Question

Draw a diagram of a gametophyte of an angiosperm. Label any four parts. Why is sporopollenin considered the most resistant organic material?

Answer 1

Hint: Pollen mother cells undergo meiosis and form microspores. This process is known as microsporogenesis. The microspores form a tetrad by arranging themselves into a cluster of four cells.

Complete answer:The pollen grain is the male gametophyte of an angiosperm. The following is the diagram of the pollen grain with four important parts.

1. Pollen grains are mostly globular in shape. However other shapes are also available.
2. Sporoderm is the wall of the pollen grain.
3. The cytoplasm of the pollen grain is rich in starch and unsaturated oils.
4. While exine is the outer layer of the pollen grain, intine is the inner layer.
5. Intine consists of pecto-cellulose.
6. Sporopollenin is the primary constituent of the exine.
7. Outer ektexine and inner endexine are formed by the differentiation of the exine.
8. Ektexine further consists of a foot layer, a baculite layer, and a tectum.
9. Pollenkitt is a yellowish, viscous sticky, and oily layer that covers the exine.
10. The main constituents of the pollenkitt (Present around pollen grain) are lipids and carotenoids.
11. A matured pollen grain possesses two cells- the vegetative cell and the generative cell.
12. The vegetative cell is bigger and its nucleus is irregularly shaped. It acts as a reservoir of food.
13. The generative cell is smaller and is present in the cytoplasm of the vegetative cell.
Sporopollenin is considered to be the most resistant material because it is a resistant fatty substance. Enzymes or any other chemical cannot degrade it. Even it is not affected by strong acidic conditions, high temperatures, or strong alkali. Pollen grains are protected by the sporopollenin.

Additional information:
1.The ability of the pollen to germinate is referred to as pollen viability. Pollen grains can be stored in pollen banks in liquid nitrogen.
2.Pollen grains can cause allergies as they float in the air.
3.Pollen grains are often used to produce food supplements and cosmetics.

Note: 1.Thus, pollens play the role of transferring haploid male genetic material from the anther of a single flower to the stigma of another flower during cross-pollination.
2.In the case of self-pollination, the same process takes place but within the same flower.