Flower Structure and Function
Flowering plants are the dominant type of plants on the earth today (about 250,000 species). Flowers are therefore the most common plant organs for sexual reproduction. Flowers produce gametes (sex cells). Flowers play a key role in pollination. Pollination is the transfer of pollen (containing the male gametes), from the anther of a flower, to the stigma (receptive surface of the female part of the flower) of the same or a different flower.
The sex of a flower an be described in three ways:
- Staminate flowers: Flowers bearing only male sex parts. These are sometimes referred to as “male flowers.”
- Carpellate/Pistillate Flowers: Flowers bearing only female sex parts. These are sometimes referred to as “female flowers.”
Hermaphrodite/Complete flowers: Flowers bearing both male and female sex parts.
- Use your textbook to read about a perfect flower.
- Using color, draw and label all parts of a perfect flower.
- Bring a sample of a flower to class.
petal sepal stamen anter style pollination
ovary pistil meiosis stigma filament angiosperm
- To identify the reproductive parts of an angiosperm
- To understand how complete flower structure allows for both cross and self-pollination.
- To know how Mendel used pea plants as an experimental organism to determine the laws of heredity.
- Observe your flower specimen. Use a magnifying glass to see greater details of flower part structures. On your data sheet write three detailed descriptive sentences of your particular flower.
- The diagram shown below is a typical flower. Your flower may be slightly different, but will have the same types of flower parts.
Using your forceps, carefully take the
flower apart and set them on a sheet of
- Use the diagram to identify each part.
- Draw your own diagram of each part
in the spaces provided on your data
sheet. Use your magnifying glass or
dissecting microscope to see and draw
- Label your drawings and answer the
- Drawing Lab Dissection Diagrams:
- Petals and Sepals
1. Count the colored
petals on your flower.
2. Remove enough petals
from the flower so that
you can observe the inner parts.
- Stamen and Anther
1. Do you see a large stalk-like part in the center of the flower? This part is called the pistil. Surrounding the pistil are several upright stalks.
2. Examine the anther with a hand lens.
3. Add a drop of sugar solution to a microscope slide. (The sugar solution will imitate the sugary surface of the stigma.) The pollen tube uses the sugar to produce energy for growth.
4. Place a yellow anther in the drop of solution and stir it around with a stirring rod.
5. Remove the anther and add a cover slip over the drop of solution.
6. Examine the pollen under a microscope.
7. Draw a diagram of what you see.
- Stigma, Pistil and Ovary
1. Draw and label a diagram of the stigma, pistil and ovary.
2. Use the razor blade to cut open the ovary of the flower. Half the class will do a cross-sectional cut. The other half will do a longitudinal cut. Ask your teacher which group you are in. Be sure to record on your data sheet which cut you made.
3. Draw a diagram of what you see. If the ovary is mature, you may observe a number of chambers inside it. These chambers contain the seeds that are forming. Label your diagram to show the chambers and the seeds.
Part Two: Read and Learn Activity
1. Read about pollination in your textbook. Be prepared to discuss your answers in a classroom discussion.
2. In your own words, write a function for each of the following flower parts: stamen, carpel, ovary, anther, ovule
3. Write a definition for pollination.
4. Describe how pollen travels from one flower to the next for pollination. Write down 2-3 of your ideas.
5. Clean-up your lab station as directed by your teacher. Answer the conclusion questions.
- What is an angiosperm? Do all plants have flowers? Why do some plants have flowers?
- What parts of the flower are considered sterile? What is the purpose of the sterile parts? Which parts are used by the plant for reproduction?
- What is the difference between a complete and an incomplete flower?
What type of flower did Mendel’s pea plants have?
- What is a stamen? Describe the male parts of the flower.
- What is a pistil? Describe the female parts of the flower.
- What is meiosis? Where in the flower does meiosis occur? (Is there more than one place?)
- How is the stigma adapted for its function?
- In your own words, write a paragraph describing sexual reproduction in flowers. What is pollen? Describe pollination. What is the difference between pollination and fertilization? What will the plant make if fertilization occurs?
- Can you think of any other ways plants reproduce themselves? List your ideas.
- Why would a tulip farmer not want someone to pack all of the flowers in his field? What would happen to his tulip population?