Angiosperm Plant Reproduction Chap' 28

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Angiosperm Plant Reproduction (Chap. 28)

• Know the following in a typical plant
• sepal, petal, stamen, anther, filament, pollen,
  pistil, stigma, style, ovule, and ovary

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Sexual Reproduction

• Pollination
• the transfer of pollen from an anther to a stigma
• some flowers color, shape, and fragrance attract
  pollinators and others simply use wind

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Fertilization

• a zygote is formed by the fusion of a male gamete
  (a pollen grain produced by the anther) and a
  female gamete (ovules in the ovaries)
• Process
• after pollination, one cell in the pollen grain
  called the tube cell makes enzymes that digest
  the tissue ahead of it and the pollen grain
  progresses through the style towards the ovary

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• two other cells in the pollen grain called sperm
  cells finally penetrate the ovule (various
  maternal cells) in the ovary in a process called
  double fertilization
• one sperm fertilizes the egg cells that
  eventually becomes the zygote
• other sperm fertilizes the central cell that
  produce the endosperm (nutritive tissue in seeds)

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(sperm cell)
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Seed Dormancy and Dispersal

• lose most of their water and can lie dormant up
  to 10,000 years
• primarily dispersed by wind, water, and animals
  (inside and outside)

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Germination of the Seed
Conditions needed for germination

• Water to re-hydrate the dry tissue and the
  hydrolysis of storage compounds such as starch
  into their simple monomers such as glucose.
• Oxygen is needed for aerobic respiration
• Seeds have an optimum temperature for enzymatic
  activity leading to germination.

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Metabolic events of germination

• Absorption of water to rehydrate living cells in
  the seed and cause it to burst
• Water activates a plant hormone gibberellin
• Gibberellin stimulates the production of amylase
  (that catalyzes the digestions of starch into
  maltose) and then maltose is hydrolyzed by
  maltase into glucose.

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• 4. The embryo absorbs glucose and uses it for
  respiration
• 5. Cell division, growth and elongation occur in
  the embryo . The radicle starts growing downwards
  into a root and the plumule starts growing
  upwards into a shoot.
• 6. As the nutrients in the cotyledons are
  consumed and exhausted, the first leaves start to
  appear and the plant starts to photosynthesize
  and make its own food.

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Asexual Reproduction
Vegetative propagation

• the development of new individuals from a
  fragment of the plant
• genetically identical to the parent plant
• ensures desirable qualities of a crop
• 5 types that occur in some plants
• 1. cuttings cut and put pieces of stem in water

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• 2. adventitious buds (suckers) buds form on
  underground roots or stems
• 3. leaf generation shoots emerge on the margins
  of a leaf

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• 4. runner or stolons wispy stems that snake
  away from the parent plant and eventually develop
  roots and stems. ex) strawberries
• 5. tubers thick underground stems. ex) potatoes

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Apomixis

• seeds produced without the union of sperm and egg
• egg fails to under go meiosis and diploid
  condition is retained
• occurs naturally in about 400 plant species
• can be good in extreme environmental conditions
  however lack the variability that is necessary
  for evolution of the plant