Plant Control System

• Phototropism: directional growth of a plant in response to the stimulus of light
• Stems exhibit positive phototropism, meaning that they grow towards light

  • allows the shoots to obtain the sunlight required for photosynthesis
• Roots show a weak negative phototropism because they grow away from the light.

  • allows roots to grow into the soil and obtain water and minerals
• Gravitropism: growth of plants in response to the Earth's gravitational force

  • exhibited by roots as they grow in the same direction as gravity (down)
  • stems exhibit a negative gravitropism as they grow opposite of gravity (up)