Pleonotoma
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publication ID |
https://doi.org/ 10.5252/adansonia2023v45a12 |
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DOI |
https://doi.org/10.5281/zenodo.8015261 |
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persistent identifier |
https://treatment.plazi.org/id/039687DC-FFD6-912C-8F4B-C715FA12ACE0 |
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treatment provided by |
Felipe |
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scientific name |
Pleonotoma |
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IV. Pleonotoma View in CoL View at ENA clade
TAXONOMIC INFORMATION. — This clade contains a single genus, Pleonotoma , with four phloem wedges in transversal section.
TOTAL NUMBER OF SPECIES IN THIS CLADE. — 16 species ( Lohmann & Taylor 2014; Gomes et al. 2020).
STUDIED SPECIES. — Five species, Pleonotoma dendrotricha Sandwith , P. melioides (S.Moore) A.H.Gentry , P. orientalis Sandwith , P. tetraquetra (Cham.) Bureau , and P. stichadenia K.Schum.
Regular phloem
Fibers are absent, with sclereids found otherwise ( Fig. 9A View FIG ). Sclereids are arranged in clusters, differentiating close to the cambial zone ( Fig. 9A, C View FIG ). Because these sclereids have tapering ends, they are considered fibersclereids ( Fig. 9C View FIG ). Assemblages present ( Fig. 9B View FIG arrowhead).
Variant phloem
General configuration. Fibrous ( Fig. 9D View FIG ) to semi-fibrous ( Fig. 9E View FIG ), typically with one tangential row of sieve tubes surrounded by phloem parenchyma and fibers ( Fig. 9E View FIG ), presenting, therefore, a tangential arrangement ( Fig. 9E View FIG ).
Sieve-tube elements. As seen in transverse section, each sieve element is associated with 1-3 companion cells ( Fig. 9E, F View FIG ). The sieve elements are generally in multiples of two, ranging from solitary to multiples of 4-5 in a tangential arrangement ( Fig. 9E View FIG ), sometimes in clusters. Sieve elements of two distinct diameters can be found adjacent to each other ( Fig. 9E View FIG ). Sieve elements of narrower radial diameter can be, moreover, found associated with a parenchyma band.As seen in longitudinal section, the sieve elements are long (> 1 mm) and their end walls are inclined, bearing sieve plates with more than 30 sieve areas.
Axial parenchyma. The phloem parenchyma is sieve-tube-centric to sieve-tube-centric incomplete ( Fig. 9E, F View FIG ). A parenchyma band of 3-4 rows of cells is associated with narrower sieve elements.In addition, radial rows of phloem parenchyma cells are often present, sometimes lignified ( Fig. 9E View FIG ).
Fibers. Present as either fiber bands of 2-3 rows of cells ( Fig. 9E View FIG ) or as the fibers constituting the ground tissue where all other cells are embedded ( Fig. 9D View FIG ).
Rays. The limiting rays are lignified only to the xylem face ( Fig. 9E View FIG ). The wedge rays are non-lignified, even when crossing the fiber bands ( Fig. 9E, F View FIG ).
Crystals. Prismatic crystals are abundant, both in the phloem and ray parenchyma ( Fig. 9F View FIG ), and even more common in the ray cells. The number of crystals per cells is variable, ranging from a single crystal per cell that occupies almost the entire cell lumen, to many (c. eight), but much smaller crystals per cell ( Fig. 9F View FIG ).
Periderm
A single periderm formed. The phellem is stratified, composed of thin and thick-walled cells in alternation. The phelloderm is thick, with over three cell layers, non-stratified ( 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.