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Chapter 26: The Plant Kingdom: Seedless Plants

Chapter 26: The Plant Kingdom: Seedless Plants. Charophytes. Green algae Closest ancestor to plants Evidence Charales and Coleochaetes. Fig. 29-3. Chara species, a pond organism. 5 mm. Coleochaete orbicularis, a disk-shaped charophyte that also lives in ponds (LM ). 40 µm.

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Chapter 26: The Plant Kingdom: Seedless Plants

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  1. Chapter 26: The Plant Kingdom: Seedless Plants

  2. Charophytes • Green algae • Closest ancestor to plants • Evidence • Charales and Coleochaetes

  3. Fig. 29-3 Chara species, a pond organism 5 mm Coleochaete orbicularis, a disk-shaped charophyte that also lives in ponds (LM) 40 µm

  4. Features of Charophytes that promoted evolution of multicellular land plants • 1) Cellulose synthesizing complexes nearly identical (during cell wall formation) • 2) Apical cells – allow filaments to increase in length • 3) Plasmodesmata – communication between neighboring cells • 4) Both retain and care for zygote

  5. Adaptations to Life on Land • Cuticle • Waxy, aerial, prevents desiccation • Stomata • Pores on surface of leaves, stems  Gas exchange • Gametangia • Multicellular sex organs • Embryo develops within female gametangium (protected)

  6. 7 Characteristics of Plants • Multicellular, eukaryotic • Photosynthetic • Waxy cuticle • Terrestrial • Stomata and guard cells • Complex fertilization • Cell walls of cellulose and lignin

  7. Alternation of Generations • Switch between haploid and diploid • Both multicellular • Dominant generation • Haploid (n) = gametophyte • Mitosis – haploid gametes • Antheridia – sperm • Archegonia - egg • Diploid (2n) = sporophyte • Meiosis – haploid spores • Zygote (sperm + egg)  multicellular embryo (in archegonium)

  8. Fig. 29-5b Embryo 2 µm Maternal tissue Wall ingrowths 10 µm Placental transfer cell (outlined in blue) Embryo (LM) and placental transfer cell (TEM) of Marchantia (a liverwort)

  9. Fig. 29-5a Gamete from another plant Gametophyte (n) Mitosis Mitosis n n n n Spore Gamete MEIOSIS FERTILIZATION Zygote 2n Mitosis Sporophyte (2n) Alternation of generations

  10. Fertilization  zygote  embryo mature sporophyte  sporogenous cells  meiosis  spores  mature gametophyte  archegonia or antheridia  egg/sperm

  11. Check your Understanding • 1. What are the benefits of a lands existence for plants? • 2. What traits are shared by both charophytes and land plants? • 3. What is the role of each generation in the alternation of generations life cycle?

  12. 4 Major Plant Groups • Bryophytes • Small, nonvascular, seedless, use haploid spores • Ferns • Seedless, vascular, spores • Gymnosperms • Vascular, seeds (unprotected) • Angiosperms • Vascular, flowering, seed in a fruit

  13. Fig. 29-7 Origin of land plants (about 475 mya) 1 Origin of vascular plants (about 420 mya) 2 Origin of extant seed plants (about 305 mya) 3 Liverworts Nonvascular plants (bryophytes) Land plants Hornworts ANCES- TRAL GREEN ALGA 1 Mosses Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants Vascular plants 2 Pterophytes (ferns, horsetails, whisk ferns) Gymnosperms 3 Seed plants Angiosperms 50 500 450 400 0 350 300 Millions of years ago (mya)

  14. Mosses and other Bryophytes • Nonvascular – so small • Mosses, liverworts, hornworts • Moist environment – growth and reproduction • 3 phyla • Bryophyta • Hepaticophyta • Anthocerotophyta

  15. Mosses - Bryophyta • Dense colonies or beds • Individual plant • Rhizoids (absorb) • Upright, stem like • Leaf like blades • No true roots, stems or leaves • Alternation of generations • 3 groups: peat moss, granite moss, true moss

  16. Fig. 29-9d Polytrichum commune, hairy-cap moss Sporophyte (a sturdy plant that takes months to grow) Capsule Seta Gametophyte

  17. Fig. 29-8-3 Raindrop Sperm “Bud” Antheridia Male gametophyte (n) Key Haploid (n) Protonemata (n) Diploid (2n) “Bud” Egg Gametophore Spores Archegonia Female gametophyte (n) Spore dispersal Rhizoid Peristome FERTILIZATION Sporangium (within archegonium) MEIOSIS Seta Zygote (2n) Capsule (sporangium) Mature sporophytes Foot Embryo Archegonium Young sporophyte (2n) 2 mm Female gametophytes Capsule with peristome (SEM)

  18. Moss Gametophyte

  19. Moss spores

  20. Moss protonema

  21. Fig. 29-9a Gametophore of female gametophyte Thallus Sporophyte Foot Seta Capsule (sporangium) Marchantia polymorpha, a “thalloid” liverwort 500 µm Marchantia sporophyte (LM)

  22. Moss importance • Ecological • Form soil, prevent erosion • Rainforest beauty • Commercial • Peat moss (sphagnum) • Absorb and hold water • Soil conditioner – add to sand • Fuel source – if dried

  23. Fig. 29-11a (a) Peat being harvested

  24. Liverworts - Hepaticophyta • Dominant gametophyte • Thallus – body – flattened, lobed • No leaves, stems, roots • Resemble lobes of liver • Underside – rhizoids – anchor • No stomata – some surface pores • Others • Leafy liverworts – no lobes

  25. THALLOID Liverwort

  26. Fig. 29-9b Plagiochila deltoidea, a “leafy” liverwort

  27. Basics of liverwort life cycle • Sexual - Similar to mosses • Asexual • Form gemmae in gemmae cup

  28. Hornworts - Anthocerotophyta • Inconspicuous thalloids • Disturbed habitats – fallow fields, roadsides • Cell structure – single chloroplast • Sporophyte projects out of thallus like horn

  29. Fig. 29-9c An Anthoceros hornwort species Sporophyte Gametophyte

  30. Lycophytes: Vascular Tissue • Seedless vascular plants • Stems, roots, leaves • Conducting cells • Lignin • Cooksonia = rhyniophyte • Microphylls • Club mosses

  31. Club mosses - Lycophyta • Coal deposits • True roots, rhizomes, aerial stems • Short, erect branches • Evergreen

  32. Fig. 29-15a Lycophytes (Phylum Lycophyta) 2.5cm Isoetes gunnii, a quillwort Strobili (clusters of sporophylls) Selaginella apoda, a spike moss 1cm Diphasiastrum tristachyum, a club moss

  33. Lycophyte

  34. CYU • 1. Name two features of lycophytes significant to the evolution of land plants.

  35. Seedless Vascular Plants – Pterophyta (Pteridophytes) • Ferns, horsetails, whisk ferns • Adaptations • Vascular – xylem and phloem • Support • Conduction • larger • Most – true roots, stems, leaves • Megaphylls

  36. Ferns • Most abundant – warm, tropics • True roots, stems, leaves • Fronds

  37. Fig. 29-15f Athyrium filix-femina, lady fern 25 cm

  38. Fig. 29-13-3 Key Haploid (n) Diploid (2n) Antheridium Spore (n) Young gametophyte Spore dispersal MEIOSIS Sporangium Mature gametophyte (n) Sperm Archegonium Egg Mature sporophyte (2n) New sporophyte Sporangium Zygote (2n) FERTILIZATION Sorus Gametophyte Fiddlehead

  39. Fern Sorus

  40. Fern – Older sporangium

  41. Fern germinating

  42. Fern Gametophyte

  43. CYU • How is the life cycle of a fern different from the life cycle of a moss?

  44. Whisk ferns - Psilotophyta • Simplest vascular • Stems – • horizontal underground • Vertical aerial - photosynthesize • Lack true roots, leaves • Dichotomous branching – stem divides into 2 equal halves

  45. Fig. 29-15h Psilotum nudum, a whisk fern 2.5 cm

  46. Horsetails - Sphenophyta • Ancient – coal deposits • Wet, marshy • True roots (rhizome), stems (aerial), small leaves • Hollow, jointed stems – silica – gritty • Scouring rushes – pots/pans

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