Origin of the Land Plants

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Origin of the Land Plants
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Alternation of Generations
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Charophycean Algae

• Dont display alternation of generations
• Most closely related to land plants by homology
• Organisms are haploid
• Examples Chara and Coleochaete
• Single-celled zygote produces haploid spores by
  meiosis
• Gametes are bi-flagellate

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Homologies Between Charophyceans and Land Plants

• Chloroplasts have chlorophyll a b, carotenoids
  and other accessory pigments
• Cell walls with cellulose (20-26)
• Peroxisomes with anti-photorespiration enzymes
• Phragmoplasts for cell plate formation
• Rosette cellulose-synthesizing complexes
• Molecular systematics DNA, rRNA, chloroplast DNA

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Chara Pond Algae
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Challenges of Moving to Land

• Lack of moisture
• Ultraviolet light
• Separation of water, minerals, and carbon source
  (CO2)
• Lack of support for the plant body
• Rapidly changing environmental conditions

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Bryophytes

• Nonvascular plants
• Dominant form is the haploid gametophyte
• Swimming gametes require water
• Diploid dependent sporophyte produces haploid
  spores by meiosis.
• Spores grow into gametophyte plants that produce
  haploid gametes by mitosis.
• Mosses, liverworts, hornworts

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Liverwort
Gemmae cups of Marchantia
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Marchantia
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Moss
Sporophyte and capsule
Gametophyte plant (n)
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Polytrichum - Moss
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Peat Bogs Store Carbon
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Spagnum Moss
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VASCULAR PLANTS(TRACHEOPHYTES)
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Pteridophytes (Seedless Vascular Plants)

• Branched, independent sporophytes
• Sporophytes are the dominant plant
• Asexual reproduction Spores
• Sexual reproduction Gametes
• Swimming gametes require water
• Possess Xylem and Phloem
• True roots, stems and leaves in some groups

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Lycophyta Club Mosses
Pterophyta Whisk Ferns
Pterophyta Ferns
Sphenophyta Horsetails
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Lycophyta

• Woody trees dominating Carboniferous period (300
  mya)
• Epiphytes Air Plants
• Club-shaped spore-bearing cones called strobili
• Spores very flammable

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Sphenophyta

• Woody trees during Carboniferous period
• Hollow ribbed stems jointed at nodes
• Silica (silicon dioxide) granules
• Equisetum hyemale or Scouring rush

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Polypodium fern
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Fern Life Cycle
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Sori on lower side of frond
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Sorus and mature sporangium
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Fern Prothalus(Gametophyte Plant)
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