Use of plant hormones

• how do plant shoots show positive phototropism?

  • one side of the shoot is in the light, causing auxin to move to the shaded side
  • at the shaded side, the cells are stimulated to grow - the shoot bends towards the light
  • as a result, photosynthesis can occur at a faster rate
• How do plant shoots show negative gravitropism?

  • In a horizontal shoot, auxin accumulates in the lower side due to gravity.
  • Cells on the lower side of shoot grow more, causing the shoot to bend away from the direction of gravity.
  • As a result, more light is usually available for photosynthesis.
• How do plant roots show positive gravitropism?

  • In a horizontal root, auxin accumulates in the lower side, causing cells to grow less.
  • The root bends in the direction of gravity
  • As a result, more water and nutrients are available to the plant roots.
• What are the uses of auxins?

  • weedkillers - causes cells to grow at a rapid rate, causing plant death
  • rooting powder - causes new plant to grow very quickly
  • tissue culture - promotes growth of roots and shoots
• Uses of ethene

  control of food ripening in the food industry - allows fruit to be ripened just before they are sold
• Uses of gibberellins

  • termination of seed dormancy
  • promotion of flowering
  • increase of fruit size