gibberellins

gibberellins , 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.

gibberellin Any of a group of plant hormones that stimulate cell division, stem elongation and response to light and temperature. They have been used to increase crop yields.

gibberellin Any of a group of plant growth substances chemically related to terpenes and occurring naturally in plants and fungi. They promote elongation of stems, e.g. bolting in cabbage plants, and the mobilization of food reserves in germinating seeds, and are influential in inducing flowering and fruit development. Commercially available gibberellins, such as gibberellic acid, are used to manipulate the onset of sexual maturity in various species, e.g. to induce cone-bearing in young conifer trees.