The Role of Gibberellin in Germination of Barley
- Gibberellins are a type of plant growth regulator involved in controlling seed germination and stem elongation
- When a barley seed is shed from the parent plant, it is in a state of dormancy (contains very little water and is metabolically inactive)
- This allows the seed to survive harsh conditions until the conditions are right for successful germination (e.g. the seed can survive a cold winter until temperatures rise again in spring)
- The barley seed contains:
- An embryo – will grow into the new plant when the seed germinates
- An endosperm – a starch-containing energy store surrounding the embryo
- An aleurone layer – a protein-rich layer on the outer edge of the endosperm
- When the conditions are right, the barley seed starts to absorb water to begin the process of germination
- This stimulates the embryo to produce gibberellins
- Gibberellin molecules diffuse into the aleurone layer and stimulate the cells there to synthesise the enzyme amylase
- In barley seeds, it has been shown that gibberellin does this by regulating genes involved in the synthesis of amylase, causing an increase in the transcription of mRNA coding for amylase
- The amylase hydrolyses starch molecules in the endosperm, producing soluble maltose molecules
- The maltose is converted to glucose and transported to the embryo
- This glucose can be respired by the embryo, providing the embryo with the energy needed for it to grow
Gibberellin Seed Germination Diagram
The role of gibberellin in the germination of a barley seed
