CLASS: XII PRACTICAL @ TO STUDY POLLEN GERMINATION ON A SLIDE. скачать в хорошем качестве

CLASS: XII PRACTICAL @ TO STUDY POLLEN GERMINATION ON A SLIDE.

Aim: To study pollen germination on a slide. Principle: In nature, pollen grains germinate on the compatible stigmas of the carpel. Pollen grains can also be induced to germinate in a synthetic medium. During germination, intine (inner wall) of pollen grain emerges out as pollen tube through one of the germ pores in exine (outer wall). Requirements: Freshly plucked seasonal flowers (Vinca/balsam/Jasmine/lily/ pomegranate/grass/ Petunia), beaker, sucrose, microscope and cavity slide, cover slip. Procedure: The first step involves the preparation of a sucrose solution. This is done by dissolving 10 g of sucrose 50 ml of water. Pour a few drops of this solution onto the cavity slide. Then, use a brush or fingers to gently dust a few pollen grains from the stamen of mature flowers. Let the slide set for 20-30 minutes. Then, use the microscope to view the slide. Observation: The pollen grains will germinate when submerged in the sugar rich nutrient medium. This is characterized by the enlargement of the vegetative/tube cell. It emerges through one of the germ pores, eventually forming a pollen tube. The generative cell nucleus grows into the pollen tube and makes two male gametes (sperm nuclei). The male gamete is either spherical or lenticular in outline. Inference: Different stages of germinating pollens are observed. Some pollens are in their initial stage of germination while others have quite long pollen tube containing tube nucleus and two male gametes. Precautions: 1. Flowers should be freshly plucked. 2. Use clean cavity slide to observe the pollen grains. 3. The slides should not be disturbed, otherwise position of pollen grains will get changed. 4. During observations pollen grains must be properly dipped in nutrient solution.