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Plant Growth Hormones

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GCSE Biology Core (Topic 2, Responding to change) Mind Map on Plant Growth Hormones, created by daniifarrell on 12/23/2013.
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Mind Map by daniifarrell, updated more than 1 year ago
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Created by daniifarrell over 8 years ago
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Resource summary

Plant Growth Hormones
  1. Plants respond to stimuli
    1. Light
      1. Phototropism
        1. the growth of a plant in response to light. Shoots are positively phototropic
      2. Gravity
        1. Geotropism
          1. The Growth of a plant in response to gravity, roots are positively geotropic
        2. moisture
          1. a plants growth response it called a tropism
          2. Growth Hormones
            1. Auxin
              1. controls growth at the tips of shoots and roots
                1. Auxin is produced in the tips and diffuses backwards to stimulate the cells just behind the tips to elongate
                  1. When a shoot tip is exposed to light more auxin accumulates on the side that's in the shade this makes the cells elongate faster so the shoot bends towards the light.
                    1. Roots are positively Geotropic when a root is growing sideways, gravity produces an unequal distribution of auxin in the tip with more auxin on the lower side.
                    2. Gibberellin
                      1. stimulates seed germination, stem growth and flowering
                        1. it stimulates plants to grow by stem elongation. If a dwarf variety of a plant is treated it will become tall.
                      2. commercial uses
                        1. As a selective weedkiller
                          1. been developed from plant growth hormones which only effects broad-leaved plants
                            1. disrupts normal growth pattern which kills them but the grass and crops are fine
                          2. cuttings with rooting powder
                            1. adding rooting powder will produce roots rapidly
                              1. this enables growers to produce lots of clones of really good plant
                            2. controlling the ripening of fruit
                              1. allows the fruit to be picked while it's still unripe
                                1. ripening hormone is added so it will ripen on the way to the shops and be perfect
                              2. seedless fruit
                                1. growth hormones are applied to unpollinated flowers so that the fruit grows but the seeds dont
                                  1. hormones are also used to make seedless grapes but they are fertilised first
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