Adenocalymma

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 : 195-196

XV. Adenocalymma clade

TAXONOMIC INFORMATION. — This clade contains a single genus, Adenocalymma , with four to multiples of four phloem wedges in transversal section. In the most recent circumscription of the genus ( Fonseca & Lohmann 2019), Adenocalymma houses four genera recognized in previous classification systems (see Fischer et al. 2004; Table 1 ), Adenocalymma , Gardnerodoxa Sandwith , Memora , and Neojobertia Baill.

TOTAL NUMBER OF SPECIES IN THIS CLADE. — 76 species ( Fonseca & Lohmann 2019).

STUDIED SPECIES. — 13 species, Adenocalymma adenophorum (Sandwith) L.G.Lohmann , A. alboaurantiacum (Faria & Proença) L.H.Fonseca & L.G. Lohmann , A. bracteatum (Cham.) DC. , A. acutissimum (Cham.) Miers. , A. divaricatum Miers. , A. flaviflorum (Miq.) L.G.Lohmann , A. longilineum (A. Samp.) L.G.Lohmann , A. mirabilis (Sandiwth) L.H.Fonseca & L.G.Lohmann , A. nodosum (Silva Manso) L.G.Lohmann , A. peregrinum (Miers.) L.G.Lohmann , A. salmoneum J.C.Gomes , A. tanaeciicarpum (A.H.Gentry) L.G.Lohmann , and A. validum (K.Schum.) L.G.Lohmann.

Regular phloem

Thin to thick fiber bands ( Fig. 17A , 18A ), assemblages absent or present (present in Adenocalymma bracteatum , A. divaricatum , A. salmoneum , and A. validum ).

Variant phloem

The variant phloem of Adenocalymma is by far the most diverse in Bignonieae . In fact, besides from the wedge number, either four or in multiples of four, Adenocalymma species can range from non-fibrous, semi-fibrous ( Fig. 17B ) to fibrous, with axial elements ranging from radially to tangentially arranged, sometimes with radial groups of 2-3 sieve tiubes ( Fig. 17B ), sometimes in clusters. Given the high diversity of the secondary phloem of Adenocalymma , we here divide them in three distinct groups based on their phloem structures.

Group 1: Non-fibrous Adenocalymma

Six of the analyzed species were included in this group: Adenocalymma adenophorum , A. bracteatum , A. flaviflorum , A. longilineum , A. nodosum , and A. peregrinum .

General configuration. Non-fibrous ( Fig. 18B ), with approximately 7-13 rows of sieve tubes and phloem parenchyma between fiber bands. The axial elements present a radial to diffuse arrangement.

Sieve-tube elements. As seen in transverse section, each sieve element is associated with 2 companion cells, one at each corner of the sieve element ( Fig. 18C ). The sieve elements are generally in multiples of 2-3, sometimes solitary ( Fig. 18C ). Sieve tubes of narrower radial diameter are present in A. nodosum associated with a tangential parenchyma band. As seen in longitudinal section, the sieve elements are short (<1 mm) and their end walls are inclined, bearing sieve plates with 7-14 sieve areas.

Axial parenchyma. The phloem parenchyma intermingles all other cells ( Fig. 18B, C ), and form radial rows of 3-5 cells at certain portions. A tangential band is also present in Adenocalymma nodosum .

Fibers. Fiber bands of 2-5 rows of cells are present ( Fig. 18B ).

Rays. The limiting rays are lignified only to the xylem face. The wedge rays are non-lignified, except when crossing the fiber bands ( Fig. 18B ) and except in A. longilineum , which present portions of the rays lignified even when not touching the fiber bands.

Crystals. Crystals are absent in Adenocalymma peregrinum . Prismatic crystals are present in A. adenophorum , A. flaviflorum , A. longilineum and A. nodosum , being restricted to the ray cells crossing the fiber bands in A. adenophorum and A. flaviflorum and being scattered and rare in phloem and ray parenchyma cells of A. nodosum .

Group 2: Semi-fibrous Adenocalymma

Three of the analyzed species were included in this group: Adenocalymma comosum , A. mirabilis , and A. salmoneum .

General configuration. Semi-fibrous ( Fig. 17B, C , 18E ), exhibiting wavy fiber bands ( Fig. 17B , 18E ). The axial elements show a tangential arrangement ( Fig. 18E ).

Sieve-tube elements. As seen in transverse section, each sieve element is associated with one companion cell. The sieve elements are generally in multiples of 2-3 ( Fig. 17B ), rarely solitary, with sieve elements in both radial and tangential rows, sometimes in clusters ( Fig. 18E ). As seen in longitudinal section, the sieve elements are short (<1 mm) and their end walls are inclined, bearing sieve plates with 7-12 sieve areas.

Axial parenchyma. The phloem parenchyma forms the background tissue ( Fig. 17B ), it is complete in A. salmoneum ,

and without this arrangement in A. comosum . In addition, radial rows of 4-7 cells of phloem parenchyma are present in some places.

Fibers. Fiber bands wavy, in some portions thicker than in others ( Fig. 17B, C , 18E ).

Rays. The limiting rays are lignified only to the xylem face. The wedge rays can be non-lignified or lignified, especially when crossing the fiber bands ( Fig. 17B, C , 18E ).

Crystals. Crystals are very abundant, being styloid and acicular in A. comosum , prismatic to styloid in A. mirabile ( Fig. 17C ), prismatic in A. salmoneum , and prismatic and acicular in A. validum .

Group 3: Fibrous Adenocalymma

Three of the analyzed species were included in this group: Adenocalymma alboaurantiacum , A. divaricatum , and A. validum .

General configuration. Fibrous ( Fig. 18D, F, G ), presenting a matrix of fibers in which all other cells are embedded ( Fig. 18D, F, G ). The axial elements show a tangential arrangement ( Fig. 18D, F ).

Sieve-tube elements. As seen in transverse section, each sieve element is associated with one companion cell, sometimes two in A. validum , one in each corner of the sieve element. The sieve elements occur in multiples of 2-3, sometimes solitary ( Fig. 18F ). As seen in longitudinal section, the sieve elements are short (<1 mm) and their end walls are inclined, bearing sieve plates with 7-10 sieve areas. Reticulated sieve plates are present in A. divaricatum .

Axial parenchyma. The phloem parenchyma is sieve-tube-centric incomplete in A. validum , complete in A. alboaurantiacum ( Fig. 18F ), and A. divaricatum . Radial rows of phloem parenchyma can be also detected alternating with sieve elements and near the ray cells.

Fibers. A matrix of fibers is present ( Fig. 18D, F, G ). Fibers are more abundant in A. divaricatum ( Fig. 18D ) than in the other species studied.

Rays. The limiting rays are lignified only to the xylem face, but with some portions lignified also to the phloem face ( Fig. 18D ). The wedge rays have randomly alternating portions lignified and non-lignified ( Fig. 18D ).

Crystals. All species in this group present crystals in the ray cells ( Fig. 18F, G ). They are prismatic in A. divaricatum , prismatic in A. salmoneum , and prismatic and acicular in A. validum ( Fig. 18F, G ).

Periderm

A single periderm is formed ( Fig. 17A ) in all species, except for Adenocalymma flaviflorum , which also forms a rhytidome. The phellem can be non-stratified and evenly thin-walled in A. bracteatum and A. flaviflorum or non-stratified and evenly thick-walled in A. comosum , A. divaricatum , A. peregrinum , and A. salmoneum ( Table 2 ). The phellem is stratified in A. mirabile and A. validum , with alternating thin and thick-walled cells ( Fig.17A ). In Adenocalymma validum , there is also an alternation of cells with dark content and cells without any conspicuous content. The phelloderm is non-stratified ( Fig. 17A ), thin in A. comosum and A. peregrinum , or thick-walled, in A. bracteatum , A. divaricatum , A. flaviflorum , A. mirabile , A. salmoneum , and A. validum ( Table 2 ). Lenticels are stratified in Adenocalymma comosum , A. peregrinum , A. salmoneum , and A. validum and non-stratified, with unlignified filling tissue in A. flaviflorum ( Table 2 ). Lenticels were not observed in A. mirabile .

Figures

FIG. 17. — Secondary phloem of Adenocalymma mirabile: A-C, Adenocalymma mirabile transverse-sections; A, regular phloem. Thin to thick fiber bands. Periderm with stratified phellem, with alternating thin and thick-walled, lignified cells. Phelloderm thick, with over 3 cell layers; B, overall view of the variant phloem. Non-fibrous to semi-fibrous phloem. Fiber bands thin to thick, U-shaped in several portions. Limiting ray lignified to both xylem and phloem face; C, detail of the variant phloem. Rays alternate in being lignified or not. Prismatic crystals present in rays (arrowheads). Sieve tubes in short radial or tangential multiples. Abbreviations: pe, periderm; x, secondary xylem. Scale bars: A, C, 200 μm; B, 300 μm.

FIG. 18. — Secondary phloem of Adenocalymma: A-G, transverse sections; A, Adenocalymma bracteatum, thin fiber bands. Single periderm with a thin-walled phellem,and a thick-walled phelloderm; B, Adenocalymma flaviflorum variant phloem.Non-fibrous,sieve tubes in radial multiples of 2 till 5 cells.Rays lignify when crossing the fiber bands; C, Detail of the variant phloem of Adenocalymma flaviflorum. Sieve tubes typically with two companion cells, each lying on a different corner.Axial parenchyma as the background tissue; D, Adenocalymma divaricatum variant phloem.Fibrous-phloem.Sieve tubes in tangential arrangement. Rays with portions lignified and non-lignified; E, Adenocalymma comosum variant phloem.Semi-fibrous phloem. U-shaped fiber bands. Sieve tubes in radial multiples of two to three cells, rarely solitary; F, G, Adenocalymma alboaurantiacum variant phloem. Fibrous-phloem. Sieve tubes with a tangential arrangement. Rays sometimes lignify when crossing the fiber bands. Axial parenchyma sieve-tube-centric. Crystals abundant; G, detail of the styloid crystals in rays (arrowhead). Prismatic crystals also present.Abbreviations:cz, cambial zone;pe, periderm;x, secondary xylem.Scale bars:A,D, 200 μm; B,E, 150 μm;C,G,50 μm;F, 100 μm.