Plants- tropism and auxins

• Why do plants need to respond to stimuli?

  To survive in their environment
• How do plants sense light?

  By growing their shoots towards it
• What do plants sense to grow their roots downwards?

  Gravity
• What do some plants sense to climb around objects?

  Touch
• How do plants rely on hormones compared to animals?

  Plants rely entirely on hormones, no nervous system
• What are auxins?

  Plant hormones that control growth
• Where do auxins accumulate in shoots?

  On the shaded side
• What is phototropism?

  A response to light in plants
• What is geotropism?

  A response to gravity in plants
• How do shoots respond to light?

  Shoots grow towards the light
• How do shoots respond to gravity?

  Shoots grow away from the ground
• How does auxin affect shoot growth in response to light?

  Auxin accumulates on the shaded side
• What happens to the growth rate of cells on the shaded side of a shoot?

  They grow faster than sunny side cells
• How does gravity affect auxin distribution in shoots?

  Auxin accumulates on the lower side
• How do roots respond to light?

  Roots grow away from the light
• What happens to auxins in roots when exposed to light?

  They accumulate on the lower shaded side
• How do auxins affect root growth?

  They inhibit growth in roots
• How does gravity affect root growth?

  Auxins accumulate on the lower side
• What is the result of auxins accumulating on the lower side of a root?

  The upper side grows faster, curving downwards
• What are the key responses of plants to environmental stimuli?

  • Phototropism: response to light
  • Geotropism (gravitropism): response to gravity
  • Touch response: climbing around objects
• What are the differences in auxin effects on shoots and roots?

  • Shoots: Auxins stimulate growth
  • Roots: Auxins inhibit growth
• What are the characteristics of positive and negative tropisms in plants?

  • Positive tropism: growth towards stimulus
  • Negative tropism: growth away from stimulus
• What is the process called when plant shoots grow towards light?

  Phototropism
• What do scientists believe controls phototropism in plants?

  Plant hormones
• What is the name of the hormone produced at the tips of shoots?

  Auxin
• What happened when scientists removed the tips of the shoots?

  The shoots did not grow towards the light
• What does covering the tips of shoots with foil indicate about their sensitivity?

  Tips are sensitive to light
• What was the result when the lower parts of the shoots were covered with foil?

  The shoots grew towards the light normally
• How do auxins help shoots grow towards light?

  • Auxins produced at the tip
  • Concentrate on the darker side
  • Trigger faster growth on the darker side
  • Causes the shoot to bend towards light
• What is the term for plant roots growing towards gravity?

  Gravitropism
• How do auxins behave in roots compared to shoots?

  Auxins inhibit cell growth in roots
• What causes roots to grow towards gravity?

  Auxins concentrate on the lower side
• What are the roles of gibberellins and ethylene in plants?

  • Gibberellins: Start seed germination
  • Ethylene: Controls cell division and fruit ripening
• Which students need to know about gibberellins and ethylene?

  Higher-tier students
• Where can students find more questions on plant hormones?

  In the vision workbook
• Phototropism 1. Light intensity affects the rate of elongation 2. Light intensity affects the direction of elongation

  
• Geotropism- the growth of a plant towards gravity.