Distyly and pollen dimorphism in<Emphasis Type="Italic"> Damnacanthus</Emphasis> (Rubiaceae) |
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Authors: | Email author" target="_blank">Akiyo?NaikiEmail author Hidetoshi?Nagamasu |
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Institution: | (1) Department of Botany, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo, Kyoto 606–8502, Japan,;(2) , The Kyoto University Museum, Kyoto, Japan, |
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Abstract: | We document distyly in Damnacanthus (Rubiaceae) and investigate pollen morphology in the genus. Within nine taxa in Japan (four species, four varieties and one
form), five show distyly. Non-distylous taxa of Damnacanthus always have a long style and short stamens. We examined the pollen morphology of all taxa of Damnacanthus in Japan. The pollen grains of Damnacanthus are 3- to 5-orthocolporate or sometimes loxocolporate. Polymorphic pollen is sometimes observed even within a single flower.
Pollen dimorphism is associated with distyly; pollen grains from short-styled (thrum) flowers are significantly larger than
those from long-styled (pin) flowers, and the muri are smooth in pin flowers whereas the pollen grains of thrum flowers have
minute granules on the top and/or on the sides. In non-distylous taxa, in which the style is longer than stamens, the muri
are always provided with minute granules. Interestingly, the pollen grains with granules in the non-distylous taxa contrast
with the pollen of the distylous taxa, because granulate pollen grains are found only in thrum flowers. Although Damnacanthus is a stenopalynous genus, the number of colpi is useful for delimiting taxa. Based on palynological characters, we conclude
that Damnacanthus should be revised.
Electronic Publication |
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Keywords: | Damnacanthus Heterostyly Pollen morphology Rubiaceae |
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