This Class 12 Biology practical focuses on observing pollen germination on the stigma using a permanent slide or scanning electron micrograph (SEM). The aim is to help students understand how pollen grains land on the stigma, hydrate, and form a pollen tube, which plays a crucial role in fertilization.
Under the microscope, students can clearly identify pollen grains, the stigma surface, and the emerging pollen tubes growing toward the ovary. SEM images provide a detailed 3D view, showing the intricate structure of the stigma and pollen attachment.
This experiment highlights key reproductive processes such as pollination, pollen tube formation, and fertilization pathways in flowering plants. It strengthens understanding of plant sexuality and is highly useful for CBSE Class 12 board preparations.
By making labelled diagrams and noting observations, students improve their biology practical record and gain clarity for viva questions and competitive exams.
AIM:- Pollen germination on stigma through a permanent slide or scanning electron micrograph.
Material Required:
- China Rose
- Boric Acid
- Forceps
- Microscope
- Sucrose (10 g)
- Coverslips
- Slide
- Dropper
Procedure:
1. The first step is to prepare the nutrient rich solution by mixing sucrose and boric acid together in water.
2. Pluck stigma from China rose (bisexual flower) using forceps.
3. Put the stigma on the slide.
4. Now with the help of a dropper, add a dropwise solution on the slide and hold for 20 seconds.
5. Cover with cover slide.
6. Observe under a microscope
Observation:
The germination of pollen grains in nutrient rich medium can be seen as the vegetative cells enlarge. The nucleus grows and gives rise to a pollen tube which emerges from one of the germ pores. Followed by the growth of the pollen tube, two male gametes (spherical or lenticular in shape) are formed. The pollen grains that Whereas the pollen grains which do not germinate are known as non-viable pollen grains.
Precautions:
Some precautions as mentioned below should be taken while conducting the experiment:
- Use freshly plucked flowers only
- Use fresh and dry slides.
- Use only 1-2 drops of sucrose solution
Class 12 Biology Lab Manual – Final Practical | Complete Lab Experiment File
A. List of Experiments
1. Prepare a temporary mount to observe pollen germination.
2. Study the plant population density by quadrat method.
3. Study the plant population frequency by quadrat method.
4. Prepare a temporary mount of onion root tip to study mitosis.
5. Isolate DNA from available plant material such as spinach, green
pea seeds, papaya, banana etc.
B. Study and observe the following (Spotting):
1. Flowers adapted to pollination by different agencies (wind, insects, birds).
2. Pollen germination on stigma through a permanent slide or scanning electron
3. Identification of stages of gamete development, i.e., T.S. of testis and T.S. of
ovary through permanent slides (from grasshopper/mice).
4. Meiosis in onion bud cell or grasshopper testis through permanent slides.
5. T.S. of blastula through permanent slides (Mammalian).
6. Mendelian inheritance using seeds of different colour/sizes of any plant.
7. Prepared pedigree charts of any one of the genetic traits such as rolling of tongue,
blood groups, ear lobes, widow's peak and colour blindness.
8. Controlled pollination - emasculation, tagging and bagging.
9. Common disease causing organisms like Ascaris, Entamoeba, Plasmodium, any
fungus causing ringworm through permanent slides, models or virtual images or
specimens. Comment on symptoms of diseases that they cause.
10. Models specimens showing symbiotic association in lichens, root nodules of
leguminous plants, and parasitic mode of nutrition shown by Cuscuta on host.
11. Flash cards / models showing examples of homologous and analogous organs.
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