[Morphoregulatory effects of xanthene derivatives].

Of the compounds tested especially xanthene-9-carboxylic acid [I], applied via the roots (10(-4)M), strongly affected the morphogenesis of tomato plants. The leaves were deformed, the laminae reduced, the internodes shortened and the growth of axillary buds was stimulated. Geo- and phototropism of wheat and rye seedlings were disturbed. The observed effects are very similar to the influence of the structurally related derivatives of 9-hydroxyfluorenecarboxylic acid-(9) [II], known as "morphactins".