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Presentation 18 - Plant Hormones

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Presentation 18 - Plant Hormones

  1. 1. Plant hormones
  2. 2. Hormones <ul><li>from Gr. to excite   </li></ul><ul><li>natural chemical messengers transported to target cells </li></ul><ul><li>minute concentrations = substantial change </li></ul><ul><li>growth regulators </li></ul>
  3. 3. Plants respond to stimuli
  4. 4. Plant hormones coordinate growth, development and responses to stimuli <ul><li>Tropisms </li></ul><ul><li>growth responses </li></ul><ul><li>organs curve towards (+) or away from (-) a stimulus </li></ul><ul><li>ex. phototropism, thigmotropism, gravitropism </li></ul>
  5. 5. Studies on phototropism <ul><li>towards or away from light </li></ul><ul><li>differential growth of cells on opposite sides of a shoot or coleoptile </li></ul><ul><li>cells on darker side elongate faster than those on the light side </li></ul><ul><li>experiments by Darwin and son and FW Went </li></ul><ul><li>due to auxin distributions </li></ul>
  6. 6. Went experiment

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