Plant Hormones

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Plant Hormones

• Plant growth regulators

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What does a plant need to respond to in its
environment?

• Light
• Water
• Gravity

Positively phototrophic
Positively geotrophic
Positively hydrotrophic
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How are plant growth factors different from
animal hormones?

• They exert an influence by affecting growth
• Produced and released by cells through out the
  plant rather than organs.
• They affect the tissues or nearby tissues that
  release them, not distant target organs.

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Examples

• Auxin effects growth of the plant example
  IAA (the one you need to know about.
• Cytokinins - growth control in fruit
• Ethylene - promote ripening on the tree
• Gibberellins promote seed germination

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How IAA works
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Experiments

• What doe these prove?

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• Page 160 has the final lot of experiments
  explaining the action of IAA

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geotropism