Stegmata in Orchidales: character state distribution and polarity |
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Authors: | J. DAHL MØ LLER,HANNE RASMUSSEN F.L.S. |
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Affiliation: | Institute of Plant Anatomy and Cytology, Sølvgade 83, University of Copenhagen, DK-1307 Copenhagen K, Denmark |
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Abstract: | The- distribution of stegmata in Orchidales is given for 130 species representing 105 genera. The stegmata occur in leaves and stems as longitudinal files of silica cells. lining fibre bundles or vascular bundle sheaths. The silica bodies contained in orchid stegmata arc of two major kinds, spherical and conical. The species investigated are characterized either by a single kind of silica body or by lack of silica cells. Absence of stegmata and presence of stegmata with conical bodies are the two most common character states in the order. The stegmata containing spherical bodies characterize Vandeae and Eriinae, Podochilinae, and Dendrobiinae within Epidendreae Comparison of character slates of the various groups within the family is used for a discussion of evolutionary polarity. The function of silica accumulation is reconsidered in the light of the epiphytic life-form of many of the investigated orchids. |
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Keywords: | Evolutionary polarity Orchidales outgroup comparison phylogeny silica cells stegmata |
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