Page 34 - Biology - XII

Q19. Sunfl ower has disc fl orets and ray fl orets. Which of these is a complete fl ower?
Ans. Disc fl oret
Q20. How are nocturnal fl owers pollinated?
Ans. By insect

Q21. Where are male fl owers located in a maize plant?
Ans. Male fl owers are located at the top of a plant.
Q22. Bifi d stigma is present in which fl ower?
Ans. Sunfl ower
Q23. Name a bird that pollinates fl owers.
Ans. Hummingbird.

Q24. Name an ornithophilous fl ower.
Ans. Silk cotton

Q25. Female fl owers in maize have fi ne, long, silky, golden-white threads. What are these structures?
Ans. Styles

SPOT - 4

Pollen Germination on Stigma—Slide

Objective
To study the pollen germination on stigma through a permanent slide.

Principle/Theory
The process of transfer of pollens from the stamens to the Pollen
stigma of a fl ower is called pollination. Once they land on
the stigma, the pollens start to germinate by giving out a Stigma tissue
pollen tube. Pollen tube is made up of cellulose and can
be stained with a cotton blue dye. Gametes
Pollen tube
Materials Required
A permanent slide of pollen germination and compound
microscope Tube nucleus

Procedure
1. Observe the specimens. Fig. 6.11: Pollen germination on
stigma (Diagrammatic)
2. Compare the comments mentioned.

3. Draw the diagram in your record fi le and write comments for each spot.

Comments
1. It is the slide of pollen germination.
2. Some pollens can be seen with a pollen tube.
3. In some pollens, the pollen tube is short or not yet developed while in others it is long/large in length.

4. Pollen tube carries two male gametes.
5. The larger is vegetative gametophyte while smaller is generative gametophyte.

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