Plus Two Botany Chapter 3 -
Sexual Reproduction in Flowering Plants
Important Question Answer Part-01
1. Write a note about stamen ?
A)-There are two parts of stamen – the long and slender stalk called the filament, and the terminal generally bilobed structure called the anther. The proximal end of the filament is attached to the thalamus or the petal of the flower. The number and length of stamens are variable in flowers of different species. If you were to collect a stamen each from ten flowers (each from different species) and arrange them on a slide, you would be able to appreciate the large variation in size seen in nature.
2.Explain the structure of microsporangium ?
A)-In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. The innermost wall layer is the tapetum. It nourishes the developing pollen grains. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus.
3.Write a note about structure of pollen grain
Answer
• Pollen grains are generally spherical measuring about 25-50 micrometers in diameter. It has a prominent two-layered wall. The hard outer layer called the exine is made up of sporopollenin which is one of the most resistant organic material known.
• It can withstand high temperatures and strong acids and alkali. No enzyme that degrades sporopollenin is so far known. Pollen grain exine has prominent apertures called germ pores where sporopollenin is absent.
• Pollen grains are well-preserved as fossils because of the presence of sporopollenin.
• The inner wall of the pollen grain is called the intine. It is a thin and continuous layer made up of cellulose and pectin. The cytoplasm of pollen grain is surrounded by a plasma membrane.
• When the pollen grain is mature it contains two cells, the vegetative cell and generative Cell.
• The vegetative cell is bigger, has abundant food reserve and a large irregularly shaped nucleus.
• The generative cell is small and floats in the cytoplasm of the vegetative cell.
4.What is pollen allergy?
A)-Pollen grains of many species cause severe allergies and bronchial afflictions in some people often leading to chronic respiratory disorders– asthma, bronchitis, etc. It may be mentioned that Parthenium or carrot grass that came into India as a contaminant with imported wheat, has become ubiquitous in occurrence and causes pollen allergy
5.What are the benefits of pollengrains ?
A)-Pollen grains are rich in nutrients. It has become a fashion in recent years to use pollen tablets as food supplements. In western countries, a large number of pollen products in the form of tablets and syrups are available in the market. Pollen consumption has been claimed to increase the performance of athletes and race horses.
6. Explain the structure of gynoecium
A)-The gynoecium represents the female reproductive part of the flower. The gynoecium may consist of a single pistil (monocarpellary) or may have more than one pistil (multicarpellary). When there are more than one, the pistils may be fused together (syncarpous) or may be free (apocarpous). Each pistil has three parts ,the stigma, style and ovary. The stigma serves as a landing platform for pollen grains. The style is the elongated slender part beneath the stigma. The basal
bulged part of the pistil is the ovary. Inside the ovary is the ovarian cavity (locule). The placenta is located inside the ovarian cavity.
Botany Chapter -01 Notes
Chapter -01 Question Answer Part-01 Click Here
Chapter 01- Question Answer Part-02 Click Here
Chapter -01 Textual Activities Part-01 Click Here
Chapter -01 Textual Activities Part-02 Click Here
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