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Original Article • Acta Bot. Bras. 36 • 2022 • https://doi.org/10.1590/0102-33062021abb0150 linkcopy

Open-access Endemic Papilionoideae of the Caatinga: a contribution to the palynological knowledge of Leguminosae

AuthorshipSCIMAGO INSTITUTIONS RANKINGS

    ABSTRACT

    Papilionoideae is the most diverse subfamily of Leguminosae, representing approximately 39 % of its species. Although it is particularly species rich and diverse in the Caatinga, the main phytophysiognomy of the semiarid Northeast Region of Brazil, little is known about the pollen morphology of the species that occur there. This study analyzes and describes the pollen morphology of the 27 species of Papilionoideae endemic to the Caatinga. Pollen grains were acetolyzed, mounted on permanent slides, measured, described and photomicrographed using light and scanning electron microscopy (LM and SEM, respectively). The main variable morphological features were pollen grain size, shape, amb, apertural type and exine ornamentation under LM (microreticulate, reticulate, psilate or finely scabrate) and SEM (microreticulate, reticulate, rugulate, granulate, fossulate and perforate). High intergeneric morphological heterogeneity was observed while morphological variation within each genus was subtle. Nonetheless, size, endoaperture shape, fastigium presence/absence and exine ornamentation were found to be important characteristics for the identification of some species.

    Keywords: pollen morphology; semiarid; Leguminosae; LM; SEM.

    Introduction

    Leguminosae is considered the third largest family of angiosperms with 19,500 species and 770 genera currently distributed among six subfamilies: Cercidoideae, Detarioideae, Duparquetioideae, Dialioideae, Papilionoideae and Caesalpinioideae (LPWG 2013; LPWG 2017).

    Papilionoideae is the most species rich and diverse subfamily within Leguminosae with approximately 14,000 species and 500 genera distributed among 28 tribes (Lewis et al. 2005; LPWG 2017). The subfamily is distributed worldwide and includes representatives of varied habits. Flower morphology is the most specialized among Leguminosae and is mainly related to pollination by bees (Judd et al. 2009). Papilionoideae accounts for a significant portion of the taxonomic diversity of the Caatinga biome in Brazil, representing approximately 39 % of the species of Leguminosae found there (Queiroz 2009).

    The Caatinga is an exclusively Brazilian biome that covers most of the Northeast Region of the country and has a rich diversity of plants, fungi and animals (Silva et al. 2003; Forzza et al. 2010). The vegetation has peculiar characteristics that help them adapt to the physical characteristics of the environment such as high temperatures and lack of water (Costa et al. 2010). Physiognomies of the Caatinga include subshrubs, shrubs and short deciduous trees, with crooked trunks, thorns and wax, in addition to some succulent species and annual herbs (Leal et al. 2003). There is also significant flower diversity and a high number of endemic species in the biome (Giulietti et al. 2002).

    The family Leguminosae is known for its richness and diversity and is the angiosperm family with the greatest number of species in the Caatinga (Forzza et al. 2010). Papilionoideae is the most species rich subfamily of Leguminosae (Queiroz 2009), however, little is known about the pollen morphology of the endemic species of the subfamily.

    Palynological studies of legumes describe the family as generally a eurypalynous group (Salgado-Labouriau 1973; Miranda & Andrade 1990; Roubik & Moreno 1991; Silvestre-Capelato & Melhem 1997; Souza et al. 2004; 2014; Buril et al. 2011; Silva et al. 2016) and that it may provide the basis for important investigations within the area of applied palynology, thus confirming the need to better understand its morphopalynous characteristics.

    In general, the pollen grains of Papilionoideae are dispersed in monads that vary from small to large and among 3-colpate, 3-colporate or rarely porate with a microreticulate, reticulate, psilate or scabrate exine and the presence/absence of a fastigium or costa (Salgado-Labouriau 1973; Miranda & Andrade 1990; Buril et al. 2011). However, detailed palynological research is scarce for species of Leguminosae, especially those that are endemic to the Caatinga. Silva et al. (2016) analyzed and described the pollen morphology of 144 species in an area of caatinga in Canudos, state of Bahia, out of which 30 belong to Leguminosae and 11 to the subfamily Papilionoideae. Buril et al. (2011) studied palynous typification in an area of caatinga in the state of Pernambuco and provided palynological descriptions for 35 species of Papilionoideae. These authors reported that the subfamily is palynologically homogenous but pointed out some variation with respect to apertures, shape, scope and exine stratification. Nonetheless, systemic studies of endemic taxa of the Caatinga are still insufficient. Therefore, this study aimed to reduce this knowledge gap by analyzing and describing the pollen morphology of species of Papilionoideae that are endemic to the Caatinga.

    Material and Methods

    Twenty-seven species of five tribes (Brongniartieae, Crotalarieae, Dalbergieae, Phaseoleae, Sophoreae) of the subfamily Papilionoideae, family Leguminosae, considered endemic to the Caatinga by Forzza et al. (2010) were subjected to palynological analysis. Floral buds in preanthesis (from three specimens whenever possible) were acquired from the following herbaria: Universidade Federal de Feira de Santana (HUEFS), Herbário Prisco Bezerra (EAC) and Herbário RADAMBRASIL (HRB) (Tab. 1).

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    Table 1
    Specimens investigated in the morphological analysis of pollen grains of Papilionoideae (Leguminosae)

    The acetolysis method of Erdtman (1960) was used to prepare pollen grains of all species for light microscopy (LM). After chemical preparation, the pollen grains were mounted in glycerinated gelatin on slides with a coverslip, sealed with paraffin, and measured, described and photomicrographed using a Zeiss Axioskop microscope. The slides were deposited in the pollen collection of the Laboratory of Palynological Studies of Universidade do Estado Bahia, Senhor do Bonfim - BA. For analysis by scanning electron microscopy (SEM), fresh (with little polyniferous material) and acetolyzed pollen grains were rinsed in an ethanol series up to 100%, pipetted onto specimen stubs. After ethanol evaporation, the stubs were coated with gold by vacuum evaporation and photographed using either a Zeiss LEO 1430 VP microscope (SEMLab, Biological Sciences Department, Universidade Estadual de Feira de Santana) or a Jeol JSM-6390LV microscope (Instituto Gonçalo Muniz - IGM / Fiocruz, Salvador, Bahia).

    Pollen grains were described based on the glossaries of Punt et al. (2007) and Hesse et al. (2009). Measurements of the main morphometric parameters (equatorial and polar diameters) were made, whenever possible, on 25 pollen grains within eight days after mounting (Salgado-Labouriau 1973). Other parameters (diameter of apertures and thickness of exine) were measured on 10 randomly-chosen pollen grains. Quantitative data were submitted to statistical analyses adequate for the sample size. The arithmetic mean (χ), standard deviation (Sχ), standard error (σ), 95 % confidence interval (CI) and coefficient of variation (CV) were calculated for all of the diameters of the pollen grains with a sample size of 25, while only the arithmetic mean was calculated for parameters with a sample size of less than 25.

    Results

    Palynological analysis revealed morphopalynous heterogeneity to the level of genus among the studied Papilionoideae, with subtle intrageneric morphological variation (Tabs. 2, 3) (Figs. 1-5). Thus, the subfamily Papilionoideae can be considered eurypalynous, but not the genera of this study. The main variable morphological features detected among the pollen grains were related to size (small, medium and large), shape (prolate to suboblate), amb (subcircular to subtriangular), apertural type (colpi and colpori) and exine ornamentation under light microscopy (microreticulate, reticulate, psilate or finely scabrate) and under SEM (microreticulate, reticulate, rugulate, granulate, fossulate, perforate).

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    Table 2
    Morphopolinic characteristics of species of Leguminosae (Papilionoideae) endemic to the Caatinga. (S= small, M= medium, L= large, Pr= prolate, PS= prolate spheroidal, Sp= subprolate, Sb= suboblate, OS= oblate spheroidal).

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    Table 3
    Morphometric pollen data for species of Leguminosae (Papilionoideae) endemic to the Caatinga. (P= polar axis, E= equatorial axis, Epv= equatorial axis in polar view, R= range, AI= polar area index, Ecto= Length x width of the ectoaperture, Endo= Width x height of the endoaperture, SEX= sexine, NEX= nexine).

    Aeschynomene L.

    Species included: Aeschynomene carvalhoi G.P.Lewis, Aeschynomene lewisiana Afr.Fern, Aeschynomene monteiroi A.Fern. & P.Bezerra, Aeschynomene sabulicola L.P.Queiroz & D.B.O.S.Cardoso, Aeschynomene soniae G.P.Lewis (Fig. 1A-L).

    Pollen grains small, spheroidal prolate to prolate, amb predominantly subcircular; 3-colporate, ectoapertures long and narrow, endoapertures circular to lolongate (A. carvalhoi, A. monteiroi and A. soniae (Fig. 1 A-B, G-H, K-L)) or circular to lalongate (A. lewisiana and A. sabulicola). Under SEM, apertural membrane granulate with sparsely distributed granules and areolae in center of colpori in A. carvalhoi (Fig. 1B) and A. monteiroi (Fig. 1I); fastigium present in most species; exine microreticulate, reticulate in A. sabulicola and A. soniae, heterobrochate in most species; sexine predominantly thicker than nexine.

    Figure 1
    Pollen grains of species of Papilionoideae endemic to the Caatinga. A-B: Aeschynomene carvalhoi G.P.Lewis. A. Polar view; B. Equatorial view. C-D: Aeschynomene lewisiana Afr.Fern. C. Polar view; D. Equatorial view (SEM). E-F: Aeschynomene marginata var. grandiflora Benth. E. Polar view; F. Equatorial view. G-H: Aeschynomene monteroi A.Fern. & P.Bezerra. G. Polar view (SEM); H. Equatorial view (SEM). I-J: Aeschynomene sabulicola L.P.Queiroz & D.B.O.S.Cardoso. I. Equatorial view; J. Equatorial view (SEM). K-L: Aeschynomene soniae L.P.Queiroz & D.B.O.S.Cardoso. K. Polar view; L. Equatorial view. Arrow: Fastigium. Scales = 10 µm.

    Cratylia Mart. ex Benth.

    Species included: Cratylia mollis Mart. ex Benth. (Fig. 2A-B).

    Pollen grains medium in size, subprolate to prolate spheroidal, amb subtriangular; 3-colporate, ectoapertures wide, endoapertures lalongate, sometimes slightly constricted in the middle and thick on upper and lower parts. Under SEM, margins psilate; fastigium absent; exine microreticulate, heterobrochate; sexine thicker than nexine.

    Figure 2
    Pollen grains of endemic Papilionoideae of Caatinga. A-B: Cratyllia mollis Mart. ex Benth. A. Polar view (SEM); B. Equatorial view. C-D: Crotalaria bahiensis Windler & S.G.Skinner. C. Polar view (SEM); D. Equatorial view (SEM). E-F: Crotalaria brachycarpa Benth. E. Polar view; F. Equatorial view (SEM). G-H: Crotalaria harleyi Windler & S.G. Skinner. G. Equatorial view; H. Equatorial view (SEM). I-J: Crotalaria holosericea Nees & Mart. I. Polar view; J. Equatorial view. K-L: Dioclea grandiflora Mart. ex Benth. K. Polar view; L. Equatorial view. Scales = 10 µm.

    Crotalaria L.

    Species included: Crotalaria bahiensis Windler & S.G.Skinner, Crotalaria brachycarpa Benth., Crotalaria harleyi Windler & S.G. Skinner., Crotalaria holosericea Nees & Mart. (Fig. 2C-J).

    Pollen grains medium in size, subprolate to prolate, amb subcircular; 3-colporate, ectoapertures long, narrow, sometimes constricted in the middle, endoapertures lalongate rectangular (C. harleyi and C. holosericea), lolongate (difficult to observe in C. brachycarpa). Under SEM, apertural membrane finely granular in C. brachycarpa and C. harleyi; fastigium present in most species; exine microreticulate, heterobrochate; sexine thicker than nexine, maybe equally thick in C. harleyi.

    Dioclea Kunth

    Species included: Dioclea grandiflora Mart. ex Benth., Dioclea marginata Benth. (Figs. 2K-L, 3A-C).

    Pollen grains large, suboblate in one specimen of D. grandiflora, amb subcircular; 3-colporate, ectoapertures long with fine, narrow extremities, endoapertures lalongate with a slight middle constriction in D. grandiflora (Fig. 2L); lens-shaped structure that is resistant to acetolysis is present beneath the apertures of the pollen grains (Fig. 3B). Under SEM, margins finely fossulate, fastigium absent; exine psilate under LM and SEM; sexine thicker than nexine; visibly long and fine columella in D. marginata.

    Figure 3
    Pollen grains of species of Papilionoideae endemic to the Caatinga. A-C: Dioclea marginata Benth. A. Polar view (SEM); B. Lens-shaped structure, in polar view; C. Equatorial view. D-E: Discolobium hirtum Benth. D. Polar view; E. Equatorial view. F-H: Galactia remansoana Harms. F. Polar view (SEM); G. Equatorial view (SEM); H. Equatorial view. I-J: Harpalyce riparia São-Mateus, L.P.Queiroz & D.B.O.S.Cardoso. I. Equatorial view; J. Polar view. K-L: Luetzelburgia auriculata (Allemão) Ducke. K. Equatorial view, pollen grain 3-aperturate; L. Equatorial view. pollen grain 4-aperturate. Scales = 10 µm.

    Discolobium Benth.

    Species included: Discolobium hirtum Benth. (Fig. 3D-E).

    Pollen grains medium in size, oblate spheroidal, amb subcircular; 3-colporate, ectoapertures long and very narrow, endoapertures fused laterally forming endocingulum; fastigium absent; exine microreticulate-rugulate under LM and SEM; sexine thicker than nexine.

    Galactia P.Browne

    Species included: Galactia remansoana Harms (Fig. 3F-H).

    Pollen grains medium in size, spheroidal prolate to subprolate, amb (sub)triangular; 3-colporate, ectoapertures long, large, endoapertures lalongate. Under SEM, margins psilate, rare granules on apertural membrane; fastigium absent; exine reticulate, heterobrochate.

    Harpalyce MOc. & Sessé ex DC.

    Species included: Harpalyce riparia São-Mateus, L.P.Queiroz & D.B.O.S.Cardoso (Fig. 3I-J).

    Pollen grains large, prolate, amb subtriangular; 3-colpate, colpi long, large, with fine extremities; exine finely microreticulate, heterobrochate; sexine thicker than nexine; visibly long and fine columella.

    Luetzelburgia Harms

    Species included: Luetzelburgia auriculata (Allemão) Ducke, Luetzelburgia bahiensis Yakovlev. (Figs. 3K-L, 4A-B).

    Pollen grains medium in size, subprolate to spheroidal prolate, amb subcircular; 3-colporate (3-(4)colporate in L. auriculata), ectoapertures long, constricted in the middle (L. bahiensis), endoapertures lalongate (difficult to observe in L. bahiensis). Under SEM, apertural membrane finely granular, with sparse granules, and presence of rugulae in the central area of the colporus of L. auriculata; exine microreticulate, heterobrochate; sexine slightly thicker than nexine.

    Figure 4
    Pollen grains of species of Papilionoideae endemic to the Caatinga. A-B: Luetzelburgia bahiensis Yakovlev. A. Polar view; B. Equatorial view. C-D: Platymiscium pubescens subsp. zehntneri (Harms) Klitgaard. C. Polar view; D. Equatorial view. E-F: Poecilanthe ulei (Harms) Arroyo & Rudd. E. Polar view (SEM); F. Equatorial view. G-H: Pterocarpus ternatus Rizzini. G. General view (SEM); H. Equatorial view. I-J: Pterocarpus villosus (Mart. ex Benth.) Benth. I. Polar view (SEM); J. Equatorial view (SEM). K-L: Pterocarpus zehntneri Harms. K. Polar view; L. Equatorial view (SEM). Scales = 10 µm.

    Platymiscium Vogel

    Species included: Platymiscium pubescens subsp. zehntneri (Harms) Klitgaard. (Fig. 4C-D).

    Pollen grains small, prolate spheroidal, amb subcircular; 3-colporate, ectoapertures long and very narrow, endoapertures lalongate, rectangular to ovalate with middle constriction, fastigium present; exine finely microreticulate; sexine thicker than nexine.

    Poecilanthe Benth.

    Species included: Poecilanthe ulei (Harms) Arroyo & Rudd (Fig. 4E-F).

    Pollen grains small, subprolate, amb subtriangular; 3-colpate, slightly constricted in the middle; exine microreticulate, heterobrochate. Under SEM, exine fossulate-perforate; sexine thick as nexine.

    Pterocarpus Jacq.

    Species included: Pterocarpus ternatus Rizzini, Pterocarpus villosus (Mart. ex Benth.) Benth., Pterocarpus zehntneri Harms (Fig. 4G-L).

    Pollen grains small, subprolate to prolate, amb subcircular, subtriangular in P. ternatus; 3-colporate, ectoapertures long, with irregular outline in P. ternatus, constricted in the middle in P. zehntneri; endoapertures circular (difficult to observe in P. ternatus) circular to lolongate in P. villosus, circular to lalongate in P. zehntneri; fastigium present in P. zehntneri; exine microreticulate; exine in apertural area with same ornamentation as mesocolpium in P. villosus and P. zehntneri, whereas rugulate near the ectoapertures and microreticulate heterobrochate in the mesocolpium in P. ternatus; sexine thicker than nexine, but equally thick in P. villosus.

    Stylosanthes Sw.

    Species included: Stylosanthes seabrana B.L.Maass & 't Mannetje (Fig. 5A-B).

    Pollen grains medium in size, prolate, amb subcircular; 3-syncolpate, colpi long and narrow, finely microreticulate apertural membrane present. Under SEM, apertural membrane with irregular pattern; exine reticulate, heterobrochate; sexine thicker than nexine.

    Figure 5
    Pollen grains of species of Papilionoideae endemic to the Caatinga. A-B: Stylosanthes seabrana B.L.Maass & 't Mannetje. A. General view (SEM); B. Equatorial view. C-F: Zornia echinocarpa (Moric.) Benth. C. Polar view; D. General view (SEM); E. Equatorial view; F. Equatorial view (SEM). G-H: Zornia gardneriana Moric. G. Polar view; H. Equatorial view. I-J: Zornia harmsiana Standl. I. Polar view; J. Equatorial view. K-L: Zornia tenuifolia Moric. K. Polar view; L. Equatorial view. Scales = 10 µm.

    Zornia J.F.Gmel.

    Species included: Zornia echinocarpa (Moric. ex Meisn.) Benth., Zornia gardneriana Moric., Zornia harmsiana Standl., Zornia tenuifolia Moric. (Fig. 5C-L).

    Pollen grains small and medium in size, subprolate to spheroidal prolate, amb circular, subcircular in Z. echinocarpa and Z. tenuifolia; 3-colpate, colpi long and large with fine extremities, margins finely scabrate, apertural membrane granulate-scabrate, however, the margins in Z. echinocarpa are finely rugulate and the apertural membranes are with conspicuous rugulae, with lateral fusions mainly in the central areas and sparse granules in the peripheral areas; exine microreticulate, heterobrochate with smaller lumina around the apertures in Z. gardneriana and Z. harmsiana, and exine reticulate, heterobrochate, also with reduced lumina around the apertures in Z. echinocarpa and Z. harmsiana. Under SEM, exine microreticulate or reticulate; sexine thicker than nexine.

    Discussion

    The palynological characteristics of the analyzed species of the genus Aeschynomene were homogeneous. However, the species, A. sabulicola and A. soniae can be separated from the others due to their possessing a reticulate exine. In general, the species of Aeschynomene endemic to the Caatinga exhibited morphopalynous characteristics similar to those reported in the literature for other species of the genus regarding size, aperture and exine stratification (Salgado-Labouriau 1973; Carreira et al. 1996; Buril et al. 2011; Silva et al. 2016). However, with the exception of Buril et al. (2011), other authors did not mention the presence of a fastigium for species of this genus.

    The results here for Cratyllia mollis pollen grains were similar to those of Carreira et al. (1996) for C. argentea, differing only with regards to the amb, which they described as triangular. Miranda & Andrade (1990) also investigated species of Cratyllia and registered the presence of a psilate exine. Silva et al. (2016) studied the pollen of species that occur in the vegetation of Canudos, Bahia, and described Cratyllia mollis, which was corroborated by the present study.

    Pollen grains of the genus Crotalaria, characterized as medium-sized 3-colporate, were relatively homogeneous, making it difficult to delimit species. However, C. bahiensis, C. harleyi and C. holosericea diverged from the others due to the presence of a fastigium, and C. brachycarpa due to a reticulate exine. The results obtained here for Crotalaria are generally in accordance with the literature for other species of the genus (Salgado-Labouriau 1973; Carreira et al. 1996; Melhem et al. 2003; Silva et al. 2010; Buril et al. 2011; Mouga & Dec 2012). However, Silva et al. (2010) described the exine of C. micans as perforated and Melhem et al. (2003) described the pollen grains of C. bracystachia as having a margin.

    The pollen grains of Dioclea were large and with the sexine being twice as thick as the nexine. The results for Dioclea grandiflora were very similar to those found by Miranda & Andrade (1990) and Buril et al. (2011) for the same species. However, Miranda & Andrade (1990) considered the exine ornamentation as granular or psilate, whereas the present study found it psilate or finely scabrate. There are no descriptions in the literature of the pollen grains of D. marginata, but here they were found to be very similar to those of D. grandiflora.

    The pollen grains of Discolobium hirtum had general similarities with the other genera with regards to size and exine ornamentation. Given that no palynological reports were found in the literature for the species of this genus, the description provided here is apparentley new.

    The results for Galactia remansoana were similar to those described by Moreti et al. (2007) for Galactia glaucescens and Galactia striata, and Buril et al. (2011) also for G. striata, with respect to size, type and number of openings and pollen grain shape. The amb, described here as subtriangular, is intermediate between the as circular and triangular descriptions by Moreti et al. (2007) and Buril et al. (2011), respectively. On the other hand, the endoaperture shape described here as lalongate differs from the lolongate described for G. striata by Buril et al. (2011). The reticulate and heterobrochate results for exine ornamentation were consistent only with Buril et al. (2011), since Moreti et al. (2007) described the exine of both species studied by them as microreticulate. The presence of margins and granules on the apertural membrane was not reported by either of these studies.

    The pollen grains of Harpalyce riparia were relatively crumpled and scarce, which made it difficult to make measurements and describe them. However, it was possible to recognize some characteristics similar to those found by Salgado-Labouriau (1973) and Lozano-Garcia (1979) for H. brasiliana and H. aboresencens, respectively, differing only in size, which, in this study, was slightly larger.

    The two species of Luetzelburgia analyzed here were homogeneous; however, one specimen of L. auriculata had 3(4)-colporate pollen grains, a character not observed in any other species of Papilionoideae endemic to the Caatinga. Buril et al. (2011), described the pollen grains of L. auriculata but did not mention 3(4)-colporate pollen grains.

    The pollen grains of Platymiscium pubescens subsp. zehntneri showed similar morphology to those of the genera Aeschynomene and Pterocarpus; however, P. pubescens subsp. zehntneri could be separated by the presence of a very conspicuous fastigium, which was not evidenced by other authors who studied species of this genus. In general, the characteristics observed in here have also been reported for other species of the genus with respect to size, apertural type and exine stratification (Barth 1964; Roubik & Moreno 1991; Jiménez-B 1996; Klitgaard 2005). Nevertheless, Klitgaard (2005) described the presence of an operculum in pollen grains of P. floribundum var. floribundum, P. lasiocarpum, and P. stipulare, which was not evidenced in the present investigation.

    Poecilanthe ulei had pollen grains that followed the general pattern for Papilionoideae - small, 3-aperturate with a microreticulate exine. The characters found here for P. ulei were very similar to the description of Souza et al. (2014).

    The pollen grains of Stylosanthes seabrana had characteristics similar to those of species of the genus Zornia. Nevertheless, S. seabrana could be differentiated by the union of the colpi at their ends (syncolpate), which was not observed in Zornia. The results found here for S. seabrana were similar to those found by Silvestre-Capelato & Melhem (1997) for S. guianensis and S. viscosa, Carreira et al. (1996) for S. hispida and Carreira & Barth (2003) for S. humilis. However, there were some disagreements with Silva et al. (2016), who considered the pollen grains of S. seabrana to be 3-colporate with circular endoapertures.

    The pollen grains of the species of Zornia analyzed here were very similar; however, Z. harmsiana and Z. gardneriana could be separated from the others by their small size and the latter also by exine ornamentation (homobrochate microrreticulate). The results found in the present work were in agreement with those of Silva et al. (2016) for Z. echinocarpa. However, that study analyzed pollen grains of Z. brasiliensis and Z. sericea and described them as 3-colporate, which was not observed for any of the species of the genus analyzed here.

    In general, the pollen grains of species of Papilionoideae endemic to the Caatinga were small, spheroidal prolate to subprolate with subcircular to subtriangular amb, 3-colporate or 3-colpate and microreticulate or reticulate. These results were consistent with those found in the literature (Fergusson & Skvarla 1988; Silvestre-Capelato & Melhem 1997; Buril et al. 2011).

    The results reported here corroborate the eurypalynous character of Papilionoideae as indicated by previous studies with representatives of the group (Barth 1964; Salgado-Labouriau 1973; Sowunmi 1973; Miranda & Andrade 1990; Roubik & Moreno 1991; Silvestre-Capelato & Melhem 1997; Buril et al. 2011; Silva et al. 2016). However, some genera were homogeneous, making it difficult to identify species from palynological analysis alone. On the other hand, pollen grain size, endoaperture shape, fastigium presence/absence and exine ornamentation were found to be important characteristics for the identification of some species.

    Acknowledgements

    We thank: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES for granting a scholarship to the first author; herbaria EAC, HUEFS and HRB for providing palynological material; and Instituto Gonçalo Muniz - IGM / Fiocruz and the State University of Feira de Santana (UEFS) for making scanning electron microscopes available to obtain electrophotomicrographs.

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    Publication Dates

    • Publication in this collection
      29 Apr 2022
    • Date of issue
      2022

    History

    • Received
      10 May 2021
    • Accepted
      29 Nov 2021
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