THE INFLUENCE OF THE EMBRYONIC AXIS AND CYTOKININS ON RESERVE MOBILIZATION IN GERMINATING LUPIN SEEDS

The influence of the embryonic axis and cytokinins (CKs) on reserve mo bilization has been examined in yellow lupin (Lupinus luteus L. cv, JS G 6167) seed during germination and during early growth for up to 9d i n the dark, The study included determination of starch, soluble sugars , proteins, and amino acid content, Amylolytic and proteolytic enzyme activity was also measured in untreated cotyledons with intact embryo (attached) or detached cotyledons (embryo removed), and in detached co tyledons following treatment with CKs namely, dihydrozeatin, (diH)Z, a nd 6-benzylaminopurine, BAP. Generally, the detached cotyledons showed reduced mobilization and decreased enzymatic activity in comparison t o attached cotyledons, indicating the importance of the embryonic axis in this process, However, a rise in protease activity and free amino acid content was detected in 9-d-old detached cotyledons suggesting th at the end products do not necessarily inhibit enzyme activity. While (diH)Z was partially effective in inducing reserve mobilization and en zymatic activity in detached cotyledons, the effect of BAP was more. p ronounced and appeared to replace the embryonic axis, The embryonic ax is of this species has recently been shown to synthesize CKs which are transported to the cotyledons, are highly stable and induce cotyledon expansion and chlorophyll synthesis, The results of the present inves tigation and previous studies from this laboratory collectively indica te that the regulation of reserve mobilization in yellow lupin seeds a ppears to be mediated, at least in part, by a stimulus, probably a CK, emanating from the embryonic axis.