Coordination in plants

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Coordination in plants
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• Response of plants to the stimulus is much
  slower and usually respond to stimulus movement
  of growth.
• This sort of response is called a TROPISM.
• - phototropism
• - geotropism

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• Phototropism respons to light.
• - positive phototropism- the shoot grows
  towards the light.
• Geotropism respons to gravity.
• - negative geotropism shoots tend to grow
  away from pull of gravity.
• - positive geotropism roots tend to grow
  towards the pull of gravity.

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• Why is it important for plants to root and
  stem behave in this way?
• Which part of a shoot is sensitive to light?
• Which part of a shoot responds to light?

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• The part of a shoot sensitive to light is the
  tip.
• The part of the shoot which responds to the
  stimulus is the part just below the tip.
• These two parts of the shoot must be
  communicating with one another by means hormones.
• Plant hormones are chemical that affect the
  activites of particular cells.
• They may move in the phloem (by diffusion or
  active transport from cell to cell).

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• Auxin
• Made all the time by the cells in the tip of the
  shoot
• Diffuses downwards from the tip
• Make the cells just behind the tip get longer
• (stimulates cell elongation).

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Plant hormones are used in food production

• Weedkillers contain plant hormones (a type of
  auxin). Selective Weedkillers kill weeds in
  lawns or in cereal crops.
• Plant hormones are used to help the fruits to
  grow larger or to ripen well.