Abstract
Five phenolic compounds were isolated using paper chromatography from the tissue affected with rhizome rot fungus of lotus, Fusarium bulbigenum var. nelumbicolum (table 1 and figure 1). The compounds were found to exist as much in the resistant variety (Shina) as in the susceptible (Usu), except two of them existed comparatively less in the latter variety. Healthy inner tissue of rhizome contains less of such compounds, whereas healthy epidermal tissue contains the same amount as affected tissue (table 2). One of the compounds was identified as chlorogenic acid from its ultraviolet absorption and by use of various reagents (table 3 and figure 2).
Juice prepared from the tissue near the infection showed a inhibitive effect against spore germination of the causal fungus, although when boiled they lost the ability (table 6). Juice from the healthy tissues both inner or epidermal had little effect (tables 4 and 5).
Abnormal metabolism in the tissue near the infection in resistant variety were also investigated. The results were as follows:
1) The amount of inorganic phosphorus compounds was less in the tissue just beyond the infection than in the healthy, and that of acidsoluble organic phosphorus compounds was much in the former, especially in resistant variety. Concerning the amounts of nucleic acid, lipid, and protein phosphorus compounds, no determinative results were obtained (tables 8 and 9, figures 3 and 4).
2) Dehydrogenase activity in the resistant variety was somewhat higher than in the susceptible and it was raised two days after infected (table 10).
3) More increased rate of respiration was observed in the tissue near the infection than in the healthy tissue, especially in resistant variety (table 11 and figure 5).
4) Phosphatase activities showed an increase from 36 to 60 hours after infection in resistant variety (table 12 and figure 6).
The results just outlined would suggest that the phenolic compounds found in the tissue near the infection have no closer correlation with a inhibitive action of resistant variety against the causal fungus. Rather than this, numerous efforts must be paid in future to confirm the abnormal metabolism between host-parasite interaction, only in which the basic mechanism of resistance in plants may be sought.
