Changes in enzyme activity during elongation and tuberization of stolons of Solanum tuberosum L. cultured in vitro

Isolated stolons of Solanum tuberosam L. were cultured in vitroin the presence of kinetin, which induced tuber initiation orgibberellic acid which inhibited initiation. Progressive changes in enzyme activity, at the locus of tuberinitiation, were monitored at specified intervals. In the presenceof kinetin soluble invertase activity was decreased with timewhereas gibberellic acid (GA) evoked substantial increases inactivity. Acid phosphatase activity was enhanced by GA but changedonly slightly under tuber inducing conditions. Enzymic hydrolysisof glucose-6-phosphate and fructose-6-phosphate decreased duringthe course of tuber induction but increased in the presenceof GA. In contrast hydrolysis of 3'AMP was stimulated undertuber inducing conditions. GA evoked substantial increases in peroxidase activity duringthe initial stages of incubation while under tuber inducingconditions increased activity was only observed after 5 days.Substantially higher levels of IAA oxidase activity were associatedwith tuber initiation. RNase activity decreased with time undertuber inducing conditions but showed an initial stimulationin the presence of GA. These results are discussed with referenceto the role of these enzymes in carbohydrate metabolism andthe regulation of hormone levels. (Received February 29, 1972; )