A STUDY ON INCREASE IN O-DIPHENOL OXIDASE ACTIVITY DURING INCUBATION OF SLICED SWEET POTATO TISSUE

The increase in o-diphenol oxidase activity and polyphenol con-tent was investigated in slices excised from sweet potato roots. o-Diphenol oxidase activity increased in a sigmoidal fashion over a 100 hour period. The increase in polyphenols occurred over a shorter period of time and was evident before an increase in o-diphenol oxidase activity could be detected. Thus, it seemed that the increase in polyphenol content might be involved in the enhancement of o-diphenol oxidase activity. However, the above correlation was not found in different kinds of experiment including pretreatment with either vacuum infiltration or wet conditioning. It has been observed by many researchers that the activity of o-diphenol oxidase (polyphenol oxidase) [EC 1.10.3.1 o-quinol:02 oxidoreductase] in-creases in the tissue of many plants following cutting or infection by pathogens (1). In sweet potato roots, o-diphenol oxidase activity increased in response to cutting or infection {2,3). This paper deals with the increased polyphenol oxidase activity and polyphenol content in slices of sweet potato roots. The relationship between the increase in o-diphenol oxidase activity and the increase in polyphenol content was examined and discussed in this paper. MATERIALS AND METHODS Experimental materials Norin No. 1, a variety of sweet potato was used for the experiments. The roots stored at 10-11 ° were scrubbed in water, immersed in 0.1% sodium hypochlorite solution for 30 min to sterilize the outer parts, and transferred to running tap water. They were cut vertically in 2 cm thick-ness, and the round slices were incubated at 28-30 ° under high humidity. They were called block tissue. For another way, the roots were cross sectionally cut in 2 mm thickness by a bacon slicer to prepare thin slices, This paper constitutes part 51 of the phytopathological chemistry of sweet potato with black rot