By GC-MS Gibberellin A20-13-O-glucoside (GA20-13-O-Glc) and GA8-2-O-Glc could be identified as endogenous GA-conjugates in mature grains of both barley varieties Hordeum vulgare L. cv. Himalaya and cv. Salome. The thesis reports for the first time on changes of the pool size of these conjugates together with those of the agluca during seed ripening by internal standard quantifi-cation. The amounts of GA20-13-O-Glc were found to climax during milk ripeness of cv. Himalaya and at late yellow ripeness of cv. Salome. Later on both, GA20-13-O-Glc and GA20, declined toward ripeness, but their ratio became inverse. The obtained data give evidence, that GA20-13-O-Glc is a permanent cocomitant of GA20 during seed ripening and undergoes metabolsm as rapid as free gibberellins. During the imhibition of in situ labelled GA20-13-O-Glc of barley caryopses increase of labelled GA20 after 6 hours simultaneously a decrease of the 13-O-glucoside could be observed, giving the first evidence for the reconversion of a GA-O-glucoside in vivo by GC-MS. The subsequent increase of labelled GA1 after 12 hours indicates the presence of enzymes of gibberellinbiosynthesis in dormant seeds, when de novo biosynthesis starts after about 20 hours imhibition. The investigations of the distribution of GA20-13-O-Glc and GA20 in mature grains of both barley varieties showed, that in cv. Himalaya GA20-13-O-Glc is localized predo-minantly in the embryo-containing part, whereas cv. Salome accumulated the conjugate exclusively in the endosperm. This could be important for the spezific induction of α-amylase in the compartments. The results of the dissertation show, gibberellinconjugates represent the source of an early GA-signal, that could enable grain to start the initial germination processes independing from de novo biosynthesis.