Gibbérelline

The gibbérelline (of Gibberella fujikuroi ) is a family of Phytohormone. One says also acid gibberellic , they are named G or GA followed by a figure (from 1 to 110). The GA3 is the best known one.

History

It was highlighted for the first time by the phytopathologist Eiichi Kurosawa in 1926, at Gibberella fujikuroi (Ascomycète parasite of the Riz which lengthens the stems exaggeratedly). Between 1935 and 1938, Teijiro Yabuta (1888-1977) isolates and purifies the substance at the origin of the disease. In 1954-55 one determines the chemical structure of the acid gibberellic (GA3).

Structure and ways of biosynthesis

It is a family of composed with 19 or 20 Atome S of Carbone S.
Les gibbérellines presents combined forms (i.e. associated with a sugar such as the Glucose).

Places of synthesis

The synthesis proceeds on the level of the Méristèmes, of the final buds racinaires and caulinaires, the young sheets and the embryo.

Effects

In experiments, its inoculation in rice, as in various other plants causes an exaltation of the growth. The gibbérellines act primarily on the cells of the Entrenœud S which they lengthen. It also contribute to the lifting of the Dormance of seeds and to débourrement of the bud S (Vernalisation). By doing this, they are thus opposed to the effects of the abscissic Acide . They can shift the measurement of time at the plants. The treatments the gibbérellines replace the long days and cause the flowering of plants during the short days of the winter.

With the difference of the Auxine S, the gibbérellines do not inhibit nor do not stimulate the growth of the roots.

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