Morphology of pollen and orbicules in some Dioscorea species and its systematic implications |
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Authors: | PETER SCHOLS CAROL A FURNESS PAUL WILKIN SUZY HUYSMANS ERIK SMETS FLS |
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Institution: | Laboratory of Plant Systematics, Institute of Botany and Microbiology, K. U. Leuven, Kard Mercierlaan 92, B-3000 Leuven, Belgium;Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE |
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Abstract: | Pollen and orbicule morphology of 35 Dioscorea L. species is described based on observations with light microscopy, and scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the genus. Pollen is mostly bisulcate (sometimes monosulcate) with a perforate, microreticulate or striate sexine. Our results indicate that pollen data may be significant at sectional rank. The close relationship between sections Asterotricha and Enantiophyllum proposed by Burkill and Ayensu is supported by pollen morphology as all species investigated share bisulcate, perforate pollen with small perforations and a high perforation density. Macromorphological differences between the two compound-leaved sections Botryosicyos and Lasiophyton are also supported by pollen morphology; pollens of these two sections have very different perforation patterns. Orbicules in Dioscorea are mostly spherical and possess a smooth or spinulose surface. The latter is often correlated with a striate sexine. |
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Keywords: | pollen aperture pollen ultrastructure sectional classification sexine ornamentation |
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