Vegetative Plant Development

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Vegetative Plant Development

• Chapter 36

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Angiosperm Embryo Development
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Establishing Three Tissue Systems

• Protoderm will become dermal tissue
• protects plant from desiccation
• Ground meristem will form ground tissue
• function in food and water storage
• Procambium will form vascular tissue
• perform water and nutrient transport

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Establishing Three Tissue Systems

• Root and shoot formation
• established during globular stage of development
• formation of each controlled independently
• Morphogenesis
• globular stage gives rise to heart-shaped embryo
  with cotyledons produced by embryonic cells

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Establishing Three Tissue Systems

• Food storage
• starch, lipids, and proteins produced throughout
  embryogenesis
• sporophyte transfers nutrients via suspensor in
  angiosperms

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How Seeds Form

• Protective seed coat forms from outer layers of
  ovule cells
• embryo either surrounded by nutritive tissues, or
  amassed food in cotyledons
• seed resistant to drought and other unfavorable
  conditions
• vehicle for dispersal

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How Seeds Form

• Adaptive importance of seeds
• maintain dormancy until better conditions arise
• afford maximum protection to young plant at most
  vulnerable developmental stage
• contain adequate food supply until photosynthetic
  food supply available
• adapted for dispersal

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How Seeds Form

• Specific germination triggers
• exposure to heat or fire
• leaching inhibitory chemicals from seed coats
• passage through animal intestines

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How Fruits Form

• Fruits are mature ovaries.

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How Fruits Form

• Dispersal of fruits
• vertebrate digestive tracts
• bright colors
• animal coats
• hooked spines
• wind
• wings
• water
• buoyant

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Mechanisms of Germination

• Germination begins when a seed absorbs water and
  resumes metabolism.
• may fail to germinate without additional
  environmental signals
• stratified - held at low temperatures

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Mechanisms of Germination

• Utilization of reserves
• Germination and early seedling growth require the
  utilization of metabolic reserves stored in
  starch grains of amyloplasts.
• cereal cotyledons modified into scutellum
• mediated by gibberellic acid and abscisic acid

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Summary

• Establishing the Root-Shoot Axis
• Establishing Three Tissue Systems
• How Seeds Form
• How Fruits Form
• Mechanisms of Germination

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