Angiosperm Plant Reproduction (Chap. 28)

							      Angiosperm Plant Reproduction
               (Chap. 28)
  Know the
  following in a
  typical plant:
• sepal, petal,
  stamen, anther,
  filament,
  pollen, pistil,
  stigma, style,
  ovule, and
  ovary
 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
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
– 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)
(sperm cell)
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)
 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.
Metabolic events of germination

1. Absorption of water to rehydrate living
   cells in the seed and cause it to burst
2. Water activates a plant hormone
   gibberellin
3. Gibberellin stimulates the production of
   amylase (that catalyzes the digestions of
   starch into maltose) and then maltose is
   hydrolyzed by maltase into glucose.
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.
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
2. adventitious buds (suckers) – buds form on
  underground roots or stems
3. leaf generation – shoots emerge on the
  margins of a leaf
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
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