1. Vascular Plants

2. Generalized life cycle

3. Moss life cycle

4. Spore -> Gametophyte

5. Gametophyte -> Zygote

6. Zygote -> mature sporophyte

7. Sporophyte -> spores

8. Vascular Plants

9. Vascular Plants Branching sporophyte in Silurian
First vascular plants in Devonian
First flowering plants
Age of Ferns
First fossil of non-algal land plant in Silurian mya
Liverwort spore tetrads - end of Ordovician

10. Fossils Probable embryophyte spores at 450 Ma
Cooksonia fossils in Silurian (ca. 430 Ma)

11. Plants like Cooksonia lacked a vascular system
Dichotomously-branching axes
Terminal sporangia
No roots or leaves

12. Over-time became larger, more complex, and acquired a vascular system

13. Living vascular plants (Tracheophytes)
Stems and roots (often leaves)

14. Living vascular plants (Tracheophytes)
Stems and roots
Sporophytes dominate the life-cycle

15. Sporophyte dominance
Gametphyte
Tree fern

16. Why sporophyte dominance?
Spore dispersal by wind: aided by height
Competition for light (gametophyte constrained by the need for water)

17. Living vascular plants (Tracheophytes)
Stems and roots
Sporophytes dominate the life-cycle
A vascular (transport) system

18. Vascular system
Xylem (water transport) and phloem (metabolite transport)
Stem
Vascular Bundle
Xylem
Phloem
Root

19. Xylem Composed primarily of Tracheids Elongated, dead, cells
Cell wall impregnated with lignin
Transport of water from soil to leaves

20. Phloem Transport via sieve elements Elongated, living cells
Transport of sugars, hormones, etc.

21. 3 Major groups of Vascular plants
Seed plants (gymnosperms and angiosperms)
Lycophytes (club mosses and their relatives)
Moniliforms (ferns and fern allies)

22. Major tracheophyte taxa
Seed Plants (ca. 290,000 species)
Lycophytes (ca. 1,100 species)
Ferns and allies (ca. 11,000 species)
Tracheophytes that are not seed plants are sometimes called “pteridophytes”

23. Vascular plant phylogeny
bryophytes
lycophytes
Ferns +
Seed plants
Microphylls
Cooksonia
Megaphylls
Vascular tissue,
Roots
Branched sporophyte

24. Organ systems origins
Stems - dichotomous branching

25. Organ systems origins
Stems
Leaves
Microphylls

26. Organ systems origins
Stems
Leaves
Microphylls
Megaphylls

27. Organ systems origins
Stems
Leaves
Microphylls
Megaphylls
Roots

28. Homospory versus Heterospory

29. An important variation: Heterospory
Megasporangium
Microsporangium
Lycopodium
(homosporous)
Selaginella (heterosporous)

31. Heterospory
Microspores and megaspores produced in different sporangia on different leaves (microsporophylls; megasporophylls)
Microspores grow into male gametophytes
Megaspores grow into female gametophytes - remains within spore wall

32. Homospory Haploid Diploid sperm zygote egg sporophyte gametophyte
spore

33. Heterospory Haploid Diploid zygote egg sperm sporophyte microspore
female
gametophyte
male
gametophyte
microspore
megaspore

34. Heterospory evolved many times. Why?
Increases potential for outcrossing
Specialization of function between micro- and megagametophyte permits greater efficiency (less cost)

35. 3 Major groups of Vascular plants
Seed plants (gymnosperms and angiosperms)
Lycophytes (club mosses and their relatives)
Moniliforms (ferns and fern allies)

36. Moniliforms
Spermatophyta
Lycophyta
Pryer et al. 2001

37. Lycophytes 380 Ma old 1100 spp. Microphylls only
Sister group to the other living vascular plants

38. Lycophytes 380 Ma old 1100 spp. Microphylls only lycophytes Ferns +
Seed plants
Microphylls
Megaphylls

39. Lycophytes Lycopodium Selaginella Clubmoss (Lycopodium) Isoetes

40. Carboniferous lycopods up to 40 m
Sigillaria
Lepidodendron

41. Lycopodium life cycle I
Sporophyte makes sporangia often in a “strobilus”
Sporangium

42. Lycopodium life cycle I
Sporophyte makes sporangia often in a “strobilus”
Sporophyll
Sporangium

43. Lycopodium life cycle II
Spores dispersed by wind: germinate into a minute gametophyte
Spore
Thallus
Spore
Rhizoids

44. Lycopodium life cycle III
Gametophyte produces archegonia and antheridia (bisexual)
Biflagellate sperm fertilize egg cells
New sporophyte grows
Archegonial neck

45. Lycophyte diversity 3 Major groups Lycopodiaceae (club mosses)
Selaginella
Isoetes

46. Lycopiaceae Approximately 400 species
Dominated Carboniferous, up to 40 m tall
form much of modern coal
Homosporous
Archegonia and Antheridia can take 6-15 years to mature

47. Selaginella Approximately 700 extant species Heterosporous
Moist habitats or "resurrect"
Selaginella umbrosa

48. Isoetes
Approximately 200 species
Grow in water or dried pools

49. Moniliforms
Spermatophyta
Lycophyta

50. Ferns and fern allies (moniliforms)
Includes ferns (Pterophyta) and two small groups (Psilophyta and Sphenophyta)
ca. 12,000 spp.
Homosporous or heterosporous
Megaphylls (lost in Psilophyta and Sphenophyta)
Ecologically important especially as tropical epiphytes

51. Moniliforms
Ferns and Fern Allies

52. Ferns and Fern Allies
Equisetum
Psilotum

53. Ferns and Fern Allies
eusporangiate ferns
Sporangium wall has 2 or more cell layers

54. Ferns and Fern Allies
leptosporangiate ferns
Sporangium wall has 1 cell layer

55. Ferns and Fern Allies
Psilotum and Ophioglossum

56. Psilotaceae/Psilophyta
Psilotum (2 spp.) and Tmesipteris (15 spp.)
No roots and reduced or absent leaves, photosynthetic stems
Sporangia on lateral branches
Homosporous
Thought to be "primitive vascular plants", but more likely simplified due to association with fungi.

57. Psilotaceae Psilotum Sporangium Tmesipteris Psilotum
Reduced forked leaves
Psilotum

58. Psilotum
Dichotomizing stem, no roots
Long-lived gametophytes

59. Ophioglossaceae Adder's tongue, eusporangiate ferns
Homosporous
Worldwide, common in disturbed areas
Botrychium (~60 spp.) and Ophioglossum (30 spp.)
Ophioglossum can have upwards of 1400 chromosomes - perhaps more then any other organism

60. spore bearing sporophore
Ophioglossaceae
Sterile blade

61. Botrychium virginianum
Ophioglossaceae

62. Ferns and Fern Allies
Equisetum

63. Equisetaceae Horse tails
Equisetum (15 spp.)
Homosporous
Dates back to Devonian, with 20 m high stems - lots of diversity in Carboniferous forests
Extant species "living fossils"
Leaves whorled, fused into sheaths at base, only microphylls

64. Equisetum

65. Extinct trees
Calamites (Carboniferous)
Calamites

67. Equisetum gametophyte (hermaphroditic)

68. leptosporangiate ferns

69. Osmunda Most ferns species are Leptosporangiate Ferns
Large megaphylls (fronds) unfold lengthwise from a "fiddlehead"
Osmunda

70. Section through sorus Sporangium Sporangia are arranged in sori Sori
Indusium
Sporangia
Sori
Section through sorus
Sporangia are arranged in sori
Sporangium

71. Fern gametophyte (prothallus)

74. Ferns Tree ferns (Cyatheaceae) Maidenhair fern Walking fern
Epiphytic fern (Platycerium)

75. Leptosporangiate ferns
App. 11,000 species in recognized groups (most of fern diversity)
Cover 4 of the major clades
Marsileaceae
Osmundaceae
Cyatheaceae
Polypodiaceae

76. Marsileaceae Salvinia Marsilea Mostly aquatic
Leave blade divided into 2-4 leaflets (clover-like)
Heterosporous
- megagametophytes with only one archegonium
Symbiotic with cyanobacteria, fertilized rice fields
Spores remain viable for a century
Salvinia
Marsilea

77. Osmundaceae Sporangia loose, not in sori Homosporous Osmunda Todea
Leptopteris

78. Cyatheaceae Tree fern growth Sporangia in sori on bottom of leaf
Stem usually single and erect
Alsophila
Cyathea

79. Polypodiaceae Asplenium Nephrolepis Elaphoglossum Adiantum Polypodium
Pteris
Tectaria

80. Main points Features of vascular plants Homospory versus heterospory
Megaphylls vs. microphylls
Life cycle of the fern
Fern allies: Psilotum, Equisetum