Plant hormones

• Describe how growth occurs in plants

  • Elongation (cells get longer)
  • Cell division (2 genetically identical diploid cells)
  • Cell differentiation ( cells become specialised + have specific function)
• Where does growth occur in plants

  Tips of roots and shoots of meristems
• What word is used to describe the growth of plants towards or away from light

  Phototropism
• Where is auxin produced


  Tips of roots+shoots
• What is gravitropism


  When plants move toward/away from gravity
• How is auxin transported around the plant 


  Via water + diffuses backwards to cells
• What is the function of auxin 


  Plant hormone -> controls growth at tips of roots and shoots + stimulated cell elongatuon
• True or false: Auxin promotes growth in the roots and inhibits growth in shoots 


  False -> promotes growth in shoots + inhibits growth in roots
• What is tropism 


  Plant movement in response to stimuli
• Does auxin promote or inhibit growth in the stem 


  Promotes
• What happens in negative gravitropism in the stem


  • Moving away from gravity
  • Gravity causes auxin to move to underside of shoots
  • Auxin causes cells on underside to elongate
  • Shoots grow against gravity-upwards
• What happens in positive gravitropism in the roots 


  • Auxin goes to underside of roots due to gravity
  • Auxin inhibits growth in underside
  • Root grows towards gravity
• What happens in positive phototropism in the stem

  • Auxin diffuses to shaded side of the shoot
  • Cells on shaded side elongate
  • Causes shoot to move towards light
• What happens in negative phototropism in the root


  • Auxin diffuses to shaded side of root
  • Auxin inhibits growth
  • Shaded side elongates
  • Root starts to grow back towards soil
• What happens if the shoots are in the dark

  • Auxin grows on all side to look for sunlight
• What happens if you cut off the tip


  No tip= no growth as auxin is NOT produced
• What happens if you put the tip back after cutting it

  • Auxin produced in tip
  • Tip still attached to plant = auxin can diffuse to cause growth
• Describe the practical to investigate tropism 


  • Place cress seeds in petri-dish lined with moist filter paper
  • Surround in petri-dish with black card + cut hole on one side
  • Shine light into hole
  • Leaves cress seeds for 1 week + observe response to light
• What is the conclusion from investigating tropism 


  • The ones directly underneath light = grows straight up
  • The ones not in any light = grows upwards as auxin distributes evenly
  • The ones near the light = grows as auxin diffuses to shaded side
• What are 2 control variables of the tropism practical


  Temperature + Water
• Explain one way the experiment could be improved 


  • Repeat it several times
  • Find mean
  • Find anomaly