THE HOST‐PARASITE RELATIONSHIP BETWEEN ZIZANIA CADUCIFLORA TURCZ. AND USTILAGO ESCULENTA P. HENN. IV. GROWTH SUBSTANCES IN THE HOST‐PARASITE COMBINATION

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Abstract
SUMMARY: The mycelial and sporidial stages of Ustilago esculenta could synthesize IAA in vitro, especially if the medium contained tryptophan. Extract from culms of its host, Zizania caduciflora, contained tryptophan and was a suitable medium for the production of IAA. Significant levels of IAA occurred in non‐sporulating and sporulating culms. The culms also contained three cytokinins (presumed to be zeatin and zeatin riboside with one unidentified). Total amounts of cytokinins were (kinetin equivalents): unswollen culm, 8·5 μg 100 g‐1; non‐sporulating culm, 11·9 μg 100 g‐1; sporulating culm, 1·3 μg 100 g fresh wt‐1. U. esculenta was able to produce zeatin in culture but the other cytokinins originated from the host or host‐parasite combination. A possible sequence of events is proposed to explain the formation of gau sun from the flowering culm.