Jasmonic acid (JA) was isolated from yam leaves (Dioscorea batatas), with the guidance of assay for tuber-inducing activity which was carried out by cultures of single-node segments of potato stems in vitro, and identified by HPLC and mass spectrometry. The level of endogenous JA in the leaves of the plants, which being 5×10−7M at the first harvest, increased continuously with the growth of the plants. The effect of exogenous JA on the tuberization of yam plants was examined in vitro, and it was found to have strong tuber-inducing activity. The threshold concentration of JA for induction of yam tuberization was ca. 10−7M. These results suggest that tuberization of yam plants is controlled b
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