gibberellins (jĭbˌərĕlˈĭnz) [key], a group of growth-regulating substances of plants, having complex chemical structure, of which the best known, gibberellic acid, is noted for its promotion of stem growth. In Japan it was long known that when rice seedlings were attacked by the fungus Gibberella fujikuroi they would grow to several times their normal height and then die, a phenomenon the Japanese called "the foolish seedling disease." A substance that caused these same effects was isolated from the fungus and named gibberellin. Other gibberellins exist rather widely in plants, and only an excess appears to cause abnormal effects. Gibberellins are used commercially in agriculture and horticulture to break dormancy, to speed up flowering and fruiting, and to stimulate the production of seedless fruits in the absence of pollination.