plant hormones

• auxin is a...


  plant growth hormone
• auxin


  a plant growth hormone that controls growth near the tips of shoots and roots in response to light and gravity and is produced in the tips of plants
• auxin is produced in the...

  tips and moved backwards to stimulate the cell elongation process which occurs in the cells just behind the tips
• what happens if the tip of a plant shoot is removed?

  no auxin is available and the shoot may stop growing
• what does extra auxin promote?

  growth in the shoot but inhibits growth in the root - producing the desired result
• phototropism


  a plant's growth response to light
• gravitropism


  a plant's growth response to gravity
• geotropism


  a plant's growth response to gravity
• hydrotropism


  a plant's growth response to water
• chemotropism


  a plant's growth response to chemicals
• thigotropism


  a plant's growth response to touch
• positive ...tropism


  growth towards ...
• negative ...tropism


  growth away from...
• shoots grow ... light

  towards
• what happens 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 faster on the shaded side, so the shoot bends towards the light
• shoots grow ... gravity


  away from
• what does gravity do to a shoot tip?

  when a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side. this caused the lower side to grow faster, bending the shoot upwards
• roots grow ... gravity

  towards
• what does gravity do to plant roots?

  in a root extra auxin inhibits growth. this means the cells on top elongate faster, and the roots bend downwards
• positive phototropism


  the stem tip of a plant grows towards light to absorb more sunlight for increased growth
• negative phototropism


  the root tips of a plant grows away from light to find shade/soil faster to reduce its chance of drying out
• positive geotropism


  the root tips of a plant grows towards gravity to get deeper into the roots to increase plant stability and find more mineral ions for growth
• negative geotropism


  the stem and plant shoots grows away from gravity to increase growth even while underground or in the dark
• auxin uses


  - killing weeds: disrupt broad leaf weed growing patterns

  - growing from cuttings from rooting powder: will produce new roots and make clones of mother

  - growing cells in tissue culture: stimulates cells to divide and form roots and shoots
• what does gibberellin do?

  stimulates seed germination, stem growth and flowering
• gibberellin uses


  - controlling dormancy: flower at unusual times of year

  - inducing flowering: will flower with no change to environment otherwise needed

  - growing larger fruit: grow larger to meet other types
• how is ethene produced in plants?

  from the aging parts of a plant
• what does ethene do to plants?

  influences the growth of plants by controlling cell division and stimulates enzymes that cause fruit to ripen
• ethene uses


  stimulates the ripening of fruit - ripening can also be delayed with the use of chemicals that block ethene's effect or react with ethene to remove it from the air