The translocation of antibiotics in higher plants. 4. Systemic fungicidal activity and chemical structure in griseofulvin relatives

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Abstract
No direct correlation was found between in vitro and systemic fungicidal activities among griseofulvin relatives. In an attempt to elucidate the reasons for this disparity, the translocation and breakdown of a selected group of griseofulvin relatives in broad bean was studied by the methods outlined in the preceding paper. All the compounds, whether neutral, acidic or basic, were taken up through the root system. Compounds active in vitro and as systemic fungicides were closely related to griseofulvin in structure, were translocated unchanged and acted directly against the pathogen. Compounds active in vitro but inactive as systemic fungicides did not attain the appropriate minimal concentration in the shoots. This was either because the compounds were degraded in the roots or because their solubilities operated against translocation from root to shoot. Compounds inactive in vitro but showing weak systemic fungicidal activity were extensively degraded in the tissues and owed their activity to an indirect mechanism, possibly by affecting the biochemistry of the host plant. A systemic fungicide based on the griseofulvin structure should have high activity in vitro, coupled with chemical stability in the tissues and a low oil-water partition coefficient.