The Distribution of Cytokinins in Tuberizing Potatoes

Potato tubers (Solanum tuberosum L.) stored at low temperaturein the dark for a prolonged period of time develop a disorderknown as ‘little potato’. This phenomenon involvesthe formation of stolons and new tubers, the reserves for thelatter being obtained from the parent tubers. A study of thedistribution of endogenous cytokinins in the various regionsof the system showed it to be very complex. Zeatin ribosideappeared to be the major cytokinin throughout the whole system.It was present in the highest levels at the stolon tips andin the smallest little potatoes. The internodal sprout tissue,which can be regarded as a link between the parent tubers andthe bulking little potatoes, contained the highest total levelof cytokinin. The total activity was greater due to the presenceof higher levels of compounds which co-eluted with zeatin andzeatin glucoside. It is possible that the cytokinin glucosideis either a translocatoly or storage form in the present system.The decreased levels of the glucoside at the stolon tips andin the bulking little potatoes could well be the result of hydrolysisor perhaps its active participation in the tuberizing process.