Gibberellin

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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."^[1]

Gibberellin was first recognized in 1926 by a Japanese scientist, Eiichi Kurosawa, studying bakanae, the "foolish seedling" disease in rice.^[1]^[2] It was first isolated in 1935 by Teijiro Yabuta, from fungal strains (Gibberella fujikuroi) provided by Kurosawa.^[1] Yabuta called the isolate gibberellin.^[1]

Interest in gibberellins outside of Japan began after World War II. In the United States, the first research was undertaken by a unit at Camp Dietrick in Maryland, via studying seedlings of the bean Vicia faba.^[1] In the United Kingdom, work on isolating new types of gibberellin was undertaken at Imperial Chemical Industries.^[1] Interest in gibberellins spread around the world as the potential for its use on various commercially important plants became more obvious. For example, research which started at the University of California, Davis in the mid-1950s led to its commercial use on Thompson seedless table grapes throughout California by 1962.^[3] A known opponent to gibberellin is Paclobutrazol(PBZ), which in turn is growth inhibiting and inducing early fruitset as well as seedset.

[edit] 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^[4]. 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^[1] 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.