Prepare a temporary mount to observe pollen germination

Aim: To Observe pollen germination by preparing temporary mount.

Material/Apparatus Required:

• Fresh mature flower like Tradescantia jasmine, lily, Vinca, China Rose, Petunia, etc.
• Glass slide
• Glass rod
• Sucrose
• Potassium nitrate
• Boric acid
• Compound microscope
• Cover slip
• Beaker
• Distilled water
• Dropper
• Magnesium sulphate

Principle:

Pollen Grains: Pollen grains represent the male gametophytes. For example, if the open anthers of any flower is seen, yellowish powdery pollen are found. They are generally spherical in shape 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. The exine has prominent apertures called germ pores. The inner wall of pollen grain is called the intine. It is a thin and continuous layer made up of cellulose and pectin.

Pollen Grains Germination: In nature, pollen grains germinate on the compatible stigmas of carpels. This process is called pollen pistil interaction. They can also induce to germinate in a synthetic medium using chemical which favour pollen germination such as 10% sucrose solution.

During germination, intine (inner wall) of pollen grain emerges out as pollen tube through one of the germ pores in exine (Outer wall).

Procedure:

1. Prepare the medium for pollen germination by dissolving 10 grams sucrose, 20 mg potassium nitrate, 30-gram magnesium sulphate and 10-gram boric acid in 100 ml of distilled water.
2. Using a glass rod, stir the solution to mix it well.
3. Using a dropper, take some medium and put two drops of it on a clean glass slide.
4. Now, take a fresh mature flower and dust a few pollen grains from its stamen on to the drop on the slide.
5. After few minutes, place the glass slide on the stage of the compound microscope.
6. Observe the slide carefully under a microscope at regular intervals.

Observation:

1. Initially pollen grains are observed as uni-nucleated, which at time of liberation becomes two celled.
2. The pollen grains take up the medium and start germinating. At first stage, the tube cell enlarges and emerges out of the germ pores of a pollen grain to form a pollen tube.
3. The pollen tube further grows in the same manner as it grows through the style to the ovary of the flower.
4. The nucleus of the tube cells and germinative cell passes into it and descent towards the tip of a pollen grains.
5. Very soon generative cell divides into two male gametes.
6. Each male gametes so formed lenticular to spherical in shape.

Result:

Pollen germination was observed on the slide.

Precautions:

1. Freshly plugged flower should be used.
2. Procedure should be performed at room temperature.