Variations in Sex Expression and the Reproductive Function of an Evergreen Broad-leaf Understorey Species, Eurya japonica Thunb. (Theaceae)

Abstract

Variations in sex expression and the reproductive function of Eurya japonica Thunb., evergreen broad-leaf understorey species, were investigated at a Quercus serrata secondary forest in Okayama City and at a burnt pine forest in Kure City, southwestern Japan. A few individuals (1.5–16.4% of flowering individuals) produced flowers similar to hermaphrodite flowers in shape (hermaphrodite-type flowers), whereas most of individuals did either male or female flowers. Trends in the data for germination test of seeds and pollen grains and observed state of pollen production in hermaphrodite-type flowers indicated that hermaphrodite-type flowers were divided into two types according to their reproductive function: hermaphrodite flowers which produced both fertile seeds and pollen grains; and ‘pseudo-hermaphrodite’ flowers, functionally female ones, which produced fertile seeds and no pollen grains. Individuals having hermaphrodite flowers always had male flowers. Individuals having pseudo-hermaphrodite flowers, on the other hand, always had female flowers. Thus, sex expression of individuals was classified into three types: male individuals which produced only male flowers (44.8–53.6% of flowering individuals); female individuals which produces only female flowers (32.4–44.8%) and those which produced both female and pseudo-hermaphrodite flowers (2.3–19.6%); and andromonoecious individuals which produced both male and hermaphrodite flowers (1.8–6.5%). Therefore, sex types of E. japonica was classified as polygamodioecy from a functional view point.