Instructor’s Copy

Lab Worksheet – Flowers, For Me!

Part A: Stems

Pour a small amount of the food coloring in water into your test tube. Snip off the bottom of the white flower your teacher has given you (you need a freshly cut surface on your stem for this part) and place the flower into the test tube. Let this sit until the end of class. What do you see?

The petals of the flower should be turning the color of the dye. If not, leave overnight. If the xylem are large enough, the students might be able to look at the cut surface of the stem and see the individual xylem because of the dye.

Part B: A “Typical Flower”

Flowering plants belong to the class angiospermae which is subdivided into two subclasses, monocots and dicots. Monocots usually possess flower parts in multiples of three. Dicots have flower parts in multiples of four or five.

Flowers specialize in sexual reproduction. They grow from a flower stalk called a pedicel. The floral parts are inserted in the receptacle. A complete flower has four rings of floral parts. The outer ring of floral parts if formed by several leaf-like structures called sepals. These are usually, but not always, green. This ring of parts acts as a wrap which protects the developing bud. The next ring of parts are the petals which are brightly colored to attract pollinators.

The center of the flower contains the female reproductive structure, the pistil. Surrounded by the male reproductive structures, the stamen. Each stamen has a slender stalk or filament with a sac at the top called an anther.

The female flask-shaped carpel has a swollen base or ovary which contains ovules, later to become seeds.

Part C: Flower Variation

Not all flowers are “typical”. Flowers with both male and female parts are perfect flowers. Flowers with only male parts are called staminate flowers. Flowers with only female parts are called pistilate flowers.

Symmetry is a characteristic used by botanists to help identify flowers. Some flowers are radially symmetrical (can be cut in half many ways to will still produce two identical halves), other are bilateral (can only be cut one way to produce two identical halves).

Name the kind of symmetry exhibited by each of the following.

1.  radial symmetry

2.  bilateral

Flowers of plants in the Sunflower Family (Compositae Family) appear to be single blossoms, but are actually like a bouquet of flowers. If you examine a daisy closely, you would notice many small tube-shaped flowers in the center. These are called disc flowers. Along the margin of a daisy are strap-shaped ray flowers. Sometimes composite flowers have only ray or only disc flower types. A thistle is an example of a composite flower consisting of many disc flowers, but not ray flowers.

Label each flower type.

1.  disc flower

2.  ray flower

Part D: The seed.

A seed is, in one sense a packaged plant. Everything a plant needs to begin growing is inside this “package”. Seeds typically consist of an embryo, stored food, and a seed coat. Angiosperms with two cotyledons are dicots while those with one cotyledon are monocots.

On the concave side of a bean is an oval scar called a hilium which is where the seed was attached to the ovary wall. A tiny pore found near one end of the hilium is the opening in the ovule wall where the pollen tube grew through called the microphyle.

Inside the seed is the embryo plant.

Label the seed.

1. seed coat

2. hilium

3. microphyle

4. embryo plant

Part E: Examples

1. Draw and label your first flower here. (Depends on flowers procured by teacher – should be regular flower.)

Flower Leaf

2. What color are the petals? Depends on flower.

3. How many petals does this flower have? Depends on flower.

4. The flowers are (ray flowers, disk flowers, both ray and disk flowers).

For questions 5 & 6, look at the information on the last page.

5. The veins in the leaves are (parallel, branching). Depends on flower.

6. The leaf arrangement is ______. Depends on flower.

7. This flower is (complete, staminate, pistilate). Depends on flower.

8. How many ovules does this flower have? Depends on flower.

9. Is this flower a monocot or a dicot? Explain how you know. Depends on flower. Can go by

leaves (parallel for monocot, branching for dicot) or # of petals (monocots = multiples of 3,

dicots = multiples of 4 or 5).

10. Draw and label your second flower here. Should be a composite – daisies are cheapest.

Flower Leaf

11. What color are the petals? Depends on flower.

12. How many petals does this flower have? Depends on flower.

13. The flowers are (ray flowers, disk flowers, both ray and disk flowers).

For questions 14 & 15, look at the information shown below.

14. The veins in the leaves are (parallel, branching). Depends on flower.

15. The leaf arrangement is ______. Depends on flower.

16. This flower is (complete, staminate, pistilate). Depends on flower.

17. How many ovules does this flower have? Depends on flower.

18. Is this flower a monocot or a dicot? Explain. Depends on flower.

19. Angiosperms are the most successful group of plants on Earth because of their many

adaptations. List one adaptation of the plant parts observed in lab today and explain how it has

made angiosperms so successful. Students requiring enrichment may be assigned to do 2 or

more reasons to receive credit for each of these.

Leaves: Leaves are green because they contain chlorophyll that enables plants to make

food. If students research, they might also include that stomata regular water loss and

waxy coating on some leaves protect from drying out.

Stems: Xylem tubes help plants get water through the plant so the plant can grow

taller. Students also may list that they provide the plant support and get the leaves and

flowers above most ground plants to help in increased food production and pollination.

Seeds: Allow the next generation of plants to grow because they have a food supply.

Students may also include that different types of seed coats allow the embryo plant to

be transported away from the parents to decrease competition for soil and nutrients.

Ex. some have burrs to attach to animals, some are light and feathery so they can be

carried by the wind, etc.

Flowers: Colorful to attract pollinators. May also point out that the ovaries (fruit) are

eaten by many animals so that the seeds can be carried to new areas.

Veins:

Leaf arrangement: