ENDOGENOUS FURANOTERPENE-INDUCING FACTOR FOUND IN MECHANICALLY INJURED SWEET-POTATO ROOTS

When mechanically injured sweetpotato roots are kept under low humidit y (Dry, RH 60-70%) such that their wound-healing is not completed, fur anoterpenes (FT) including ipomeamarone (Ip) are produced by these phy sical stresses. Hitherto, it was known that these sweetpotato phytoale xins were produced by biological or chemical stresses. In this paper, the endogenous FT-inducing factor in these physically stressed roots w as fractionated and examined for its properties. FT-inducing activity was estimated by measurement of Ip or FT occurring in slices of sweetp otato that were dosed with each of the fractions and then incubated. I nducing activity was not found in the injured roots kept under high hu midity in which FT were not produced, but it was found in those in a s tage prior to production of FT under low humidity. The active extract was successively fractionated through various types of M-r size cut me mbranes and then through SEP-PAK cartridges. Through these fractionati ons, a QMA-adsorbed component between 500 and 3000 M-r showed marked F T- and also Ip-inducing activity. The activity of this acidic componen t was not affected by heat and protease, but the activity completely d isappeared upon hydrolysis with acid and glycosidases. These results, as well as the chemical analyses, suggest that the endogenous FT-induc ing activity is caused by some uronic fragments.