The systematic value of pollen morphology in trees and shrubs species of Bauhinia L. (Caesalpinioideae- subg. Bauhinia - sect. Pauletia) occurring in Brazil

ARTICLES

The systematic value of pollen morphology in trees and shrubs species of Bauhinia L. (Caesalpinioideae- subg. Bauhinia - sect. Pauletia) occurring in Brazil¹

Fábio de França Moreira^I; Ângela Maria Studart da Fonseca Vaz^II; Claudia Barbieri Ferreira Mendonça^I; Vania Gonçalves-Esteves^I,*

^IUniversidade Federal do Rio de Janeiro, Museu Nacional, Rio de Janeiro, RJ, Brazil

^IIInstituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rio de Janeiro, RJ, Brazil

ABSTRACT

We analyzed the pollen grains of 30 taxa of the genus Bauhinia L., within five series: Aculeatae (9 species); Acuminatae (1 species); Cansenia (17 species); Pentandrae (2 species); and Perlebia (1 species). The pollen grains were acetolysed, after which they were photographed and analyzed under light microscopy. Non-acetolysed pollen grains were analyzed under scanning electronic microscopy. Characters such as shape, size, exine and aperture constitution were studied. The species were separated by a dichotomous key, which showed pollen grains that were classified as very large; isopolar or apolar; oblate, suboblate, oblate spheroidal or spherical; large or small in terms of the polar area; inaperturate, 3-porate or (3-7)-colpate; and microreticulate or reticulate, with or without supratectal elements (gemmae, bacula, clavae). The variation in pollen morphology confirms the eurypalynous status of the genus Bauhinia.

Key words:Bauhinia, Brazil, Leguminosae, palynology

Introduction

Bauhinia L. is a pantropical genus, a member of the subfamily Caesalpinioideae (Leguminosae), with approximately 300 species. Wunderlin et al. (1987) divided Bauhinia into 4 subgenera, 22 sections and 30 series. Six sections of three subgenera have native representatives in the neotropics: Bauhinia (sect. Bauhinia, sect. Pauletia, sect. Amaria); Elayuna (Raf.) Wunderlin, K. Larsen & S. Larsen (sect. Benthamia); and Phanera (Lour.) Wunderlin, K. Larsen & S. Larsen (sect. Schnella, sect. Caulotretus).

The infrageneric taxonomic organization of Bauhinia proposed by Wunderlin et al. (1987) consists of a group of species represented by trees, shrubs or subshrubs, multicaules, sometimes semi-scandent, although never with tendrils. The branches may have pairs of adpetiolar spines or are unarmed, and have extrafloral nectaries and well-developed intrastipular trichomes on the inner surface of the stipules. The hypanthium is short-turbinate or, in general, long and tubular, the calyx is spathaceous or irregularly adnate at the apex and opens at the base in 2-5 lobes. The fruit is woody or coriaceous and dehiscent. The taxonomic arrangement of Wunderlin et al. (1987) is used in this study.

Several investigators have examined the pollen of Bauhinia species, including Barth & Bousada (1964), Smith (1964), Palácios-Chávez (1970), Larsen (1975), Schmitz (1977), Ferguson (1986), Gamerro & Fortunato (2001) and Novaes (2005). The genus Bauhinia has pollen grains in monads, rarely in tetrads (Larsen 1975, Fergunson & Banks 1994), with a very wide range of characters such as shape, exine ornamentation, type and number of apertures; i.e., the genus is eurypalynous (Palacios-Chávez 1970; Salgado-Labouriau 1973; Ferguson 1987; Gamerro & Fortunato 2001). The study of pollen grains of Bauhinia has proved an important aid in elucidating the taxonomy of the genus, confirming the classification of the tribes (Schmitz 1973), and can also be used to help determine subgenera (Smith 1964).

Few other studies have examined the pollen grains of the species of Bauhinia, especially the native Brazilian taxa. Vaz (2001) noted that the pollen morphology is known for only a few species of section Pauletia and emphasized the need for studies on the external morphology of pollen.

In the present study, we analyzed the pollen of 30 tree and shrub species of Bauhinia, subg. Bauhinia sect. Pauletia series Aculeatae,Acuminatae,Cansenia,Pentandrae and Perlebia occurring in Brazil, in order to support an eventual revision of the genus in the neotropics. Our objective was to expand knowledge of the attributes of the pollen of this group.

Material and methods

Pollen grains of 30 Bauhinia species were examined. The samples were obtained from the anthers of flower buds of specimens held in the following Brazilian herbaria: the Herbarium of the Ecological Reserve of the Brazilian Institute of Geography and Statistics (code, IBGE); the Herbarium of the Botany Department of the National Museum in Rio de Janeiro (code, R); and the Herbarium of the Rio de Janeiro Botanical Garden (code, RB). Acronyms are according to Thiers (continuously updated).

Whenever possible, four specimens of each species were analyzed and compared in order to obtain accurate results (^{Appendix 1}). The permanent slides from this study are stored in the Álvaro Xavier Moreira Laboratory of Palynology of the Botany Department at the Federal University of Rio de Janeiro/National Museum.

Pollen grains were prepared by acetolysis with the method developed by Erdtman (1952), as modified by Melhem et al. (2003) for light microscopy. Pollen grains for scanning electron microscopy were placed on stubs covered with carbon tape and sputter-coated with gold. Samples were then examined using a scanning electron microscope (JSM-5310; JEOL, Tokyo, Japan) in the Hertha Meyer Laboratory of Cell Ultrastructure at the Biophysics Institute of the Federal University of Rio de Janeiro.

One specimen of each species was chosen for statistical treatment and illustrations, and is indicated by an asterisk (*) after the collector's name (^{Appendix 1}). Measurements in equatorial view (polar diameter and equatorial diameter) were taken for 25 pollen grains per sample. Means, standard deviations, and 95% confidence intervals (CIs) were calculated. For measurements of equatorial diameter in polar view (EDPV), apocolpium side, apertures and exine thickness, the arithmetic means of 10 measurements were used. Ten similar measurements of pollen grains were made on additional material, from another collection, to check the stability of the data (treated further as comparison material).

The number of supratectal elements was established from a 50 µm² area on the surface of the pollen in polar view.

The terminology used for pollen descriptions follows Punt et al. (2007), which takes into consideration elements of size, shape, number of apertures, and sexine ornamentation. The descriptions of the polar area and aperture size were made according to the classification system established by Faegri & Iversen (1966) for the polar area index.

Results

We evaluated the pollen of 30 tree and shrub species of Bauhinia L. sect. Pauletia, within five series:

Aculeatae-B. acreana (Fig. 1-3); B. aculeata (Fig. 4-5); B. affinis (Fig. 6-7); B. albicans (Fig. 8-12); B. catingae (Fig. 13-14); B. forficata and B. mollis (Fig. 15-17); B. ovata (Fig. 18-21); and B. platypetala (Fig. 22-24)

Acuminatae-B. acuminata (Fig. 25-27)

Cansenia-B. acuruana (Fig. 28, 29); B. angulicaulis (Fig. 30-32); B. brevipes (Fig. 33-34); B. cheilantha; B. cupulata (Fig. 35-37); B. curvula (Fig. 38-40); B. dubia (Fig. 41-44); B. dumosa (Fig. 45-48); B. goyazensis (Fig. 49); B. holophylla (Fig. 50); B. longicuspis (Fig. 51); B. longifolia (Fig. 52-55); B. membranacea (Fig. 56); B. rufa (Fig. 57-58); B. subclavata (Fig. 59-60); B. ungulata (Fig. 61-63); and B. viscidula (Fig. 64-65)

Pentandrae-B. pentandra (Fig. 66-68); and B. vespertilio (Fig. 69-73)

Perlebia-B. bauhinioides (Fig. 74-77)

 

 

 

 

 

The palynological descriptions are arranged according to the following pollen features: size; polarity; dispersal unit; shape, number, and type of apertures; and exine sculpture. The results are presented in Tab. 1-4.

 

Size and polarity

In the group evaluated, the pollen grains were classified as very large in polar view (Tab. 2): 77.5-137.5 µm in polar diameter; and 102.5-170.0 µm in equatorial diameter. Isopolar pollen grains were found in members of the series Aculeatae,Cansenia,Pentandrae, and Perlebia. Apolar pollen grains were found only in the series Acuminatae (B. acuminata).

Dispersal unit and shape

All species examined had pollen grains arranged in monads (Tab. 2). Oblate pollen grains were found in B. aculeata (ser. Aculeatae), B. acuruana,B. brevipes,B. cheilantha,B. curvula,B. longifolia,B. rufa,B. subclavata (ser. Cansenia) and B. bauhinioides (ser. Perlebia). Suboblate pollen grains were found in B. albicans,B. catingae,B. platypetala (ser. Aculeatae), B. cupulata,B. dubia,B. dumosa,B. goyazensis,B. holophylla,B. longicuspis,B. ungulata, B. viscidula (ser. Cansenia), B. pentandra and B. vespergilio (ser. Pentandrae). Oblate spheroidal pollen grains were found in B. acreana,B. affinis,B. forficata,B. mollis,B. ovata,B. platypetala (ser. Aculeatae) and B. angulicaulis (ser. Cansenia). B. acuminata (ser. Acuminatae) and B. angulicaulis (ser. Cansenia) had spheroidal and prolate spheroidal pollen grains, respectively. In B. membranacea, the form could not be established, because the pollen grains were found only in polar view.

Polar area and apertures

A small polar area was found in all species of the series Aculeatae,Pentandrae, and Perlebia, and in B. angulicaulis (ser. Cansenia). The polar area was large in most of the species of the series Cansenia (Tab. 1).

Inaperturate pollen grains were found in B. acuminata (ser. Acuminatae) (Fig. 25, 26). Aperturate pollen grains occurred as follows: 3-porate in B. cheilantha (ser. Cansenia); 3-colpate in most species of the series Cansenia; 3(4)-colpate in B. dubia (ser. Cansenia); 5-colpate in B. vespertilio (ser. Pentandrae); 4(5)-colpate in B. albicans (ser. Aculeatae) and B. bauhinioides (ser. Perlebia); 5(6)-colpate in B. pentandra (ser. Pentandrae), 6-colpate in most of the species of series Aculeatae, and 6(7)-colpate in B. mollis (ser. Aculeatae).

In the series Aculeatae, the colpi were long and covered by a thin, transparent, ornamented membrane. Colpi were granulated in B. albicans (Fig. 12) and B. platypetala (Fig. 24) and smooth in B. catingae (Fig. 13); the apex was acute in most species and rounded in B. albicans (Fig. 11), with costae only in B. affinis (Fig. 6).

In most species within the series Cansenia, the colpi were short, the margo being pronounced only in B. cupulata (Fig. 35, 36) and long only in B. angulicaulis. The apex was rounded in most species and acute in B. curvula, covered by a thin membrane, transparent, with gemmae and/or verrucae, and rarely granulate. Bauhinia cheilantha (Fig. 33) was the only species to show slightly elongated pores (Tab. 3). The longest colpus was found in B. ungulata (ca. 110.2 µm) and in B. curvula (ca. 58.8 µm). The colpus was widest in B. rufa (ca. 55.0 µm) and narrowest in B. angulicaulis (ca. 26.8 µm) (Tab. 3).

In the series Pentandrae, the colpi were long with a slightly rounded apex, covered by a thin membrane, transparent, and ornamented (Fig. 71). The colpus was longest and widest in B. vespertilio (ca. 78.0 × 8.8 µm) (Tab. 3). In B. bauhinioides (ser. Perlebia) the colpi were long and covered by a thin membrane, transparent, and lightly ornamented (Fig. 76, 77), with a rounded apex (Fig. 75) (Tab. 3).

Ornamentation and stratification of exine

In the species of the series Aculeatae, the sexine was reticulate or microreticulate, with supratectal elements in the shape of gemmae, bacula or clavae. Reticulate sexine was present in B. acreana (Fig. 3), B. aculeata (Fig. 5), B. catingae (Fig. 14), B. mollis (Fig. 17) and B. ovata (Fig. 21). The sexine was microreticulate in B. affinis (Fig. 7), B. albicans (Fig. 9, 10), B. forficata and B. platypetala (Fig. 23). The muri were straight, smooth and simplicolumellate, with supratectal elements in the shape of clavae (Fig. 1, 5), gemmae (Fig. 10) or bacula (Fig. 24). The occurrence of the three types of supratectal elements was variable among the taxa; although there was a predominance of a given type in most species. There was no predominance in B. mollis, which had a the highest number of supratectal elements (ca. 25). The lowest number (ca. 6) was observed in B. aculeata and B. acreana (Tab. 4). The sexine was thicker than the nexine in B. acreana,B. aculeata,B. albicans,B. catingae and B. ovata; as thick as the nexine in B. platypetala; and thinner than the nexine in B. affinis, B. forficata and B. mollis (Tab. 3).

In B. acuminata (ser. Acuminatae), the sexine was reticulate; muri sinuous, smooth and simplicolumellate (Fig. 26); supratectal elements in the shape of gemmae and bacula (Fig. 27); and lumina ornamented (Tab. 4). The sexine was as thick as the nexine (Tab. 3).

In the series Cansenia, the sexine was reticulate in most species, microreticulate in B. cheilantha (Fig. 34) and B. ungulata (Fig. 62, 63); and perforate in B. cupulata (Fig. 87), in which the mesocolpium was conspicuously undulate, resembling rugulae, and the apocolpium was slightly undulate. The muri of the sexine were simplicolumellate in all species; reticulate in most species (Figs. 32, 39, 44, 50, 56, 59, 65); microreticulate in B. cheilantha (Fig. 34) and B. ungulata (Fig. 62, 63); and perforate with the surface in the mesocolpium, conspicuously undulate, resembling rugulae, and slightly undulate in the apocolpium only in B. cupulata (Fig. 35, 36). The muri were straight or sinuous, low or high in the intersections, with or without perforations, some species showing interruptions in some areas that nevertheless did not close the lacunae; the lumina were ornamented or not, with small lumina surrounding the larger lumina. In most species, there were five types of supratectal elements (scabrae, gemmae, clavae, bacula and verrucae) with or without a predominance of any given type (Tab. 4). The nexine was thicker than the sexine in most species; approximately the same thickness as the sexine in B. angulicaulis and B. dubia; and thinner than the sexine of B. cupulata (Tab. 3).

In the series Pentandrae, the sexine was microreticulate, with supratectal elements in the shape of scabrae and gemmae (Fig. 69, 73) the muri were straight, smooth and simplicolumellate. scanning electron microscopy analysis showed the mesocolpial regions undulate from pole to pole (Fig. 67, 72). Bauhinia vespertilio was the species with the highest number of supratectal elements (ca. 28) (Tab. 4). The sexine was thinner than the nexine (Tab. 3).

In B. bauhinioides (ser. Perlebia), the sexine was microreticulate (Fig. 77), with muri that were straight, smooth and simplicolumellate, with approximately 11 supratectal elements (scabrae and gemmae) (Tab. 4). The nexine was thicker than the sexine (Tab. 3).

Dichotomous key to Bauhinia species, based on pollen characters

^{Clique para ampliar}

Discussion

Bauhinia acuminata (ser. Acuminatae) differs from all other species by presenting inaperturate pollen grains separated in the key based on this characteristic. The species B. bauhinioides was the only one belonging to the series Perlebia and had pollen grains 4(5)-colpate with a microreticulate sexine. These features placed it next to B. albicans (ser. Aculeatae) in the pollen key. The species of the series Pentandrae could not be separated in the key because their pollen was similar. The series Aculeatae formed two groups in the key, based on the type of sexine, which was microreticulate (B. affinis,B. forficata, and B. platypetala) or reticulate (B. acreana,B. aculeata,B. catingae,B. mollis, and B. ovata). Other features such as the number and type of supratectal elements were similar among the species of this series; i.e., some heterogeneity exists within this group. The taxa B. cheilantha and B. ungulata fell rather far from each other in the key, closer to representatives of other series. A large part of the species of the series Cansenia were united in the pollen key, based on the number and type of aperture (3(4)-colpate).

The species studied here all showed very large pollen grains. However, they differed primarily with respect to shape; amb; polar area; presence or absence of aperture (number and type); and sexine ornamentation. The members of the genus Bauhinia analyzed here showed predominantly reticulate pollen grains; only one species (B. cupulata) differed from the pattern, with the sexine perforate, although the mesocolpium was conspicuously undulate, with rugulae, and the apocolpium was slightly undulate. Some species differed from the others in the type of muri, which were low in B. dubia; with a smaller lumina around the larger lumina in B. angulicaulis,B. brevipes, and B. membranacea; sinuous in B. curvula and B. viscidula; and with elevations at the intersections in B. holophylla and B. ungulata. Other features were also important, and the key effectively differentiated the species by the shape of the pollen grain; aperture dimensions; and number and type of supratectal elements (scabrae, gemmae, clavae or bacula).

According to Salgado-Labouriau (1973), all Caesalpinioideae have pollen grains in monads. However, pollen grains in tetrads were found in representatives of the subgenus Bauhinia by Wunderlin et al. (1987), although those authors did not mention which species have this characteristic. In the present study, we found pollen grains only in monads, in agreement with Salgado-Labouriau (1973).

Melhem & Salgado-Labouriau (1963) described the pollen grains of species of the Leguminosae of the Cerrado. Among the taxa studied, the authors analyzed two of the species discussed in the present study: B. holophylla and B. rufa. Our results corroborate those described for B. rufa and differ with respect to B. holophylla in terms of the shape (oblate) and the sexine/nexine ratio.

Barth & Bousada (1964) studied the pollen grains of three species of Bauhinia, including B. forficata, which was analyzed here. The authors described the pollen grains of B. forficata as having a pore-type aperture and supratectal elements of the spine type, differing from our observation that this species has supratectal elements of the clava type and aperture of the colpus type.

The variability of supratectal elements has been demonstrated by various authors, showing that Bauhinia species can have supratectal elements ranging from scabrae to bacula. The presence of verrucae, bacula, gemmae and scabrae was previously reported by Palacios-Chávez (1970). This wide variation was observed in our study; the absence of supratectal elements of the scabra type was characteristic of the pollen grains of the representatives of the series Aculeatae. The similarity between some supratectal elements might explain the lack of specificity in the descriptions of pollen grains in certain studies.

Schmitz (1973) examined the pollen of 100 species of Bauhinia, with simplified descriptions based mainly on the number and type of aperture, shape and sexine ornamentation. Among the species treated by that author and also studied here are the following: Perlebia acuminata (= B. acuminata), Pauletia acuruana (= B. acuruana), P. affinis (= B. affinis), P. angulicaulis (= B. angulicaulis), P. bauhinioides (= B. bauhinioides), P. curvula (= B. curvula), P. forficata (= B. forficata), P. holophylla (= B. holophylla), P. longifolia (= B. longifolia), P. rufa (= B. rufa), P. ungulata (= B. ungulata) and P. viscidula (= B. viscidula). Comparing the results of Schmitz (1973) with those of our study, the pollen descriptions generally agree for the species B. acuruana,B. curvula,B. rufa,B. ungulata and B. viscidula. Note that Bauhinia curvula was characterized by Schmitz (1973) as having pollen grains with supratectal processes in the form of verrucae. This characteristic corroborates our results, albeit found only in three of the taxa studied here. Our observations regarding B. acuminata diverged from those of Schmitz (1973), who classified the pollen as 3-4(5)-aperturate, whereas we classified it as inaperturate. The variations in the number of apertures indicated by Schmitz (1973) for B. bauhinioides and B. longifolia were not observed in this study. Schmitz (1973) classified B. platypetala as 3-colporate, rugulate to striated; whereas we observed six colpi and a reticulate sexine. The classification of the number of apertures of B. forficata (3(4)-colpate), does not agree with our observation of 6-colpate pollen grains.

Wunderlin (1976) considered B. affinis a synonym of B. aculeata, along with numerous other binomials, including B. catingae and B. albicans. The proximity of the species mentioned by Wunderlin (1976) was confirmed by the pollen characters observed in this study. These taxa belong to the series Aculeatae and have pollen grains with supratectal processes such as clavae or bacula. This type of ornamentation, together with other characters, places these species in the series Aculeatae with regard to pollen characters.

Guinet (1981) reported that the vast majority of the representatives of the subfamily Caesalpinioideae have 3-colporate pollen grains, with some colpate and a few porate. Despite that author's assertion regarding the predominance of colpori in the subfamily, our results for the pollen grains of species of the genus Bauhinia showed that practically all taxa had colpate pollen, which probably indicates that the section Pauletia does not follow the aperture type pattern found in Caesalpinioideae. The only exception, B. cheilantha, had a pore-type aperture. Porate pollen grains were observed in the genus Bauhinia, in B. seleriana, by Palacios-Chávez (1970). The species B. acuminata showed no apertures, differing from all other species examined here. Inaperturate pollen grains were observed in B. tomentosa by Vishnu-Mitre & Sharma (1962).

Wunderlin et al. (1987) established five series under the section Pauletia: Acuminatae,Ariaria,Cansenia,Pentandrae and Perlebia, making use of macro- and micromorphological characters, including those of pollen. Of those series, only Ariaria was not analyzed here. The palynological characters used by the authors in the formulation of the series were as follows: for the series Cansenia, including ca. 50 species-pollen grains (3-7)-colpate or (3-7)-colporoidate, sexine reticulate, usually with supratectal processes; for the series Perlebia, with only one species-pollen grains 3-7-colpate, sexine reticulate with supratectal processes; and for the series Pentandrae, comprising ca. seven species-pollen grains 3-7 colporate, sexine reticulate with supratectal processes. Comparing the results obtained here with those of Wunderlin et al. (1987), the observations for the series Cansenia and Perlebia were similar. However, descriptions for the series Pentandra differ, because Wunderlin et al. (1987) reported colporate pollen grains, whereas we found that the species B. pentandra and B. vespertilio both have apertures of the colpus type.

Vaz (2001) carried out a taxonomic study of 58 species of Bauhinia sect. Pauletia, native to or cultivated in Brazil. Among those taxa, the author analyzed the pollen grains of seven species, six of which were also analyzed here. The author divided the species into five pollen types (type B. acuminata, type B. catingae, type B. pentandra, type B. ungulata, and type B. tarapotensis). Vaz (2001) defined the pollen types mainly on the basis of the classification of the aperture, amb and shape of pollen grains. Unfortunately, we could not accept the pollen types established by Vaz (2001), due to the presence of important characters related to muri that were not examined by those authors.

Vaz & Tozzi (2003) considered the series Cansenia to be well-defined and recognizable by the type of terminal aphyllous inflorescence, called pseudo-raceme with foliaceous bracts, as well as the floral bracts and bracteoles associated with pollen grains of type 3-(4)-colpate, angulaperturate. The pollen morphology described in the present study differs significantly for some species, especially as regards the type of supratectal elements, shape of the reticulum, and type of the muri. We note that those authors included B. cheilantha in the series Cansenia, although that species was previously assigned to another group by Bentham (1870). Our results show that the pollen of B. cheilantha shares many features with other species of the series Cansenia, although it was the only member of the series that had apertures of the pore type. Also according to Vaz & Tozzi (2003), B. cupulata is often confused with B. longifolia, especially when they occur sympatrically. Our results show a large difference between those two taxa in terms of the pollen morphology. Bauhinia cupulata has, among other characters, pollen grains with a perforate sexine and without supratectal elements; whereas B. longifolia has reticulate pollen grains with supratectal elements of the scabra and gemma types. These respective differences in pollen were also observed by Ferguson (1986). We believe that these characters can help discriminate between the two species.

Santos et al. (2012) examined the pollen grains of 15 species of Bauhinia occurring in Caatinga areas of Bahia, some of them also analyzed here: B. aculeata, B. acuruana, B. bauhinioides, B. brevipes, B. cheilantha, B. dumosa, B. forficata, B. pentandra and B. subclavata. Comparing their results with our own, we found differences in the size of pollen grains of B. acuruana, B. bauhinioides, B. cheilantha and B. dumosa which those authors described as large and we classified as very large. The differences in the size of pollen grains might be related to the technique of preparation for light microscopy (10% KOH) used by Santos et al. (2012). The exine measurements, as well as the shape of the muri, also showed a large discrepancy because that author described the species with sinuous muri and the exine thicker than or the same as the nexine; whereas we observed that the pollen grains of the same species have straight muri, with the sexine thicker than the nexine only in B. aculeata. According to Santos et al. (2012), the number of apertures varies among B. aculeata,B. bauhinioides and B. brevipes. Although we did not observe such variation among those species, we did see similar variations among other species. This heteromorphism in the number of apertures in Bauhinia species has been reported by other investigators (Schmitz 1973; Gamerro & Fortunato 2001). Also according to Santos et al. (2012), the pollen grains of B. cheilantha,B. dumosa and B. subclavata have microreticulate exine, whereas we found the exines to be reticulate in those species. We obtained similar results in the classification of supratectal elements (gemmae, clavae and verrucae), although Santos et al. (2012) made no mention of the presence of bacula in any species, which were observed here in B. brevipes and B. subclavata. Regarding the type of aperture of the latter species, Santos et al. (2012) considered it to be the pore type but did not provide measurements.

Vaz & Tozzi (2005), in making a synopsis of Bauhinia sect. Pauletia in Brazil, used palynological characters for the composition of key species. Our results differ from theirs for the series Cansenia, because we found no colpori in the species examined here. These authors indicated that B. acreana belongs to the B. forficata complex and is accepted by some authors as a synonym of this. Considering our observations of pollen reported here, we can conclude that these taxa are actually quite similar, confirming the taxonomic observations. The species can be separated, mainly by the fact that the sexine is microreticulate in B. forficata and reticulate in B. acreana, although they share other characters. In their taxonomic analysis of populations of B. affinis,B. catingae,B. albicans and B. aculeata, considering that these species occur in geographical areas that are not connected, Vaz & Tozzi (2005) decided to retain these as separate species, based on the characters of leaves and branches. Although the palynological characters indicate a close similarity between these species, it was possible to separate them based mainly on the shape, aperture number and sexine ornamentation. Vaz & Tozzi (2005) considered B. mollis a distinct species, isolated in the series Aculeatae by the shape of the bud, which has a clavate outline and a median-region constriction that divides the calyx into two parts. However, considering the pollen characters, the species is located well within the series Aculeatae in that it shares many characters with the other representatives, differing mainly with respect to heteromorphism of the number of apertures (6(7)-colpate).

Across palynological studies of B. forficata, there are discrepancies regarding the classification of the type of aperture: Leonhardt & Lorscheitter (2008) termed the aperture of B. forficata a colporus, whereas Barth & Bouzada (1964) stated that B. forficata has apertures of the pore type. The observations made in the present study indicate that the apertures of B. forficata should be classified as colpi.

Various investigators have used pollen characters to aid in formulating taxonomic arrangements, including Melhem & Salgado-Labouriau (1963), Smith (1964), Palacios-Chavez (1970), Schmitz (1973), Larsen (1975), Larsen & Larsen (1983), Ferguson & Pearse (1986) and Ferguson (1990). Vishnu-Mitre & Sharma (1962) observed that a system of plant taxonomy based only on the pollen morphology can hardly be regarded as natural, although the authors recognized the importance of pollen grains as an aid to taxonomic studies.

The present study has established that representatives of the series Aculeatae,Cansenia,Pentandrae and Perlebia differ from those of the series Acuminatae mainly in that Acuminatae representatives are inaperturate, whereas the taxa within the series Cansenia were heterogeneous (B. cheilantha was the only species that had apertures of the pore type). Knowledge of pollen characters is important to improving the taxonomic organization of the genus Bauhinia.

Acknowledgments

We are grateful to Noêmia Alves, of the Biophysics Institute of the Federal University of Rio de Janeiro, for her assistance with the scanning electron microscopy. This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, National Council for Scientific and Technological Development) and the Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ, Foundation for the Support of Research in the State of Rio de Janeiro).

Submitted: 23 August, 2012

Accepted: 4 March, 2013

Apendix 1 - Specimens examinated

Bauhiniaacreana Harms.: BRAZIL. Acre: Acrelândia. BR-364, Km 85; Faz. do SR. Natalícia Gomes Silva, 12/II/2000, I.S. Riveiro 274 (RB); Ceará: Guaramiranga. Serra de Baturité, 13/II/1966, Andrade Lima, A.D 66-4437 (RB); Pará: Serra de Santarém, 20/III/1926, A. Ducke s/nº (RB20320); Mun. Altamira. km 74 da estr. Transamazônica, no rumo de Itaituba, 26/VII/1971, *P. Cavalcante 2802 (RB).

Bauhinia aculeata Vell.: BRAZIL. Rio de Janeiro: Jardim Botânico do Rio de Janeiro, cultivada no arboreto, 06/XII/2005, *A.C.L.N Rodrigues s/nº (RB); Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, 01/XI/1996, A. Vaz et al. 1179 (RB); cultivada no canteiro 1E, 19/XI/1999, A. Vaz 1183 (RB).

Bauhinia acuminata Vell.: Brazil. Bahia: Santa Cruz de Cabrália, Estação Ecol. do Pau Brasil, km 16 a W de Porto Seguro. rod. BR 367. Elev.: 40, s/data, *Santos, F.S. s/nº (RB).

Bauhinia acuruana Moric.: BRAZIL. Bahia: Mun. Macaúbas, Estrada para Canatiba, próximo ao alto, 18/I/1997, G. Hatschbach et al. 65926 (RB); Minas Gerais: Várzea de Palma, Estrada Várzea de Palma a Serra do Cabral, 16/I/1996, G. &M. Hatschbach 64192 et J. M. Silva (RB); Manga, Gleba A, DIJ, 13/II/1990, M.B. Horta et al. s/nº (RB309579); Jaíba, 18/XII/1996, *E. Tameirão Neto 2264 (RB).

Bauhinia affinis Vog.: BRAZIL. Paraná: Guaraniaçu, Guarani, 07/XI/1963, E. Pereira 7758 (RB); Santa Catarina: Luiz Alves. 16 Km em direção a Massaranduba, s/data, *R.L.C. Bortoluzzi, 1285 (RB).

Bauhinia albicans Vog.: BRAZIL. Espírito Santo: Venda Nova do Imigrante. Alto Bananal. Elev.: 1000M, 15/I/1995, G. Hatschbach 61505 (RB); Rio de Janeiro: Mun. Cabo Frio. Estrada do Guriri, antiga estrada que liga Búzios à Cabo Frio, 22/II/2006 *C.L.N. Rodrigues 165 (RB); Estr. do Guriri, após a entrada para as dunas do Peró (beira de estrada), 15/XII/1996, P.R. do C. Farág 297 (RB).

Bauhinia angulicaulis Harms.: BRAZIL. Brasília: Bacia do Rio São Bartolomeu, 04/VIII/1981 E.P. Heringer et al. 7309 (IBGE); adjacências da mata após o córrego cachoeirinha, afluente margem esquerda do Rio Paranoá, 26/V/1982, B.A.S. Pereira 263 (IBGE); Bacia do Rio São Bartolomeu, Adjacências do córrego Forquilha, 07/V/1981 *E.P. Heringer et al. 6921 (IBGE).

Bauhinia bauhinioides Macbride: BRAZIL. Brasília: Campus da UnB em frente ao IBAMA, 24/VI/1989, *V.F. Ferreira 4110 (RB); Mato Grosso do Sul: Corumbá. Vazante (próx. a divisa da invernada Canjiqueiral) Faz. Azurizal; Nabileque; Pantanal. Elev.: 90m, 28/IX/1987, A. Pott 3476 (RB); Porto Murtinho. Rio Apa, Faz. Santa Cruz, 24/III/1998, H.C. de Lima 5558 (RB).

Bauhiniabrevipes Vogel: BRAZIL. Bahia: Mun. Barreiras. Coleta efetuada no km 30 da BR-242, Rod. Barreiras/Ibotirama, 04/VI/1991, H.S. Brito 338 (RB); Mun. Caetité, Rodovia para Guanambi, caatinga, 13/VI/2004, *G. Hatschbach 77808 (RB); Minas Gerais: Brasilândia de Minas. Fazenda Brejão. Adjacências de vereda próxima ao Rio Paracatu, 11/VII/2000, J.A. Lombardi 3965 (RB); Tocantins: Conceição do Tocantins. Rod. TO-050, Km 375, Fazenda São José. próximo do Rio Santa Isabel. Elev.: 400 m. 11/V/2000, G. Hatschbach 70881 (RB).

Bauhinia catingae Harms.: BRAZIL. Bahia: Mun. Feira de Santana Estrada Federal de Terra, Serra do Tambor, 30Km antes de Morro do Chapéu, s/data, I. & C. Geettsberger 14-2273 (RB); Santa Inês; propriedade Pedrão, 09/III/1958, A.D. de Andrade Lima 58-2913 (RB); Mun. Maracás. estr. para Contendas do Sincorá, 6 km sw de Maracás, afloramentos graníticos, 15/III/1980, G. Martinelli 6658 (RB); Mun. Jacobina, Margem da Estrada (Saída), 20/II/2000, * F.S. Cavalcanti et al. 629 (RB).

Bauhinia cheilantha (Bong.) Steud: BRAZIL. Mato Grosso: Mun. Poconé, rodovia Transpantaneira (MT 060) que liga Poconé a Porto Jofre, a aproximadamente 45km de Poconé, 28/I/1989, A. Vaz 597 (RB); Minas Gerais: CD 03, 14/VI/1983, Teixeira & Carvalho s/nº (RB309577); Pernambuco: Serra do Cruzeiro, na estrada Triunfo - Sítio dos Nunes, 28/III/1970, *Andrade-Lima 70-5845(RB); Rio de Janeiro: Jardim Botânico do Rio de Janeiro, 17/VIII/1937, J. G. Kuhlmam s/nº (RB35780).

Bauhinia cupulata Benth.: BRAZIL. Goiás: Mun. de Colinas do Sul, Minacu/Niquelândia, Fazenda Saracura, estrada de manutenção das torres, 08/IV/1999, Walter et al. 13 (RB); Mun. de Teresina de Goiás Km 14 da estrada Teresina de Goiás/Nova Roma, entroncamento que vai para Campos Belos, aproximadamente 13º 30' S 47º 30' W. Gr,. 03/VIII/ 1996, *B.A.S. Pereira & D. Alvarenga 3115 (RB); Mato Grosso: Mun. dos Guimarães, Salgadeira, 12/III/1997,G. Hatschbach et al. 16740 (RB); Tocantins: Mun. Lagoa da Confusão, fazenda Formosa da Javaós, na margem direita do Rio Formoso. Latitude 51º 39' e longitude W 49º 51', 17/VIII/1998, V.L. Gomes Klein et P. Delprete 3448 (RB).

Bauhinia curvula Benth.: BRAZIL. Brasília: Bacia do Rio São Bartolomeu, 11/III/1981, E.P. Heringer et al. 6417 (BGE); Bacia do Rio São Bartolomeu, 14/V/1980, *E.P. Heringer et al. 4786 (IBGE); Goiás: Mun. Niquelândia ca 4km de Muquem Altitude 495m 14º31'14''S & 48º0910811W, Folha Uruaçu SD 22-Z-B, 08/V/1998, M.L. Fonseca et al. 1824 (RB); Plantas do planalto do Brasil, serra dos cristais, 17ºS, 48ºW, 07/III/1966, H.S. Irwin et al. s/nº (R162112).

Bauhinia dubia G. Don.: BRAZIL. Maranhão: Mun. Santa Luzia, margens da estrada da Fazenda Cacique, já próximo a ferrovia Carajás, mata de terra firme com relevo ondulado, 27/III/1983, M.G. Lobo et al. 310 (RB); Pará: Tomé Açu, margem da estrada que vai para a fazenda Curiman próximo ao Igarapé Ipiranga, floresta virgem, solo argiloso, 03/I/1977, O.C. Nascimento 409 (RB); Paraná: 10km a leste pela Rodovia para Campos Belos, Tocantins, 10/XI/1991, *G. & M. Hatschbach 56043 (RB); Piauí: Bocaina. Prox. a estaca 44 Alto do Sangradouro, elev.: 285 m., 14/XII/1999, M.R.A. Mendes 163 (RB).

Bauhinia dumosa Benth.: BRAZIL. Brasília: Reserva Biológica do IBGE 16º56'41''S & 47º53'07''W. Altitude 1100m. Córrego Taquara, 31/VIII/1995, *F.C.A. Oliveira & D. Alvarenga 442 (RB); Goiás: Mun. Alto Paraíso, Chapada dos Veadeiros PARNA, estrada para a sede, solo argiloso pedregoso. Relevo: Plano 1120m, 14º09'41''S & 47º46'30''W, 15/VIII/1995, R. Marquete et al. 2288-A (RB); Mun. Niquelândia, próximo ao povoado de Macedo, ca 07km da Mina de Níquel Tocantins, coord: 14º 26' 43''S 48º 25' 51''W, 18/IX/1996, M. Aparecida da Silva & C.C.S. Ferreira 3113 (RB); Mun. de Niquelândia morro à esquerda entre Niquelândia e a companhia de Níquel Tocantins (CNT), ca de 4km da CNT, coord. 14º23'26''S & 48º26'13''W. 15/VIII/1996, R.C. Mendonça et al. 2572 (RB).

Bauhinia forficata Link.: BRAZIL. Rio de Janeiro: Mun. de Piraí, estação ecológica de Piraí, 21/II/1984 I.M. Silva et al. 195 (RB); Mun. Rio de Janeiro, estrada Vista Chinesa, 02/II/1996, C. Garcia 08 et al. (RB); Mun. Rio de Janeiro, cultivada atrás da Sistemática do JBRJ, 19/I/1994, *A.M.S. da F. Vaz 1010 (RB); Mun. Rio de Janeiro "cultivado" no JBRJ. xi-g, placa 450, s/data, s/coletor (RB385295).

Bauhinia goyazensis Harms.: BRAZIL. Goiás: Niquelândia. km 31 em direção a Muquem, próximo ao Córrego Dois Irmãos. Elev. 470, s/data, *Fonseca, M.L. 1837 (RB); Campinorte, Fazenda Barro Vermelho, Elev. 535, s/data, M.A. Silva 3834 (RB); Niquelândia. Km 4 de Muquem, Elev.: 495, s/data, M.L. Fonseca 1816 (RB).

Bauhinia holophylla (Bong.) Steud.: BRAZIL. Brasília: Área da Marinha próximo à BR 040, campo cerrado com solo úmido, 16/XII/1991, R.C. Mendonça et al. 1992 (IBGE); BR - 251 -Km 1, 5/IX/1978, E.P. Heringer et al. 2001 (IBGE); Reserva Ecológica do IBGE. Coord. 15º56'41''S 47º58'07''W alt. ca 1100m, entre a sede e a chácara, 06/II/1995, M. Aparecida da Silva 2482 (IBGE); Reserva ecológica do IBGE,15º57'42''S & 47º 52'51''W, 28/X/1997, *R. Marquete & R.C. Mendonça 2830 (RB).

Bauhinia longicuspis Benth.: BRAZIL. Amazonas: BR 319, rod. Manaus-Porto Velho, a 15km de alt., mun. de Humaitá, 10/IV/1985, *C.A. Cid Ferreira 5393 (RB); Mato Grosso: Km 274 Xavantina - Cachimbo road. Dry Forest roadside, 18/XI/1967, D. Philcox et al. 3127 (RB); Pará: Porto Trombetas, Oriximiná, Estrada para Igarapé das Pedras, 10/III/2001, S.M. de Faria et al. 2377 (RB); Porto Trombetas, Oriximiná, Estrada para Igarapé das Pedras, 10/III/2001, S.M. de Faria et al. 2376 (RB).

Bauhinia longifolia (Bong) Steud.: BRAZIL. Mato Grosso: Mun. Nova Xavantina, Reserva Biológica Mario Vianna, s/data, *B.S. Marimom BS-286 (RB); Mato Grosso do Sul: Bonito. Rod. Guia Lopes da Laguna a Bonito, 09/III/2003, G. Hatschbach 74424 (RB); Mun. Aquidauana, Serra de Maracaju, Rodovia Ecológica 19/III/2003, G. Hatschbach et al. 74934 (RB); Rio de Janeiro: Teresópolis, Campo Limpo, Granja. 28/V/1977, Lucia Freire Carvalho 532 (RB).

Bauhinia membranacea Benth.: BRAZIL. Goiás: Guarani de Goiás. Fazenda Forquilha, Elev. 450m, 05/III/2001, M.L. Fonseca 2412 (RB); Bahia: Correntina, 28/I/1967, G.K. Gottsberger 11-28167 (RB); Minas Gerais: Juramento, Rio Piedosa, III/2005, *A.A. Miranda-Melo s/nº (RB 425589).

Bauhinia mollis (Bong) D.Dietr.: BRAZIL. Goiás: Mun. Hidrolândia, Faz. Nova Fátima a 2km da BR. 153, 19/X/1983, M.H. Rezende 06 (RB); Mato Grosso do Sul: Mun. Bonito, Estrada Bonito, Fazenda São Geraldo, 10,5km Lat. 21º13'29.8''S Long. 56º31'29.5''W. Alt 300m, 11/II/2002, V.J. Pott. 5945 et al. (RB); Rio Formoso, 01/II/1998, *O. S. Ribas & L.B.S. Pereira 2406 (RB); Mun. Bodoquena Rod. - MS - 178, 20km S de Bodoquena, 08/II/1998, O.S. Ribas & L.B.S. Pereira 2596 (RB).

Bauhinia ovata Vog.: BRAZIL. Espírito Santo: Mun. Linhares, Reserva Florestal de Linhares, Estrada Mantegueira km1188, mata de Tabuleiro, 22/XI/1985, D. A. Folli 559 (RB); Reserva Florestal de Linhares - CVRD Próximo estrada 154 Talhão 507, 02/X/1972, A. M. Lino 116 (RB); Minas Gerais: Aimorés, Mata do Varejão, Borda de mata, 20/X/1997, M.F. de Vasconcelos s/nº (RB343802); Braúnas, 27/IX/1997, *E. Tameirão Neto 2552 (RB).

Bauhinia pentandra (Bong) Steud.: BRAZIL. Mato Grosso do Sul: Bonito. Projeto Guaicurus, cerca de 4-5km N. 09/XI/2002, G. Hatschbach 73977 (RB); Mato Grosso: Cáceres. Gleba Facão, Rodovia para o Rio Jacobina, 05/V/1995, G. Hatschbach 62293 (RB); Rod. BR-163, Próximo de km 699, Torre da Embratel (Mun. Rio Verde), 06/XI/1996, G. Hatschbach 65361 (RB); Mato Grosso, 10/XI/1977, *C. Almeida 379 (RB).

Bauhinia platypetala Burch. ex Benth.: BRAZIL. Distrito Federal: Res. Ecol. do IBGE, 11/III/1992, B.A.S. Pereira 2045 (RB); Maranhão: Mun. Buriti Bravo, IX/1984, F.M.D. Hora & S.B. Silva 03 (RB); Carroxo BR-226, prox. Pousada do Cacique Barra do "corda", s/data, P. Martins & E. Nunes s/nº (RB); Piauí: Teresina, Larg. 60m, próximo ao Surrear, 10/IV/2001, *F.A.R. Soares 134 (RB).

Bauhinia rufa (Bong) Steud.: BRAZIL. Brasília: Córrego Landim, ca 20km N.E., D.F. Elevation 900m, 04/V/1966, H.S. Irwin et al.s/nº (R161556); Universidade de Brasília 12/IV/1963, E. Santos 1704 & J. Sacco 1937 (R); Minas Gerais: Mun. Diamantina, estrada para São Gonçalo Rio das Pedras, 1161 ms.m., campo rupestre 18º10'18''S e 43º42'24''W, 07/X/2003, M.G. Bovini & L.C.Giordano 2379 (RB); Mun. de Niquelândia, CNT. ca 5,5km a direita da Mina de Níquel. Coord.14º24'02''S & 48º25'20''W, 28/XI/1996, *M.L.M. Azevedo et al. 1076 (RB).

Bauhinia subclavata Benth.: BRAZIL. Ceará: Crato. Chapada do Araripe, 31/III/1985, *A.G. Fernandes s/nº (RB287906); Maranhão: São João dos Patos, Buriti Largo, 14/IV/1980, A.G. Fernandes s/nº (RB287904).

Bauhinia ungulata Jacq.: BRAZIL. Mato Grosso do Sul: Mun. Ladário; Logradouro- Fazenda Vale do Paraíso - Morro Sta. Cruz, 17/V/2001, Damasceno Junior et al. 2405 (RB); Campo grande, Rita Vieira, 24/IX/1993, C.A.C. 2878 (RB); Mun. Sonora, Rod. BR-163, Km 811, 03/V/1995, G. Hatschbach et al. 62202 (RB); Campo Grande, Reserva de cerrado, 24/VIII/2000, *A.L. Barros s/nº (RB375092).

Bauhinia vespertilio S. Moore: BRAZIL. Mato Grosso: Mun. Cárceres, Mt-343, Rio Pirapatonga, 24/X/1995, *G. Hatschbach et al. 63842 (RB); Mun. Carceres, BR-070 Serra do Manguezal, 07/XI/1996, G. Hatschbach et al. 65377 (RB).

Bauhinia viscidula Harms.: BRAZIL. Brasília: Taguatinga, Confluência córregos cana do Reino / Vicente Pires, 25/VIII/1981, E.P. Heringer 7352 (IBGE); Reserva Ecológica do IBGE, cerrado. Ponto 32 s/data, M.L.M. Azevedo & Rogério D. Lopes 790 (IBGE26454); Reserva Ecológica do IBGE, Foto: 953, Faixa 21, Ponto 33, 23/VII/1990, *M.L.M. Azevedo & F.C.A. Oliveira s/nº (IBGE).

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Appendix 1

1

Based on the Doctoral thesis of the first Author

Publication Dates

• Publication in this collection
  22 July 2013
• Date of issue
  June 2013

History

• Received
  23 Aug 2012
• Accepted
  04 Mar 2013