Exercise 02

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).

Requirement: Calcium nitrate, boric acid, sucrose, distilled water, petridish, slides, coverslips, brush, needle, microscope, and mature pollen grains of Tradescantia/balsam/ Jasmine/lily/pomegranate/grass/Vinca/China rose/Petunia.

Procedure:

(i) Prepare the pollen germination medium by dissolving 10g sucrose, 30mg calcium nitrate and 10mg boric acid in 100ml of distilled water. Alternatively 10% sucrose solution can also be used.

(ii) Take a drop of medium or 10% sucrose solution on a cover slip and sprinkle mature pollen grains on the drop.

(iii) Invert the cover glass on to a slide

(iv) After 10 minutes, observe the slide under microscope.

(v) Count

(a) total number of pollen grains seen in the microscope field, and

(b) the number of pollen grains that have germinated.

Observation:

Several pollen grains germinate and put forth pollen tubes. Count the total number of pollen grains and the number of germinated pollen grains in 3-5 different microscope fields. Tabulate your observations and calculate the percentage of pollen germination.

Name of the plant used as source of pollen…………………………

Number of pollen grains in a field of microscope = N

Number of germinated pollen grains in a field of microscope = n

Discussion:

Although pollen grains of many species germinate in this medium, the percentage of germinations and the time taken for germination varies in different species. Draw a germinating pollen grain and label.