Plant Hormones Isolated from “Katahdin” Potato Plant Tissues and the Influence of Photoperiod and Temperature on Their Levels in Relation to Tuber Induction

Qualitative and quantitative analyses were carried out on vegetative tissues of potato (Solanum tuberosum cv. “Katahdin”) in search of natural products thought to play a role in tuber induction. Tissues were obtained from plants initially grown in a growth chamber under noninducing conditions (30°C day and 28°C night with an 18-h photoperiod), and then half of the plants were moved to inducing chambers (28°C day and 13°C night with a 10-h photoperiod) for 10 days prior to tissue harvest. Plants from each chamber were then harvested at 2-day intervals for 10 days, separated into above- and belowground portions, and the lyophilized tissues were extracted and subjected to rigorous purification and separation using high-performance liquid chromatography. This was followed by identification and quantification using combined gas chromatography-mass spectrometry. Compounds isolated and identified included gibberellic acid; cytokinins cis-zeatin riboside, trans-zeatin, trans-zeatin riboside, and isopentenyladenine; and jasmonates jasmonic acid, tuberonic acid and its methyl ester, methyl 7-isocucurbate, and 9,10-dihydromethyljasmonate. Methyl 7-isocucurbate and 9,10-dihydromethyljasmonate were detected for the first time in potato tissue as endogenous compounds. Cytokinin and jasmonate levels generally increased under inducing conditions, whereas gibberellic acid levels declined progressively during the 10-day sampling period. Only gibberellic acid, jasmonic acid, and cis-zeatin riboside levels were significantly influenced by induction.