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What causes tropisms?

What causes tropisms?. Tropisms are caused by the plant hormone auxin or indolacetic acid (IAA). Auxins promote cell elongation. This can be shown using light on plant coleoptiles (the protective sheath covering the emerging shoot). Complete Worksheet ‘Interpreting Phototropism Experiments’

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What causes tropisms?

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  1. What causes tropisms? • Tropisms are caused by the plant hormone auxin or indolacetic acid (IAA). Auxins promote cell elongation. • This can be shown using light on plant coleoptiles (the protective sheath covering the emerging shoot)

  2. Complete Worksheet ‘Interpreting Phototropism Experiments’ Key terms – • coleoptile – shoot • Mica – impermeable substance • Gelatine – permeable substance

  3. Conclusion – Auxin and phototropism • During photosynthesis, when light strikes the coleoptile from one side, auxin produced in the tip moves to the shaded side as it descends the coleoptile. More auxin accumulates on the dark side causing elongation of these cells and the unequal growth which results in the tip bending toward the light.

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