Ontogeny and structure of the acervulate partial inflorescence in Hyophorbe lagenicaulis (Arecaceae; Arecoideae)

Abstract

Aims The palm tribe Chamaedoreeae displays flowers arranged in a complex partial inflorescence called an acervulus. This type of partial inflorescence has so far not been reported elsewhere in the largest palm subfamily Arecoideae, which is traditionally characterized by flowers predominantly arranged in triads of one central female and two lateral male flowers. The ontogenetic basis of the acervulus is as yet unknown and its structural diversity throughout the genera of the Chamaedoreeae poorly recorded. This study aims to provide critical information on these aspects. † Methods Developmental series and mature inflorescences were sampled from plants cultivated in international botanical gardens and wild populations. The main techniques employed included scanning electronic microscopy and serial anatomical sectioning of resin-embedded fragments of rachillae. † Key Results Inflorescence ontogeny in Hyophorbe lagenicaulis demonstrates that the acervulus and the inflorescence rachilla form a condensed and cymose branching system resembling a coenosome. Syndesmy results from a combined process of rapid development and adnation, without or with reduced axis elongation. Acervulus diversity in the ten taxa of the Chamaedoreeae studied is displayed at the level of their positioning within the inflorescence, their arrangement, the number of floral buds and their sexual expression. † Conclusions The results show that a more general definition of the type of partial inflorescence observed within the large subfamily Arecoideae would correspond to a cyme rather than to a floral triad. In spite of their common cymose architecture, the floral triad and the acervulus present differences with respect to the number and arrangement of floral buds, the superficial pattern of development and sexual expression.

Comparative inflorescence development in selected Andean Santalales

“…Th e term coenosome was also coined by Troll (1964) , to refer to an apparently compact branch that is formed by two or more condensed branching systems (see also Weberling, 1989 ;Endress, 2010 ). Examples of coenosomes formed by syndesmy occur in Cordia (Boraginaceae; Baillon, 1862a ;Troll, 1964 ;Uhlarz and Weberling, 1977 ), Ficus (Moraceae; Bernbeck, 1932 ), chamaedoreoid palms ( Uhl and Moore, 1978 ;Ortega-Chávez and Stauff er, 2011 ), the aquatic Hydatella (Hydatellaceae; Endress, 2010 ), Enhalus (Hydrocharitaceae;Troll, 1964 ), some Podostemaceae ( Rutishauser and Grubert, 1999 ;Jäger-Zürn, 2003, and most likely Balanophora (Balanophoraceae; Eberwein et al, 2009 ). Given that some of these taxa have racemose (e.g., Mourera , Podostemaceae) and other have cymose partial infl orescences (e.g., Cordia , Dendrophthora , Phoradendron ), it is likely that syndesmy is a congenital fusion that can aff ect both types of infl orescence architecture.…”

“…Our observations on the members of Phoradendreae examined coincide with the reports of syndesmy in palm acervuli (an acervulus defi ned as a cyme formed by "a double row of 2-10 or more, closely appressed, sessile fl owers"; Uhl and Moore, 1978 : p. 197), as in both families partial infl orescences are fused to the main axis of the infl orescence, lack bracteoles, and the fl owers develop basipetally and are gradually displaced from the axil of the subtending bract to an extra-axillary position ( Uhl and Moore, 1978 ;Ortega-Chávez and Stauff er, 2011 ). In Stichiantus minutifl orus (Rubiaceae) and Capparis micracantha (Capparaceae), serial (but not collateral) accessory buds develop basipetally, likely as a result of fusion between the axillary meristem of cymes and the main axis of the fl owering shoot ( Winkler, 1931 ;Buchner, 2000 ).…”

Phylogeny and evolution of life-history strategies in the Sycophaginae non-pollinating fig wasps (Hymenoptera, Chalcidoidea)

“…The classification and the taxonomic limits of the group have been modified several times. Sycophaginae have been classified as a subfamily of Torymidae [ 35 - 38 ], or of Agaonidae [ 33 ]. Presently, they are not assigned to a family [ 39 ] and their phylogenetic position within Chalcidoidea remains unknown [ 40 ].…”

Diel Patterns of Activity for Insect Pollinators of Two Oil Palm Species (Arecales : Arecaceae)

“…The genus Elaeis contains two species of oil palm, the African oil palm Elaeis guineensis Jacquin and the American oil palm E. oleifera (Kunth) Cortés. Both oil palm species are monoecious; each individual of these palms produces unisexual male and female inflorescences ( Adam et al 2011 ), which are produced in alternate cycles. As a result, oil palm reproduction requires cross-pollination by insects ( Syed 1979 ).…”