gibberellin n : a plant hormone isolated from a fungus; used in promoting plant growth

English

Noun

1. Any of a class of diterpene plant growth hormones first isolated from the fungus Gibberella fujikuroi.

Gibberellins (GAs) are plant hormones that regulate growth and influence various developmental processes, including "stem elongation, germination, dormancy, flowering, sex expression, enzyme induction and leaf and fruit senescence."

Gibberellin was first recognized in 1926 by a Japanese scientist, Eiichi Kurosawa, studying bakanae, the "foolish seedling" disease in rice. It was first isolated in 1935 by Teijiro Yabuta, from fungal strains (Gibberella fujikuroi) provided by Kurosawa. A known opponent to gibberellin is Paclobutrazol(PBZ), which in turn is growth inhibiting and inducing early fruitset as well as seedset.

Chemistry

Chemically, all known gibberellins are diterpenoid acids that are synthesized by the terpenoid pathway in plastids and then modified in the endoplasmic reticulum and cytosol until they reach their biologically-active form. All gibberellins are derived from the ent-gibberellane skeleton, but are synthesised via ent-kaurene. The gibberellins are named GA1....GAn in order of discovery. Gibberellic acid, which was the first gibberellin to be structurally characterised, is GA3.

As of 2003 there were 126 GAs identified from plants, fungi and bacteria.

Gibberellins are produced in greater mass when it’s cold. They stimulate cell elongation, breaking and budding, seedless fruits, and seed germination. They do the last by breaking the seed’s dormancy and acting as a chemical messenger. Its hormone binds to a receptor and Ca+2 activates a protein, calmodulin, and the complex binds to DNA, producing an enzyme to stimulate growth in the embryo.

References