Plant Hormones and their Commercial Uses

  • Created by: Davwi
  • Created on: 09-03-19 16:40


  • Auxin is a hormone that controls growth near the tips of shoots and roots.
  • It controls the growth of a plant in response to light (phototropism) and gravity (geotropism or gravitropism).
  • Auxin is produced in the tips and moves backwards to stimulate the cell elongation process that occurs in the cells just behind the tips.
  • If the tip of a shoot is removed, no auxin is available and the shoot may stop growing.
  • Extra auxin promotes growth in the shoot but inhibits growth in the root.
  • When a shoot tip is exposed to light, more auxin accumulates on the side that's in the shade than the side that's in the light.
  • This makes the cells grow (elongate) faster on the shaded side, so the shoots bend towards the light.
  • When a shoot grows sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side.
  • This causes the lower side to grow faster, bending the shoot upwards.
  • A root growing sideways will also have more auxin on its lower side.
  • But in a root, the extra auxin inhibits growth. This means the cells on top elongate faster, and the root bends downwards.

Commercial uses of Plant Hormones

  • Auxins are useful for controlling plant growth.
  • Most weeds growing in fields of crops or in a lawn are broad-leaved, in contrast to grasses and cereals which have very narrow leaves. 
  • Selective weedkillers have been developed using auxins, which only affec the broad-leaved plants. They totally disrupted their normal growth patterns, which soon kills them, whilst leaving…


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