http://plantsinmotion.bio.indiana.edu/plantmotion/flowers/flower.html

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Today Plant Reproduction W Genetic
Engineering of Plants
http//plantsinmotion.bio.indiana.edu/plantmotion/
flowers/flower.html
2
Fig 29.7
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Seeds and pollen allow seed plants to reproduce
without water
Fig 30.2
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Fig 38.4
Animal pollinators move pollen from one plant to
another
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Fig 38.4
Plants reproduce, reward animals with sugar
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Fig 38.2
a typical flower
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Fig 38.2
Angiosperm Life Cycle
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Fig 38.5
Each pollen grain has 3 nuclei, two sperm and one
for the pollen tube
N
N
N
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Fig 38.5
Each pollen grain has 3 nuclei, two sperm and one
for the pollen tube
sperm
N
N
tube nuclei
N
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Pollen tubes can grow quite long
corn stigma
corn seeds
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The pollen tube grows to the egg and the sperm
fuse with the egg zygote and polar nuclei
endosperm
Fig 38.5
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Fig 38.7
The zygote then develops into an embryo
surrounded by the endosperm and seed coat the
seed
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Fig 38.8
The seed must contain enough nutrients to nourish
the embryo until it can begin photosynthesis
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Seed size is a good indicator of how much energy
is stored to support early seedling growth.
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Which seed likely requires light to germinate?
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Fig 38.11
Seed dispersal can be by wind or often also by
animal
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Fig 38.10
Fruits Animals can get nutrients to disperse
seeds
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Fig 38.9
Seed Germination...
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Capsaicin is a deterrent to seed eating mammals
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Capsaicin is a deterrent to seed eating mammals
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Is this plant reproducing sexually?
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Problem of Inbreeding

• Close relatives have a higher probability of
  carrying the same genetic defects
• Decreases genetic diversity

see pg 813 and/or http//users.rcn.com/jkimball.ma
.ultranet/BiologyPages/S/SelfIncompatibilty.html
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How do plants avoid inbreeding?Some plants, like
humans, separate the sexes--i.e., some plants
have only male flowers and others only female
flowers.
male plant
female plant
Fig 38.13
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Some plants physically separate the anthers and
stigmas
Fig38.13
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Some plants separate the anthers and stigmas
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How do plants avoid inbreeding?

• Some plants, like humans, separate the
  sexes--i.e., some plants have only male flowers
  and others only female flowers.
• Some plants separate the anthers and stigmas.
• Some plants have a cellular mechanism for
  avoiding inbreeding self-incompatibility

see pg 813
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What is self-incompatibility?

• Plants, like animals have the ability to
  distinguish self tissue from non-self tissue.
• In humans, generally non-self tissue is rejected,
  so tissue transplants can be a problem.
• In some plants self-pollen is rejected(
  self-incompatibility), and only non-self pollen
  is allowed to fertilize the eggs.

see pg 813
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Some signaling steps are known

• This SI method requires that a factor from the
  pollen recognizes a factor from the stigma

see pg 813
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In sporophytic SI the reaction happens on the
stigma surface

• If the male factor from pollen is recognized as
  self by the female factor on the stigma surface,
  then this recognition induces the stigma to
  secrete a substance that prevents the pollen from
  germinating.
• the substance secreted by the stigma that
  inhibits self-pollen from germinating is unknown.

see pg 813
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Only pollen from different plants can germinate
see pg 813
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Self-incompatibility

• Self-incompatibility (SI) is a method by which
  some plants avoid inbreeding
• The two main mechanisms of SI are different from
  one another one stops the pollen on the surface,
  the other stops the pollen in the style.
• Both methods require that a factor from the
  pollen recognize a female factor made by the
  flower, and in both methods this recognition
  initiates the SI reaction.

see pg 813
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Fig 38.2
Angiosperm Life Cycle
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Evolution does not always go forwardSome
angiosperms disperse pollen by wind
Fig38.4
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Today Plant Reproduction W Genetic
Engineering of Plants
http//plantsinmotion.bio.indiana.edu/plantmotion/
flowers/flower.html