15.2.3

Gibberellins

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Gibberellins

Gibberellins have a role in seed germination and stem elongation.

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Seed germination

  • Seeds are initially dormant (inactive).
  • When a seed begins to absorb water, gibberellin synthesis is stimulated.
  • Gibberellins promote seed germination by stimulating amylase synthesis.
    • Synthesising amylase enables the digestion of the starch in the endosperm of the seed, so the developing plant can access energy stored inside.
  • In wheat and barley seeds, the endosperm acts as starch storage.
  • Amylase breaks down starch into glucose. Glucose is then respired to produced ATP.
Illustrative background for Stem elongationIllustrative background for Stem elongation ?? "content

Stem elongation

  • Gibberellins play a role in determining how tall or short a plant is.
  • Of particular importance is the Le/le gene.
  • The dominant Le allele codes for a key enzyme in the gibberellin synthesis pathway.
    • Gibberellins stimulate mitosis and cell elongation. Plants containing the Le allele grow tall.
  • The recessive le allele codes for a non-functional version of the enzyme. So, the resulting plants cannot produce gibberellins
    • So, homozygous recessive plants grow short.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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