Phytopathological Chemistry of Black-rotted Sweet Potato

Part 3. Some Knowledges concerning the Penetration of Ceratostomella fimbriata into the Cells of Sweet Potato

Abstract

The examinations were carried out about the effect of the metabolic substances of the fungus to sweet potato, and about the microscopic histoanatomy of black-rotted sweet potato. In the latter, the many staining methods were examined and improved so as to be suitable for our study.
The metabolic substances were found to be unpoisonous to the tissues of sweet potato, and if poisonous, they might be weak in property or negligible in amount. The facts coincides with the results of the anatomic experiments.
The penetrating processes of the fungus were assumed to be as follows; the fungus secreted locally cellulase, pectinase etc. to decompose the cell membrane and penetrated into the cells which were killed.
It was found that, in the injured part, the substances similar to melanin produced by the oxidation of polyphenols were adhered obviously not only to the cells but to the mycellium. The fact gives support for the conclusion “the polyphenolic and guinoid 'substances inhibit the penetration of the fungus into the cells cooperating with bitter substances and resins in the injured part”, as described in the last report.
Lignin layer was observed to occurr at the sound part adjacent most closely to the injured part, under the appropriate environment, and inhibit the penetration of the fungus.