The genus Piptadenia Benth.: pollen morphology and taxonomic implications

Template: Editora Letra1 | www.editoraletra1.com.br This is an open-access article distributed under the terms of the Creative Commons Attribution License. | 1 Original Article doi: https://doi.org/10.1590/1677-941X-ABB-2024-0125 Acta Botanica Brasilica , 2025, 39: e20240125 Received May 06, 2024; Accepted 30 December, 2024. Editor-in-Chief: Thaís Elias Almeida; Associate Editor: Cláudia Mendonça How to cite: Duarte AFT, Oliveira AC, Ribeiro PG, Queiroz LP, Santos FAR. 2025. The genus Piptadenia Benth.: pollen morphology and taxonomic implications. Acta Botanica Brasilica 39: e20240125. doi: 10.1590/1677-941X-ABB-2024-0125 The genus Piptadenia Benth.: pollen morphology and taxonomic implications Ana Flávia Trabuco Duarte1,* , Débora Cavalcante de Oliveira1 , Pétala Gomes Ribeiro1 , Luciano Paganucci de Queiroz1  & Francisco de Assis Ribeiro dos Santos1  1 Universidade Estadual de Feira de Santana, Departamento de Ciências Biológicas, Programa de Pós-Graduação em Botânica, Feira de Santana, BA, Brazil. *Corresponding author: [email protected] ABSTRACT The genus Piptadenia Benth. has undergone several changes in its circumscriptions throughout its history, given the difficulty of its phylogenetic placement. Considering that palynological contributions have been significant for differentiating taxa within the Mimoseae tribe , the present study aims to characterize the representatives of the genus as well as describe the pollen grains of some taxa still unpublished in the literature. Three types of pollen grains were identified based on the number of grains per polyad considering the number of pollen grains and their ornamentation. However, other palynological characters are similar among species, supporting the monophyly of the genus. All species showed similarities, especially regarding size and shape, varying mainly in the number of pollen grains composing the polyads (8, 12, and 16). This variation has already been confirmed by morphological and molecular data. This study presents unprecedented palynological characterization of the species: Piptadenia affinis, P. cuzcoënsis, P. gonoacantha, P. imatacae, P. killipii, P. micracantha, and P. robusta. Keywords: diversity, exine, genus, morphology, palynotaxonomy, Piptadenia Benth., pollens, taxonomic Introduction In Bentham’s study (1840), the genus Piptadenia Benth. was divided into three sections: Eupiptadenia Benth., Pityrocarpa (Benth.) Britton & Rose, and Niopa (Benth.) Britton. Furthermore, Piptadenia was also included in the tribe Piptadenieae due to the presence of glands on the anthers. Nonetheless, the boundaries of the tribe were expanded to include taxa lacking endosperm in the seed (Bentham, 1875). Piptadenia sensu Bentham (1840) was distinguished from other genera of the tribe by the presence of flattened legumes and thin valves. The genus lacks specialized fruit, which is characteristic of other Mimoseae Bronn genera, such as Entada Adans. and Anadenanthera Speg. Fruits were unknown for some of the species treated by Bentham (1840), and even a consistent fruit type was not present within the Piptadenia. Later, Brenan (1955) reorganized Piptadenia and closely related genera based mainly on fruit shape, dehiscence type, and seed characteristics. Piptadenia was restricted to species with winged seeds and without endosperm, while the genus Pityrocarpa Benth. included species with non-winged Template: Editora Letra1 | www.editoraletra1.com.br Duarte et al. 2 | Acta Botanica Brasilica, 2025, 39: e20240125 seeds, presence of endosperm, and smooth testa. Brenan’s typification (1965) was not accepted, and Pityrocarpa was again included within Piptadenia, while species with winged seeds were transferred to Parapiptadenia Brenan by Cowan & Brenan (1960). Subsequently, phylogenetic analyses by Jobson & Luckow (2007) demonstrated the polyphyly of Piptadenia (sensu Brenan, 1955). Jobson & Luckow (2007) also confirmed the polyphyly of Piptadenia, previously reported by Luckow et al. (2003). These findings indicated the genus Pityrocarpa to be the sister group of Pseudopiptadenia Rauschert, despite weak support. Additionally, a polytomy among the genera Parapiptadenia, Microlobius C.Presl, and Stryphnodendron Mart. was evidenced. The species Piptadenia viridiflora (Kunth.) appears separated from Pityrocarpa, suggesting its repositioning, possibly as a new genus. In addition to phylogenetic analyses, the pollen morphology of Piptadenia viridiflora (polyads with 8 pollen grains, acalymmate, ovoidshaped, and disposed in two opposite tetrahedral tetrads) also showed a distinction from the group. Polyads with eight pollen grains are recorded in some species from the extinct informal group Piptadenia such as Pityrocarpa moniliformis (Benth.) Luckow & Jobson, Microlobius foetidus (Jacq.) M.Sousa & G.Andrade, and species of Mimosa L. However, the bitetrad arrangement observed in Piptadenia viridiflora is common in Mimosa species (Lima et al., 2008), unlike the arrangement in Pityrocarpa moniliformis and M. foetidus, which exhibit pollen grains arranged in six peripheral and two central positions. The exine ornamentation of the pollen grains in Piptadenia viridiflora was found to be distinct from other species within the Piptadenia group. The isolated position of P. viridiflora, as revealed by molecular analyses and supported by morphological evidence, led Ribeiro et al. (2018) to propose the establishment of the new genus Lachesiodendron P.G. Ribeiro, L.P. Queiroz & Luckow. Consequently, the monophyly of Piptadenia was strongly supported following the exclusion of P. viridiflora. Although Piptadenia can be identified by a combination of macromorphological characters, its phylogenetic positioning has represented a challenge, leading to the proposal of several circumscriptions throughout its history. Palynological studies have played a significant role in differentiating taxa within the Mimoseae, a group extensively studied for its pollen morphology (Erdtman, 1952; Van Campo & Guinet, 1961; Barros, 1963; Barth & Yoneshigue, 1966; Guinet, 1969; Sorsa, 1969; Barth & Silva, 1963; Jiménez, 1996; Silvestre-Capelato & Melhem, 1997; Caccavari, 1987; 2002; Du Bocage et al., 2008; Lima et al., 2008; Santos & Romão, 2008; Buril & Santos, 2010; Santos-Silva et al., 2013; Cruz et al., 2017; Medina-Acosta et al., 2018; Duarte et al., 2021; Soares et al., 2022). Caccavari (1987; 2002) reported that Piptadenia s.l. can be considered as a eurypalynous group. Despite the significant diversity of pollen within the Piptadenia group, morphological and structural traits remain useful for distinguishing it from other Mimoseae groups, whose species exhibit pollen grains arranged in tetrads and/or polyads (Caccavari, 2002). This study aims to advance palynological knowledge of representatives of the genus Piptadenia, including descriptions of the pollen morphology of species that remain unpublished in the specialized literature, and discuss palynological data that could be relevant in a taxonomic context. Materials and Methods Pollen samples from 21 (twenty-one) species of the genus Piptadenia were analyzed. Pollen material was collected from exsiccates deposited in the following herbaria: BMCB, CEPEC, F, HUEFS, IAN, INPA, MBM, MO, NY, RB, SP, and US (acronyms following Thiers 2023 [continuously updated]). Whenever possible, three specimens were sampled for each species. The analyzed material is cited in Appendix 1. Pollen grains were acetolyzed following the methodology proposed by Erdtman (1960), in which the pollen material was removed from the anthers of fertile floral buds and remained in the acetolysis solution for two minutes. Permanent slides were mounted in glycerin gelatin and sealed with paraffin. For each sample, four slides were mounted in transparent gelatin and one in gelatin stained with safranin, for better observation of the characters. The grains were measured and microphotographed using a Leica ICC50 W light microscope (LM). The mounted slides were included into the pollen library of the Laboratory of Plant Micromorphology of the State University of Feira de Santana (PUEFS). For scanning electron microscopy analysis (SEM), acetolyzed pollen grains were washed and dehydrated in an ascending hydroethanolic series (50%, 70%, 90%, and 100%), remaining about 10 minutes in each bath. The absolute alcohol containing the pollen grains was dripped directly onto the specimen holder of the scanning electron microscope. After total drying, they were metalized by evaporation of gold in a high vacuum and electron micrographed in the JEOL 6390LV microscope from the Electronic Microscopy Platform of the Oswaldo Cruz Foundation – Gonçalo Moniz Research Center. For palynological characterization, the following morphometric characters were measured: major and minor diameter, whenever possible, in 25 randomly selected polyads. The other parameters, sexine, nexine, and exine thickness of ten grains, were also randomly selected. The morphometric characters were statistically analyzed by calculating the arithmetic mean (x), the sample standard deviation (s), the standard deviation of the mean (sx), Pollen morphology of Piptadenia Template: Editora Letra1 | www.editoraletra1.com.br Acta Botanica Brasilica, 2025, 39: e20240125 | 3 the coefficient of variation (CV), and the 95% confidence interval (CI) for pollen parameter measurements with a sample size of 25, For the other measurements with a sample size of ten, only the arithmetic mean was calculated. Pollen grains were described according to their main morphological attributes: size, shape, number of grains per polyad, types of apertures, types of ornamentation, and exine ornamentation. The palynological terminology followed Punt et al. (2007) and Halbritter et al. (2018). The specimens analyzed are listed below: Piptadenia adiantoides (Spreng.) J.F. Macbr.- Brazil, Minas Gerais: Serra do Cipó., Santana do Riacho, Pirani, J.R. 5029 (HUEFS); Brazil, Bahia: Feira de Santana, Moraes, M.V. 471ª (HUEFS); - , Oliveira, R.P. 599 (HUEFS). Piptadenia buchtienii Barneby - Dorr, L.J; Barnett, L.C. & Lewis, M. s/n (NYBG); Bolivia, La Paz: Nor Yungas, Beck, St. G 8727 (NYBG). Piptadenia floribunda Kleinhoonte – Brazil, Pará: Almeirim, Pires, M.J. & Silva, N. s/n (INPA); -, Mori, S. & Bolten, A. 12 (NYBG); -, Gran Ville de Crozier, J.J. F. 13823 (NYBG). Piptadenia gonoacantha (Mart.) J.F.Macbr. – Brazil, São Paulo: São Paulo, Rossi, L. 145 (HUEFS); -, Campos, M.B.S. 57 (HUEFS); Brazil, Minas Gerais: Juiz de Fora, Pifano, D.S. 252 (CESJ). Piptadenia imatacae Barneby - Ecuador, Sucumbios: Putumayo, Cerón, E. C. 9794 (MO). Piptadenia irwinii G.P.Lewis - Brazil, Bahia: Palmeiras, Queiroz, L.P. de 12652 (HUEFS); Bahia, Brazil: Licínios de Almeida, Jardim, J.G. 3303 (HUEFS); Brazil, Bahia: Morro da Torre, Jequié, Queiroz, L. P. de 12887 (HUEFS). Piptadenia killipii J.F.Macbr.- Peru, San Martín: San Martín, Belsmaw, C. M. 3159 (F); San Martín, Peru: Alto Rio Huallaga, Klug, G. 4333 (F); Bahia, Brazil: Juçari, Belém, R.P.; Pinheiro, R.S 2345 (IAN). Piptadenia laxipinna G.M.Barroso – Brazil, Minas Gerais: São Pedro do Suaçuí, Davidse, T.P.G. Ramamoorthy & Vital, D.M. 11491 (MO); -, Timaná, M. & Smith, P. 1465 (MO). Piptadenia micracantha Benth. – Brazil, Minas Gerais: Tombos, Oliveira, J.E. de 327 (HUEFS); Brazil, Bahia: Igrapiúna, Reserva Ecológica Michelin, Queiroz, L.P.de 327 (HUEFS). Piptadenia paniculata Benth. – Brazil, Minas Gerais: Juiz de Fora, Krieger L. 1093 (HUEFS); Brazil, Paraná: Morretes, Hatschbach, G. 1650 (HUEFS); Brazil, Rio de Janeiro: Guapimirim, Estação Ecológica Estadual de Paraíso, de Lima, H. C. 4357 (HUEFS). Piptadenia peruviana (J.F.Macbr.) Barneby – Peru, Loreto: Klug, G., 2927 (NYBG); -, Schunke Vigo, J. & Grahan, J. G. 514981 (MO). Piptadenia pteroclada Benth – Brazil, Amazonas: São Paulo de Olivença, Froes, R. L. 20805 (IAN); Ecuador, Sucumbíos: Lago Agrio Bosque Húmedo Tropical, Neill, D. 7201 (MBM); Peru, Loreto: Retinga Central, Padre Isla, Prov. Maynas, Encarnacións, F. & Merjia, K. 25137 (MBM); Peru, Loreto: Maynas, Plowman, T.; Schultes, R.E. &. Tovar, O. 18 (INPA). Piptadenia ramosissima (Mart. ex Colla) Benth. – Brazil, Bahia: Jussari, Nascimento, F.M.F 1564 (HUEFS); Brazil, Bahia: Rui Barbosa, Serra do Orobó, Queiroz, L.P.de 9915 (HUEFS). Piptadenia retusa (Jacq.) P.G.Ribeiro, Seigler & Ebinger – Brazil, Sergipe: Monte Alegre de Sergipe, Machado, W. J 362 (HUEFS); Brazil, Sergipe: Canindé de São Francisco, Silva, A.C.C. 289 (HUEFS); - , Aristeiguieta, L. 7470 (MO). Piptadenia santosii Barneby ex G.P.Lewis – Brazil, Minas Gerais: Salto da Divisa, Lombardi, J.A. 5044 (BMCB); Brazil, Bahia: Prado, Santos, T.S. 2729 (CEPEC). Piptadenia trisperma (Vell.) Benth. – Brazil, Rio de Janeiro: Rio de Janeiro, Jacarepaguá, Hoehne, F.C. 111 (SP); Brazil, Rio de Janeiro: Maricá, Lewis, G.P. & de Lima, H.C. 1191 (HUEFS). Piptadenia uaupensis (Benth.) Spruce – Brazil, Amazonas: Tonantins, Ducke 1592 (IAN); Knowles, E. 551 (INPA); Brazil, Pará: Santarém, Silva, M. & s/n (MG). Piptadenia uliginosa Britton & Killip – Colombia, Bolívar: Volcanes: Killip, E.P. & Albert, C. S. 14140 (US); Colombia, Campeche Atlántico: Depto. del Atlantico, Dugand, A. 5328 (US); -, Lima, J.R. 571 (RB); - , Lima, J.R. 647 (RB); Lima, J.R. 460 (RB). Results Pollen grains in Piptadenia are represented by polyads ranging in size from 15.7-43.6 µm (small to medium) (Table 1), with 8, 12, and 16 pollen grains (Fig. 1K). Polyads are mostly spheroidal, with pollen grains regularly arranged (Table 2). The type of aperture was not evidenced. Individual pollen grains are spheroidal and irregularly arranged. Exine Commonly, the exine exhibited a thickness ranging from 0.76 µm in P. peruviana to 1.37 µm in P. floribunda, with sexine equal to nexine in general. Sexine thicker than nexine is presented in pollen grains from P. affinis, P. cuzcoensis, P. floribunda, P. peruviana, P. santosii, and P. uaupensis, while nexine thicker than sexine was registered only in P. pteroclada. The analyzed species exhibited four patterns regarding the exine ornamentation of the polyads: a) Rugulate in P. adiantoides, P. affinis, P. buchtienii, P. cuzcoënsis, P. floribunda, P. imatacae, P. laxipinna, P. micracantha, P. pteroclada, P. robusta, P. santosii and P. uliginosa (Fig. 1B, D, F–G, J; Fig. 2C, E, J; Fig. 3D, F, J); b) Areolate in P. gonoacantha, P. killipii, P. peruviana, P. ramosissima and (Fig. 1H; Fig. 2B, H, L); Template: Editora Letra1 | www.editoraletra1.com.br Duarte et al. 4 | Acta Botanica Brasilica, 2025, 39: e20240125 Table1. Morphometric characters (µm) of polyads from Piptadenia species (Leguminosae). Species/ Specimen Largest diameter Shortest diameter Exine Sexine Nexine x±sx Range x±sx Range Piptadenia Benth. Piptadenia adiantoides (Spreng.) J.F.Macbr. Pirani, J.R. 5029 (HUEFS) 23.2±1.1 22.5-25 16.1±1.9 15-22.5 1 0.5 0.5 Moraes, M.V. 471ª (HUEFS) 23.1±1.0 22.5-25 17±1,1 15-17.5 1 0.5 0.5 Oliveira, R.P. 599 (HUEFS) 22±2.1 23-25.2 16.2±1.8 15-23 1 0.5 0.5 Piptadenia affinis Burkart Segir, G.D.S. & Frainer, G. 716 (ICN) 28.4±1.75 25-30 23.6±2.29 20-27.5 1.04 0.56 0.48 Piptadenia buchtienii Barneby Dorr, L.J; Barnett, L.C. & Lewis, M. s/n (NY) 25.2±1.8 24-26.2 18.2±1.8 16.2-19 1 – – Beck, St. G. 8727 (NY) 26.2±2.2 23.1-28.4 17±2.2 15.1-18.7 1 – – Piptadenia cuzcoënsis Barneby Foster, R. B. 12789 (NY) 37.1±1.8 35-40 30.8±2.4 25-35 0.98 0.68 0.30 Piptadenia floribunda Kleinhoonte Pires, M.J. & Silva, N. s/n (INPA) 37.9±2.2 32.5-40 29.9±2.6 25-32.5 1.09 0.67 0.42 Mori, S. & Bolten, A. 12 (NY) 34.3±2.2 25-42.5 27.7±2.6 25-32.5 1.37 0.46 0.91 Gran Ville de Crozier ,J.J. F.13823 (NY) 31.3±1.9 27.5-37.5 25.6±1 25-27.5 1 0.5 0.5 Piptadenia gonoacantha (Mart.) J.F.Macbr. Rossi, L. 145 (HUEFS) 21.2±1.2 20-22.5 19.3±1.1 17.5-20 1 0.5 0.5 Campos, M.B.S. 57 (HUEFS) 18.4±1.4 17.5-22.5 17.1±0.9 15-17.5 1 0.5 0.5 Pifano 252, D.S. (HUEFS) 19.4±1.3 18-22.5 17.3±1.1 16.1-18 1 0.5 0.5 Piptadenia imatacae Barneby Cerón, E. C. 9794 (MO) 38.1±1.6 35-40 32.4±2.8 29.2-40 1 – – Piptadenia irwinii G.P.Lewis Queiroz, L.P.de 12652 (HUEFS) 21.7±1.3 20-25 18.4±1.8 17.5-22.5 1 0.5 0.5 Jardim,J.G. 3303 (HUEFS) 21.2±1.2 20-22.5 17.9±0.9 17.5-20 1 0.5 0.5 Queiroz,L. P. de 12887 (HUEFS) 22.2±1.3 20-25 20.1±1.3 17.5-22.5 1 0.5 0.5 Piptadenia killipii J.F.Macbr. Belsmaw, C. M. 3159 (F) 18.3±1.1 17.5-20 14.6±1.8 12.5-17.5 1 – – Klug, G. 4333 (F) 18.7±1.2 17.5-20 15.4±1.3 12.5-17.5 1 – – Belém, R.P., Pinheiro, R.S 2345 (IAN) 21.6±1.2 20-22.5 18.6±1.7 15-22.5 1 – – Piptadenia laxipinna G.M.Barroso Davidse, T.P.G. Ramamoorthy & Vital, D.M. 11491(MO) 29.5±1.9 27.5-32.5 25.1±1.3 22.5-30 1 0.5 0.5 Timaná, M. & Smith, P. 1465 (MO) 31.2±1.7 25-33.7 22±1.1 20.5-23 1 0.5 0.5 Piptadenia micracantha Benth. Oliveira, J.E.de 327 (HUEFS) 15.7±1.1 15-17.5 15.7±1.1 15-17 1 0.5 0.5 Queiroz, L.P.de 15663 (HUEFS) 18.9±1.9 17.5-22.5 16.6±1.7 15-20 1 0.5 0.5 Piptadenia paniculata Benth. Krieger, S.V.D. P.L. 1093 (HUEFS) 34.3±2.1 30-37.5 28.2±2.6 22.5-30 1 0.5 0.5 Hatschbach, G. 1650 (HUEFS) 28.1±2.1 25-32.5 28.1±2.1 25-32.5 1 0.5 0.5 de Lima, H. C. 4357 (HUEFS) 36.8±2.4 25-40 31.7±3.3 27.5-35 1 0.5 0.5 – – Pollen morphology of Piptadenia Template: Editora Letra1 | www.editoraletra1.com.br Acta Botanica Brasilica, 2025, 39: e20240125 | 5 Table1. Cont. Species/ Specimen Largest diameter Shortest diameter Exine Sexine Nexine x±sx Range x±sx Range Piptadenia peruviana (J.F.Macbr.) Barneby Klug, G. 2927 (NY) 35.7±1.8 32.5-37.5 32.1±2.1 30-35 1.13 0.6 0.53 Schunke Vigo, J. & Grahan, J. G. 514981 (MO) 35.5±1.7 32.5-40 29.2±2.2 25-32.5 0.76 0.38 0.38 Piptadenia pteroclada Benth. Froes, R .L. 20805 (IAN) 33.1±3.4 30-37.5 27.8±2.9 25-32.5 1 – – Neill, D. 7201(MBM) 33.1±2.5 30-37.5 29.3±1.9 25-32.5 0.98 0.29 0.69 Encarnacións, F. & Merjia, K. 25137 (MBM) 31.7±1.1 30-32.5 28.2±1.5 25-30 1 0.29 0.71 Plowman,T.; Schultes, R.E. &. Tovar, O. 18 (INPA) 29.6±2.8 25-32.5 22.9±0.9 22.5-25 – – – Piptadenia ramosissima (Mart. ex Colla) Benth. Nascimento, F.M.F 1564 (HUEFS) 20.5±1.9 17.5-22.5 17.6±0.5 17.5-20 1 0.5 0.5 Queiroz, L.P.de 9915 (HUEFS) 20.8±2 17.5-22.5 17.8±1 17.5-21 1 0.53 0.53 Piptadenia retusa (Jacq.) P.G.Ribeiro, Seigler & Ebinger Machado, W. J. 362 (HUEFS) 24.4±1.9 20-27.5 18.2±1.1 17.5-20 1 – – Silva, A.C.C. 289 (HUEFS) 22±2.1 20-26 17.9±1.6 16.8-19.1 1 0.5 0.5 Aristeiguieta, L. 7470 (MO) 24±1.9 22.1-27.5 19.5±2 18.1-20 1 0.5 0.5 Piptadenia robusta Pittier Pittier, H. 8297 (MO) 30.5±1.6 27.5-32.5 25.7±2.2 22.5-30 1 0.5 0.5 Piptadenia santosii Barneby ex G.P.Lewis Lombardi, J.A. 5044 (BMCB) 40.8±3.6 35-40 33.4±2.8 30-37.5 1.28 0.64 0.63 Santos, T.S. 2729 (CEPEC) 43.6±2.8 40-47.5 32.2±2 30-35 1 0.7 0.3 Piptadenia trisperma (Vell.) Benth. Hoehne, F.C. 111 (SP) 22±1.2 20-24.6 17±2 16.2-21 1 – – Lewis, G.P. & de Lima, H.C. 1191 (HUEFS) 23.5±1.4 20-25 18.8±1.6 17.5-22.5 1 – – Piptadenia uaupensis Spruce ex Benth. Ducke 1592 (IAN) 30.8±2.5 27.5-35 25.1±1.9 22.5-27.5 1.12 0.56 0.56 Knowles, E. 551 (INPA) 34.9±2.5 30-37.5 28±3.1 25-35 1 0.6 0.4 Silva, M. & Sousa, R. (MPEG) 34.9±1.9 30-37.5 27.9±2.6 25-35 1 – – Piptadenia uliginosa Britton & Killip Killip, E.P.& Albert,C. S. 14140 (US) 30,1±2,7 24.2-36 22.1±2 20-25 1 0.5 0.5 Dugand, A. 5328 (US) 32,2±2,2 28-35.5 26.2±2.4 22-27 1.1 0.56 0.56 Lima, J.R.571 (RB) 30 ±1.5 27.5-38.5 24.8±1.6 22.5-30 1 0.5 0.5 Lima, J.R. 647 (RB) 31.2±2.4 20-30 25.7±2.2 20-22.5 1.2 – – Lima, J.R. 460 (RB) 25.8±2.8 26.4-35.5 27.7±1.5 21.2-28 1 0.5 0.5 Legend: x = rithmetic mean /sx= standard deviation – c) Verrucate in P. irwinii, P. retusa, P. trisperma, and P. uaupensis (Fig. 1L; Fig. 2L; Fig. 3B, H); d) Granulate in P. paniculata (Fig.2-G). The presence of Ubisch bodies was registered in P. affinis, P. buchtienii, P. gonoacantha, P. paniculata, P. pteroclada, and P. uliginosa. In other hand, regarding the shape of the polyads, the ovoid shape was registered in P. adiantoides, P. affinis, P. irwinii, P. killipii, P. pteroclada, P. ramosissima, P. re tus a, and P. santosii, (Fig. 1A; Fig. 3A, E) while the remaining species exhibited a spheroidal shape (Fig. 2D; Fig. 3G, I, K). Based on the number of pollen grains per polyad, three types of pollen grains are here recognized: Type 1 – Polyads with16 pollen grains (Fig. 3C, I), predominantly spheroidal, ovoid only in P. killipii, the largest diameter measuring 29.86-38.1 µm. Rugulate exine ornamentation in P. laxipinna, P. imatacae, and P. uliginosa, areolate in P. killipii, P. peruviana, granulate in P. paniculata, Template: Editora Letra1 | www.editoraletra1.com.br Duarte et al. 6 | Acta Botanica Brasilica, 2025, 39: e20240125 Figure 1. Polyads of Piptadenia (Leguminosae) species analyzed under Light Microscopy (LM) and Scanning Electron Microscopy (SEM). P. adiantoides - A. Ovoidal polyad, B. Rugulate ornamentation. P. affinis - C.Polyads with 8 pollen grains. P. buchtienii - D. Detail of rugulate ornamentation. P. cuzcoënsis - E. Polyads with 12 pollen grains, F. Rugulate ornamentation. P. floribunda - G. Rugulate ornamentation. P. gonoacantha - H. Areolate ornamentation. P. imatacae - I. Polyads with 16 pollen grains, J. Detail of rugulate ornamentation. P. irwinii - K. Ovoidal polyad, L. Verrucate ornamentation. Scales: 10 µm (A, C, E,I, K), 5 µm (B, F, G, H, K), 1 µm (D, J). Pollen morphology of Piptadenia Template: Editora Letra1 | www.editoraletra1.com.br Acta Botanica Brasilica, 2025, 39: e20240125 | 7 Table2. Qualitative characters of the polyads from Piptadenia species (Leguminosae). Species Size Shape Pollen grain number per polyad Exine Sexine:Nexine/N Ubisch bodies Type Piptadenia adiantoides Small Ovoid 12 Rugulate S=N -2 Piptadenia affinis Medium Ovoid 8Rugulate S>N + 3 Piptadenia buchtienii Medium Spheroidal 12 Rugulate - + 2 Piptadenia cuzcoënsis Medium Spheroidal 12 Rugulate S<N - 2 Piptadenia floribunda Medium Spheroidal 12 Rugulate S<N - 2 Piptadenia gonoacantha Small Spheroidal 12 Areolate S=N + 2 Piptadenia imatacae Medium Spheroidal 16 Rugulate - - 1 Piptadenia irwinii Small Ovoid 8Verrucate S=N - 3 Piptadenia killipii Small Ovoid 16 Areolate S=N - 1 Piptadenia laxipinna Medium Spheroidal 16 Rugulate S=N - 1 Piptadenia micracantha Small Spheroidal 8Rugulate S=N - 3 Piptadenia paniculata Medium Spheroidal 16 Granulate S=N + 1 Piptadenia peruviana Medium Spheroidal 16 Areolate S>N - 1 Piptadenia pteroclada Medium Ovoid 12 Rugulate S<N + 2 Piptadenia ramosissima Small Ovoid 8Areolate - - 3 Piptadenia retusa Small Ovoid 8Verrucate S=N - 3 Piptadenia robusta Medium Spheroidal 12 Rugulate S=N - 2 Piptadenia santosii Medium Ovoid 12 Rugulate S>N - 2 Piptadenia trisperma Small Spheroidal 8Verrucate - - 3 Piptadenia uaupensis Medium Spheroidal 16 Verrucate S>N - 1 Piptadenia uliginosa Medium Spheroidal 16 Rugulate S=N + 1 Legend: S = sexine / N= nexine and verrucate in P. uaupensis. Included taxa: P. imatacae, P. peruviana, P. uliginosa, P. killipii, P. laxipinna, P. paniculata, and P. uaupensis. Type 2 – Polyads with 12 pollen grains (Fig. 2F, K); predominantly spheroidal, occasionally ovoid in Piptadenia adiantoides, Piptadenia pteroclada, and Piptadenia santosii. The largest diameter measuring 19.33-42.5 µm. Areolate exine ornamentation in P. gonoacantha, and rugulate exine in P. adiantoides, P. buchtienii, P. cuzcoënsis, P. floribunda, P. pteroclada, P. robusta, and P. santosii. Included taxa: P. adiantoides, P. buchtienii, P. cuzcoënsis, P. floribunda, P. gonoacantha, P. pteroclada, P. robusta, and P. santosii. Type 3 – Polyads with eight pollen grains (Fig. 1C, E); predominantly ovoid, possibly spheroidal only in P. micracantha and P. trisperma. The largest diameter measuring 17.3-28.4 µm. Verrucate exine ornamentation in P. irwinii, P. retusa, P. trisperma, areolate in P. ramosissima, and rugulate in P. affinis and P. micracantha. Discussion Pollen Morphology The species of Piptadenia exhibit similarities in the size and shape of their polyads but show variation in the number of pollen grains per polyad and in exine ornamentation. This aligns with findings reported by Caccavari (2002), who highlighted significant palynological variation among Piptadenia species. The size of the polyads ranged from small to medium, with medium-sized polyads being predominant. This observation is consistent with findings in the literature for various species of the Template: Editora Letra1 | www.editoraletra1.com.br Duarte et al. 8 | Acta Botanica Brasilica, 2025, 39: e20240125 Figure 2. Pollen grains of species of Piptadenia (Leguminosae) analyzed under Light Microscopy (LM) and Scanning Electron Microscopy (SEM). P. killipii - A. Ovoidal polyad, B. Areolate ornamentation. P. laxipinna -C. Rugulate ornamentation. P. micracantha - D. Spheroidal polyad, E. Rugulate ornamentation. P. paniculataF. Polyad with 16 pollen grains, G. Granulate ornamentation. P. peruviana - H. Areolate ornamentation. P.pteroclada - I. Ovoidal polyad, J. Rugulate ornamentation. P. ramosissima - K. Polyad with 8 pollen grains,L. Detail of areolate ornamentation. Scales: 10 µm (A, F, I, K), 5 µm (D, G, J, L), 1 µm (B, C, E, H). Pollen morphology of Piptadenia Template: Editora Letra1 | www.editoraletra1.com.br Acta Botanica Brasilica, 2025, 39: e20240125 | 9 Figure 3. Pollen grains of species of Piptadenia (Leguminosae) analyzed under Light Microscopy (LM) and Scanning Electron Microscopy (SEM). P. retusa - A. Ovoidal polyad, B. Verrucate ornamentation. P. robusta - C. Polyad with 12 pollen grains, D. Rugulate ornamentation. P. santosii - E. Ovoidal polyad, F. Rugulate ornamentation. P. trisperma - G. Spheroidal polyad, H. Verrucate ornamentation. P. uaupensis - I. Spheroidal polyad, J. Rugulate ornamentation. P. uliginosa - K. Spheroidal polyad, L. Rugulate ornamentation. Scales: 10 µm (A, C, E, G), 5 µm (B, F, H, I), 1 µm (D, J, K, L).