Auxins

• Auxins were first isolated from human urine
• Examples of auxin

  • Natural - IAA, IBA
  • Synthetic - NAA, 2-4-D
• Auxins help to initiate rooting in stem cuttings, an application widely used for plant propagation
• Auxins promote flowering e.g. in pineapples
• Auxins help to prevent fruit and leaf drop at early stages but promote the abscission of older mature leaves and fruits.
• Growing apical bud inhibits the growth of the lateral (axillary) buds, a phenomenon called apical dominance
• Removal of shoot tips (decapitation) usually results in the growth of lateral buds. It is widely applied in tea plantations, hedge-making.
• Auxins also induce parthenocarpy, e.g., in tomatoes
• Auxins are widely used as herbicides. 2, 4-D, widely used to kill dicotyledonous weeds, does not affect mature monocotyledonous plants
• Auxin also controls xylem differentiation and helps in cell division