The Role of Gibberellin in Stem Elongation
- In some plants species their height is partially controlled by their genes
- The Le gene dictates the height of some plants
- It has two alleles: Le and le
- The dominant allele Le produces tall plants when present
- The recessive allele le produces shorter plants when present (in a homozygous individual)
- The gene regulates the production of an enzyme that is involved in a pathway that forms active gibberellin GA1
- Active gibberellin is a hormone that helps plants grow by stimulating cell division and elongation in the stem
- The recessive allele le results in a non-functional enzyme
- It is only one nucleotide different to the dominant allele
- This causes a single amino acid substitution (alanine -> threonine) in the primary structure of the enzyme
- This change in primary structure occurs at the active site of the enzyme, making it non-functional
- Without this enzyme no active gibberellin is formed and plants are unable to grow tall
- Plants that are homozygous for the recessive allele le are dwarves
- Some farmers apply active gibberellin to shorter plants to stimulate growth
