Transcript 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