Gibberellin like Substances in Parts of Developing Barley Grain

In husks, the activity of gibberellin-like substances extracted with aqueous methanol (M-“free” GAs) showed a maximum on the 9th day after pollination. In developing embryos, M-“free” GAs showed no biological activity, whereas biological active component(s) were obtained when the embryos were extracted with Tris buffer. The “free” GAs found in the buffer homogenates (B-“free” GAs) of developing embryos showed a maximum of activity on the 33rd day after pollination. Bound GAs recovered from the precipitated protein of the buffer homogenate (“Protein-bound” GAs) were found in embryo and endosperm. Developing endosperm generally contains the major amount of the extractable gibberellin-like substances. In this tissue, the amount of all examined fractions (M-“free” GAs, B-“free” GAs and “protein-bound” GAs) increased after pollination to reach a maximum on the 21st day, before decreasing to a minimum at grain maturity. Moreover, the curves for dry weight increase and gibberellin like substances follow a remarkably similar course, with the latter reaching its maximim slightly earlier than the former one. This result indicates that gibberellines may participate in the regulation of the accumulation process in the endosperm of barley grain.