Chapter 23: The great and mighty Angiosperms

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Chapter 23 The great and mighty Angiosperms!!!

• Flowers Take Over the World

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Angiosperms The most diverse group

• 235,000 species
• Dominant life forms on planet Earth
• From very small (e.g. Wolffia)

Wolffia flower
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Giant flowers

• To the very largestinking corpse lily
• AndRafflesia

Amorphophallus titanumthe Stinking corpse lilly
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Parts of the flower

• We covered 23.2 in labyou are responsible for
  this

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What distinguishes angiosperms?

• Double Fertilization
• One sperm (1N) from male gametophyte (pollen
  grain) unites with egg (1N) to form embryo (2N)
• Another sperm (1N) unites with female gametophyte
  tissue (2N) to make endosperm (3N) or food for
  embryo
• Double fertilization in some gymnosperms, but
  doesnt make endosperm, just two babies (remember
  Gnetum?)

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Other traits that distinguish angiosperms

• Ovules develop into seeds in a carpel (part or
  parts of the ovarythink of the sections of an
  orange)
• These ovaries develop into fruits

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Angiosperms are divided into two groupsmaybe!

• Dicotyledones or dicots
• Monocotyledones or monocots
• What traits distinguish them?
• Lets draw a phylogeny!!

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Life Cycle of Angiosperms

• Note Im skipping 23.2 in lecture, but you are
  responsible for that material (covered in lab)!!!
• Lets start with pollen
• Anthers contain cells that undergo meiosis to
  make microspores
• Microspores make two cells a tube cell and a
  generative cell
• These two cells make up the pollen grain or
  microgametophyte

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Angiosperm Life Cycle
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Pollination angiosperm sex as seen by the male

• The pollen grain is transported by wind, animals
  or water to the stigma, the part of the pistil
  that receives pollen
• The pollen germinates by forming a pollen tube
  from the tube cell
• Two sperm are made from the generative cell
• These travel down the tube cell, which tunnels
  through the stigma and style and eventually to
  the ovary
• More on pollination in chapter 24

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Fertilization sex seen through an angiosperm
womans eyes

• Ovaries contain ovules. This is what goes on in
  the ovules
• The megasporocyte makes megaspores (by what
  process?), one of which becomes the
  ________________?
• The megagametophyte (or embryo sac) has 7 cells
  and 8 nuclei (usually)

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Now Mrs. Flower is ready to have sex with Mr.
Flower

• The pollen tube allows two sperm into the
  nucellus opening or micropyle
• One sperm fertilizes the egg the other sperm
  fertilizes the 2-nucleated cell to make
• a 3N endosperm (lunch)
• This is double fertilization
• Wrap the baby with a lunch in a paper bag (the
  integuments or what becomes the seed coat) and
  you get.

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A SEED!!
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Put the seed inside the mature ovary and you get.
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A FRUIT
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Seed development

• Monocots
• One cotyledon or seed leaf
• Lots of endosperm
• Endosperm is transferred to cotyledon

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Seed development (cont)

• Dicots
• Two cotyledons
• Can transfer food reserves of endosperm directly
  to embryo OR via the cotyledons

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Monocot vs. Dicot Seeds

• One last thing about monocots
• They usually have protective sheaths around their
  stems, called coleoptiles

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Germination requirements

• Usually must be warmabout room temp or above
• Must have water available to activate enzymes
  (e.g. that break down starch in endosperm to
  sugar)
• Must have oxygen (water-logging is anaerobic)

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Germination linked to environment

• Some seeds can take waterlogging
• Many need fire e.g. serotinous cones
• Some can take the cold (germinate just above
  freezing)

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Hypogeous vs. epigeous germination

• Hypogeous
• Below-ground germination
• Example peas
• Epigeous
• Cotyledons come out of the ground
• Example beans

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Chapter 24 stuff

• Pollination syndromes
• Traits that are coordinated between flowers and
  pollinators

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Bee pollination

• Intelligent and social
• High constancy
• High energy requirements
• See in UV

• Can be complex
• Colors are usually blue, purple, yellow, white
  (not red)
• Nectar guides

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Bee pollination
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Bat pollination

• Night blooming
• Fragrant
• Very often white
• Lots of nectar
• Often pendulous

• High energy
• Nocturnal
• Color blind
• Excellent sense of smell

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Bats as pollinators
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Bird pollination

• No smell
• Lots of nectar
• Reds
• Tubular shaped often (hummingbirds and sunbirds)
• diurnal

• High energy requirement

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Butterfly Pollination

• Butterflies need large landing platform
• Flowers are often tubular and long for butterfly
  proboscis
• Fragrantbutterflies can smell (with their feet!)

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