LABORATORY 2: Flowers
The goal of this laboratory exercise is to familiarize you with flowers, their structure, variation, and importance to the flowering plant. By the end of today’s laboratory exercise you should be able to recognize and identify the parts of a flower, and to briefly describe their importance to the life of a flowering plant. Through the study of flower morphology, you will also become accustomed to the correct use of a dissecting microscope.
Carefully EXAMINE all floral material provided using the following exercise and questions as a guideline. To gain an ultimate familiarity with floral morphology, compare the material against descriptions and definitions in your lecture hand-outs.
1. Flowers are arranged in structures called inflorescences. Inflorescences can be arranged in a variety of ways. DRAW simple diagrams of the following inflorescences: solitary, spike, raceme, panicle, umbel, catkin, and head.
2. DRAW a longitudinal section of a typical flower labeling the following parts: receptacle, calyx, sepals, corolla, petals, perianth, pedicel, ovary, ovule, style, stigma, pistil, gynoecium, anther, filament, stamen, and androecium.
3. EXAMINE by dissection the floral material provided making longitudinal and transverse (cross) sections of the flower and its parts. On a separate sheet of paper, SKETCH the flowers and label the parts. Then, FOR EACH FLOWER, answer the following questions:
A. Is the flower actinomorphic (regular) or zygomorphic (irregular)?
B. How many sepals are present? Petals?
Stamens? Carpels? To count carpels, count the style branches
and/or count the zones of placentation by cross- sectioning the ovary.
C. Is the ovary inferior or superior?
D. Is the flower from a monocotyledonous or
1. What purposes do flowers serve?
2. What is the difference between a monoecious and a dioecious plant in terms of their flowers?
3. What is a fruit? What is a mature ovary?
4. What is a seed? What is a mature ovule?
5. What is the difference between an ovule and a seed?
6. What are two ways to count the number of carpels present in a pistil? What is a carpel?
7. What is the difference between a perfect and a imperfect flower?
8. What is a gynoecium? What is an androecium?
9. What is a pollinium? We saw pollinia in two different flowers, those of the Asclepiadaceae and Orchidaceae families. What is the purpose of the pollinium in the life histories of these plants?
10. A sunflower may look like a single flower, but it is definitely not. Exactly what is a sunflower?
11. What is a zygomorphic (irregular) flower? What is an actinomorphic (regular) flower?
12. A Gladiolus flower is quite large and showy. A grass flower is small, inconspicuous, and non-showy. Based on this information, what can you say about the pollination of each of these?
13. Be able to name and count flower parts if given a fresh flower.
14. What is a complete flower? What is an incomplete flower?
15. Where are pollen grains produced and from where are they released?
16. Name the parts of a flower which make up the pistil.
17. What is a compound pistil? What is a simple pistil?
18. Why do you think a sunflower inflorescence so strongly resembles a flower? What purpose, in terms of the evolution of such a structure, might this type of inflorescence serve?
19. Name the parts which make up a stamen.
20. Know the difference between a longitudinal section and a transverse (cross) section; for example, of an ovary.
21. Know how to properly adjust a dissecting microscope.
22. We have now covered the vegetative and floral
parts of the typical flowering plant. Make a table which contrasts
the vegetative and floral characters of monocots and dicots.
(i.e., How can you differentiate between monocots and dicots using vegetative and floral characters?)