Seeded plants(class)

• all plants share:
  • autotrophs
  • cell walls
• all land plants:
  • multicellular embryos
  • alteration of generations
  • apical meristems
  • multicellular gametangia
• ferns onwards:
  • vascular system
  • sporophyte dominant
• gymnosperm + angiosperms
  • dependent embryo
  • seeds
  • multicellular
  • protected by seed coat
  • can remain dormant for long time till conditions are right
  • can be dispersed away from parents via wind, water, animals
  • contain own food supply
• Charophytes = basal taxon
• Key adaptations:
  • reduced gametophyte stage (within the seed)
  • better for reproduction (protected from environment, gain nutrient from parent)
  • heterospory
  • two types of spores (megaspore → female gametophyte; microspore → male gametophyte)
  • adds extra structures (megasporangia, microsporangia)
  • beneficial for genetic variation, in case of inbreeding
  • ovules (mature into seeds)
  • integument → megasporangium → meiosis → megaspore(n)→ female gametophyte (n) → archegonium (n) → egg(n)
  • integument→ seed coat; female gametophyte → food supply; egg (+sperm) → zygote (2n)
  • integument: diploid structure protecting seed
  • pollen
  • microsporangium (2n), microsporocyte (2n) →meiosis → microspore (n) → mature pollen grain (n) → pollination → growth of pollen tube → discharge of nonmobile sperm into female → fertilization → zygote → embryo
• sporophyte → sporophyll →sporangia
• Gymnosperms
• most are conifers
• “naked-seed” plants
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