporopollenin on the outer exine which provides resistance to the pollen grain from the destructive agents. 
• The sporopollenin is absent at certain regions. These regions are called as the germ pores. 
• This is the region through which the germ tube emerges out during pollination. 

• In maize and castor plants, unisexual flowers are present. 
• The flowers are known as unisexual when there are separate sex organs in separate flowers. 
• However, both the male and female flowers can be present on the same plant. Since there are separate flowers which prevent autogamy. 
• But both the flowers are borne on the same plant. This induces the chances of geitonogamy. 

• Schizanthus pinnatus is a flowering plant. The flower is zygomorphic and there are five stamens. 
• There are only two fertile stamens. These are the stamen which bears the anthers and can produce pollen grains. 
• The three stamens are modified and converted to form staminodes. 

Geitonogamy is a type of self-pollination. It is sometimes distinguished from the fertilizations that can result from it, geitonogamy. In the flowering plants, pollen is transferred from a flower to another flower. And in animal pollinated systems it is accomplished by a pollinator visiting multiple flowers on the same plant. 

Geitonogamy is functionally cross-pollination involving the pollinating agent. And genetically it is similar to autogamy. Geitonogamy is not possible for strictly dioecious plants.

The correct option is B.

• In Salvia, there is a special mechanism which is called as the lever mechanism or pipe mechanism. 
• It favours the pollination method of entomophily where the pollinating agents are the insects. 
• When a pollinator probes a male stage flower for nectar, then the lever present in the plant causes movement in stamens. 
• When the pollinator withdraws from the flower, then the lever returns back.
• Thus, the correct option is D.

• The anther in angiosperms consists of four layers epidermis, endothecium, middle layer, and tapetum. 
• Before dehiscence of the anther, the endothecium develops a fibrous and thickened portion made of callose majorly. 
• This layer helps in anther dehiscence and pollen grain dispersal. Thus the correct answer is option D.

• The pollen tube is formed by the germination of the vegetative nucleus and have the wall made up of cellulose and pectin only.
• Exine is the outer covering of pollen grain which is highly sculptured with sporopollenin.

• Castor has unisexual flowers carrying either male or female reproductive organs. 
• Flowers with male reproductive organs (stamen) are termed as staminate flowers while those carrying only carpel are termed as pistillate flowers. Unisexuality helps to avoid autogamy.
  Hence, the correct answer is A. 

In the Pinus, winged pollen grains exist. It is an outgrowth of exine on the two lateral sides to make the wings of pollen. It is the characteristic feature, only in Pinus. In Pinus, some surface tissues of the ovuliferous scale are still attached to the seed. Thus forming a membranous wing.

Thus the correct answer is Exine.

The correct option is B.

• Male and female gametes are not having cell walls. 
• Also, the plasma membrane of the gametes is closed to the plasma membrane of the cell which surrounds them inside the pollen grain.
• Thus both B and C are true.
• The correct option is D.