Plant Hormones

• auxin is a plant hormone
• hormones in plant control

  • growth of roots & shoots
  • seed germination
  • fruit formation/ripening
  • leaf fall
• tropisms

  directional growth response
• 2 types of tropisms

  • positive - growing towards stimulus
  • negative - growing away from stimulus
• Geotropism/Gravitropism

  response to gravity
• phototropism

  response to light
• hydrotropism

  response to water
• shoots

  grows towards light against the force of gravity
• roots

  grow towards moisture in direction to the force of gravity
• auxins in stems - stimulate growth of cells

  in roots - inhibit growth of cells
• auxins are produced in tips of plant
• auxin in a plant diagram

  A) auxin spreads equally down both sides of the plant

  B) auxin collect on the shady side

  C) light

  
• when auxin collects on the shaded side it causes quicker cell growth /elongation.
• plant hormones

  • gibberellins - initiate seed germination
  • ethene - controls ripening of fruit
• auxin uses

  • killing weeds - selective weedkillers disrupts normal growth pattern soon killing them
  • growing cuttings from root powder - promotes root growth
  • growing cells in tissue culture - grow clones
• gibberellins uses

  • controlling dormancy - make seeds germinate at times they wouldnt germinate
  • induced flowering - plants can flower without any change to their environment
  • growing larger fruit