Class 12 Biology - Reproduction in Organisms

Activities

Activity 1.1: Pollen Germination

Aim/Objective: To study the germination of pollen grains on a nutrient medium.

Materials Required:

• Fresh flowers (Hibiscus, Pea, or Balsam)
• Microscope slides
• Cover slips
• 10% Sucrose solution
• Microscope
• Dropper

Procedure:

1. Prepare a 10% sucrose solution.
2. Place a few drops of the sucrose solution on a clean glass slide.
3. Dust some fresh pollen grains from the flower onto the drops on the slide.
4. Leave the slide undisturbed for about 15�30 minutes.
5. Observe the slide under a low-power microscope.

Observation:

• Many pollen grains will be seen germinating, with a long tube-like structure (pollen tube) emerging from each grain.

Explanation:

• Pollen grains require a specific nutrient medium (rich in sugar) to initiate germination. In nature, the stigma of a flower provides this sugary secretion. The sucrose solution in this activity mimics the stigmatic fluid, stimulating the vegetative cell of the pollen grain to produce a pollen tube through a germ pore.

Conclusion:

• Pollen grains germinate to form pollen tubes when provided with a suitable sugary medium, which is the first step in the process of fertilization in flowering plants.