A LevelBiologyOCRRevision Notes5. Communication, Homeostasis & Energy5.5 Plant & Animal Responses5.5.5 Gibberellin

Gibberellin (OCR A Level Biology)

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The Role of Gibberellin in Stem Elongation & Seed Germination

Experimental evidence for the role of gibberellin in stem elongation

  • Gibberellins are a group of hormones that help plants grow by stimulating cell division and elongation in the stem
  • Dwarf plant varieties have been shown to have very low levels of gibberellins
    • This is often due to a mutation in a gene involved in the synthesis of gibberellins

  • Under experimental conditions, treating these dwarf varieties with gibberellins results in them growing to the same height as normal varieties
  • Some farmers apply gibberellin to shorter plants to stimulate growth

Experimental evidence for the role of gibberellin in seed germination

  • The fact that gibberellins stimulate germination and the breaking of dormancy has been shown by many experiments
  • For example:
    • Seeds of mutant varieties of the Arabidopsis plant that do not produce gibberellins can be induced to germinate if gibberellins are applied
    • Seeds of certain lettuce varieties that require light in order to germinate can be made to germinate in the dark if gibberellins are applied

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    Alistair

    Author: Alistair

    Expertise: Biology & Environmental Systems and Societies

    Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.