Self- and Interspecific Incompatibility in the Convolvulaceae

Species of the Convolvulaceae were screened for both self- and cross-incompatibility reactions. Self-fertile species (38 found) were mostly weedy or ornamental annuals. Self-incompatible species (13 found) were large-flowered perennials (one exception) with extrorse dehiscence of anthers. Both self- and inter-specific incompatibilities were caused chiefly by failure of pollen to germinate. In addition, pollen tubes frequently failed to pass from stigma to style. This latter phenomenon was associated chiefly with crosses between partially sterile species. From a physiological standpoint, self-incompatibility thus resembles, and may have evolved from, a generally occurring system of interspecific incompatibility.