Stizophyllum

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 : 179-180

II. Stizophyllum clade

TAXONOMIC INFORMATION. — This clade contains a single genus, Stizophyllum , with four phloem wedges in transversal section ( Fig. 4A ).

TOTAL NUMBER OF SPECIES IN THIS CLADE. — Three species ( Lohmann & Taylor 2014).

STUDIED SPECIES. — Three species, Stizophyllum inaequilaterum Bureau & K.Schum. , S. perforatum (Cham.) Miers , and S. riparium (Kunth) Sandwith.

Regular phloem

Thick fiber bands ( Fig. 8B ), assemblages present ( Fig. 8C ).

Variant phloem

General configuration. Fibrous phloem ( Fig. 8A, D ), with some non-fibrous, parenchyma bands in alternation ( Fig. 8A, D ). Axial elements with either a tangential ( Fig. 8A ) or a radial arrangement ( Fig. 8D ).

Sieve tube elements. As seen in transverse section, each sieve element is associated with 1-3 companion cells ( Fig. 8E ), lying on the same corner of the sieve tube ( Fig. 8E ). The sieve elements are generally arranged in multiples of 2-3 in a radial or tangential disposition, sometimes in clusters ( Fig. 8E ). Sieve tubes of narrower radial diameter can be found associated with a parenchyma band ( Fig. 8D ). Such sieve tubes are found in radial multiples of 2-4 cells. As seen in longitudinal section, the sieve elements are thinner than 1 mm, with end walls inclined, bearing sieve plates with 6-10 sieve areas ( Fig. 8F ). Ray sieve-tube elements are common ( Fig. 8F ).

Axial parenchyma. The phloem parenchyma is sieve-tube-centric incomplete ( Fig. 8D, E ), not surrounding the entire sieve tube or sieve tube group, and commonly lignified ( Fig. 8E ). A parenchyma band of 3-4 rows of cells is present ( Fig. 8A, D ) associated with narrower sieve elements. In addition, radial rows of axial parenchyma cells are present in some places, sometimes entirely lignified

Fibers. Fibers form a matrix where all other cells can be found ( Fig. 8A, D, E ).

Rays. The limiting rays are lignified to both xylem and phloem sides, with a radial row of non-lignified cells between them ( Fig. 8A ). The wedge rays have randomly alternating portions that can be lignified or non-lignified ( Fig. 8D, E ).

Crystals. Acicular crystals are present in most of the phloem and ray parenchyma cells.

Periderm

Only one periderm is present. The phellem is stratified, composed of thin and thick-walled cells disposed in alternation. The phelloderm is thick, with more than three layers of cells, non-stratified ( Table 2 ).

Figures

FIG. 4. — Overall stem architecture of Bignoniaceae lianas: A, Stizophyllum riparium, transverse section (TS), stem with four phloem wedges. Hollow stem. Note phloem wedge with lateral steps; B, Tanaecium pyramidatum, TS, Phloem wedge devoid of lateral steps. Extremely wide rays limit the phloem wedges; C, Tynanthus cognatus, TS, Narrow lateral steps forming an almost perfect V pattern; D, Mansoa difficilis, wide steps, not forming a perfect V pattern. Scale bars: A, 0.5 cm; B, 1 mm; C, 400 μm; D, 200 μm.

FIG. 8. — Secondary phloem of Stizophyllum and Martinella: A-E, G-I, transverse sections: F, longitudinal radial section; A-F, Stizophyllum riparium; A, overall view of the phloem wedge, with a fibrous phloem, with alternating parenchymatic bands; B, regular phloem. Thick fiber bands, multisseriate rays; C, detail of the regular conducting phloem, showing narrow sieve tubes (arrowheads) and assemblages (arrow); D, variant phloem, fibrous, with sieve tubes solitary or in radial multiples, parenchyma band present; E, detail of the variant phloem. Sieve tubes with one to three companion cells, lying on the same side of the sieve tube (yellow arrowhead). Axial parenchyma sieve-tube-centric incomplete;F, heterocellular mixed rays, sieve tubes with compound sieve plates (arrowheads), radial sieve element present (arrow); G-I, Martinella obovata; G, regular phloem. Thin fiber bands, multisseriate rays; H, overall view of the phloem wedge, non-fibrous phloem; I, detail of the variant phloem. Sieve tubes solitary or in radial multiples. Fiber bands thin. Abbreviations: cz, cambial zone; fb, fiber bands; iw, interwedge;lr, limiting ray; pw, phloem wegde; rp, regular phloem; se, sieve element; x, secondary xylem.Scale bars:A, H, 1 mm; B, D, 200 μm; C, E, 50 μm; F, I, 100 μm; G, 500 μm.