Early Development of the Plant Body

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Early Development of the Plant Body

• Chapter 22

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• True or False
• Embryogenesis is the formation of an embryo.
• The developing embryo in angiosperms is
  photosynthetic.

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Embryogenesis

• Embryogenesis- formation of an embryo.
• The first two divisions are transverse and
  establish embryo polarity.
• Upper Pole- chalazal pole.
• Consists of an apical cell that gives rise to an
  embryo proper, which will eventually give rise to
  the mature embryo.
• Lower Pole- micropylar pole.
• Consists of a basal cell that gives rise to a
  suspensor.
• Establishment of polarity fixes the structural
  axis on which the lateral appendages will be
  later arranged.

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Proembryos
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Embryo Proper and the Primary Meristems

• The embryo proper is tissue that differentiates
  to form 3 primary meristems.
• Primary Meristems
• Protoderm- forms the epidermis of the plant by
  periclinal divisions of the outer cells of embryo
  proper.
• Procambium- forms the vascular tissue of the
  plant by vertical divisions.
• Ground meristem- forms the ground tissue of the
  plant by vertical divisions.

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• The apical meristem in angiosperms
  ___________________________.
• A) is a region of tissue at the tip of shoots
  and roots that is responsible for programmed cell
  death.
• B) is a region of tissue at the tip of shoots
  and roots that forms new cells.
• C) coordinates hormone production much like the
  brain in mammals
• D) produces the bark we see on trees
• E) none of the above

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Apical Meristems

• Apical Meristem- regions of tissue at the tip of
  shoots and roots that forms new cells.
• As the embryo matures new cell formation
  gradually becomes restricted to the apical
  meristems.
• Shoot Apical Meristem- positioned between the two
  embryonic leaves in eudicots and lateral in
  monocots.
• Radicle- embryonic root.

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Seed Terms

• Hypocotyl- stemlike axis below the cotyledons.
• Hypocotyl-root axis- an undistinguished radicle.
• Epicotyl- stemlike axis above the cotyledons.
• Plumule- the first bud of an embryonic shoot.
• Pericarp- the fruit wall, which develops from the
  wall of the ovary.

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The stored food occurs in the cotyledons.
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The stored food occurs in the endosperm.
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The stored food occurs in the endosperm.
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• Which of the following effects seed germination?
• A) water
• B) oxygen
• C) light and temperature
• D) hormones
• E) all of the above

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Seed Germination

• Dependent on external and internal factors.
• External (Environmental)
• Water
• Oxygen
• Temperature
• Light
• Internal (Biological)
• Hormones- gibberellins.
• Epigeous- cotyledon/s are carried above ground
  level.
• Hypogeous- cotyledon/s remain underground.

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True or False The onion has an epigeous type
of seed germination.