Flower Structure

Remember that the flower is the reproductive organ of angiosperms and has been largely responsible for the success of those plants. In this activity, you will learn how the structures of a flower serve the reproductive function.

Materials:

slide and coverslip                  scalpel

compound microscope            one fresh flower

binocular microscope

Procedure:

1. Examine the outside parts of the flower. Identify the sepals. Describe the petals.

What is the function of the sepals?

      a) How do the petals differ from the sepals? (petals are colored and usually larger)

      b) What function do petals have? (attract insect pollinators)

2. Carefully strip away the sepals and petals with the probe or scalpel blade to examine the reproductive structures. Identify the filaments and anthers. If your flower does not have anthers there are some on the front bench.

      c) How many stamens are present (or would have been) in your flower?

      d) If there are no stamens, why might they have been removed? (florists remove them to avoidallergies and staining clothing)

      e) Is the flower a monocot or dicot? How can you tell? (can tell by number of flower parts)

      f) How might pollen be carried from the anther to the female part of the flower? (wind, insect, otheranimal - answers will vary depending on the flower)

3. Prepare a wet mount of some pollen and examine. Make a sketch.

4. Find the carpel and identify the stigma, style, and ovary.

      g) How is the stigma of your flower adapted to capture and hold pollen? Describe at least two such adaptations? (answers will vary but could include tall, sticky, large, colorful)

5. Use a probe or scalpel to cut into the ovary lengthwise. Gently open the ovary. Locate the ovules using the binocular microscope if you need to.

      h) Approximately how many ovules do you see?

      i) How do the sperm reach the egg? (swim through a tube in the style)

      j) Describe where pollination and fertilization occur. What is the primary difference between these two processes? (pollination is pollen landing on the stigma; fertilization is a sperm reaching an egg)

      k) What do the ovary and ovules become? (ovary - fruit; ovules - seed)

l) Based on the anatomy you observed, what kind of pollinator would your flower likely have used and state the evidence on which you based your decision? (most will be insect (or at least, animal)because flowers are large and brightly colored)