Main Article Content
Abstract
Croceous glands are yellowish glands that occur exclusively in some species of Senega Spach (Polygalaceae). These glands are especially conspicuous in reproductive organs, such as the fruits, but their structure, origin, and secretion are still uncertain. The objective of this study is to determine the nature of the croceous glands in Senega from an analysis of the fruits of Senega longicaulis (Kunth) J.F.B. Pastore. Flowers and fruits at different developmental stages were analysed through light microscopy and scanning electron microscopy to investigate the origin, structure, and composition of the secretion of the glands. Croceous glands of the pericarp are cavities that originate early, while still in the ovary, through a schizolysigenous process. In addition, new glands are formed de novo during fruit development, and the persistent calyx observed surrounding the fruit, also has such cavities. The secretory tissue is constituted by a single layer of epithelial cells, lining a spheroidal lumen that stores the secretion. The exudate is composed of essential oils, indicating functions related to protection against herbivory and microbial attacks. Our results partially diverge from previous reports, and further comprehensive analyses of Polygalaceae glands are essential to understand the nature of croceous glands and the evolution of defence strategies within the family.
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Copyright (c) 2026 Layse K. C. Lopes, Ana C. A. A. Dias, José Floriano B. Pastore, Diego Demarco

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References
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- Bennett, R.N., Wallsgrove, R.M., 1994: Secondary metabolites in plant defence mechanisms. New Phytologist 127, 617–633. https://doi.org/10.1111/j.1469-8137.1994.tb02968.x
- Cain, A. J., 1947: The use of Nile blue in the examination of lipoids. The Quarterly Journal of Microscopical Science 88, 383–392. https://doi.org/10.1242/jcs.s3-88.3.383
- Chodat, R. H., 1893: Monographia polygalacearum. Memoires de la Société de Physique et d’Histoire Naturelle de Genève 31, 1–500.
- Costa, E. R., Tangerina, M. M. P., Ferreira, M. J. P., Demarco, D., 2021: Two origins, two functions: the discovery of distinct secretory ducts formed during the primary and secondary growth in Kielmeyera. Plants 10, 877. https://doi.org/10.3390/plants10050877
- Costa, E. R., Demarco, D., 2024: Development and holocrine secretion of resin ducts in Kielmeyera appariciana (Calophyllaceae). Plants 13, 1757. https://doi.org/10.3390/plants13131757
- David, R., Carde, J. P., 1964: Coloration différentielle des inclusions lipidiques et terpéniques des pseudophylles du Pin maritime au moyen du réactif Nadi. Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences 258, 1338–1340.
- Demarco, D., 2023: Histochemical analysis of plant secretory structures. In: Pellicciari, C., Biggiogera, M., Malatesta, M. (eds.), Histochemistry of single molecules. Methods and protocols, 2nd ed., 2566, 291–310. Humana Press, New York. https://doi.org/10.1007/978-1-0716-2675-7_24
- Demarco, D., Castro, M. M., Ascensão, L., 2013: Two laticifer systems in Sapium haematospermum – new records for Euphorbiaceae. Botany 91, 545–554. https://doi.org/10.1139/cjb-2012-0277
- Duarte-Almeida, J. M., Clemente, M. S., Arruda, R. C. O., Vaz, A. M. S. F., Salatino, A., 2015: Glands on the foliar surfaces of tribe Cercideae (Caesapiniodeae, Leguminosae): distribution and taxonomic significance. Anais da Academia Brasileira de Ciências 87, 787–796. https://doi.org/10.1590/0001-3765201520140151
- Fahn, A., 1979: Secretory tissues in plants. Academic Press, London.
- Fernandes, V. F., Thadeo, M., Dalvi, V. C., Marquete, R., Silva, J. X. B., Pereira, L. J., Meira, R. M. S. A., 2018: How to distinguish cavities from ducts in Casearia Jacq. (Salicaceae): anatomical characterization and distribution. Flora 240, 89–97. https://doi.org/10.1016/j.flora.2018.01.007
- Freitas, C. D. T., Demarco, D., Oliveira, J. S., Ramos, M.V., 2024: Review: Laticifer as a plant defense mechanism. Plant Science 346, 112136. https://doi.org/10.1016/j.flora.2018.01.007
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- Gregory, M., Baas, P., 1989: A survey of mucilage cells in vegetative organs on the dicotyledons. Israel Journal of Botany 38, 125–174. https://doi.org/10.1080/0021213X.1989.10677119
- Holm, T., 1929: Morphology of North American species of Polygala. Botanical Gazette 88, 167–185. https://doi.org/10.1086/333988
- Jensen, W. A., 1962: Botanical histochemistry: principles and practice. W. H. Freeman and Co., San Francisco.
- Johansen, D. A., 1940: Plant microtechnique. McGraw-Hill, New York.
- Jorge, A. C. S., Filgueira, J. P. P. S., Lopes, L. K. C., Aguiar-Dias, A. C. A., 2024: Croceous glands in Polygala adenophora DC. (Polygalaceae): structure, histochemical, and functional aspects. Acta Amazonica 54, e54bc23109. http://dx.doi.org/10.1590/1809-4392202301091
- Ladd, P. G., 2024: Myrtaceae anther glands: morphology, anatomy and variation in glandular contents. Australian Journal of Botany 72, BT23073. https://doi.org/10.1071/BT23073
- Lange, B. M., 2015: The evolution of plant secretory structures and emergence of terpenoid chemical diversity. Annual Review of Plant Biology 66, 139–159. https://doi.org/10.1146/annurev-arplant-043014-114639
- Lillie, R. D., 1965: Histopathologic technic and practical histochemistry. 3rd ed. McGraw-Hill, New York.
- Lüdtke, R., Souza-Chies, T. T., Miotto, S. T. S., 2013: The genus Polygala L. (Polygalaceae) in Southern Brazil. Hoehnea 40, 1–50. https://doi.org/10.1590/S2236-89062013000100001
- Mendes, K. R., Fortuna-Perez, A. P., Rodrigues, T. M., 2019: Leaflet anatomy of Poiretia Vent.(Leguminosae, Papilionoideae, Dalbergieae) with emphasis on internal secretory structures in support of taxonomy. Flora 260, 151484. https://doi.org/10.1016/j.flora.2019.151484
- Metcalfe, C. R., Chalk, L., 1950: Anatomy of the dicotyledons: leaves, stem and wood in relation to taxonomy with notes on economic uses. 2 vol. Clarendon Press, Oxford.
- Milani, J. F., Rocha, J. F., Teixeira, S. P., 2012: Oleoresin glands in copaíba (Copaifera trapezifolia Hayne: Leguminosae), a Brazilian rainforest tree. Trees 26, 769–775. https://doi.org/10.1007/s00468-011-0642-y
- O'Brien, T. P., Feder, N., McCully, M. E., 1964: Polychromatic staining of plant cell walls by toluidine blue O. Protoplasma 59, 368–373. https://doi.org/10.1007/BF01248568
- Paschoalini, G. O., Pirani, J. R., Demarco, D., El Ottra, J. H. L., 2022: Revisiting pericarp structure, dehiscence and seed dispersal in Galipeeae (Zanthoxyloideae, Rutaceae). Brazilian Journal of Botany 45, 415–429. https://doi.org/10.1007/s40415-021-00779-9
- Pastore, J. F. B., 2018: A new species and new combination in Polygala sect. Timutua series Timoutoideae from Brazil. Kew Bulletin 73, 1–6. https://doi.org/10.1007/s12225-018-9773-2
- Pastore, J. F. B., Harley, R. M., 2009: Polygala tacianae (Polygalaceae), a new endemic species from Chapada dos Veadeiros region, Goiás state, Brazil. Kew Bulletin 64, 705–708. https://doi.org/10.1007/s12225-009-9159-6
- Pastore, J. F. B., Martinez, A., Abbott, J. R., Neubig, K., 2023: Toward new generic delimitations in Polygalaceae II: Senega. Annals of the Missouri Botanical Garden, 108, 126–249. https://doi.org/10.3417/2023754
- Pearse, A. G. E., 1985: Histochemistry: theoretical and apllied. 4th ed., 2 v. C. Livingstone, Edinburgh.
- Pizzolato, T. D., 1977: Staining of Tilia mucilages with Mayer's tannic acid-ferric chloride. Bulletin of the Torrey Botanical Club 104, 277–279. https://www.jstor.org/stable/2484311
- Svedsen, A. B., Verpoorte, R., 1983: Chromatography of alkaloids. Elsevier, New York.
- Teixeira, S. P., Rocha, J. F., 2009: Oil glands in the Neotropical genus Dahlstedtia Malme (Leguminosae, Papilionoideae, Millettieae). Brazilian Journal of Botany 32, 57–64. https://doi.org/10.1590/S0100-84042009000100006
- Tölke, E. D., Lacchia, A. P. S., Lima, E. A., Demarco, D., Ascensão, L., Carmello-Guerreiro, S. M., 2021: Secretory ducts in Anacardiaceae revisited: updated concepts and new findings based on histochemical evidence. South African Journal of Botany 138, 394–405. https://doi.org/10.1016/j.sajb.2021.01.012
- Tölke, E. D., Medina, M. C., Souto, A. L., Marques, J. P. R., Alves, G. G. N., Gama, R. L., Pirani, J. R, Demarco, D., 2022: Diversity and evolution of secretory structures in Sapindales. Brazilian Journal of Botany 45, 251–279. https://doi.org/10.1007/s40415-021-00778-w
- Waterman, P.G., 1992: Roles for secondary metabolites in plants. In: Chadwick, D. J., Whelm, J.(eds.), Secondary metabolites: their function and evolution, 255–275. Wiley, Chichester. https://doi.org/10.1002/9780470514344.ch15
References
Aguiar-Dias, A. C. A., Cardoso-Gustavson, P., 2011: Ontogeny of the mucilage ducts of Polygala angulata DC.(Polygalaceae). The Journal of the Torrey Botanical Society 138, 255–261. https://doi.org/10.3159/TORREY-D-11-00014.1
Aguiar-Dias, A. C. A., Yamamoto, K., Castro, M. M., 2012: Anatomia foliar de cinco espécies de Polygala de restinga e cerrado. Rodriguésia 63, 395–404. https://doi.org/10.1590/S2175-78602012000200012
Bennett, R.N., Wallsgrove, R.M., 1994: Secondary metabolites in plant defence mechanisms. New Phytologist 127, 617–633. https://doi.org/10.1111/j.1469-8137.1994.tb02968.x
Cain, A. J., 1947: The use of Nile blue in the examination of lipoids. The Quarterly Journal of Microscopical Science 88, 383–392. https://doi.org/10.1242/jcs.s3-88.3.383
Chodat, R. H., 1893: Monographia polygalacearum. Memoires de la Société de Physique et d’Histoire Naturelle de Genève 31, 1–500.
Costa, E. R., Tangerina, M. M. P., Ferreira, M. J. P., Demarco, D., 2021: Two origins, two functions: the discovery of distinct secretory ducts formed during the primary and secondary growth in Kielmeyera. Plants 10, 877. https://doi.org/10.3390/plants10050877
Costa, E. R., Demarco, D., 2024: Development and holocrine secretion of resin ducts in Kielmeyera appariciana (Calophyllaceae). Plants 13, 1757. https://doi.org/10.3390/plants13131757
David, R., Carde, J. P., 1964: Coloration différentielle des inclusions lipidiques et terpéniques des pseudophylles du Pin maritime au moyen du réactif Nadi. Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences 258, 1338–1340.
Demarco, D., 2023: Histochemical analysis of plant secretory structures. In: Pellicciari, C., Biggiogera, M., Malatesta, M. (eds.), Histochemistry of single molecules. Methods and protocols, 2nd ed., 2566, 291–310. Humana Press, New York. https://doi.org/10.1007/978-1-0716-2675-7_24
Demarco, D., Castro, M. M., Ascensão, L., 2013: Two laticifer systems in Sapium haematospermum – new records for Euphorbiaceae. Botany 91, 545–554. https://doi.org/10.1139/cjb-2012-0277
Duarte-Almeida, J. M., Clemente, M. S., Arruda, R. C. O., Vaz, A. M. S. F., Salatino, A., 2015: Glands on the foliar surfaces of tribe Cercideae (Caesapiniodeae, Leguminosae): distribution and taxonomic significance. Anais da Academia Brasileira de Ciências 87, 787–796. https://doi.org/10.1590/0001-3765201520140151
Fahn, A., 1979: Secretory tissues in plants. Academic Press, London.
Fernandes, V. F., Thadeo, M., Dalvi, V. C., Marquete, R., Silva, J. X. B., Pereira, L. J., Meira, R. M. S. A., 2018: How to distinguish cavities from ducts in Casearia Jacq. (Salicaceae): anatomical characterization and distribution. Flora 240, 89–97. https://doi.org/10.1016/j.flora.2018.01.007
Freitas, C. D. T., Demarco, D., Oliveira, J. S., Ramos, M.V., 2024: Review: Laticifer as a plant defense mechanism. Plant Science 346, 112136. https://doi.org/10.1016/j.flora.2018.01.007
Garcia, T. B., Costa, E. R., Kikuchi, T. Y. S., Aguiar-Dias, A. C. A., Demarco, D., 2020: Coalescent cavities: a novel process of secretory duct formation in Theobroma L. (Malvaceae). In: Demarco, D. (ed.), Plant ontogeny: studies, analyses and evolutionary implications, 1–20. Nova Science, New York.
Gerlach, D., 1984: Botanische Mikrotechnik: Eine Einführung. 3rd ed.. Georg Thieme, Stuttgart.
Gregory, M., Baas, P., 1989: A survey of mucilage cells in vegetative organs on the dicotyledons. Israel Journal of Botany 38, 125–174. https://doi.org/10.1080/0021213X.1989.10677119
Holm, T., 1929: Morphology of North American species of Polygala. Botanical Gazette 88, 167–185. https://doi.org/10.1086/333988
Jensen, W. A., 1962: Botanical histochemistry: principles and practice. W. H. Freeman and Co., San Francisco.
Johansen, D. A., 1940: Plant microtechnique. McGraw-Hill, New York.
Jorge, A. C. S., Filgueira, J. P. P. S., Lopes, L. K. C., Aguiar-Dias, A. C. A., 2024: Croceous glands in Polygala adenophora DC. (Polygalaceae): structure, histochemical, and functional aspects. Acta Amazonica 54, e54bc23109. http://dx.doi.org/10.1590/1809-4392202301091
Ladd, P. G., 2024: Myrtaceae anther glands: morphology, anatomy and variation in glandular contents. Australian Journal of Botany 72, BT23073. https://doi.org/10.1071/BT23073
Lange, B. M., 2015: The evolution of plant secretory structures and emergence of terpenoid chemical diversity. Annual Review of Plant Biology 66, 139–159. https://doi.org/10.1146/annurev-arplant-043014-114639
Lillie, R. D., 1965: Histopathologic technic and practical histochemistry. 3rd ed. McGraw-Hill, New York.
Lüdtke, R., Souza-Chies, T. T., Miotto, S. T. S., 2013: The genus Polygala L. (Polygalaceae) in Southern Brazil. Hoehnea 40, 1–50. https://doi.org/10.1590/S2236-89062013000100001
Mendes, K. R., Fortuna-Perez, A. P., Rodrigues, T. M., 2019: Leaflet anatomy of Poiretia Vent.(Leguminosae, Papilionoideae, Dalbergieae) with emphasis on internal secretory structures in support of taxonomy. Flora 260, 151484. https://doi.org/10.1016/j.flora.2019.151484
Metcalfe, C. R., Chalk, L., 1950: Anatomy of the dicotyledons: leaves, stem and wood in relation to taxonomy with notes on economic uses. 2 vol. Clarendon Press, Oxford.
Milani, J. F., Rocha, J. F., Teixeira, S. P., 2012: Oleoresin glands in copaíba (Copaifera trapezifolia Hayne: Leguminosae), a Brazilian rainforest tree. Trees 26, 769–775. https://doi.org/10.1007/s00468-011-0642-y
O'Brien, T. P., Feder, N., McCully, M. E., 1964: Polychromatic staining of plant cell walls by toluidine blue O. Protoplasma 59, 368–373. https://doi.org/10.1007/BF01248568
Paschoalini, G. O., Pirani, J. R., Demarco, D., El Ottra, J. H. L., 2022: Revisiting pericarp structure, dehiscence and seed dispersal in Galipeeae (Zanthoxyloideae, Rutaceae). Brazilian Journal of Botany 45, 415–429. https://doi.org/10.1007/s40415-021-00779-9
Pastore, J. F. B., 2018: A new species and new combination in Polygala sect. Timutua series Timoutoideae from Brazil. Kew Bulletin 73, 1–6. https://doi.org/10.1007/s12225-018-9773-2
Pastore, J. F. B., Harley, R. M., 2009: Polygala tacianae (Polygalaceae), a new endemic species from Chapada dos Veadeiros region, Goiás state, Brazil. Kew Bulletin 64, 705–708. https://doi.org/10.1007/s12225-009-9159-6
Pastore, J. F. B., Martinez, A., Abbott, J. R., Neubig, K., 2023: Toward new generic delimitations in Polygalaceae II: Senega. Annals of the Missouri Botanical Garden, 108, 126–249. https://doi.org/10.3417/2023754
Pearse, A. G. E., 1985: Histochemistry: theoretical and apllied. 4th ed., 2 v. C. Livingstone, Edinburgh.
Pizzolato, T. D., 1977: Staining of Tilia mucilages with Mayer's tannic acid-ferric chloride. Bulletin of the Torrey Botanical Club 104, 277–279. https://www.jstor.org/stable/2484311
Svedsen, A. B., Verpoorte, R., 1983: Chromatography of alkaloids. Elsevier, New York.
Teixeira, S. P., Rocha, J. F., 2009: Oil glands in the Neotropical genus Dahlstedtia Malme (Leguminosae, Papilionoideae, Millettieae). Brazilian Journal of Botany 32, 57–64. https://doi.org/10.1590/S0100-84042009000100006
Tölke, E. D., Lacchia, A. P. S., Lima, E. A., Demarco, D., Ascensão, L., Carmello-Guerreiro, S. M., 2021: Secretory ducts in Anacardiaceae revisited: updated concepts and new findings based on histochemical evidence. South African Journal of Botany 138, 394–405. https://doi.org/10.1016/j.sajb.2021.01.012
Tölke, E. D., Medina, M. C., Souto, A. L., Marques, J. P. R., Alves, G. G. N., Gama, R. L., Pirani, J. R, Demarco, D., 2022: Diversity and evolution of secretory structures in Sapindales. Brazilian Journal of Botany 45, 251–279. https://doi.org/10.1007/s40415-021-00778-w
Waterman, P.G., 1992: Roles for secondary metabolites in plants. In: Chadwick, D. J., Whelm, J.(eds.), Secondary metabolites: their function and evolution, 255–275. Wiley, Chichester. https://doi.org/10.1002/9780470514344.ch15
