Botanical Journal of the Linnean Society, 2012, 168, 377–394. With 6 figures Gynoecium and fruit histology and development in Eugeissona (Calamoideae: Arecaceae) ALEXEY V. F. Ch. BOBROV1*, JOHN DRANSFIELD2 FLS, MIKHAIL S. ROMANOV3 and 4 EKATERINA S. ROMANOVA Downloaded from https://academic.oup.com/botlinnean/article/168/4/377/2416104 by guest on 27 September 2021 1Department of Biogeography, Geographical Faculty, M. V. Lomonosov Moscow State University, Moscow, 119991, Russia 2Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, UK 3Department of Dendrology, Main Botanical Garden nm. Tsitsin N. V. RAS, Botanicheskaya st., 4, 127276, Moscow, Russia 4Botanical garden, Biological Faculty, M. V. Lomonosov Moscow State University, Moscow, 119991, Russia Received 14 June 2011; revised 18 August 2011; accepted for publication 6 December 2011 The Malesian genus Eugeissona, with six species, is sister to all other Calamoideae, which are in turn sister to all other Arecaceae. The structure of its gynoecium and fruit is thus potentially of great interest in understanding gynoecium evolution in calamoid palms and in Arecaceae as a whole. The wall of the incompletely trilocular gynoecium of Eugeissona is thick and differentiated into several topographic zones, with a well-developed vascular system even before pollination. During gynoecium and fruit development, the outer and inner epidermises are little specialized and form the exocarp and endocarp (obliterated in the mature fruit), respectively. In contrast, the mesophyll of the carpels differentiates strongly and is markedly specialized: four massive topographic zones are easily distinguished within the mesocarp. The peripheral zone of the mesocarp forms the body of the scales (a synapomorphy for Calamoideae). The second and the fourth zones are multilayered and parenchymatous with a massive derived vascular system in the former. The third zone of the mesocarp comprises a stout sclerenchymatous pyrene, made of fibre-like sclereids, the innermost bundles of the derived vascular system and dorsal, ventral and lateral vascular bundles. The fruits of all other Calamoideae lack the sclerenchymatous pyrene and thus differ dramatically from Eugeissona fruits. The similarity of the processes of histogenesis during gynoecium and fruit development in Eugeissona with those in Nypa and borassoid palms, suggests these features could be plesiomorphic for the family. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168, 377–394. ADDITIONAL KEYWORDS: Borasseae – carpel wall structure – Nypa – pericarp anatomy – pyrene – scales – vasculature. INTRODUCTION Eugeissona is thus of great importance for developing perspectives of gynoecium and fruit development in The genus Eugeissona Griff. has recently been shown the family. The gynoecium of Eugeissona (and all to be sister to all other Calamoideae, which are in genera of Calamoideae) is termed ‘incompletely turn sister to all other Arecaceae (Asmussen et al., trilocular’ (Dransfield & Uhl, 1998; Dransfield et al., 2006; Dransfield et al., 2008; Baker et al., 2009). An 2008). Nevertheless, the fruits of Eugeissona differ investigation of gynoecium and fruit development of from those in other genera of Calamoideae in the development of a thick sclerenchymatous pyrene in the pericarp. The dramatic difference in the general structure *Corresponding author. E-mail: [email protected] of the fruit of Eugeissona from other taxa of © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168, 377–394 377 378 A. V. F. Ch. BOBROV ET AL. Calamoideae was recognized by Beccari (1913), highly specialized fruits: both apocarpous (Schippia Corner (1966) and Dransfield (1970); Beccari sup- concolor Burret) and syncarpous (Chuniophoenix posed that the fruit of Eugeissona is the ‘connecting Burret, Kerriodoxa elegans J.Dransf., Sabal Adans.) link’ between the fruits of Calamoideae and monospermous berries (Bobrov et al., 2008b). A much Arecoideae tribe Cocoseae, which also have a thick more complex structure of the pericarp (and the pecu- sclerenchymatous pyrene. Nevertheless, the histoge- liar mode of the pyrene development) is described for nesis of the pyrene in Eugeissona has not been syncarpous fruits of Coryphoideae tribe Borasseae described in the literature. Recent data support the (Romanov et al., 2011), which are referred to pyre- isolated position of Eugeissona among Calamoideae, naria of the Latania type. In contrast, fruits of most which is also supported by other morphological char- species of Calamus L. are monospermous (a few are acters (Dransfield et al., 2008); for example, the dispermous or trispermous) paracarpous berries Downloaded from https://academic.oup.com/botlinnean/article/168/4/377/2416104 by guest on 27 September 2021 branching by putative dichotomy of the apical mer- covered with gynoecial scales, making the structure istem (Fisher, Goh & Rao, 2008), partial centrifugal of the fruits more complex (Bobrov, Romanov & stamen development (Uhl & Dransfield, 1984) and by Melikian, 2011). Thus, the problem of what consti- unique nectar with high concentrations of alcohol, tutes the plesiomorphic and what the derived state in securing pollination by small arboreal mammals (slow the structure of the pericarp of Arecaceae remains loris, pentailed tupaias, etc.) (Wiens et al., 2008). unsolved, and an investigation of gynoecium and fruit Since the time of Drude (1887), palms with apoc- structure in Eugeissona will contribute to an analysis arpous gynoecia have tended to be treated in tradi- of which characters should be treated as plesiomor- tional classifications as the most archaic (Hutchinson, phic for Calamoideae and palms in general. 1973; Moore, 1973; Imkhanitzkaya, 1985; Takhtajan, 1987). In the first edition of Genera Palmarum (Uhl & Dransfield, 1987), Coryphoideae was considered to be MATERIAL AND METHODS the least specialized subfamily, and the presumed Material of Eugeissona species fixed in formalin– most archaic taxa of the subfamily were genera with acetic acid–alcohol (FAA) and dry herbarium speci- apocarpous gynoecia in Corypheae subtribe Thrinaci- mens were used in the present study (see Table 1). nae (Dransfield & Uhl, 1998). The interpretation of Morphometric information for all studied develop- apocarpous palms as primitive agreed with the gen- mental stages is given in Table 2. Standard anatomi- erally accepted evolutionary concept of gynoecium cal protocol was used for anatomical investigations types, according to which the apocarpous gynoecium (Bondartzev, 1954; Prozina, 1960; O’Brien & McCully, is the least specialized and the coenocarpous (i.e. 1981). The liquid-fixed gynoecia were embedded in syncarpous, paracarpous and lysicarpous) derived wax and transverse (TS) and longitudinal sections (Bessey, 1915; Takhtajan, 1964; Hutchinson, 1973). (LS) at 9–15 mm were made with a Jung rotary micro- Recent DNA sequence data have shown that Calam- tome. These sections were stained with safranin and oideae, all representatives of which have paracarpous fast green, and TS and LS (15–30 mm) of developmen- gynoecia, are sister to the rest of Arecaceae (Asmus- tal stages of Eugeissona fruits were carried out with sen et al., 2006; Dransfield et al., 2008; Baker et al., a sliding microtome from the samples embedded in 2009), with the possible implication that the gyno- paraffin. These sections were stained with phloroglu- ecium with free carpels found in some Coryphoideae cinol and hydrochloric acid to study details of lignifi- and Nypa Steck should be treated as secondarily cation of cell walls in different topographical zones of apocarpous, reopening the question of which type of the pericarp and were preserved in glycerine. All gynoecium is plesiomorphic in the palms. sections were studied with a light microscope. The The structure of apocarpous fruits of the investi- details of gynoecial scale development (= pericarp gated representatives of Coryphoideae is rather spe- surface) and of fruit-wall structure were also exam- cialized and cannot be treated as plesiomorphic ined with scanning electron microscopy (Camscan (Bobrov, Romanov & Romanova, 2008b). The mode of S-2), after critical-point drying and sputter coating development and structure of the stone of ‘coryphoid’ with gold palladium. fruits, described by Murray (1973) for Rhapidophyl- lum hystrix H.Wendl., Livistona R.Br., Pritchardia Seem. & H.Wendl., and Washingtonia H.Wendel. and TERMINOLOGY studied by us in Trachycarpus H.Wendel., Chamae- At all developmental stages, three histogenetic zones rops humilis L., Rhapis L.f and Guihaia J.Dransf., of the pericarp derived from the outer epidermis, S.K.Lee & F.N.Wei (Bobrov, Džalilova & Melikian, mesophyll and inner epidermis of the ovary wall were 2007a; Bobrov & Romanov, 2007; Bobrov, Romanov & recognized: exocarp, mesocarp and endocarp. The rec- Melikian, 2008a) is treated as specialized. Moreover, ognition of these zones as histogenetic, but not topo- a number of representatives of Coryphoideae have graphic, is important for developmental studies © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168, 377–394 GYNOECIUM AND FRUIT DEVELOPMENT IN EUGEISSONA 379 Table 1. Investigated species and specimens Eugeissona insignis, J. Dransfield no. JD747, 27.3.68, Bako National Park, Sarawak, alt. 10 m, in kerangas forest, RBG Kew Palm group collection and BH spirit collection, gynoecium stage 4 Eugeissona insignis, J. Dransfield no. JD754,