Cytokinin-cytokinin-Induced tuber formation Tuber Formation on Stolons of Solanum tuberosum

Kinetin-induced tuberization of isolated stolons was investigated with regard to accumulation of labelled kinetin, starch, protein and nucleic acid synthesis. Using kinetin-8-¹⁴C, it was found that more labelled meterial appeared at the locus of tyber formation that in other parts of the stolon. Substantial accumulation was evident before visible signs of tuber formation. The basal portion of the stolon also accumulated substantial amounts of labelled material. Kinetin-treated stolons showed extensive starch accumulation which was not evident in gibberellic acid-treated or untreated stolons. Starch accumulation occurred before any visible sign of tuber formation. There was no marked differences in the ability of the apical 0.5 cm of kinetin-treated and untrated stolons to incorporate ¹⁴ C uridine into RNA and ¹⁴C leucine into TCA precipitable protein. From these results it was concluded that kinetin-induced tuber formation may not involve the synthesis of new proteins. It is suggested that kinetin may be regulating tuber formation by suppressing starch hydrolase activity and stimulating starch synthetase activity whereas gibberellic acid inhibits tuber formation by promoting starch hydrolase activity or by suppressing starch synthesizing enzymes.