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2. Resources Chapter Presentation Visual Concepts Transparencies Standardized Test Prep

3. Chapter 30 Plant Reproduction Table of Contents Section 1 Plant Life Cycles Section 2 Sexual Reproduction in Flowering Plants Section 3 Dispersal and Propagation

4. Section 1 Plant Life Cycles Chapter 30 Objectives • Describethe life cycle of a moss. • Describethe life cycle of a fern. • Describethe life cycle of a gymnosperm. • Compare homospory and heterospory.

5. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Mosses • The life cycle of mosses alternates between clumps of gametophytes (the dominant generation) and a sporophyte that consists of a spore capsule on a bare stalk. • Moss gametophytes produce gametes in two types of reproductive structures: antheridia (singular, antheridium), and archegonia (singular, archegonium).

6. Section 1 Plant Life Cycles Chapter 30 Alternation of Generations

7. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Mosses, continued • An antheridium is a male reproductive structure that produces hundreds of flagellated sperm by mitosis. • An archegonium is a female reproductive structure that produces a single egg by mitosis. • Sperm break out of the antheridia and swim to archegonia. One sperm fertilizes one egg to produce a diploid zygote. • The zygote undergoes repeated mitotic division and forms a sporophyte, which remains on the gametophyte.

8. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Mosses, continued • Soon, the cells at the tip of the sporophyte will form a sporangium, called a capsule. • A capsule of a moss is the part of the sporophyte that will create haploid spores. • Mosses will only produce one type of spore. When only one type of spore is produced it is called homospory.

9. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Mosses, continued • When the spores are mature, the capsule will split open, and the spores are carried away by the wind. • Spores that land in favorable environments may germinate and grow into new gametophytes.

10. Section 1 Plant Life Cycles Chapter 30 Life Cycle of a Moss

11. Section 1 Plant Life Cycles Chapter 30 Life Cycle of Mosses

12. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Ferns • The life cycle of ferns is similar to mosses, but it is also different. • Most ferns are homosporous and produce a sporophyte that grows from the gametophyte. • However, the sporophyte, not the gametophyte, is the dominant generation in ferns.

13. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Ferns, continued • The fern’s gametophytes are tiny and are anchored to the soil by rhizoids. They can produce both antheridia and archegonia. • Water must be present in order for the egg to be fertilized. • Once the egg is fertilized, it will soon form a zygote and then a sporophyte.

14. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Ferns, continued • Once the sporophyte can survive on its own, the gametophyte will die. • Once mature, a fern sporophyte will have leaves that are called fronds. • Fronds grow from an underground stem, or rhizome, and contain cells on their underside that develop into sporangia.

15. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Ferns, continued • In many ferns, the sporangia on the underside of a frond are clustered together. • A cluster of sporangia is called a sorus. The sorus will produce haploid spores. • Once the spores have matured, they will be carried away by air currents. When the spores land, they may grow into new gametophytes.

16. Section 1 Plant Life Cycles Chapter 30 Life Cycle of a Fern

17. Section 1 Plant Life Cycles Chapter 30 Life Cycle of Ferns

18. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Gymnosperms • Gymnosperms will produce two types of spores—male microspores and female megaspores. • Microspores will grow into male gametophytes, and megaspores will grow into female gametophytes. • When different types of asexual spores are produced it is called heterospory.

19. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Gymnosperms, continued • The microspores of heterosporous plants produce male gametophytes that stay attached to the sporophyte and develop into pollen. • Pollen allows sexual reproduction in seed plants to take place independent of seasonal rains or other periods of moisture.

20. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Gymnosperms, continued • However, gymnosperm sexual reproduction can take more than two years. • During the first summer, a mature pine tree produces separate female and male cones, which produce male (microsporangia) and female (megasporangia) sporangia. • The following spring, the cells in all sporangia undergo meiosis and divide to produce haploid spores.

21. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Gymnosperms, continued • Megasporangia are haploid spores that produce megaspores, which develop into megagametophytes, or female gametophytes. • A thick layer of cells called an integument surrounds and protects each megasporangium. • Each integument has a small opening where pollen can enter, called the micropyle. • Together, a megasporangium and its integument form a structure called an ovule.

22. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Gymnosperms, continued • Microsporangia produce microspores, which develop into microgametophytes, or male gametophytes. • A pollen grain is a microgametophyte of a seed plant.

23. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Gymnosperms, continued • The male cones of a pine release huge numbers of pollen grains into the wind. • When the pine pollen lands on a female cone, it will drift between the cone scales until they reach the ovules. • The transfer of pollen, the male gametophyte, to ovules, the female gametophyte, is called pollination.

24. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Gymnosperms, continued • During pollination, the pollen grain is drawn into the ovule through the micropyle, and induces the ovule to produce archegonia and eggs. • After pollination, the pollen grain begins to grow a pollen tube. • The pollen tube is a slender extension of the pollen grain that enables sperm to reach an egg.

25. Section 1 Plant Life Cycles Chapter 30 The Life Cycle of Gymnosperms, continued • Pine sperm do not have flagella and they do not swim to an egg. The pollen tube carries the maturing sperm to the egg. • When the pollen tube reaches an archegonium, one sperm unites with an egg to form a zygote. • Over the next few months, the zygote develops into an embryo as the ovule matures into a seed.

26. Section 1 Plant Life Cycles Chapter 30 Life Cycle of a Conifer

27. Section 1 Plant Life Cycles Chapter 30 Life Cycle of Conifers

28. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Objectives • Identifythe four main flower parts, and state the function of each. • Describegametophyte formation in flowering plants. • Relateflower structure to methods of pollination. • Describefertilization in flowering plants.

29. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Parts of a Flower • Early land plants lacked leaves and roots and consisted of only stems. • Leaves evolved from branches of stems, and flowers are considered to be highly specialized branches and the parts of a flower to be specialized leaves. • The specialized leaves of a flower form on the swollen tip of a floral “branch”, which is called a receptacle.

30. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Parts of a Flower, continued • Flower parts are usually found in four concentric whorls, or rings. • The outer whorl is called the sepals, which protects the other parts of a developing flower before it opens. • Petals make up the next whorl, and can vary drastically between plants. Some plants have brightly colored petals, and other plants have petals that are small or absent.

31. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Parts of a Flower, continued • The male reproductive structures are stamens, each of which consists of an anther and a filament, and are found on the third whorl of the flower. • An anther contains microsporangia, which produce microspores that develop into pollen grains. • A stalklike filament supports an anther.

32. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Parts of a Flower, continued • The innermost whorl contains the female reproductive structures, which are called carpels. • One or more carpels fused together make up the structure called a pistil, which is the main female reproductive structure in flowering plants.

33. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Parts of a Flower, continued • The base of a pistil contains the ovary, which will produce eggs in ovules. • A style, which is usually stalklike, rises from the ovary. • The tip of the style is called the stigma, which usually is sticky or has hairs in order to trap pollen grains.

34. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Floral Structure

35. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Parts of a Flower

36. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Parts of an Angiosperm

37. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation • In angiosperms, gametophytes develop within the reproductive structures of flowers. • Embryo sacs, which are the female gametophytes in angiosperms, form within the ovary of the pistil. • Pollen grains, the male gametophytes, form within the anthers of the stamens.

38. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation, continued Embryo Sac Formation • In flowers, ovules form in the ovary of a pistil. • An angiosperm ovule consists of a megasporangium surrounded by two integuments, which do not completely enclose the megasporangium. • At one end of the ovule is the micropyle, through which a pollen tube can enter.

39. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation, continued Embryo Sac Formation, continued • An ovule contains a large diploid cell called a megaspore mother cell. • A megaspore mother cell undergoes meiosis and produces four haploid megaspores. • The maturing megaspore undergoes three mitotic divisions, which produce a cell that has eight haploid nuclei.

40. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation, continued Embryo Sac Formation, continued • The haploid, megaspore nuclei migrate to certain locations within the cell. • The nuclei are initially arranged in two groups of four at the top and bottom of the cell. • Two nuclei will come to the center from the ends or poles and are called polar nuclei. These are the nuclei that will eventually fuse with the sperm cells.

41. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation, continued Embryo Sac Formation, continued • The other six nuclei within the megaspore mother cell help the polar nuclei be fertilized by the sperm and then eventually die after fertilization occurs. • The megaspore mother cell is now called the embryo sac and contains eight nuclei—seven smaller cells and a large central cell that encloses all the other cells.

42. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation, continued Embryo Sac Formation, continued • The embryo sac is also known as the mature female gametophyte, or megagametophyte. • The surrounding integuments and the embryo sac now form a mature ovule, which when fertilized will develop into a seed.

43. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Formation of A Female Gametophyte

44. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Ovule Formation in an Angiosperm

45. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation, continued Pollen Grain Formation • An anther contains four microsporangia, or pollen sacs. • Initially, the pollen sacs contain many diploid cells, and are called microspore mother cells. • Each of these microspore mother cells will undergo meiosis and produce four haploid microspores.

46. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation, continued Pollen Grain Formation, continued • Each microspore undergoes mitosis and produces two haploid cells that do not separate. • Once the cells are haploid, a thick wall then develops around the microspore. • The resulting two-celled structure is a pollen grain, which is the male gametophyte, or microgametophyte.

47. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Gametophyte Formation, continued Pollen Grain Formation, continued • The larger of the two cells is the tube cell, from which the pollen tube will form. • The generative cell, which is enclosed in the tube cell, will divide by mitosis to form two sperm.

48. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Formation of A Male Gametophyte

49. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Pollen Grain Formation

50. Section 2 Sexual Reproduction in Flowering Plants Chapter 30 Parts of a Pollen Grain