Stem anatomy is congruent with molecular phylogenies placing Hypericopsis persica in Frankenia (Frankeniaceae): comments on vasicentric tracheids
Abstract:Stem and root anatomy of Hypericopsis persica is evaluated in light of molecular data reconstructing Hypericopsis within a clade of Asian Frankenia. No anatomical information contradicts the idea that Hypericopsis should be subsumed within Frankenia. Anatomy in the two genera is comparable, taking into account the unusual habit of Hypericopsis, which consists of slender, short-lived shoots from a long-lived caudex, whereas most species of Frankenia are small shrubs with long-lived shoots. Wood of the slender stems of Hypericopsis is similar to twig wood of the related Frankenia hirsuta in qualitative and quantitative features but differs from mature wood of other species of Frankenia described in previous studies in having smaller cells and little storying. Wood of Hypericopsis is rayless and is made up mostly of libriform fibers and vessel elements associated with vasicentric tracheids. Axial parenchyma is occasional at the margins of growth rings. We briefly evaluate wood characters in the context of Caryophyllales s.l. and suggest characters that may be synapomorphies of clades within this group, e.g., minute lateral wall pits apparently characterize the clade comprising Plumbaginaceae, Polygonaceae, Frankeniaceae, and Tamaricaceae. That vasicentric tracheids elongate considerably beyond the lengths of the vessel elements with which they are associated is cited as a distinct ontogenetic difference between these cell types. Likewise, numerous vessel elements comparable in diameter to vasicentric tracheids were observed. These observations are offered as reasons to reject the concept of vasicentric tracheids as simply vessel elements that are too narrow for the formation of perforation plates.
Document Type: Research Article
Affiliations: 1: USDA-Agricultural Research Service-Northern Plains Agricultural Research Laboratory, P.O. Box 463, Sidney, Montana 59270, U.S.A. 2: University of Tarbiat-Moaallem, 49 Dr. Mofatteh Avenue, Tehran 15614, Iran.
Publication date: August 1, 2003
Impact Factor (2014): 3.3
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