Plant hormones

• What stimuli can plants detect

  Light

  Gravity

  Touch
• How do plant hormones act differently to human hormones

  They only act locally whereas human hormones travel throughout our bodies
• Tropism

  A growth in response to a stimulus which may lead to a change in the direction of a shoot or root
• Auxins


  Family of plant hormones
• Where are auxins made

  In the growing tips of roots and shoots
• What happens to auxins once they’re produced

  They diffuse backwards along the root or shoot
• Phototropism

  A tropism in response to light
• Geotropism

  A tropism in response to gravity
• What effect do auxins have on plant shoots

  Stimulate growth
• What effect do auxins have on plant roots

  Inhibit growth
• Do siding accumulate on the light or dark side of a shoot/root

  Light breaks down auxin so there will be more auxins on the dark side
• Do auxins accumulate on the top or bottom side of a shoot/root

  Gravity pulls auxins downwards so there will be more auxin on the lower side
• Are shoots positively or negatively phototrophic

  Shoots are positively phototrophic, which means they will grow towards the light
• Are shoots positively or negatively gravitropic?

  Shoots are negatively gravitropic, this means they will grow away from gravity
• Are roots positively or negatively gravitropic

  Roots are negatively phototropic which means they will grow away from the light
• Are roots positively or negatively gravitropic

  Roots are positively gravitropic, this means they will grow towards gravity
• 3 plant hormones

  Auxins

  Gibberellin

  Ethene
• 3 uses of auxins in agriculture and horticulture

  In weed killers

  In rooting powders

  To promote growth in tissue cultures
• Explain how auxins can be used in weedkillers

  Auxins stimulate plant cells to divide and grow

  If large amounts of auxins are added to plant, it can disrupt their growth process by overstimulating

  This can kill plants
• What is a selective weed killer

  It only kills some types of plants, not all plants
• What does it mean for a seed to be ’dormant’

  Dormancy is the period in which seeds are inactive and do not grow or develop
• What does it mean for a seed to germinate

  Germination is the process by which a seed starts to grow and develop
• 3 uses of gibberellins

  To end seed dormancy

  To promote flowering

  To increase the size of fruits
• What is ethene used for

  Ethene stimulates fruit to ripen so it can be used in the food industry
• What is the effect of the widespread use of weedkillers on biodiversity

  Will reduce biodiversity as it kills plants