THAI FOREST BULL., BOT. 47(1): 55–68. 2019. DOI https://doi.org/10.20531/tfb.2019.47.1.09 Pollen morphology of Lecythidaceae in Southeast Asia WORANART THAMMARONG1,2, PRANOM CHANTARANOTHAI3, JOHN A.N. PARNELL4, TREVOR R. HODKINSON4 & PIMWADEE PORNPONGRUNGRUENG1,* ABSTRACT The pollen morphology of four genera and 33 taxa of Lecythidaceae in Southeast Asia was investigated, including 26 taxa of Barringtonia, one taxon each of Careya and Chydenanthus, and five taxa of Planchonia to determine which, if any, taxonomically important characters were present and the implications they have for the systematics of the family. Acetolysed and unacetolysed pollen samples were investigated using light and scanning electron microscopy (SEM). The pollen grains were found to be monads, radially symmetrical, isopolar, small to medium-sized, syntricolpate or syntricolporate, prolate spheroidal, oblate spheroidal, subprolate, suboblate or spherical in shape with marginal ridges. Marginal grooves and polar cushions are commonly present in most species. The polar ectoaperture may be open or sealed. The mesocolpial sculpturing is perforate-reticulate. The colpial surface is smooth, with sparsely or densely scattered verrucae-gemmae and with clavate to pilate elements scattered or aligned in longitudinal rows. The results indicated that pollen morphological characters can be used for identification and classification of some closely related species in the genus Barringtonia. KEYWORDS: Barringtonia, Brazil nut family, Careya, Chydenanthus, Planchonia, pollen, taxonomy Accepted for publication: 21 March 2019. Published online: 17 April 2019 INTRODUCTION base into a short or long staminal ring and an inferior or half-inferior ovary. The family Lecythidaceae is placed in the order Ericales (APG, 1998, 2016; Schönenberger et al., The classification of the family remains 2005; Reveal & Chase, 2011). It is a family of small uncertain: There is a conflict in the classifications to large trees, shrubs or rarely herbs with 22 genera of the APG (2003, 2016), that included the and 325 species (Prance, 2012), distributed mainly Napoleonaceae and Scytopetalaceae in the in the moist lowland Neotropics, tropical west and Lecythidaceae, and Prance and Mori (2004) who east Africa and tropical Asia to north Australia recognised the three as distinct families and divided (Prance & Mori, 2004). Ecologically, many species the Lecythidaceae into three subfamilies; are found in swampy forest areas, montane evergreen Barringtonioideae (Planchonioideae), Foetidoideae and mixed deciduous forests, while a few species and Lecythidoideae. The latter system was supported occur in open areas. They can be found from sea by molecular work (Mori et al., 2007). Only subfamily level to 3,500 m in altitude (Thammarong, 2017). Barringtonioideae occurs in Southeast Asia, where The family is characterised by alternate simple leaves, it contains about 70 species in five genera racemose or paniculate inflorescences or solitary (Thammarong, 2017). Taxonomic information on flowers that are hermaphroditic, actinomorphic or Southeast Asian Lecythidaceae is, unfortunately, zygomorphic with numerous stamens connate at limited to considerations of species diversity and 1 Applied Taxonomic Research Center, Department of Biology, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand. 2 Botanical Garden Organization, Queen Sirikit Botanic Gardens, P.O. Box 7, Mae Rim, Chiang Mai 50180, Thailand. 3 Department of Biology and Center of Excellence on Biodiversity (BDC), Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand. 4 Herbarium, Botany Department, School of Natural Sciences, Trinity College Dublin, the University of Dublin and Trinity Centre for Biodiversity Research, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland. * Corresponding author: [email protected] © 2019 Forest Herbarium 56 THAI FOREST BULLETIN (BOTANY) VOL. 47 NO. 1 morphology. This is problematic, as the circumscrip- made on 5–15 grains per taxon. Terminology and tion of some complex groups of Lecythidaceae taxa pollen size classes follow Walker & Doyle (1975), based on morphology may be exceptionally difficult Tsou (1994) and Hesse et al. (2009); herbarium (Prance & Mori, 1979; Mori & Prance, 1990; Prance abbreviations follow Index Herbariorum (Thiers, & Kartawinata, 2013). In other words, gross 2018, continuously updated). morphology by itself is insufficient to resolve the taxonomic problems in this family. However, pollen RESULTS morphological characteristics have proven to be diagnostic at species level in some genera in The common pollen morphological characters Lecythidaceae such as Allantoma Miers, Barringtonia of each of the studied genera are described below J.R.Forst. & G.Forst., Bertholletia Bonpl., Careya and the palynological features of each species are Roxb., Cariniana Casar., Chydenanthus Miers, summarised in Table 2. The outline of Southeast Couratari Aubl., Corythophora R.Knuth, Couroupita Asian Lecythidaceae pollen features is shown in Fig. Aubl., Crateranthus Baker f., Eschweilera Mart. ex 1A–B. Additionally, the definition of some special DC., Foetidia Comm. ex Lam., Grias L., Gustavia L., pollen characters, such as the state of marginal Lecythis Loefl.,Petersianthus Merr. and Planchonia grooves, is shown and explained in Fig. 1C–G and Blume (Erdtman, 1952; Muller, 1972, 1973, 1979; the type of polar ectoaperture in Fig. 1H–I. Tsou, 1994; John & Kuriakose, 2012). Pollen mor- Barringtonia (Figs. 2–6A–F) phological characters are also useful for separating and explaining subfamilial relationships in Pollen grains are monads, radially symmetrical, Lecythidaceae (Muller, 1972). Moreover, most isopolar, of small to medium size (Polar axis (P) = members of Barringtonioideae have specific pollen 22.0–49.0 µm, Equatorial axis (E) = 22.0–49.0 µm), characters that differentiate them from all other suboblate, subprolate, spherical, prolate spheroidal Angiosperms, i.e. marginal ridges, marginal grooves and oblate spheroidal and syntricolpate except in B. and a syntricolpate grain (Tsou, 1994). Therefore, thailandica Thammar., Pornp. & Chantar. where it is this study aimed to investigate pollen morphological syntricolporate. Marginal ridges and marginal grooves characters of the Southeast Asian Lecythidaceae in are usually present except in B. acutangula subsp. order to determine diagnostic features and evaluate spicata (Blume) Payens, B. racemosa (L.) Spreng., their taxonomic implications. B. schmidtii Warb. ex Craib and B. thailandica. Marginal grooves, when present, are usually of medium size, though they are long in B. laxiflora MATERIAL AND METHODS Thammar., Pornp. & Chantar. and B. tomentosa Pollen grain features of four genera and 33 Thammar., Pornp. & Chantar. where they are long. taxa of Lecythidaceae in Southeast Asia were Polar cushions are present. Polar ectoaperture sealed examined using compound light microscopy (LM) or open. Colpial surface is usually smooth or has and scanning electron microscopy (SEM). The list sparsely or densely scattered verrucae-gemmae of voucher specimens included in this study is given elements. Mesocolpial sculpturing is perforate- in Table 1 and includes 26 taxa of Barringtonia, one reticulate. taxon each of Careya and Chydenanthus, and five taxa of Planchonia. The pollen samples were taken Careya (Fig. 6G–I) from field collections and herbarium specimens kept Pollen grains are monads, radially symmetrical, at BO, HN and K. Voucher specimens from fieldwork isopolar, of medium size (P = 35.0–38.0 µm, E = were deposited in KKU. Pollen from field collections 40.0–48.0 µm), suboblate and syntricolporate. were acetolysed according to Erdtman (1960), while Marginal ridges and marginal grooves are present. pollen from herbarium specimens were studied Marginal grooves are circular. Polar cushions are directly. The acetolysed and unacetolysed pollen absent. Polar ectoaperture open. Colpial surface has grains were examined and photographed using LM clavate to pilate elements scattered at the polar area (Olympus CH3, Optical Co., Ltd) and a Leo 1450 and aligned in longitudinal rows at the equatorial area. VP (Cambridge, UK) SEM. Measurements were Mesocolpial sculpturing is perforate-reticulate. POLLEN MORPHOLOGY OF LECYTHIDACEAE IN SOUTHEAST ASIA (W. THAMMARONG, P. CHANTARANOTHAI, J.A.N. PARNELL, T.R. HODKINSON & P. PORNPONGRUNGRUENG) 57 Table 1. List of plant materials included in this study. Species Voucher 1. Barringtonia acutangula (L.) Gaertn. subsp. acutangula Thailand, Phangnga, W. Thammarong 536 (KKU) 2. B. acutangula subsp. spicata (Blume) Payens Thailand, Songkhla, W. Thammarong 521 (KKU) 3. B. asiatica (L.) Kurz Thailand, Trang, W. Thammarong 527 (KKU) 4. B. augusta Wall. ex Kurz Thailand, Trat, W. Thammarong 543 (KKU) 5. B. calyptrocalyx var. mollis Lauterb. Indonesia, Moluccas, A.J.G.H. Kostermans 5126 (BO) 6. B. confusa Lütjeh. & Ooststr. Indonesia, Ambon, S.N. (BO-0123478) 7. B. conoidea Griff. Indonesia, Banka, H.A.B. Bunnemeijer 2088 (BO) 8. B. curranii Merr. Philippines, Palawan, A.D.E. Elmer 13033 (BO) 9. B. fusiformis King Malaysia, Pahang, M.R. Henderson 24848 (BO) 10. B. gigantostachya var. megistophylla (Merr.) Payens Indonesia, Menubar, A.J.G.H. Kostermans 5385 (BO) 11. B. lanceolata (Ridl.) Payens Indonesia, Saggau, A. Elsener 215 (BO) 12. B. laxiflora Thammar., Pornp. & Chantar. Vietnam, Thua Thien Hue, N.T. Hiep et al. 1351 (HN) 13. B. longipes Gagnep. Laos, Bolikhamxai, A.F.G. Kerr 20758 (K) 14. B. longisepala Payens