Plant Responses

• Auxin is synthesised in cells at the tip of the shoot.

  Auxin causes the cells to elongate on one side, so the stem bends
• Define Phototropism:

  The plant’s growth response to light
• Define Tropism:

  The directional growth response to an external stimulus
• State the plant hormones that are involved in the control of abscission.

  • Auxin
  • Ethene
• State examples of a response that plants use against herbivory.

  • the production of pheromones/ tannins/ alkaloids/ phenols/ terpenoids
  • thorns
  • folding in response to touch
• Students wanted to test whether there was a significant difference between the stem lengths of the seedlings in Group A and the seedlings in Group B.

  State the name of the most appropriate statistical test for the students to use and why?

  • Unpaired t-test
  • to compare means
• State the name of a plant hormone that would be expected to affect root growth.

  Auxins
• Plants are NOT mobile so they use directional growth responses to avoid a harmful environment.
• Growth in response to the direction of light is called phototropism
• What chemical compound is first secreted from plants in response to grazing?

  Pheromones
• Molecules that bind to plant proteins that have been consumed making it harder to be absorbed are called tannins
• Why do plants fold their leaves?

  • to expose their thorns
  • to seem smaller to deter predators
  • reduce exposure to stressful abiotic conditions
• Alkaloids inhibit...

  • enzyme activity
  • protein synthesis
• Geotropism is a growth response to the direction of gravity
• The role of Ethylene:

  • promotes cellulose production in cell walls
  • causes cells to self digest on the leaf side of the abscission zone
• What inhibits seed germination?

  Abscissic acid (ABA)