Gibberellines and IAA (auxin)

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  • Created by: Georgia56
  • Created on: 13-04-18 15:12

Growth in plants

Auxins and Gibberellins are two major hormones that affect the growth of plants. They are effective at low concentrations. They are produced in one area of the plant and transported to other parts where they have an effect.

Auxins, e.g IAA

  • Indole Acetic Acid (IAA) is a produced at the growing points – root tips, shoot tips and meristems
  • IAA stimulates cell division, elongation and differentiation
  • High levels of IAA stimulates shoot growth and inhibits roots growth. This allows IAA to be used as a selective herbicide. It causes the plant shoots of broad-leaved plants to grow so rapidly that it exhausts the plant, whilst having little effect on narrow leaved plants
  • Low levels of IAA promote the growth of adventitious roots in cuttings and can therefore be used as a rooting powder
  • IAA is destroyed by light and this leads to the phototropic effect (plants moving towards the light). IAA on the side nearest the light is destroyed and therefore the cells do not undergo as much division and elongation, whilst those on the opposite side are…

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