CHANGES IN THE LEVELS OF FREE IAA AND CYTOKININS IN POTATO-TUBERS DURING DORMANCY AND SPROUTING

Changes in the levels of free indol-3-ylacetic acid (IAA) and free cyt okinins were determined in the course of dormancy and sprouting period in potato tubers (Solanum tuberosum L., cv. Nevskii) stored at 4-degr ees-C. The same analyses were performed in potato tubers after Ethrel application, which prolongs dormancy. No significant changes were foun d in free IAA level during dormancy followed by a rapid decrease durin g sprouting. After Ethrel application a significant lower IAA level wa s found 3 weeks after application, but further on no changes in free I AA level between treated and non-treated tubers were detected. Cytokin in level was relatively low and constant till sprouting and increases then by about 55 %, mainly due to an increase in the level of zeatin r iboside and isopentenyladenosine. Ethrel application decreased cytokin in level during dormancy slightly, but postpones the increase coupled with sprouting by about 1 month. Thus, IAA does not seem to have a sig nificant effect on tuber dormancy, while cytokinins are probably neces sary for sprouting initiation.