| Abstract: | The influence of the embryonic axis and cytokinins (CKs) onreserve mobilization has been examined in yellow lupin (Lupinusluteus L. cv. JSG 6167) seed during germination and during earlygrowth for up to 9 d in the dark. The study included determinationof starch, soluble sugars, proteins, and amino acid content.Amylolytic and proteolytic enzyme activity was also measuredin untreated cotyledons with intact embryo (attached) or detachedcotyledons (embryo removed), and in detached cotyledons followingtreatment with CKs namely, dihydrozeatin, (diH)Z, and 6-benzylaminopurine,BAP. Generally, the detached cotyledons showed reduced mobilizationand decreased enzymatic activity in comparison to attached cotyledons,indicating the importance of the embryonic axis in this process.However, a rise in protease activity and free amino acid contentwas detected in 9-d-old detached cotyledons suggesting thatthe end products do not necessarily inhibit enzyme activity.While (diH)Z was partially effective in inducing reserve mobilizationand enzymatic activity in detached cotyledons, the effect ofBAP was more pronounced and appeared to replace the embryonicaxis. The embryonic axis of this species has recently been shownto synthesize CKs which are transported to the cotyledons, arehighly stabe and induce cotyledon expansion and chlorophyllsynthesis. The results of the present investigation and previousstudies from this laboratory collectively indicate that theregulation of reserve mobilization in yellow lupin seeds appearsto be mediated, at least in part, by a stimulus, probably aCK, emanating from the embryonic axis. Key words: Lupinus luteus, cytokinins, benzylaminopurine, dihydrozeatin, embryonic axis, lupin seeds, reserve mobilization |
