Lecture Ch. 30 ______

1
Lecture Ch. 30______

• Chapter 30 Plant Diversity II The
  Evolution of Seed Plants

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Seed Plant Reproductive Adaptations

• Reduction of the gametophyte shift from haploid
  to diploid condition female gametophyte and
  embryo remain in sporangia (protection against
  drought and ionizing radiation on land?)
• Advent of the seed multicellular sporophyte
  embryo with food supply and protective coat
  heterosporous (two types of spores)
  megaspores---gtfemale gametophyte---gteggs
  microspores---gt male gametophyte---gtsperm
• Evolution of pollen develop from microspores
  which mature into the male gametophytes
  resistant and airborne for a terrestrial
  environment eliminated water (sporopollenin
  coats)

3
Seed Plants

• P. 598 Reduced gametophyte dependent on
  sporophyte
• Gametophyte is surrounded by tissues of
  sporophyte
• Gametophyte derives its nutrition from the
  sporophyte

4
Seeds - an important means of dispersing offspring

• Seed consists of a sporophyte embryo packaged
  along with a food supply and a protective coat.
• The gametophyte develops within the confines of a
  spore p.598 (fig. C)
• Seed plants are heterosporous-means they have two
  different types of sporangia that produce two
  types of spores
• Megasporangia produce megaspores which give rise
  to female gametophytes
• Microsporangia produce microspores which give
  rise to male gametophytes

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Ovule to Seed

• Sporophylls are small reproductive leaves where
  pollen cones and ovulate cones develop
• Megasporangium is surrounded by integuments
• Megaspore develops inside the megasporangium
• Integuments, megasporangium, megaspore make up
  the ovule

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Fertilized Ovule

• Female gametophyte develops inside a megaspore
  and produces one or more egg cells
• Megaspore develops into multicellular female
  gametophyte
• Micropyle the only opening through the
  integuments-allows entry of a pollen grain
• Pollen grain contains a male gametophyte which
  develops a pollen tube that discharges

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Gymnosperm Seed

• Fertilization initiates the transformation of the
  ovule into a seed, which consists of a sporophyte
  embryo, a food supply, and a protective seed coat
  derived from the integuments

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Gymnosperms

• Cone-bearing plants
• Lack enclosed chambers (ovaries) for seeds
• Ovules and seeds develop on specialized leaves
  called sporophylls
• Ginkgo, cycads, and conifers
• All are evergreens
• Needle-shaped leaves
• Vascular tissue refinement tracheids water
  conducting and supportive element of xylem

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Angiosperms

• Most diverse and geographically widespread of all
  plants
• Flowering plants(Phy Anthophyta)
• Monocots 1 embryonic seed leaf (lilies, palms,
  grasses, grain crops)
• Dicots 2 embryonic seed leaves (roses, peas,
  sunflowers, oaks, maples)
• Vascular tissue refinement vessel elements/fiber
  cells

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The flower the defining structure of angiosperms

• Reproductive structure pollen transfer
  specialized shoot with modified leaves
• Sepals enclose flower before it opens
• Petals attract pollinators
• Stamens male anther (produces pollen), filament
• Carpels female stigma, style, ovary, ovules

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Angiosperm life cycle

• Fruit (mature ovary) seeds from ovules
• Pollen grains 2 haploid cells (immature male
  gametophytes)
• Ovules (female gametophyte embryo sac)
• Double fertilization 1 sperm w/ egg diploid
  zygote other sperm w/ 2 nuclei in center of sac
  triploid endosperm