Bark anatomy of lianescent Bignoniaceae: a generic synopsis Author Pace, Marcelo R. Author Marcati, Carmen R. Author Lohmann, Lúcia G. Author Angyalossy, Veronica text Adansonia 2023 3 2023-05-30 45 12 167 210 journal article 10.5252/adansonia2023v45a12 1639-4798 8006364 IV. Pleonotoma 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 ). Sclereids are arranged in clusters, differentiating close to the cambial zone ( Fig. 9A, C ). Because these sclereids have tapering ends, they are considered fibersclereids ( Fig. 9C ). Assemblages present ( Fig. 9B arrowhead). Variant phloem General configuration. Fibrous ( Fig. 9D ) to semi-fibrous ( Fig. 9E ), typically with one tangential row of sieve tubes surrounded by phloem parenchyma and fibers ( Fig. 9E ), presenting, therefore, a tangential arrangement ( Fig. 9E ). Sieve-tube elements. As seen in transverse section, each sieve element is associated with 1-3 companion cells ( Fig. 9E, F ). The sieve elements are generally in multiples of two, ranging from solitary to multiples of 4-5 in a tangential arrangement ( Fig. 9E ), sometimes in clusters. Sieve elements of two distinct diameters can be found adjacent to each other ( Fig. 9E ). 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 ). 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 ). Fibers. Present as either fiber bands of 2-3 rows of cells ( Fig. 9E ) or as the fibers constituting the ground tissue where all other cells are embedded ( Fig. 9D ). Rays. The limiting rays are lignified only to the xylem face ( Fig. 9E ). The wedge rays are non-lignified, even when crossing the fiber bands ( Fig. 9E, F ). Crystals. Prismatic crystals are abundant, both in the phloem and ray parenchyma ( Fig. 9F ), 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 ). 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 ).