COMPARISON OF TUBER AND SHOOT FORMATION FROM IN-VITRO CULTURED POTATOEXPLANTS

The development of axillary buds of potato (Solanum tuberosum L.) plan ts, cultured in vitro, was analyzed. Depending on the composition of t he culture medium, the buds developed into either tubers (medium with 8% sucrose), shoots (1% sucrose), or stolons (8% sucrose and 0.5 mu M gibberellin). Endogenous sugar and starch levels, and key-enzymes invo lved in the conversion of sucrose to starch were determined at differe nt stages of development. Moreover, the spatial distribution of sugar levels and enzyme activities were determined within the developing str uctures. Glucose and fructose decreased upon tuber formation, most not iceably in the swelling parts, where also starch accumulated. The acti vities of sucrose synthase, fructokinase and ADP-glucose pyrophosphory lase were highest under tuber-inducing conditions, the increase being confined to the tubers, and absent in the subtending stolons. It is co ncluded that changes in the measured parameters, observed under tuberi zing conditions, are specifically related to the formation of the tube r, and are confined to the swelling part only.