Tanaecium
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publication ID |
https://doi.org/ 10.5252/adansonia2023v45a12 |
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DOI |
https://doi.org/10.5281/zenodo.8015273 |
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persistent identifier |
https://treatment.plazi.org/id/039687DC-FFDF-9124-8F42-C455FE7CADA0 |
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treatment provided by |
Felipe |
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scientific name |
Tanaecium |
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X. Tanaecium View in CoL View at ENA clade
TAXONOMIC INFORMATION. — This clade contains a single genus, Tanaecium , with four phloem wedges in transversal section and a single species, Tanaecium tetramerum (A.H.Gentry) Zuntini & L.G.Lohmann , that lacks phloem wedges and only shows a regular phloem. Tanaecium currently includes species from seven previously recognized genera ( Table 1 View TABLE ), Arrabidaea , Ceratophytum Pittier , Pseudocatalpa A.H.Gentry , Spathicalyx J.C.Gomes, Sphingiphila A.H.Gentry , Paragonia Bureau , and Periarrabidaea A.Samp.
TOTAL NUMBER OF SPECIES IN THIS CLADE. — 21 species ( Frazão & Lohmann 2019).
STUDIED SPECIES. — Three species, Tanaecium bilabiatum (Sprague) L.G.Lohmann , T. pyramidatum (Rich.) L.G.Lohmann , and T. tetramerum (A.H. Gentry) Zuntini & L.G.Lohmann.
Regular phloem
Thin to thick fiber bands, assemblages generally present ( Fig. 13A View FIG ), but absent in T. tetramerum . Exclusively thin fiber bands occur in Tanaecium bilabiatum and T. tetramerum ( Fig. 13D View FIG ).
Variant phloem
General configuration. Semi-fibrous ( Fig. 13B, C View FIG ) to fibrous, with semi-fibrous species ( Tanaecium pyramidatum ) exhibiting fiber bands alternating with 4-8 rows of sieve elements and phloem parenchyma ( Fig. 13B, C View FIG ), and fibrous species ( Tanaecium bilabiatum ) showing a matrix of fibers that intermingle all other cells. The axial elements exhibit a diffuse to tangential arrangement ( Fig. 13B, C View FIG ).
Sieve-tube elements. As seen in transversal section, each sieve element is associated with 1-2 companion cells ( Fig. 13C View FIG ). The sieve elements are generally solitary or in multiples of 2-3 cells ( Fig. 13C View FIG ). As seen in tangential section, the sieve elements are short (<1 mm) and their end walls are inclined, bearing compound sieve plates with 16-18 sieve areas.
Axial parenchyma. The phloem parenchyma is sieve-tube-centric incomplete. In Tanaecium pyramidatum , the phloem parenchyma is much more abundant, also forming radial rows ( Fig. 13B, C View FIG ) that may be lignified in some portions ( Fig. 13B, C View FIG ), completely lignified in the nonconducting phloem. In T. bilabiatum , incomplete tangential rows may be found near the sieve elements.
Fibers. In T. pyramidatum the fiber band has 1-2 rows of cells ( Fig. 13B, C View FIG ), while in T. bilabiatum the fibers form a matrix that intermingle all other cells.
Rays. The limiting rays are lignified to both xylem and phloem faces, with a radial row non-lignified between them. The wedge rays have randomly alternating portions lignified and non-lignified ( Fig. 13B View FIG ).
Crystals. Absent.
Periderm
A single periderm is formed. The phellem is stratified in Tanaecium pyramidatum and T. tetramerum , non-stratified and thin-walled in T. bilabiatum ( Table 2 View TABLE ). The phelloderm is thick, with over three layers of cells, non-stratified. Lenticels were only observed in T. pyramidatum , non-stratified, with lignified filling cells ( Table 2 View TABLE ).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.