FLOWER DISSECTION

Students dissect a BACKGROUND DOING THE ACTIVITY variety of flowers to Now that your students can conceptualize identify floral struc- the process of pollination, they will be SETTING THE STAGE ready to observe the floral structures that tures. 1) Recall with your students your discus- help make it possible. By dissecting a sion of pollination. Ask, “What do variety of flowers and identifying their ARIZONA SCIENCE pollinators carry from one flower to the parts, students will better understand the next?” (pollen) “What happens when STANDARDS mechanics of pollination. pollen lands on the female part of the 4SC-F3 With Younger Students: flower?” (A fruit with seeds is pro- Even the youngest students enjoy dissecting duced.) OBJECTIVES flowers and identifying their parts. With K- 2) Explain that today you are going to look Students should: 2 students, it is best to have them catego- at the parts of the flowers that help make • Dissect flowers to rize and identify only three main parts: pollination happen. Point out the parts on look at their parts. petals, male parts, and female parts. a lily as you discuss them. With older • Identify male and There is no need to give the names of the students, you may want to sketch a female reproductive individual units that comprise the reproduc- floral parts diagram on the board and go structures of a flower. tive structures. over the names of the parts using both • Identify petals and With older students: the diagram and the lily. sepals of a flower. You may wish to have them identify the reproductive structures in more detail (i.e. MATERIALS have them find the anthers and filaments • A copy of Student or the stigma, style, and ovary of their Handout - Flower flowers.) Refer to the information on floral Parts Page for each structure in the teacher background infor- student mation (pages 5-6) for descriptions of • A variety of flowers floral structures. for dissection, about three per student GETTING READY • Buckets or vases Make a copy of Student Handout - for the flowers Flower Parts Page (page 16) for each • Clear tape student and for your own demonstration. • Hand lenses Assemble the materials listed in the left • Pencils or pens margin of this page. Florists will often VOCABULARY donate browning or old flowers, which Male parts (stamens) Female parts (pistil) Anther work fine. You can supplement the throw- aways by purchasing a few new specimens anther (makes pollen) stigma Filament style that clearly show floral structure. The best filament Ovary ovary (eggs inside) Petals flower types to dissect include lilies, tulips, Pistil daffodils, alstroemarias, and gladiolus. 3) Ask, “Does the pollen come from the Pollen Avoid daisies, asters, calla lilies, roses, and male or female parts of the flower?” Sepals iris, since their floral structure is not as easy (male) Show the pollen-laden anthers Stamen to discern. You may wish to have your suspended on their filaments. Rub some Stigma students bring flowers from home, as well, pollen on the students’ fingers. Style if they have flowering plants in their yards. 4) Point out the sticky stigma on the lily Set the flowers in large buckets or vases. and tell the students that this is where the pollen lands during pollination. Point to

Teacher Information Desert Discovery Class 2000 ASDM FLOWER DISSECTION where the undeveloped seeds are found in the ovary it is sticky. Follow the tube-shaped tissue (style) and explain that this develops into the fruit and seeds down from the top with your finger until you reach after pollination. the rounded base (ovary). Carefully break open 5) Show the petals and sepals, explaining their func- the ovary with your fingernail and look closely for tion. Tell them that on the lily, the sepals look the seeds or unfertilized eggs with the hand lens. Tape same as the petals. Pick out another flower with these parts to the “female parts” square on your obvious, green sepals to show that sepals can look handout. (Again, you may want to have older very different. students label the parts.) 6) Explain that you are all going to take a flower apart, 2) Have the students follow the same procedure with step by step, to see the different parts up close. their remaining flower(s). Circulate around the room to help identify parts and be sure they are putting them in the right squares. DISSECTING FLOWERS

1) Give each student a copy of Student Handout - DISCUSSION Flower Parts Page, pass out tape and hand lenses, and instruct the students to each choose two or three 1) When the students have completed their pages, ask different flowers. Remind them that the group will go them questions about what they observed while through all the steps together. Make sure no one dissecting flowers. Discuss possible answers listed in starts tearing apart their flower too soon. Follow parentheses. these steps: 1. Starting with the sepals and petals, carefully pull • Did any of the flower petals have lines or dots on apart the flower. them? What do you think these might be for? (Many 2. You may want to point out the sepals to older flowers have lines or dots on them. These are called students. (Sepals are the first or outermost tissue nectar guides. The petal acts as a landing pad for the you encounter on the stem at the base of the insect and the lines are like a map to show where to flower. They protect the flower bud before it find the nectar. Some insects see ultra-violet colors, opens and support the flower later. They are often so the nectar guides look brighter or different to them the same color as the petals.) than they do to us.) 3. Take one of the petals and tape it in the “petals” • Do some flowers have more male parts than others? square on your flower parts page. (Yes. Some flowers have only a few stamens, while 4. Choose one of the male parts (stamens) from the others of different kinds have many. Some flowers flower. (For kindergarten students, refer to these may contain only male or only female parts, or non- as “boy” parts.) Look at the pollen inside the functional parts.) anthers on top of the filaments with a hand lens. If • Is the place where the pollen lands on the female part there is enough pollen, shake some of the pollen always the same shape? (No. Stigmas can be onto your page in the “male parts” square. Take smooth-edged, fringed, or lobed, depending on the another intact stamen from kind of plant the flowers grow on. The different your flower and tape it in the surfaces and shapes help the right kind of pollen stick “male parts” square. (For to them.) older students, you may want • Does one flower usually have more male parts than to have them label the indi- female parts? (yes) Why do you think this might be vidual parts on their sheet.) important? (The role of the male parts is to produce 5. Now they should see the pollen. The more male parts there are, the more female parts (pistil) of the pollen they produce, and the more densely they fill flower. (For kindergarten students, refer to these the flower.This increases the chance that an animal as “girl” parts.) Feel the top part (stigma) to see if might touch them and pick up pollen when it comes in search of nectar.)

Teacher Information Desert Discovery Class 2000 ASDM