Metabolic Changes in Axes of Germinating Vigna unguiculata Seeds as Related to Effects of Removal of Cotyledons

[14C]-Labeled amino acids and sucrose were fed to Vigna unguiculata seeds through cut-ends of cotyledons, and incorporations of radioactivity into trichloroacetic acid- and 80% ethanol-insoluble fractions of axes, respectively, were followed during 48 h of the post-imbibition development. The results of these studies, together with determinations of changes in dry weight and protein contents after the onset of imbibition, indicated that the reserve materials stored in cotyledons were available for active growth of axes only after 12 h of post-imbibition. However, pulse-labeling experiments, where [3H]-labeled leucine and uridine were fed directly to axes attached to or detached from cotyledons, indicated that synthesis of protein and RNA in both axes was very pronounced even at earlier stages (2–8 h) of post-imbibition. Albumin and globulin proteins of axes disappeared most rapidly during the 6–12 h period of post-imbibition. Cycloheximide, α-amanitin and cordycepin added to imbibing axes inhibited the degradation of major globulin proteins, whereas the inhibitors had little effect on the degradation of major albumin proteins. Both proteolytic and amylolytic activities were found to occur in embryonic axes of ‘dry’ seeds, and increased to higher levels as the germination proceeded. Axes at early stages of germination may degrade the self-sustained reserve proteins and utilize them for the synthesis of new proteins.