Physiological Effects of Gibberellic Acid. X. Gibberellin-Like Substances by Germinating The Release of Barley Embryos

Sum,itmary. Barley embryos, completely free from endospernm, wvere excised from germinating grain at various times and al'lowed to diffuse into an aqueous medium for varying lengths of time. At the end of this time, the embrvos and ambient solutioins were separately extracted. Gibberellin-like activity in the extracts was determined with the barley endosperm bioassay using seed from the same varietv, hiarvest and treatment schedule as was employed for the emibryo diffusion experiments. Gibberellin-like sutbstances were released by embryos thTroughout the 60 hour germination period, though at no time during this period could sufficient activity be extracted from the embryos themiiselves to account for the observed release. Solvent partitionling and chromatography identified at least one major acidic component migrating at an Rf similar to that of GA3. It is concluded that the endogenous gibberellin-like substance(s) originates within the embryo during germination, and that the release of this substance('s) is temporally consistent with, and quantitatively sufficient to account for the in vivo endosperm mobilization response synldroIiie. A gilbberellin-Fke substance is uindotlubtedly the endospernm iinI)ilizinlr hormiionie.