Morphological traits of a distylous taxon, Persicaria odorata subsp. conspicua (Polygonaceae)

Heterostyly is a reproductive system in which plant populations comprise two or three morphs with different lengths of pistil and stamen. In the present study, we demonstrated clear morphological traits of Persicaria odorata subsp. conspicua, a distylous taxon. Like other distylous species, the length of the style and filament are different between the two morphs. Although the fruit size and rate of pollen viability are slightly different between the two morphs, these two morphs have functionally hermaphroditic flowers based on production of pollen and fruits. The stigma length, anther length, ovary size, and fruit size are significantly larger in pin-type flowers than in thrum-type flowers, but the diameter of the pollen and aperture are larger in thrum-type flowers than in pin-type flowers. The tepal size is larger in pin-type flowers although not significantly. However, except for these reproductive organs, we could not detect any morphological differences between the two morphs, including the tepal and leaf microstructures. We further compared the detailed morphology of the two morphs and discussed the significance of heterostyly in P. odorata subsp. conspicua.