SB6g- Uses of plant hormones

• What ways can auxins be used?

  • Selective weedkillers
  • Rooting powder
  • Promote growth in tissue culture
• Selective weedkillers

  Selective weedkillers contain auxins.

  • Weed plants compete with crop plants for water and minerals from the soil (narrow leaved crop plant, and broad leaved weed plants)
  • Broad leaves plants absorb more of the auxins than narrow leaved plants
  • This causes them to grow too quickly and die, as they are overstimulated
  • The crop plants get more water and minerals, and so grow better
• Rooting powder

  • cuttings of plants can grow into new ones
  • Dip the cutting into root powder, which contains auxins, causing it to develop roots quickly
  • This helps the cuttings grow well into fully developed plants
• Gibberellins

  • Are plant hormones that are naturally released inside a seed to start germination
  • Some seeds need s period of darkness or cold before they can germinate but plant growers can use gibberellins to make these seeds germinate without this.
• Seedless fruit

  Gibberellins sprayed on to flowers can stop seeds developing into the fruits, and can also make the fruit grow larger. Many people prefer large seedless fruit, so they are worth more money
• Photoperiodism

  • response of an organism to the number of daylight hours in a day. Some plants use this to flower at a certain time. (eg. when suitable pollinators are around)
  • However, gibberellins can override photoperiodism
• Ethene

  • Ethene is a hormone that causes fruit to ripen
  • Fruit producers often pick unripe fruit (as they are less likely to be damaged) and ripen them when needed with ethene
  • Ethene is released by plant cells when they die, leading to ripening, and then rotting
  • Ethene is a gas, so if 1 rotten apple is put into a barrel with normal apples, the gas will be absorbed, spreading ripening and eventually rotting to all the other apples
• What are other uses for Giberellins except germination?

  • Cause more flowers to grow
  • Cause bigger flowers to grow
  • Cause larger seedless fruit
• How can auxins promote growth in tissue culture?

  It can produce plant clones by using a growth medium that contains auxins (as it stimulates growth) and other minerals a plant needs.
• What are the three plant hormones?

  1. Auxins
  2. Giberellins
  3. Ethene