Sub-Concept: Flowers: Types, Structure, Function
Agricultural Context: Most agricultural crops depend upon the fertilization of flowers to produce
fruit or grain. Therefore, it is important to understand the role of the flower in crop production.
Exercise: Examine the Parts of a Flower
Applied Principle: A complete flower contains both male and female structures; some plants
produce separate male and female flower structures. In either case, the male and female
structures will contain the same elements.
Goals:
Materials:
References: Chilson, J., Hehn, D., and Sivertsen, D. (1994). South Dakota Agriscience Lab
Manual. Pierre, SD: South Dakota Office of Adult, Vocational and Technical Education.
Trudeau, M. (1994). Plant Morphology and Taxonomy. Ithaca, NY: Cornell Instructional Materials Service.
a. What flowers look like
b. What the students think flowers are for
c. Whether all plants produce flowers, and why or why not
2. Explain that this exercise will provide them with the opportunity to more closely examine just
what makes a flower tick -- they will get to dissect and examine a flower of their own.
3. Divide the class into small groups of no more than 3 students each.
4. Provide each group with a student data/instruction sheet for this exercise.
5. As a class, review the steps in the exercise, and explain what is expected of the students.
6. Provide each group with the necessary materials, and instruct them to carry out the activity.
7. While the students are working, carefully supervise them. They may need help in identifying
the parts of the actual flower, as opposed to drawings they may have seen.
8. When the activity is completed, have the class discuss the procedure and their findings.
- You will need to be very careful with the flower, since it is easy to crush or otherwise damage it.
- Be sure that all members of your group participate in the activity. For example, be sure that
everyone has the chance to examine the slides under the microscope.
Procedures/Questions:
1. How many petals are on your flower? _____________________________
2. Very carefully remove the petals from your flower. Inside, you should find one pistil and
several stamens. How many stamens did you find? ______________
3. Draw and label a picture of the male parts of your flower below. (Be sure to include the
anther, filament, and pollen in your drawing.)
4. Place one drop of water on a glass slide.
5. With a dissecting needle, carefully puncture (or scrape) the anther to remove a few grains of
pollen. [NOTE: Do not destroy or throw away the remainder of the flower; you will use it later in
the exercise.]
6. Carefully add the pollen to the water on the slide.
7. Now add one or two drops of the thionin stain and place a coverslip over it.
8. Examine the slide on a low microscope setting. Draw and label what you see below:
9. Now examine the slide under high power. Does it look any different? Draw and label any
differences below:
10. Clean off the slide and coverslip when you have finished.
11. Obtain some more pollen from the anther of the flower, and smear onto the coverslip.
12. Now place a drop of 10% sucrose solution on top of the pollen smear.
13. Use a toothpick to apply a thin layer of petroleum jelly around the depression of a slide.
14. Turn the slide over and line up the depression with the drop of solution and pollen. Carefully
bring the slide and coverslip into contact. Now turn the slide upright and examine under low
power on the microscope.
15. Pollen tubes should emerge in about 20 minutes. [NOTE: If pollen tubes do not appear
within 20 minutes, place the slide in a warm, safe place. Your particular flower may take one or
two days to produce the pollen tubes, so examine the slide periodically.] Draw and label what
you observe below:
What is the function of the pollen tube? _________________________________
_________________________________________________________________
16. While you are waiting for the pollen tubes to emerge, you may examine the pistil of your
flower. Sketch and label a diagram of the stigma, style, and ovary below:
17. Using the razor blade, carefully remove the ovary and style from the flower. Cut the structure
in half to observe the inside. Draw and label what you see below:
18. Describe how complete flowers reproduce (the process of fertilization):
19. Do plants with complete flowers always fertilize themselves? If not, how else can
fertilization/pollination occur?
20. If a plant does not have complete flowers, how can it reproduce?
TEACHER BACKGROUND SHEET
While many crops produce a perfect flower (one structure contains both male and female parts),
there are exceptions. Some plants, such as corn, contain separate male and female flowers on the
same plant. Other species have completely separate plants for male and female flowers.
(You may refer to any biology or plant science book if you feel that you need further information
about plant reproduction and flowers.)
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