水生タヌキモ属植物6種の繁殖様式  [in Japanese] A study on the reproductive biology of aquatic Utricularia species in southwestern Japan  [in Japanese]

Life cycle of six species of Utricularia was studied in the Kinki District, southwestern Japan, with special reference to their reproductive biology. Field observations and some pollination experiments revealed that failure of sexual reproduction or development of inbreeding system seemed to be widespread in aquatic Utricularia species. The fruits did not develop in U. vulgaris var. japonica because of abnormal formation of embryo sac and high percentage of abortive pollen. U.tenuicaulis was proved to be an out-breeder, but the seed set was not good in field probably due to the absence of effective pollinators. In addition, male sterility occurred in some populations of the species, resulting in a failure of sexual reproduction. In U. minor flowering was not observed during the study period. U. dimorphantha had cleistogamous (CL) as well as chasmogamous (CH) flowers and CL flowers played much greater role in its speed production than CH flowers. The populations of above four species were maintained vegetatively by turions. To the contrary, U. aurea and U. exoleta, both of which did not have turions as a means of vegetative reproduction, were shown to produce seeds efficiently by self-pollination. The position of their stigma and anthers facing to each other at dehiscence promoted the self-pollination.