Gibberellin (OCR A Level Biology): Revision Note

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