TSOTS Assignment #7: Anthers and Stigmas and Styles, Oh My!

How do flowering plants (angiosperms) like our Brassica oleracea plants reproduce? That is the basic question we will address with this lab and TSOTS assignment.

Begin by reading section 14.4 in the digital class textbook to get a basic introduction to flowering plants. Study the Figures 14.4.2, 14.4.3, and 14.4.4 very carefully to get a good idea of how flowering plants reproduce. Pay particular attention to Figure 14.4.3.

When you have finished your reading, get permission to visit the main garden where your TSOTS plants are growing and harvest two or three open flowers from your plants or those of another group. Bring these flowers 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 14.4.2 carefully. Now, follow the procedure below to complete the flower dissection.

1. 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.
2. Now, using forceps and/or your fingers, very carefully remove the sepals and petals of one of the flowers. Do you see the anthers?
3. This step can be tricky: take a picture of the image of the anthers coming out of the eyepiece of the microscope.
4. 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.
5. 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.
6. 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.

Using the photos you took to illustrate, write a paragraph explaining how fertilization occurs in flowering plant species like Brassica oleracea. Each picture you post should also include a detailed caption explaining what is shown in the photograph and how it functions in angiosperm reproduction.

Take a look at the example images below to get an idea of what you should capture in your photographs.

This image shows anthers surrounding a stigma. They are all part of the same flower. When both male and female parts appear in the same flower, the flower is said to be perfect. In some species of flowering plant, the male and female parts are located in separate flowers (some flowers are male, some are female), and yet another situation is when the male and female flowers are on entirely separate individuals (some plants are male, some are female).

Here is a view (40x) of the male reproductive anatomy of a flower, known as the stamen. It has a stalk called the filament coming up from the base of the flower and at the end of this stalk is a part called the anther. This portion of the stamen produces and releases pollen grains, which contain the plant's male gametes (sperm cells).

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).

This is a picture of a flower that has had all of the parts stripped away (sepals, petals, stamens, and the top of the carpel) EXCEPT the ovary (the large green tube on the right), which has been sliced open and has tiny ovules (immature, unfertilized seeds) spilling out--one of these ovules can be seen to the left of the ovary.

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