Growth discrepancy between filament and style facilitates autonomous self-fertilization in Hedychium yunnanense (Zingiberaceae)

Background and aims - Reproductive success through autonomous self-fertilization is thought to be one of the main advantages in plants when effective pollinators are limited. The present study examined an autonomous self-fertilization mechanism in a perennial ginger, Hedychium yunnanense. Methods - We measured the relative stigma-anther positional changes, throughout the flower's lifespan, in an effort to understand the floral mechanism that leads to autonomous seed production. Pollination treatments were carried out and pollen-ovule ratio was estimated to test its breeding system. Preliminary observations on floral biology and flower visitors were also conducted. Key results - Hedychium yunnanense is a protogynous species and anther dehiscing occurred at night on the first day of flowering. The growth discrepancy between filament and style induces a contact between stigma and anthers favoring pollen deposition onto the stigmatic surface, thus facilitating self-pollination. Fruit set and seed set from pollinator-exclusion treatment showed similar results to open pollination treatment but lower than that of cross-pollination treatment. P/O ratio was 132.7 +/- 13.4 indicating facultative autogamy. Effective pollinators were not observed in three consecutive years of observation. Conclusions - The reproductive success of H. yunnanense via autogamy seems to be an adaptive strategy under the condition of effective pollinator limitation.