Steinitz, B., Department of Plant Genetics, Institute of Field and Garden Crops, Agricultural Research Organization, POB 6, Bet Dagan 50250, Israel

Regeneration of potato (Solanum tuberosum L.) microtubers in tissue culture is used as a model simulating the developmental physiology of underground storage organ formation. Two exercises are described: (i) induction of microtubers on tissue cultured derived single nodal explants, incubated on an agar-solidified Murashige and Skoog basal medium devoid of plant growth regulators, but supplemented with high sucrose concentration; and (ii) prevention of sucrose-mediated microtuberization by adding gibberellic acid (GA3) to the medium. The objectives of these experiments were to (a) illustrate that, from a developmental standpoint, underground storage organs are shortened, thickened stems; and (b) show that sucrose participates in tuber induction in a growth regulator-like mode of action.