The Plant Kingdom: Seedless Vascular Plants

1. The Plant Kingdom: Seedless Vascular Plants Chapter 23

2. Artist’s conception of a tropical Carboniferous forest. During the Carboniferous period, North America and Europe were considerably closer to the equator than they are today and had tropical swamp forests. Carboniferous forests in drier regions farther away from the equator were sparser and more open than the one depicted here.

3. Lygodium overtaking cypress in Florida.

5. LEARNING OBJECTIVE 1 • Summarize the features that distinguish seedless vascular plants from bryophytes

6. KEY TERMS • XYLEM • Vascular tissue that conducts water and dissolved minerals • PHLOEM • Vascular tissue that conducts dissolved sugar and other organic compounds

7. Seedless Vascular Plants • Adaptations that bryophytes lack • Vascular tissues (xylem and phloem) • Dominant sporophyte generation • As in bryophytes, reproduction depends on water to transport motile sperm cells

8. Tasmanian Tree Fern

9. Evolution of Seedless Vascular Plants

10. SEEDLESS VASCULAR PLANTS LYCOPHYTES FERNS Spike mosses Club mosses Seed plants Whisk ferns Horsetails Quillworts Ferns Evolution of seeds B Evolution of microphylls Evolution of megaphylls A Ancestral vascular plant Fig. 23-2, p. 447

11. LEARNING OBJECTIVE 2 • Contrast microphylls and megaphylls

12. KEY TERMS • MICROPHYLL • Type of leaf found in lycophytes • Contains one vascular strand • MEGAPHYLL • Type of leaf found in virtually all vascular plants except lycophytes • Contains multiple vascular strands

13. True Leaves • Two basic types of true leaves, microphylls and megaphylls, evolved independently of each other

14. Evolution of Leaves

15. Stem Microphyll Vascular tissue Enation Vein Smooth stem Enation Vascular supply to enation Microphyll (one vein) (a) Microphyll evolution Thicker main stem Dichotomous end branches Equal branches Vascular tissue Thinner side branch Planation (branching in same plane) Overtopping (unequal branching) Webbing of side branch system Megaphyll (many veins) Dichotomously branching stems (b) Megaphyll evolution Fig. 23-3, p. 448

16. Stem Microphyll Vascular tissue Enation Vein Smooth stem Enation Vascular supply to enation Microphyll (one vein) Thicker main stem Dichotomous end branches Equal branches Vascular tissue Thinner side branch Planation (branching in same plane) Overtopping (unequal branching) Webbing of side branch system Megaphyll (many veins) Dichotomously branching stems (a) Microphyll evolution Stepped Art (b) Megaphyll evolution Fig. 23-3, p. 448

17. LEARNING OBJECTIVE 3 • Distinguish between the two phyla of seedless vascular plants

18. KEY TERMS • FERNS(phylum Pteridophyta) • Phylum of seedless vascular plants that reproduce by spores produced in sporangia • Undergoes alternation of generations between dominant sporophyte and gametophyte (prothallus) • Largest, most diverse group of seedless vascular plants • Whisk ferns and horsetails classified as ferns

19. KEY TERMS • LYCOPHYTES (phylum Lycopodiophyta) • Phylum of seedless vascular plants, some of which are heterosporous • Lycophytes include club mosses, spike mosses, quillworts

20. Fern Diversity

21. Fern Diversity

22. Fern Diversity

23. Fern Diversity

24. LEARNING OBJECTIVE 4 • Name and briefly describe ferns • Explain why whisk ferns and horsetails are currently classified as ferns

25. Fern Sporophytes 1 • Consist of • A rhizome that bears fronds(megaphylls) • True roots • Whisk fern sporophytes • Have dichotomously branchingrhizomes and erect stems • Lack true roots and leaves

26. Fern Sporophytes 2 • Horsetailsporophytes • Roots, rhizomes, and aerial stems are hollow and jointed • Leaves are reduced megaphylls

27. Classification • Whisk ferns and horsetails were considered distinct enough to be classified in separate phyla • DNA comparisons and similarities in sperm structure resulted in reclassification as ferns

28. Whisk Fern

29. Sporangia Aerial stem with scale-like outgrowths (no leaves) Fig. 23-9a, p. 452

30. Whisk Fern

31. Antheridia Archegonia Rhizoids (b) The gametophyte of P. nudum lives underground, nourished by mycorrhizae. Fig. 23-9b, p. 452

32. Ancient Horsetail

33. Horsetails

34. Strobilus Reproductive shoot Vegetative shoot (a) In some horsetail (Equisetum) species, both fertile shoots, which bear conelike strobili, and vegetative (nonreproductive) shoots are unbranched. Fig. 23-11a, p. 453

35. Horsetail Spores

36. Spore Elater Fig. 23-12b, p. 456

37. LEARNING OBJECTIVE 5 • Describe the life cycle of ferns • Compare their sporophyte and gametophyte generations

38. Life Cycle of Ferns 1 • Fern fronds bear sporangia in clusters (sori) • Meiosis in sporangia produces haploid spores • Fern gametophyte (prothallus)develops from a haploid spore • Bears both archegonia and antheridia

39. Life Cycle of Ferns 2 • Each archegonium contains a single, nonmotile egg; each antheridium produces numerous sperm cells • Following fertilization, diploid zygote grows by mitosis into a multicellular embryo (immature sporophyte)

40. Animation: Fern Life Cycle CLICKTO PLAY

41. Fern Life Cycle

42. Underside of enlarged mature gametophyte (prothallus) Germination of spores and development of young gametophyte Egg 5 4 Archegonium Spores released Rhizoids 3 Antheridium Sporangium HAPLOID (n) GAMETOPHYTE GENERATION Sperm cell Cells within sporangia undergo meiosis Meiosis Fertilization DIPLOID (2n) SPOROPHYTE GENERATION Zygote Sorus (cluster of sporangia) 2 6 1 Frond Leaf of young sporophyte Development of the sporophyte Leaf cross section Haploid prothallus Fiddlehead Root of young sporophyte Roots Rhizome Fern (mature sporophyte) Underside of a frond Fig. 23-5, p. 450

43. Fiddleheads

44. Sori

45. Prothallus

46. Archegonium Rhizoids Fig. 23-8, p. 451

47. LEARNING OBJECTIVE 6 • Name and briefly describe the three groups of lycophytes

48. 3 Groups of Lycophytes 1. Club mosssporophyte • true roots • rhizomes and erect or trailing aerial stems • small, scalelike microphylls

49. Club Mosses

50. Strobilus Leaves (microphylls) (a) The sporophyte of Lycopodium obscurum has small, scalelike, evergreen leaves (microphylls). Spores are produced in sporangia on fertile leaves clustered in a conelike strobilus. (b) Vegetative growth of Lycopodium complanatum, which has a creeping growth form. Like most club mosses, L. complanatum prefers moist, shady woodlands. Fig. 23-14, p. 457