Plant Hormones

• Plants can respond to changes in the external environment - these responses are usually slower than animal responses
• Plant responses to a change in the external environment include:

  Roots and shoots growing towards or away from a particular stimulus - Plants flowering at a particular time - The ripening of fruits
• A tropism is when part of a plant responds by growing in a different direction
• What is a tropism?

  When part of a plant responds by growing in a different direction
• What are the 2 types of tropism?

  Phototropism and Gravitropism
• Phototropism is a growth in response to light
• What is the stimulus for phototropism?

  Light
• Gravitropism is a growth in response to gravity
• What is the stimulus for gravitropism?

  Gravity
• What is Gravitropism sometimes called (They both mean the same thing)?

  Geotropism
• Shoots grow upwards
• Roots grow downwards
• Positively phototrophic is the term for shoots that grow towards light
• Negatively phototrophic is the term for roots that grow away from light
• Positively gravitropic is the term for roots that grow towards gravity
• Negatively gravitropic is the term for shoots that grow away from gravity
• Roots grow towards gravity and away from light
• Shoots grow towards light and away from gravity
• Auxins control tropisms
• What is the group of plant hormones that control tropisms?

  Auxins