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.