Germination of seeds of Eucalyptus regnans and E. pauciflora in 50 mg/1 gibberellic acid markedly affected seedling growth. These effects included: stimulation of leaf production and shoot extension growth; slight reduction of root growth; alteration of the root/shoot ratio, and leaf shape; reduction in total dry weight and leaf thickness. Gibberellic acid affected leaf growth through reduced cell division.
Stimulation of growth of E. camaldulensis hypocotyl by seed treatment with gibberellic acid could also be attributed to changes in cell division. No evidence of interaction between gibberellic acid and auxin was obtained.
These results are discussed in relation to effects of gibberellic acid on other plants and tissues, and it is suggested the responses are explicable in terms of mobilization of food reserves.