Cuspidaria

Pace, Marcelo R., Marcati, Carmen R., Lohmann, Lúcia G. & Angyalossy, Veronica, 2023, Bark anatomy of lianescent Bignoniaceae: a generic synopsis, Adansonia (3) 45 (12), pp. 167-210 : 186

VIII. Cuspidaria - Tynanthus clade

TAXONOMIC INFORMATION. — This clade contains two genera, Cuspidaria and Tynanthus , both with four phloem wedges in transversal section. While the circumscription of Tynanthus has remained constant in different classification systems, Cuspidaria currently includes species from three previously recognized genera (see Fischer et al. 2004; Table 1 ), Cuspidaria, Arrabidaea , and Pyrostegia .

TOTAL NUMBER OF SPECIES IN THIS CLADE. — 35 species belonging to Cuspidaria (21) and Tynanthus (14) ( Lohmann & Taylor 2014; Medeiros & Lohmann 2015; Kaehler et al. 2019).

STUDIED SPECIES. — Four species, Cuspidaria convoluta (Vell.) A.H.Gentry , C. pulchra (Cham.) L.G.Lohmann , Tynanthus cognatus (Cham.) Miers , and T. elegans (Vell.) L.G.Lohmann.

Regular phloem

Thin to thick fiber bands, assemblages present ( Fig. 11D ). Mostly thin fiber bands in T. cognatus ( Fig. 11D ).

Variant phloem

General configuration. Fibrous ( Fig. 11 A-C, E, F), with axial elements in a tangential arrangement of one row of sieve tubes, surrounded by a sieve-tube-centric phloem parenchyma ( Fig. 11 A-C). A band of parenchyma sometimes present ( Fig. 11F ).

Sieve-tube elements. As seen in transverse section, each sieve element is associated with 2-3 (sometimes over 4) companion cells that occur at the same side of the sieve element ( Fig. 11B, E ). The sieve elements generally occur in multiples of 2-3 (up to 5) radially elongated cells ( Fig. 11B ). Solitary sieve elements are also present in Cuspidaria ( Fig. 11F ). As seen in transverse section, the sieve elements are of variable length, from 400 µm to approximately 1 mm and their end walls are inclined, bearing compound sieve plates with 12- 30 sieve areas ( Fig. 11G ).

Axial parenchyma. The phloem parenchyma is typically sieve-tube-centric, surrounding the groups of sieve elements ( Fig. 11B, C, E, F ). In Cuspidaria convoluta , lignified lines of phloem parenchyma cross the entire phloem wedge ( Fig. 11C yellow arrows); some non-lignified lines are also found occasionally in this species ( Fig. 11F ).

Fibers. Fibers are very abundant, forming background tissue ( Fig. 11 A-C, F).

Rays. The limiting rays are lignified to both xylem and phloem faces ( Fig. 11A ), with a radial row non-lignified between them. The wedge rays have randomly alternating portions lignified and non-lignified. The lignified portions never bear crystals and are differentiated very close to the cambium.

Crystals. Acicular and navicular crystals are present solely on the non-lignified portions of the phloem and ray parenchyma.

Periderm

A single periderm is 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 ). In Tynanthus the lenticels are non-stratified, with unlignified filling tissue ( Table 2 ). In Cuspidaria the lenticels are stratified, with a closing layer of lignified cells ( Table 2 ).

Figures

FIG. 11. — Secondary phloem of the Cuspidaria-Tynanthus clade: A-F, transverse sections; G, longitudinal tangential section; A, overall view of the phloem at the wedge and interwedges. Fibrous variant phloem, Tynanthus cognatus; B, detail of the variant phloem. Sieve tubes radially elongated (*), generally in tangential multiples, surrounded by sieve-tube-centric parenchyma, all embedded in a matrix of fibers. Two to four companion cells per sieve tube, lying on their corner (arrows), Tynanthus cognatus; C, Fibrous phloem. Sieve tubes (*) solitary or in tangential multiples.Sieve-tube centric parenchyma, Cuspidaria convoluta; D-F, comparison of the sieve tube dimensions on regular and variant portion of Tynanthus cognatus; D, regular phloem with thin fiber bands and assemblages (arrows); E, variant phloem. Sieve tubes with two to four (or more) companion cells, lying at the same corner of the sieve tube; F, Variant phloem of Cuspidaria convoluta. Sieve tubes (*) solitary or in multiples. Parenchyma band present (arrows); G, sieve tubes are lower than 1 mm, with inclined, compound sieve plates. Rays varying from 2 to 8-seriate. Scale bars: A, G, 200 μm; B, C, 100 μm; D-F, 50 μm.