The Growth-Substance Content of Dormant Fruits ofFraxinus excelsiorL.

Abstract

The growth-substance content of fruits of F. excelsior has been examined as part of an investigation into the causes of dormancy in this species. During the growth of the embryo within the imbibed seed, a neutral ether-soluble hormone, tentatively identified as indole aceto-nitrile, is utilized. After the embryo is fully grown the seed and the excised embryo are still dormant unless chilled. A watersoluble growth inhibitor is metabolically produced in both embryo and endosperm when the dry seed is imbibed. This inhibitor remains undiminished.in activity at all stages of pretreatment of the seed, and is still present in the germinable embryo. Inhibitor is readily destroyed by an enzyme system present in the seed tissues unless care is taken to extract at low temperatures.