Chamaecrista ser. Setosae (H. S. Irwin & Barneby, 1978)

Oliveira, Jaqueline Aparecida De, Mendes, Thainara Policarpo, Souza, Alessandro Oliveira De & Silva, Marcos José Da, 2021, New taxonomic circumscription to Chamaecrista ser. Setosae (H. S. Irwin & Barneby) H. S. Irwin & Barneby (Leguminosae, Caesalpinioideae), Phytotaxa 490 (2), pp. 118-158 : 120-127

Chamaecrista ser. Setosae series taxon morphology a) Habit: The species of Chamaecrista ser. Setosae are subshrub, shrub or small tree with stems little or very branched, sometimes pending and fissured.The subshrubs vary from 12 to 120 cm tall, in Ch. scabra , Ch. obtecta , Ch. ochrosperma whose are erect, poorly or unbranched ( Figs. 1D–E ), or decumbent (e.g. Ch. campicola , Fig. 1F ). Among the shrubs are Ch. auriszerdae , Ch. coradinii , Ch. orenocensis , and Ch. setosa , which grow erect with single stems up to 5 m tall ( Fig. 1A ), or in clumps, with branches pending. Small trees are represented only by individuals of Ch. multiseta and Ch. orenocensis , which can reach up to 5.5 m tall and with a stem distally pending and supported on the vegetation. In general, in these species the stem is cylindrical, brown, or sometimes purplish or vinaceous-green or yellowish with conspicuously viscous and setose young portions.

b) Indument: All species of Setosae series present secretory trichomes, setose or setulose, whose bases are enlarged, and tectors in at least one part of the plant, a character that determines the name of the series according to Irwin & Barneby (1982); the secretory have usually light or whitish colors, while the tectors can be golden (e.g. Ch. campicola ), reddish, vinaceous, ferruginous (e.g. Ch. scabra ) or blackened (e.g. Ch. multiseta ). Both types are present in the reproductive (external surface of the sepals, ovary, and fruits) and vegetatives organs, including young branches, and can be sparse (e.g. Ch. coradinii and Ch. ochrosperma ) or densely distributed (e.g. Ch. setosa , Ch. auriszerdae , Ch campicola and Ch. obtecta ). Setulose trichomes have a prolongation up to 3 times greater than the base ( Fig. 2A ), whereas in setose the prolongations can be up to 12 times greater than the base ( Fig. 2B ). Among the setulose there are still the scabrous-setulose where the extensions are perpendicular to the insertion surface ( Fig. 2D ), and among the setose the stellate-setose, whose bases are equipped with tiny tector rays ( Fig. 2C ). Tector trichomes can be pubescent, puberulent, villous and villosule ( Fig. 2E ) and, in general, occur interspersed with secretors ( Fig. 2B ). When viewed in SEM the surfaces of the trichomes are smooth (e.g. Ch. auriszerdae , Fig. 3A ), striated or papillate (e.g. Ch. setosae ( Fig. 3D and E ) and its bases can be multi or single-celled. In the series studied, the presence and density of the trichomes helps in the determination of some species.

c) Stipules: The stipules vary from 1 to 7 mm long, the smallest being found in Ch. multiseta and the largest present in Ch. scabra . Regarding the shapes, the stipules are predominantly lanceolate with an acute apex and a truncated base, they can be persistent (e.g. Ch. ochrosperma ) or caduceus (e.g. Ch. coradinii and Ch. scabra ).

d) Leaves: The leaves are paripinnate, alternate and spiral, sessile or petiolate, distributed along the branches in an orthotropic or ascending aspect and have 1 or 2, sometimes 3, pairs of leaflets. Sessile leaves were recorded only in Ch. auriszerdae ( Fig. 4B ), while the others showed petioles up to 3 cm long (e.g. Ch. coradinii [ Figs. 4A, C and D ], Ch. multiseta , Ch. obtecta , Ch. ochrosperma Ch. scabra ) or up to 7 cm long (e.g. Ch. setosa ). The petioles, are cylindrical in cross section and canaliculated above. The pulvinus and pulvinules of these leaves are transversely rugose or smooth with trichomes similar to those of the petiole. Plagiotropic leaves, that is, angled at 90° in relation to the stem occur in most species ( Fig. 4A, B, C and D ), while ascending, and in this case, at an angle equal to or less than 45°, were found in Ch. scabra and in individuals of Ch. setosa . The leaflets are predominantly coriaceous (e.g. Ch. setosa and Ch. scabra ) or sometimes papyraceous or carthaceous (e.g. Ch. multiseta and Ch. orenocensis ), have surfaces conspicuously differentiated dorsoventrally, the adaxial surface dark green and the abaxial usually opaque-green. The apexes of these leaflets are acute, obtuse, retuse or sometimes emarginated, with or without a short mucron, while its bases are always asymmetrical. The leaflets have venation pattern brochidodromous or camptodromous-brochidodromous, with midrib impressed and sulcated on the adaxial surface and prominent on the abaxial surface, secondary veins prominent on the abaxial surface, as well as tertiary and quaternary veins prominent and in a pattern aveolate on this same surface (e.g. Ch. auriszerdae , Ch. setosa ); the secondary ones are ascending in relation to the midrib (most of species) or perpendicular and anastomosing in a submarginal vein (e.g. Ch. coradinii ). Leaf characteristics are among the most useful tools for identifying the studied species, especially in relation to the numbers, size and shapes of the leaflets. Regarding the numbers of the leaflets, most species have two pairs of leaflets that can be isomorphic (e.g. Ch setosa , Ch. auriszerdae , Ch. multiseta , Ch. ochrosperma , Ch. campicola , Fig. 4A and D ) or heteromorphic (e.g. Ch. obtecta ), where the proximal pair is reniform and two or three times smaller than the distal pair, which is suborbicular, ( Fig. 4C ). Chamaecrista scabra and Ch. auriszerdae have leaves with only one pair of leaflets ( Fig. 4B ), while C. coradinii has 2 or 3 pairs. As for the shapes of the leaflets are oblong-elliptical, elliptical (e.g. Ch. campicola , Ch. setosa ), suborbicular (e.g. Ch. auriszerdae and Ch. setosa ) or oblong-lanceolate (e.g. C. orenocensis ), or combinations thereof, in some cases in a single individual.

e) Inflorescences: The inflorescences are racemose or panicle, axillary or terminal. The panicle has two or more developed lateral branches (e.g. C. setosa , Fig. 5A ) and spaced from each other, or an “thyrsoid” aspect where the main axis has active buds that originate short and racemose branches (e.g. Ch auriszerdae and Ch. obtecta , Fig. 5B ). The racemes are usually solitary with flowers regularly distributed (e.g. Ch. ochrosperma , Ch. scabra and Ch. campicola , Fig. 5C ), or in cluster up to 4, and in this case, in a paniculiform aspect, as also found in Ch. scabra . The inflorescences can be lax or congested ( Ch. auriszerdae ), erect (e.g. Ch. auriszerdae , Fig. 5E ) or pendant (e.g. Ch. setosa , Ch. coradinii and Ch. multiseta , Fig. 5A and D ) and vary from 3.8 to 75 cm long, the smallest sizes (3.8–14 cm) being found in Ch. auriszerdae and Ch. orenocensis and the largest (75 cm) in Ch. setosa . They have tectors (e.g. Ch. coradinii ), glandular (e.g. Ch. ochrosperma , Ch. campicola , Ch. obtecta ) or mixed trichomes ( Ch. auriszerdae , Ch. scabra , Ch. orenocensis ) with green colors ( Fig. 5B, E ) or vinaceous such as in Ch. setosa and Ch. campicola , Fig. 5A, C, D ).

f) Bracts and bracteoles: Bracts are solitary at the base of the pedicel while the bracteoles are alternate or opposite and occur in pairs from half to the upper third of them. Both are persistent linear or lanceolate, membranaceous, setulose, puberulent or pubescent externally. Bracts vary from 1 to 8 mm long and bracteoles from 0.9 to 4 mm long. Bracts are lanceolate, linear, deltoid, subulate or rarely triangular, have apex obtuse or acute, entire margin, and are green-yellowish or yellowish, caduceus or persistent while bracteoles are lanceolate, deltoid, oval, subulate or ovallanceolate, acute or obtuse at apex, entire margin, light green or yellowish, rare ciliate, caduceus or persistent, yellow or green with vinaceous pigmentation and obtuse apex.

g) Buds and Flowers: The buds can be globose, ovoid, ellipsoid, orbicular with an acute apex, obtuse or acuminate, yellow (e.g. Ch. obtecta and Ch. coradinii , Fig. 6A and C ) or externally vinaceous or reddish (e.g. Ch. setosa , Fig. 6B ). The flowers are 5-merous, bisexual, dichlamydeous, heterochlamydeous, asymmetrical, dialissepalous and dialipetalous. The sepals are membranaceous, equal in size, yellow, light green or vinaceous, glabrous internally and setulose, puberulent, stellate-setulose, puberulent or glabrous externally with oblong, oval-lanceolate, oval-elliptical shapes, truncate base and apex acute or acuminate (e.g. Ch. coradinii , Fig. 6C ). The corolla is yellow, light or dark, delicately membranous, nerved and have the following composition: one adaxial petal, two upper-lateral and two lower-lateral, one of the latter asymmetrical and generally involving the reproductive system ( Fig. 6D ) except in Ch. auriszerdae whose all petals are equal ( Fig. 6E ). The petals are predominantly oboval or largely oboval, with the exception of one of the lower-lateral which is asymmetrical and falcate. The androecium is actinomorphic, composed of 10 free isomorphic stamens, with erect, basifixed anthers, laterally pubescent in the sutures, larger than the filaments, with two apical pores and mucronulate at apex. The ovary is superior, oblongoid, setulose, pubescent or puberulent with style glabrous or indumented, cylindrical and distally curved.

h) Fruits and seeds: The fruits are flat compressed, slightly elevated in the region of the seeds, elastically dehiscent and oblong. They have colors light green ( Fig. 6H ) with reddish spots, and reddish-brown ( Fig. 6G ) or ferruginous when mature, and are recovered by trichomes pubescent ( Fig. 6G ), hispid-setose ( Fig. 6F ) or puberulent ( Fig. 6H ). The seeds are oblong, orbicular or rhombic, with a smooth or slightly faveolated surface, possess colors light brown or dark and measure 3–7 mm long.

Figures

FIGURE 1: Growth patterns of shrubs and subshrubs of Chamaecrista ser. Setosae. A. Ch. setosa—shrub erect; B. Ch. setosa—subshrub erect; C. Ch. coradinii—shrub erect and branched; D. Ch. auriszerdae and E. Ch. obtecta—subshrub erect and little or unbranched; F. Ch. campicola—subshrub decumbent.

FIGURE 2: Scanning Electron Microscopy (SEM) of the types of trichomes present in the species studied. A. Setulose with base multicellular located on the adaxial surface of the leaflet in Chamaecrista auriszerdae; B. Setose in inflorescence of Ch. obtecta; C. Stellate-setulose in Ch. obtecta; D. Scabrous-setulose on the adaxial surface of the leaflet in Ch. scabra; E. Puberulent on the adaxial surface in Ch. setosa. Scale bar = 1 mm.

FIGURE 3: Scanning electron microscopy (SEM) showing the aspects of the trichomes present in the species studied. A. Chamaecrista auriszerdae—glandular in the axes of inflorescence with surface smooth, glabrous and base multicellular; B. Ch. setosa and C. Ch. auriszerdae—tectors on the adaxial face of the leaflets with apex acute; D. Ch. scabra—trichomes of inflorescence with surface striated; E. Ch. setosa—glandular trichomes in the inflorescence. Scale bar = 1 mm.

FIGURE 4: Leaves and leaflets pattern. A. Chamaecrista coradinii with leaves petiolated and orthotropic; B. Ch. auriszerdae with leaves sessile and orthotropic; C. Ch. obtecta with leaflets heteromorphic; D. Ch. multiseta with leaflets isomorphic and papyraceous.

FIGURE 5: Types and aspects of inflorescences. A. and D. Chamaecrista setosa inflorescence in panicle with main axes pendent and vinaceous; B. C. obtecta inflorescence with secondary axes thyroid; C. C. campicola raceme typical and suberect; E. Ch. auriszerdae inflorescence erect and green.

FIGURE 6: Buds, flower and fruit patterns of the species studied. A. Chamaecrista obtecta with buds green and setose; B. Ch. setosa with buds vinaceous and setulose; C. Ch. coradinii with buds with apex attenuate; D. Ch. obtecta flower with petal anterolateral falcate; E. Ch. auriszerdae flower with an petals anterolateral undifferentiated and asymmetrical; Fruits in F. Ch. coradinii; G. Ch. campicola and H. Ch. auriszerdae.