C.3.5 - control systems

• Phototropism - plant growing towards sun

  • Stem - positive, towards light
  • Roots - negative, away from light 
• Phototropism

  • Auxin - hormone produced at tip of stem making it longer
  • Abundant in shade, so shaded area is longer, making stem bend to sun
• Hydrotropism - plant growing towards water

  • Root - positive, towards water
• Gravitropism - shoots up root down 

  • Stem - negative, up against gravity
  • Roots - positive, down following gravity
• Gravitropism

  • Starch is heavier, and since it's in roots, they know which way is down