The role of endogenous cytokinins and environmental factors in flowering in the vine cactus Hylocereus undatus

It has been found that application of exogenous cytokinins at a specific time induced flower induction in Hylocereus undatus (Haw.) Britt. & Rose. The aim of the present paper is to explore the role of cytokinins in flower induction in the cacti. Since endogenous cytokinins have never been analyzed in any cactus species, the initial step was to analyze endogenous cytokinins the year-round, and especially during the flowering period, when flower bud induction occurs. We found that the areoles contained all the cytokinin groups that are found in other plants, namely, active, non-active, metabolites, and storage forms. An important finding was that the concentrations of the active forms of trans-zeatin and isopentenyladenine increased several-fold prior to the formation of flower buds in plants grown outdoors under natural Israeli conditions. Endogenous cytokinins were analyzed further in H. undatus, flowering of which was induced with various temperature and long-day regimes. Cytokinins were also a...