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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TSOTS Assignment #6: How Does Your Garden Grow?

Now it's time to put some of your recently acquired science skills and knowledge into practice.

Your first step today should be to visit your plants in the garden. Try to find your group's plants. If you can't, don't worry--the most important thing to do is to notice the changes all of the plants have experienced. Snap a few pictures with your phone's (or other device's) camera and then return to the classroom. Briefly discuss your observations with your group and then proceed to answer the following questions in a post titled "How Does Your Garden Grow?".

1. How is your plant (or any plants in our garden, for that matter) getting bigger and adding biomass? Your explanation should correctly use the terms and concepts of cell division (mitosis), photosynthesis, and cellular respiration.
2. Phosphoglycerate kinase (PKG) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) are two important enzymes used in photosynthesis. Describe how plants in the garden would make enzymes like these if a signal was sent to the nucleus of a leaf mesophyll cell to produce more of one of these enzymes. (Hint: enzymes belong to which category of biomolecule?)

Be sure to talk with your group members and other classmates about the questions as you attempt to compose your responses--together you should be able to come up with some very thoughtful explanations.



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TSOTS Assignment #5: Seed Stories, Semester 1

Now it's time to sit back for a few moments and ruminate on what you have done and experienced so far this year through doing The Story of the Seed project. What have you learned? What surprised or amazed you? What made you laugh? What made you pause and think a little deeper? What was frustrating about this project? Take five minutes to talk about it with your teammates. Listen carefully to each person's reflections on what the project has been like for him or her. What questions do you have about things you observed or experienced in the garden? OK, now, guess what? You are going to write about the experiences of one of your classmates--someone who was not on your team! Find someone from another group and work closely with that other person to summarize his/her answers to the questions above in a short paragraph that you will post under your name. Your post title should include that other person's name (e.g., "John's Seed Story"). Happy interviewing!



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