2. Lesson Overview Lesson Overview Reproduction in Flowering Plants Lesson Overview 24.1 Reproduction in Flowering Plants

3. Lesson Overview Lesson Overview Reproduction in Flowering Plants The Structure of Flowers What are flowers?

4. Lesson Overview Lesson Overview Reproduction in Flowering Plants The Structure of Flowers What are flowers? Flowers are reproductive organs that are composed of four different kinds of specialized leaves: sepals, petals, stamens, and carpels.

5. Lesson Overview Lesson Overview Reproduction in Flowering Plants The Structure of Flowers 1. Flowers are reproductive organs that are composed of different kinds of specialized leaves: sepals, petals, stamens, and carpels. This diagram shows the parts of a typical angiosperm flower.

6. Lesson Overview Lesson Overview Reproduction in Flowering Plants Sepals and Petals The 2. outermost circle of floral parts contains the sepals. Sepals A: enclose the bud before it opens, and they B: protect the flower while it is developing.

7. Lesson Overview Lesson Overview Reproduction in Flowering Plants 3. Petals, are found just inside the sepals. A: attract insects and other pollinators to the flower. Sepals and Petals

8. Lesson Overview Lesson Overview Reproduction in Flowering Plants Stamens The 4. stamens are the male parts of the flower —each stamen consists of a stalk called a filament with an anther (where pollen is made) at its tip.

9. Lesson Overview Lesson Overview Reproduction in Flowering Plants Carpels The 5. innermost floral parts are the carpels, which produce and shelter the female gametophytes and, later, seeds. Each carpel A: has a broad base forming an ovary, which contains one or more ovules where female gametophytes are produced.

10. Lesson Overview Lesson Overview Reproduction in Flowering Plants Carpels The diameter of 6. the carpel narrows into a stalk called the style. A. At the top of the style is a sticky or feathery portion known as the stigma, which is specialized to capture pollen.

11. Lesson Overview Lesson Overview Reproduction in Flowering Plants Carpels B. Botanists sometimes call a single carpel or several fused carpels a pistil.

12. Lesson Overview Lesson Overview Reproduction in Flowering Plants The Angiosperm Life Cycle How does fertilization in angiosperms differ from that of other plants?

13. Lesson Overview Lesson Overview Reproduction in Flowering Plants The Angiosperm Life Cycle How does fertilization in angiosperms differ from that of other plants? The process of fertilization in angiosperms is distinct from that found in other plants. Two fertilization events take place—one produces the zygote and the other a tissue, called endosperm, within the seed.

14. Lesson Overview Lesson Overview Reproduction in Flowering Plants The Angiosperm Life Cycle 7. Angiosperms have a life cycle that shows an alternation of generations between a diploid sporophyte phase and a haploid gametophyte stage. A: gametophytes live within the tissues of the sporophyte.

15. Lesson Overview Lesson Overview Reproduction in Flowering Plants Development of Male Gametophytes The male gametophytes—the pollen grains—develop inside anthers. First, meiosis produces four haploid spore cells.

16. Lesson Overview Lesson Overview Reproduction in Flowering Plants Development of Female Gametophytes Female gametophytes develop inside each carpel of a flower. 8. The ovules—the future seeds—are enveloped in a protective ovary—the future fruit.

17. Lesson Overview Lesson Overview Reproduction in Flowering Plants A single diploid cell goes through meiosis to produce four haploid cells, three of which disintegrate. Development of Female Gametophytes

18. Lesson Overview Lesson Overview Reproduction in Flowering Plants Development of Female Gametophytes If fertilization takes place, this egg cell will fuse with the male gamete to become the zygote that grows into a new sporophyte plant.

19. Lesson Overview Lesson Overview Reproduction in Flowering Plants Pollination Pollination is the transfer of pollen to the female portions of the flower. Some angiosperms are wind pollinated, but most are pollinated by animals. Because wind pollination is less efficient than animal pollination, 9. wind-pollinated plants, such as oak trees, rely on favorable weather and sheer numbers of pollen grains to get pollen from one plant to another.

20. Lesson Overview Lesson Overview Reproduction in Flowering Plants Pollination 10. Animal-pollinated plants have a variety of adaptations, such as bright colors and sweet nectar, to attract and reward animals.

21. Lesson Overview Lesson Overview Reproduction in Flowering Plants Pollination 11. Insect pollination is more efficient than wind pollination, giving insect-pollinated plants a greater chance of reproductive success.

22. Lesson Overview Lesson Overview Reproduction in Flowering Plants Fertilization 12.If a pollen grain lands on the stigma. A. one cell—the “generative” cell—divides and forms two sperm cells. B. The other cell becomes the pollen tube.

23. Lesson Overview Lesson Overview Reproduction in Flowering Plants Fertilization 13. The pollen tube grows into the style, where it eventually reaches the ovary and enters an ovule.

24. Lesson Overview Lesson Overview Reproduction in Flowering Plants Fertilization 14. Inside the embryo sac, two distinct fertilizations take place, called double fertilization. A: 1st, one of the sperm nuclei fuses with the egg nucleus to produce a diploid zygote, the new plant embryo.

25. Lesson Overview Lesson Overview Reproduction in Flowering Plants Fertilization B: 2nd, the other sperm nucleus fuses with two polar nuclei in the embryo sac to form a triploid (3N) cell, will grow into a food- rich tissue known as endosperm

26. Lesson Overview Lesson Overview Reproduction in Flowering Plants Fertilization The endosperm and embryo of a corn seed are shown.

27. Lesson Overview Lesson Overview Reproduction in Flowering Plants Fertilization By using endosperm to store food, the flowering plant spends very little in the way of food resources on producing seeds from ovules until double fertilization has actually taken place. The resources saved can be used to make many more seeds.

28. Lesson Overview Lesson Overview Reproduction in Flowering Plants Vegetative Reproduction What is vegetative reproduction?

29. Lesson Overview Lesson Overview Reproduction in Flowering Plants Vegetative Reproduction What is vegetative reproduction? Vegetative reproduction is the formation of new individuals by mitosis. It does not require gametes, flowers, or fertilization.

30. Lesson Overview Lesson Overview Reproduction in Flowering Plants Vegetative Reproduction 15. Many flowering plants can reproduce asexually. This process, known as vegetative reproduction, enables a single plant to produce offspring genetically identical to itself by mitosis. It does not require gametes, flowers, or fertilization. This process takes place naturally in many plants.

31. Lesson Overview Lesson Overview Reproduction in Flowering Plants Types of Vegetative Reproduction New plants may grow from roots, leaves, stems, or plantlets. A potato is an underground stem that can grow whole new plants from buds, called “eyes.”

32. Lesson Overview Lesson Overview Reproduction in Flowering Plants Types of Vegetative Reproduction 17. Strawberry plants send out stems called stolons. Nodes that rest on the ground produce roots and upright stems and leaves.

33. Lesson Overview Lesson Overview Reproduction in Flowering Plants Types of Vegetative Reproduction Many cactus species can reproduce by dropping sections of their stems. The small individuals growing at the base of the larger adults are clones

34. Lesson Overview Lesson Overview Reproduction in Flowering Plants Types of Vegetative Reproduction 17. Asexual reproduction allows a single plant to produce genetically identical offspring, enables well-adapted individuals to rapidly fill a favorable environment. One drawback of asexual reproduction is that it 18. does not produce new combinations of genetic traits, which may be valuable if conditions in the physical environment change.

35. Lesson Overview Lesson Overview Reproduction in Flowering Plants Plant Propagation To propagate plants with desirable characteristics, 19. horticulturists use cuttings or grafting (shown) to make many identical copies of a plant or to produce offspring from seedless plants.

36. Lesson Overview Lesson Overview Reproduction in Flowering Plants Plant Propagation One of the simplest ways to reproduce plants vegetatively is by cuttings. A grower cuts from the plant a length of stem that includes a number of buds containing meristem tissue. That stem is then partially buried in soil or in a special mixture of nutrients that encourages root formation.

37. Lesson Overview Lesson Overview Reproduction in Flowering Plants Plant Propagation Grafting is a method of propagation used to reproduce seedless plants and varieties of woody plants that cannot be propagated from cuttings. To graft, a piece of stem or a lateral bud is cut from the parent plant and attached to another plant, as shown.

38. Lesson Overview Lesson Overview Reproduction in Flowering Plants Plant Propagation Grafting works only when the two plants are closely related, such as when a bud from a lemon tree is grafted onto an orange tree. Grafting usually works best when plants are dormant, which allows the wounds created by the cut to heal before new growth starts.