Unit

1. Unit Plant Science

2. Problem Area Reproduction in Plants

3. Lesson Examining Parts of a Flower

4. Student Learning Objectives • 1. Describe the parts of a flower. • 2. Identify the reproductive structures of plants that exist in the flower. • 3. Describe the difference between monocot and dicot flowers. • 4. Explain the difference between pollination and fertilization. • 5. Describe environmental factors that can influence the beginning of the flowering process.

5. Terms • Monocot • Ovaries • Ovule • Perfect flower • Petal • Photoperiodism • Phytochrome • Pistil • Pistillate flower • Anther • Anthesis • Complete flower • Dicot • Fertilization • Filament • Flower • Imperfect flower • Incomplete flower

6. Terms cont. • Pollen • Pollination • Sepal • Stamen • Staminate flower • Stigma • Style • Vernalization

7. What are the major parts of flowers? • A floweris the reproductive part of flowering plants. • A. Flowers are in many shapes and colors. • B. Some flowers are attractive and have appealing fragrances. • C. Almost all flowers are important in producing fruit and seed.

8. D. The major parts of flowers are to support the production of fruit and seed. • 1. Sepals—The sepals are the green-like structures beneath the petals. Sepals offer protection to the developing bud. • 2. Petals—The petals are usually brightly colored part of the flower and serve to attract pollinators, such as insect. • 3. Stamens—The male reproductive part of the flower. • 4. Pistil—The female reproductive part of the flower.

10. What reproductive structures exist in the flower and what are their functions? • A. The stamen of the male reproductive part of the flower consists of the anther and filament. • 1. Anther—Produces the pollenor male gamete (sperm). • 2. Filament—Stalk which supports the anther. • B. The pistil or female reproductive part of the flower consists of the stigma, style and ovary. • 1. Stigma—Usually has a sticky surface for capturing pollen. • 2. Style—Tube-like and connects the stigma with the ovary. • 3. Ovary—Contains the ovulesor gametes (eggs).

11. C. Plants can be group based on their reproductive parts. • 1. Complete flower—A flower that has all four major parts (sepals, petals, stamens, and pistils). • 2. Incomplete flower—Flowers that lack one or more of the major parts, such as their petals. • 3. Perfect flower—A flower containing both stamens and pistils. • 4. Imperfect flower—A flower that lacks either stamens or pistils. • 5. Pistillate flower—A flower having pistils but no stamens. • 6. Staminate flower—A flower having stamens but no pistils.

12. How is a monocot flower different from a dicot flower? • A good way to tell the difference between a monocot and dicot is to look closely at the flowers. • A. Monocotshave flowers with flower parts in multiples of three. • B. Dicotshave flowers with flower parts in multiples of four or five.

13. What is the difference between pollination and fertilization? • Pollination occurs before fertilization. • A. Pollination—Occurs when a pollinator, such as wind, insects, or animals, transfers the pollen grains from the anther to the stigma. The pollen grains then germinate and move down the style until it reaches the ovules in the ovary. • B. Fertilization—Occurs when the pollen, or male sex cell, fuses with the egg cell to begin a new plant.

15. What environmental factors influence the formation of flowers? • A. Photoperiodism—The growth response of a plant to the length of day or more precisely the length of light and dark periods. • 1. Some plants detect the progression of seasons by reacting to the change of day length. • 2. It is not the length of day but the length of night that is important to the flowering process. • 3. Long day and short day plants differ in the photoperiodic conditions required for leaves to send the signal to flower.

16. B. Vernalization—The process by which floral induction in some plants is promoted by exposing the plants to cool temperatures for a certain length of time. • 1. Some plants bloom after a single exposure to the photoperiod required for flowering; other species need several successive days of the appropriate photoperiod. • 2. Still other plants will respond only if they have been previously exposed to some other environmental stimulus, such as a period of cold temperatures. • 3. Winter wheat for example will not flower unless it has been exposed to several weeks of temperatures below 10°C.

17. C. Phytochrome—A pigment occurring in the cytoplasm of green plants. It is associated with the absorption of light that affects growth, development, and differentiation including flowering of a plant, independent of photosynthesis. • 1. Phytochrome does not explain the flowering process in all plants because many species react to changes in temperature rather than light (ex. winter wheat). • D. Anthesis—The release of pollen from the anther, which may be before the flower opens in self-pollinated crops to several days after the flower has been open.

18. Review/Summary • What are the major parts of flowers? • What reproductive structures exist in the flower and what are their functions? • How is a monocot flower different from a dicot flower? • What is the difference between pollination and fertilization? • Describe environmental factors that can influence the beginning of the flowering process.