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Changes in polyamine titers during shoot differentiation in Cymbidium sp. (Jungfrau) protocorms were studied in order to investigate the mechanism of shoot differentiation by using auxin-inhibitors(PCIB, TIBA), hormones(GA_3, ABA, BA), and phenolic compounds (2,4-dichlorophenol, catechol). The shoot differentation and propagation of protocorms were promoted by PCIB or 2,4-dichlorophenol, and the growth of differentiated shoot were promoted by TIBA or catechol. In BA-treated protocorms, white or brown protocorms were observed. Putrescine was the most abundant polyamine during the propagation and differentiation processes. As compared with putrescine, spermidine did not show significant changes and spermine was not detected at all. Putrescine titers decreased after a temporary increase, and then again increased in the presence of GA_3, ABA, 2,4-dichlorophenol, and then again increased in the presence of GA_3, ABA, 2,4-dichlorophenol, catechol, or PCIB. But, in BA-treated protocorms, putrescine level was much lower than spermidine.
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