Begin by reading pages 342 through 349 in the class textbook to get a basic introduction to plants. Next, read sections 17.6 and 17.7 (The flower is the centerpiece of angiosperm reproduction and The angiosperm plant is a sporophyte with gametophytes in its flowers) very carefully to get a good idea of how flowering plants reproduce. Pay particular attention to Figure 17.7.
When you have finished your reading, get permission to visit the garden and harvest two or three flowers from one of the Brassica oleracea plants in the main garden. Bring them back to the classroom and, with a partner, get a dissecting microscope. If you have never used a dissecting microscope before, read this brief tutorial on dissecting microscopes first.
Study Figure 17.6B on page 350. Now, follow the procedure below to complete the flower dissection.
- Lay your flowers on the table and take a closeup picture of one of them. In the next step, looking through the dissecting microscope, you will examine all of the flower's parts that are directly involved in reproduction.
- Now, using forceps and/or your fingers, very carefully remove the sepals and petals of one of the flowers. Do you see the anthers?
- This step can be tricky: take a picture of the image of the anthers coming out of the eyepiece of the microscope.
- Now pull back the filaments and anthers to reveal the carpel (the entire female reproductive structure). Take a photograph of the carpel, focusing on the stigma.
- Take the ovary and use very sharp scissors or your fingernails to cut the ovary open lengthwise. Do you see the ovules inside? They look a bit like shiny green jelly beans attached to a central stem. Take a picture of the ovules inside the ovary.
- For extra points, take one of the anthers and tap some of its pollen onto a glass slide to prepare a wet mount slide of pollen. Ask the teacher for a compound light microscope and set it up on the lab station at which you are working. Get the pollen grains in focus at high power and try to capture a photo from the eyepiece of the microscope with your camera.
Take a look at the example images below to get an idea of what you should capture in your photographs.
|This is a view (40x) of the female anatomy of a flower called the carpel. The carpel consists of a stalk called a style with a sticky tip called a stigma. It is this sticky tip to which pollen grains adhere (get stuck).|