Effects of Different Cytokinin-like Compounds on Invertase Activity during Potato in Vitro Tuberization

The effects of different cytokinin-like compounds on invertase activities at different tuberization stages of potato ( Solanum tuberosum L. `Atlantic') were examined. Single nodal segments were cultured on MS medium plus 6% sucrose and supplemented with either 2 mg kinetin/L, 0.1 mg thidiazuron (TDZ)/L, 1.0 mg AC 243,654/L, 0.1 mg AC 239,604/L, or no cytokinin. Tissue samples for determining invertase activity were taken at three stages of tuberization: stage 1, the “hook stage”; stage 2, the “swelling stage”; and stage 3, “tuber initials.” Invertase activity was significantly affected by the interaction between cytokinin-like compounds and tuberization between cytokinin-like compounds and tuberization stages. The highest invertase activities in the stolons at stage 1 were found in kinetin and TDZ treatments. Invertase activity in the stolons on the control medium significantly increased from stage 1 to 2 and decreased at stage 3. Invertase might play a role in either stolon elongation or carbohydrate utilization by increasing the pool of reducing sugars.