Control and coordination

• What do plants rely on to coordinate growth and responses?

  Hormones
• How do plant responses help them survive?

  They grow toward resources like light and water
• What are tropisms in plants?

  • Directional growth responses
  • Positive tropism: growth toward stimulus
  • Negative tropism: growth away from stimulus
• What is phototropism?

  Growth response to light
• What happens to shoots and roots during phototropism?

  Shoots grow toward light; roots grow away
• What is gravitropism (geotropism)?

  Growth response to gravity
• What is hydrotropism?

  Growth response to water
• How do roots and shoots respond to gravity in gravitropism?

  Roots grow downward; shoots grow upward
• How do roots respond to moisture in hydrotropism?

  Roots grow toward moisture
• Why are tropisms important for plants?

  • Phototropism maximizes sunlight for photosynthesis
  • Gravitropism ensures stability and water absorption
  • Hydrotropism helps find water for survival
• What are auxins?

  Main plant hormone controlling growth
• Where are auxins produced in plants?

  In shoot and root tips
• What do auxins influence in plants?

  Cell elongation
• How do auxins control phototropism?

  1. Auxins move to shaded side of shoot
  2. Cells on shaded side elongate
  3. Shoot bends toward light
• How do auxins control gravitropism?

  • In roots: auxins inhibit growth, lower side grows slower
  • In shoots: auxins stimulate growth, lower side elongates
• What are the functions of other plant hormones?

  • Auxins: control cell elongation, phototropism, gravitropism
  • Gibberellins: stimulate seed germination and flowering
  • Ethene: controls fruit ripening
• What do gibberellins do?

  Stimulate seed germination and stem elongation
• What effect does ethene have on fruit?

  Speeds up ripening and softens fruit
• What are the steps to investigate phototropism?

  1. Take three identical seedlings
  2. Place in full light, darkness, and one-sided light
  3. Observe growth over several days
• What are the results of investigating phototropism?

  • Seedling in full light grows upright
  • Seedling in darkness grows tall but weak
  • Seedling with light from one side bends toward light
• What are the steps to investigate gravitropism?

  1. Place seedlings horizontally in the dark
  2. Observe growth over time
• What are the results of investigating gravitropism?

  • Roots bend downward (positive gravitropism)
  • Shoots bend upward (negative gravitropism)
• What are the key points of plant control and coordination?

  • Tropisms: responses to light, gravity, water
  • Auxins: promote shoot growth, inhibit root growth
  • Gibberellins: stimulate germination and flowering
  • Ethene: controls fruit ripening