plants 2-2

• How do plants respond to their environment?


  • How they know there are changes occurring
  • How they can react in a manner to allow survival
• What plants respond to

  • Damage - Wounding response
  • Light - Phototropism and photoperiod
  • Heat - Thermal response
  • Chemicals - Hormonal response

  
• Response to wounding


  1. Injury causes cells to break and release contents

  2. Enzymes are produced to heal the injury

  3. Oxidative reactions cause browning that helps heal the wound

  4. Other chemical reactions occur to start the process of cell division
• Environmental or biological stresses will cause plants to express genes to produce chemical products to deal with the stress

  
• The response may occur in a matter of minutes
• Chemical signals are produced eg. Jasmonic acid, which signal other parts of the plant that something is going on
• This in turn can cause other changes to help the plant recover from the stress
• Plants DO RESPOND to their environment
• Growth and greening in response to light

  1. Light hits plant

  2. Sends signals

  3. Cells expand

  
• Sun tracker plants


  • Facing east in the morning
  • Facing west in the evening
  • Going from east (right) to west (left)
• Sun tracker plants at night

  1. Turn east at night

  2. Face west in the day

  3. Internal clock
• Stem growth occurs on the west side at night


  Causes flowers to turn to east - waiting for the sun to rise
• Stem growth occurs on west side in daytime


  Causes flowers to bend east in the day - waiting for sun set
• Sunflower seeds produce oil
• Photoperiod


  Plant responses to different lengths of time of exposure to light

  
• Flowering response to light

  • Phytochrome protein senses light
  • Phytochrome is activated by red light

  
• Not all plants need a flowering response to light
• The spring growth response
• Seed response to temperature
• Responses of plants to environment
• Hormones respond to environmental changes
• Used to artificially ripen bananas
• If the plant talks back - seek help!