The plant‐growth‐promoting properties of gibberellic acid, a metabolic product of the fungus gibberella fujikuroi

Gibberellic acid is a metabolic product of the fungus Gibberella fujikuroi , similar in physiological properties to the gibberellins described by Japanese investigators. Supplied in a nutrient solution to wheat plants growing in water culture, it causes increased growth of the shoots, as a result of increased length of stem internodes and leaves. The leaves are narrower and paler than those of untreated plants. Under similar conditions pea seedlings develop much elongated stem internodes, but the leaves are little changed in size. These morphological responses are similar to those seen in etiolation. The total dry weight of both peas and wheat so treated is increased; if shoots alone are considered the increase in dry weight is even greater; the dry weight of roots is reduced, though this does not occur if the gibberellic acid is applied to the shoots in a lanolin paste. The increased dry weight is mainly attributable to increased carbon assimilation. Treated plants contain more soluble carbohydrate than controls, but this accounts only for a small part of the increased carbon assimilation. The increase in glucose content is particularly striking. Gibberellic acid is rapidly biologically degraded in soil.