STD 12th/ Ch-2/ Flowering plants.

1. Name the parts of an angiosperm flower in which development of male and female gametophyte place.

In an angiosperm flower, the male and female gametophytes develop in different parts of the flower.

Male gametophyte (pollen grains) develops in the anther, located at the tip of the stamen, the flower's male reproductive organ.

Female gametophyte (embryo sac) develops in the ovule, which is located in the ovary, the female reproductive organ of the flower.

2. Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events?

Fig: Microsporogenesis in detail

Microsporogenesis and megasporogenesis are two different processes involved in the development of male and female gametophytes in plants. 

Here are the differences between the two:

Definition:

Microsporogenesis refers to the process of formation of microspores or pollen grains in the anthers of a flower, which are responsible for the production of male gametes. 

On the other hand, 

Megasporogenesis refers to the process of formation of megaspores in the ovules of a flower, which are responsible for the production of female gametes.

Occurrence:

Microsporogenesis occurs in the anthers of the stamen, which are the male reproductive parts of a flower. 

Megasporogenesis occurs in the ovules of the ovary, which are the female reproductive parts of a flower.

Type of cell division:

Microsporogenesis involves meiosis, which is the type of cell division that reduces the chromosome number by half. 

Megasporogenesis also involves meiosis, but it is followed by mitosis, which results in the formation of a single functional megaspore.

Haploid cells produced:

In microsporogenesis, each meiotic division results in the formation of four haploid microspores. 

In megasporogenesis, each meiotic division results in the formation of four haploid megaspores, but only one of them survives and develops into a functional megaspore.

Resultant structures:

In microsporogenesis, the end product is the formation of pollen grains, which contain two haploid cells - the vegetative cell and the generative cell. The generative cell divides to produce two haploid male gametes. 

In megasporogenesis, the end product is the formation of the functional megaspore, which undergoes further mitotic divisions to form the female gametophyte or embryo sac.

In summary, microsporogenesis and megasporogenesis are two different processes involved in the development of male and female gametophytes in plants. Microsporogenesis produces pollen grains that contain male gametes, while megasporogenesis produces the female gametophyte or embryo sac that contains the female gametes.

Both microsporogenesis and megasporogenesis involve meiosis, which is a type of cell division that reduces the chromosome number by half. However, in megasporogenesis, meiosis is followed by mitosis, which results in the formation of a single functional megaspore.

At the end of microsporogenesis, the structure formed is the pollen grain, which contains two haploid cells - the vegetative cell and the generative cell. The generative cell further divides to produce two haploid male gametes.

At the end of megasporogenesis, the structure formed is the functional megaspore, which undergoes further mitotic divisions to form the female gametophyte or embryo sac. The mature embryo sac contains seven cells, including the egg cell or female gamete.

3. Arrange the following terms in the correct developmental sequence:

Pollen grain, Sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.

Sporogenous tissue - This is the tissue that gives rise to the pollen mother cells.

Pollen mother cell - This is a diploid cell that undergoes meiosis to produce haploid microspores.

Microspore tetrad - This refers to a group of four haploid microspores that are produced by meiosis of the pollen mother cell.

Pollen grain - Each microspore develops into a mature pollen grain, which is the male gametophyte.

Male gametes - Each mature pollen grain contains two haploid male gametes, which are released during pollination.

So, the correct developmental sequence is Sporogenous tissue → Pollen mother cell → Microspore tetrad → Pollen grain → Male gametes.

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