Floral ontogeny and anatomy of the hemiparasitic shrub Gaiadendron punctatum and a comparison of floral characters in the tribes Gaiadendrinae and Nuytsiae (Loranthaceae) / Ontogenia floral y anatomía del arbusto hemiparasítico Gaiadendron punctatum y comparación de caracteres florales en las tribus Gaiadendrinae y Nuytsiae (Loranthaceae)

Abstract Introducction: Gaiadendron punctatum is a hemiparasitic species of Loranthaceae (Tribe Gaiadendreae) that is widely distributed in mountainous regions of Central and South America. Embryological and phylogenetic studies in the family indicate a trend towards reduction of the gynoecium and ovules, the morphology of which supports the current circumscription of Tribe Gaiadendreae (Gaiadendron and Atkinsonia). Molecular phylogenetic studies suggest that Nuytsia, Atkinsonia and Gaiadendron diverged successively, forming a grade at the base of the Loranthaceae, but support values are low. Objetive: In the present study, the floral anatomy of Gaiadendron punctatum was investigated in order to provide additional data to permit comparisons among the three basal-most genera in the Loranthaceae and reevaluate their relationships. Methods: Flowers of G. punctatum were collected at different developmental stages and serial sections were prepared and analyzed by light microscopy. Results: Inflorescence development is acropetal; the flowers are bisexual with an inferior ovary surmounted by a calyculus, a ring-shaped structure lacking vascular tissue; the ovary is comprised of seven basal locules, each with an ategmic, tenuinucellate ovule. Above the locules is a mamelon that is fused with the adjacent tissues. The androecium is comprised of seven epipetalous stamens, the anthers with fibrous endothecium dehiscence through a single longitudinal slit, releasing tricolpated pollen. Conclusions: The results of this study show that Gaiadendron and Atkinsonia share versatile, dorsifixed anthers, while Gaiadendron and Nuytsia share the same mode of anther dehiscence. On the other hand, Gaiadendron shares with members of Tribe Elytrantheae an amyliferous mamelon and an unvascularized calyculus. Combined phylogenetic analyses of morphological and molecular data are desirable to determine whether Tribe Gaiadendreae comprises a clade, a grade or if the two genera are more distantly related.

Resumen Introducción: Gaiadendron punctatum es una especie hemiparásita perteneciente a uno de los tres géneros basales de la familia Loranthaceae, siendo los otros dos Nuytsia y Atkinsonia. El género está conformado por dos especies distribuidas en regiones montañosas de Sudamérica y Centroamérica. Tanto los estudios embriológicos, como los filogenéticos, indican una tendencia hacia la reducción del gineceo y de los óvulos en la familia, cuya morfología respalda la circunscripción de la tribu Gaiadendreae (Gaiadendron y Atkinsonia). Estudios filogenéticos moleculares sugieren que Nuytsia, Atkinsonia y Gaiadendron divergieron sucesivamente, formando un grado en la base de la familia Loranthaceae, pero los valores en los que se sustenta son bajos. Objetivo: En el presente trabajo se describe la anatomía floral de la especie Gaiadendron punctatum con el objetivo de complementar la información embriológica, de manera que se pueda comparar directamente la morfología floral y los caracteres embriológicos entre los tres géneros basales de la familia Loranthaceae y reevaluar sus relaciones. Métodos: Las flores de G. punctatum fueron recolectadas en diferentes estados de desarrollo, se realizaron cortes histológicos seriados, se tiñeron con azul de astra y fucsina, y se analizaron mediante microscopía óptica. Resultados: Las inflorescencias mostraron un desarrollo acrópeto, las flores bisexuales presentaron ovario ínfero con presencia de una estructura en forma de anillo, carente de tejidos vasculares llamada calículo; el ovario se compone por siete lóculos basales, cada uno con un óvulo atégmico tenuinucelar. Por encima de los óvulos, el mamelón se fusiona con los tejidos adyacentes. El androceo está conformado por siete estambres epipétalos, las anteras presentan un endotecio fibroso y granos de polen tricolpados. La dehiscencia de las anteras es mediante una sola apertura longitudinal. Conclusiones: Los resultados del presente trabajo demuestran que Gaiadendron y Atkinsonia comparten anteras dorsifijas y versátiles, mientras Gaiadendron y Nuytsia comparten el tipo de dehiscencia anteral y por otro lado Gaiadendron comparte los caracteres de mamelón amilífero y calículo no vascularizado con la tribu Elytrantheae. La clasificación del género Gaiadendron con respecto a los dos géneros basales de la familia debe ser objeto de investigación (análisis filogenético combinado) que permita dirimir si la tribu Gaiadendrae es un clado, un grado o dos géneros más lejanamente emparentados.

Redox-related gene expression and sugar accumulation patterns are altered in the edible inflorescence produced by the cultivated form of pacaya palm (Chamaedorea tepejilote).

BACKGROUND AND AIMS: The pacaya palm is a dioecious neotropical palm species that is exploited in Latin America for its male inflorescence, which is edible when immature. It is cultivated, in a non-intensive manner, in Guatemala, where a morphotype occurs that produces much larger, more highly branched inflorescences compared with wild palms. We sought to identify molecular factors underlying this phenotypic divergence, which is likely to be a product of domestication. METHODS: We performed RNA-seq-based studies on immature pacaya palm male inflorescences in order to identify genes that might be directly or indirectly affected in their expression in relation to domestication. We also measured the accumulation of a range of soluble sugar molecules to provide information on the biochemical status of the two different types of material. KEY RESULTS: A total of 408 genes were found to display significantly different expression levels between the wild and cultivated morphotypes. Three different functional categories were found to be enriched in the gene set that was upregulated in the cultivated morphotype: redox balance; secondary metabolism; and transport. Several sugars were found to accumulate at higher levels in inflorescences of the cultivated morphotype, in particular myo-inositol, fructose and glucose. CONCLUSIONS: The observed upregulation of redox-related genes in the cultivated morphotype is corroborated by the observation of higher myo-inositol accumulation, which has been shown to be associated with enhanced scavenging of reactive oxygen species in other plants and which may affect meristem activity.

Floral anatomy of Tristerix longebracteatus (Loranthaceae) / Anatomía floral de Tristerix longebracteatus (Loranthaceae)

Introduction: Most of the New World members of the Loranthaceae comprise a clade that corresponds to the tribe Psittacantheae. Previous studies on floral anatomy and development in this tribe have concentrated on the highly diversified subtribe Psittacanthinae, while the smaller subtribe Ligarineae has received less attention. A detailed anatomical description of Tristerix longebracteatus helps to fill this information gap. Objetive: The present research analyzes the anatomy of Tristerix longebracteatus flowers, detailing the structure of androecium and gynoecium, including megasporogenesis and microsporogenesis. Methodology: Anatomical serial sections of flowers at different stages of development were prepared, following processing with fixation techniques, incorporation in paraffin, microtome sectioning and staining with Astra-blue and basic fuchsin. Results: The large-sized flowers of Tristerix longebracteatus present a complex pattern of vascularization with 18-20 vascular bundles at the base of the inferior ovary. A group of three vascular bundles irrigate the 4-5 petals and associated stamens, and ten bundles continue through the gynoecium. The androecium is composed of four or five anthers with simultaneous microsporogenesis. The gynoecium as a single ovarian cavity with a central mamelon in which the archesporial tissue is oriented towards the style. The base of the style forms a nectary similar to that found in the sister genus Ligaria. Conclusions: The gynoecium with a single ovarian cavity and central mamelon is a condition shared by Tristerix (subtribe Ligarinae) and all the genera of the subtribe Psittacanthinae, except Tripodanthus. The base of the style forms a nectary similar to that found in the sister genus Ligaria. This type of stylar nectary is of taxonomic value for grouping species of the subtribe Ligarinae and difers from the annular nectary of subtribe Psittacanthinae.

Introducción: La mayoría de los miembros de la familia de Loranthaceae del nuevo mundo comprenden un clado que corresponde a la tribu Psittacantheae. Estudios previos de la anatomía floral y desarrollo en esta tribu se han concentrado en la alta diversidad de la subtribu Psittacanthinae, en tanto que la subtribu Ligarinae ha presentado menor atención. Una descripción detallada de la anatomía de Tristerix longebracteatus contribuye a llenar vacíos de información. Objetivo: la presente investigación analiza la anatomía floral de Tristerix longebracteatus detallando la estructura del androceo, gineceo, incluyendo los procesos de megaesporogenesis y microesporogenesis. Metodología: Se prepararon secciones anatómicas seriadas de flores en diferentes etapas de desarrollo, con técnicas de fijación, incorporación en parafina, corte en micrótomo y doble tinción con azul de astra y fucsina. Resultados: Las flores de gran tamaño de Tristerix longebracteatus presentan un complejo patrón de vascularización con 18-20 haces vasculares en la base del ovario inferior. Un grupo de tres haces vasculares irrigan los 4-5 pétalos y estambres asociados, y 10 haces vasculares continúan a través del gineceo. El androecio está compuesto por cuatro o cinco anteras con microsporogénesis simultánea. El gineceo presenta una sola cavidad ovárica con un mamelón central en el que el tejido arquesporial está orientado hacia el estilo. La base del estilo forma un nectario similar al que se encuentra en el género hermano Ligaria. Conclusiones: El gineceo con una sola cavidad ovárica y un mamelón central es una condición compartida por Tristerix (subtribu Ligarinae) y todos los géneros de la subtribu Psittacanthinae, excepto Tripodanthus. La base del estilo forma un nectario similar al que se encuentra en el género hermano Ligaria. Este tipo de nectario estilar tiene valor taxonómico agrupando las especies de la subtribu Ligarinae en contraste con el anillo nectarífero presente en la subtribu Psittacanthinae.

Floral anatomy of the plant Psittacanthus schiedeanus (Loranthaceae) / Anatomía floral de la planta Psittacanthus schiedeanus (Loranthaceae)

Loranthaceae hemiparasitic family comprises 76 genera and about 1 050 species distributed in temperate and tropical regions.The subtribe Psittacanthinae contains 14 genera of neotropical mistletoe including Psittacanthus with over 120 species, characterized by large, brightly colored (red, orange, yellow) flowers that are mostly pollinated by hummingbirds. During the 20th century, a number of morphological and embryological studies were conducted mainly on Old World Loranthaceae genera. More recently, attention has been focused on neotropical Psittacanthinae where among the 14 genera, floral anatomy has been examined in only seven.The aim of this study is to describe the floral anatomy of Psittacanthus schiedeanus and compares the results with those derived from related mistletoe, interpreting the variation of the floral characters of the calyculus, nectary, gynoecium and from floral dissections and serial histological sections, detailing the structure of androecium and gynoecium and anthers in the context of the new phylogenetic information. Flowers of P. schiedeanus at different developmental stages were examined using stained serial sections visualized with light microscopy. These flowers have a vascularized, cupular pedicel fused to a bracteole, a non-vascularized calyculus, an annular nectary, a unilocular gynoecium with a single central mamelon and an androecium formed by epipetalous septate stamens. The morphological comparison of pedicel, bracteole and calyculus provides support for the interpretation of the calyculus as a reduced calyx. The annular nectary seems to be a character shared by the entire subtribe Psittacanthinae, which distinguishes it from Ligarinae which has stylar nectary. The unilocular gynoecium formed by a single central structure is a character shared with other genera in Psittacanthinae except Tripodanthus. The androecium is composed of dithecal, tetrasporangiate stamens with septate locules that are here considered an adaptation for pollen releasing over an extended time period rather than previous suggestions that they result from evolutionary pressure to reduce anther size or to facilitate the nutrition of microspores in large anthers.

La familia hemiparásita Loranthaceae comprende 76 géneros y aproximadamente 1 050 especies distribuidas en regiones templadas y tropicales. La subtribu Psittacanthinae contiene 14 géneros de muérdagos neotropicales que incluyen Psittacanthus con más de 120 especies, caracterizadas por presentar flores grandes de colores brillantes (rojo, naranja y amarillo) que son polinizadas principalmente por colibríes. Durante el siglo XX se desarrollaron una serie de estudios morfológicos y embriológicos de géneros de Loranthaceae del Viejo Mundo. Recientemente, la atención se ha centrado en la subfamilia neotropical Psittacanthinae, en donde de los 14 géneros que la conforman, la anatomía floral se ha examinado solamente en siete. El objetivo de este estudio es describir la anatomía floral de Psittacanthus schiedeanus y comparar los resultados con los de otros muérdagos relacionados, interpretando la variación de los caracteres florales del calículo, nectario, gineceo y anteras en el contexto de la nueva información filogenética. Flores de P. schiedeanus en diferentes estados de desarrollo fueron examinadas mediante secciones seriadas teñidas utilizando microscopía óptica. Estas flores tienen un pedículo vascularizado y cupular fusionado con una bracteola, un cáliz no vascularizado, un nectario anular, un gineceo unilocular con un solo mamelón central y un androceo formado por estambres septados epipétalos. La comparación morfológica de pedicelo, bracteola y calículo proporciona apoyo para la interpretación del calículo como un cáliz reducido. El nectario anular parece ser un carácter compartido por toda la subtribu Psittacanthinae, que lo diferencia de la subtribu Ligarinae con nectario estilar. El gineceo unilocular formado por una estructura central única es un carácter compartido con otros géneros de la subtribu Psittacanthinae, con la excepción de Tripodanthus. El androceo está formado por estambres bitecados, tetrasporangiados con lóculos septados que aquí se consideran una adaptación para liberar polen durante un período prolongado de tiempo, en lugar de sugerencias previas que lo explican como resultado de la presión evolutiva para reducir el tamaño de la antera o para facilitar la nutrición de microesporas en anteras grandes.

Anatomía Floral de Peristethium leptostachyum (Loranthaceae) / Floral anatomy of Peristethium leptostachyum (Loranthaceae)

ResumenPeristethium leptostachyum es una especie hemiparásita de la familia Loranthaceae, distribuida en Colombia, Costa Rica, Ecuador, Perú, Venezuela y Panamá. Previamente tratada como Struthanthus leptostachyus, la especie fuerecientemente fue reubicada en Peristethium junto con otras que previamente estaban en los géneros Cladocolea y Struthanthus. La decisión de reconocer a Peristethium como género es controversial y fue tomada con base en caracteres de la inflorescencia y de la flor; en tanto que la monofilia de los tres géneros nombrados es incierta. En esta investigación se estudió la morfoanatomía de flores e inflorescencias de Peristethium leptostachyum, detallando la estructura del androceo y gineceo, así como los procesos de microgametogénesis y megagametogénesis; adicionalmente se realizaron comparaciones con especies afines y precisiones en relación con las diagnosis previas. Se recolectaron flores en diversas fases de desarrollo en Santa María (Boyacá-Colombia), se prepararon y analizaron bajo microscopio secciones histológicas teñidas con astrabluefucsina, además de disecciones bajo estereomicroscopio. Los resultados mostraron que P. leptostachyum comparte caracteres inflorenciales con Cladocolea (inflorescencia determinada, flor terminal ebracteada), pero también con Struthanthus (pares de tríadas a lo largo del eje, brácteas caducas y flores actinomorfas). Las flores de P. Leptostachyum de Santa María son claramente hermafroditas, con androceos y gineceos totalmente desarrollados; lo cual contradice la descripción hecha por Kuijt que reporta una condición dioica para esta especie. El androceo resultó afín al de Struthanthus vulgaris, con tapetum glandular y microsporogénesis simultánea; en contraste, Cladocolea loniceroides presenta tapetum periplasmodial y microesporogénesis sucesiva. El gineceo de P. leptostachyum, al igual que en Cladocolea, Struthanthus y Phthirusa, es unilocular con mamelón y tejido arquesporial orientado hacia el estilo, el cual es sólido y con tejido amilífero. P. leptostachyum es afín a Cladocolea loniceroides y difiere de Struthanthus vulgaris por presentar varios sacos embrionarios y pelvis (hipostasa) no lignificada. La presencia de un canal estilar sólido se propone como sinapomorfía de la tribu Psittacanthinae. Dado que P. Leptostachyum comparte caracteres anatómicos florales tanto con Cladocolea como con Strutanthus, la relación entre estos tres géneros no queda resuelta, se requieren estudios filogenéticos para establecer esta relación y poner a prueba las hipótesis de monofilia de cada uno de ellos.

AbstractPeristethium leptostachyum is a hemiparasite species of the family Loranthaceae, distributed in Colombia, Costa Rica, Ecuador, Peru, Venezuela and Panama. Previously treated as Struthanthus leptostachyus, the species was recently transferred to Peristethium together with other species of Cladocolea and Struthanthus. The present research describes the inflorescence and floral morphoanatomy of Peristethium leptostachyum, detailing the structure of the androecium and gynoecium and the processes of microgametogenesis and megagametogenesis, thus allowing comparison with Struthanthus and Cladocolea. Flowering material was collected in February and August 2012, in Santa María, Boyacá, Colombia. Histological sections were prepared and stained with astrablue-fuchsin and floral dissections were performed under a stereomicroscope. Peristethium leptostachyum shares inflorescence characters with Cladocolea (determinate inflorescence, ebracteate terminal flower), but also with Struthanthus (pairs of triads along the axis, deciduous bracts and actinomorphic flowers). The flowers of P. leptostachyum from Santa María are clearly hermaphrodites with androecium and gynoecium fully developed. This observation contradicts the description by Kuijt who reported this species to be dioecious. The androecium was observed to be similar to that of Struthanthus vulgaris, with a glandular tapetum and simultaneous microsporogenesis; in contrast, Cladocolea loniceroides has a periplasmodial tapetum and successive microsporogenesis. The gynoecium of P. leptostachyum, like that of Cladocolea, Struthanthus and Phthirusa, has a unilocular ovary with a mamelon and arquesporial tissue isoriented towards the style, which in turn is solid and amyliferous. Peristethium leptostachyum is similar to Cladocolea loniceroides and differs from Strutanthus vulgaris in presenting multiple embryo sacs and an unlignified pelvis (hipostase). The presence of a solid stylar canal is proposed as a synapomorphy of the tribe Psittacanthinae. Given that P. leptostachyum shares characters with both Cladocolea and Struthanthus generic placement cannot be clearly determined on the basis of anatomical evidence. Phylogenetic studies that include representative species of all three genera are desirable to test hypotheses of monophyly. The sexual system observed here in P. leptostachyum is different from that reported by Kuijt and more studies are needed to identify the factors (geographic, ecological, etc.) that influence this variation. Rev. Biol. Trop. 64 (1): 341-352. Epub 2016 March 01.

[Floral anatomy of Peristethium leptostachyum (Loranthaceae)]. / Anatomía Floral de Peristethium leptostachyum (Loranthaceae).

Peristethium leptostachyum is a hemiparasite species of the family Loranthaceae, distributed in Colombia, Costa Rica, Ecuador, Peru, Venezuela and Panama. Previously treated as Struthanthus leptostachyus, the species was recently transferred to Peristethium together with other species of Cladocolea and Struthanthus. The present research describes the inflorescence and floral morphoanatomy of Peristethium leptostachyum, detailing the structure of the androecium and gynoecium and the processes of microgametogenesis and megagametogenesis, thus allowing comparison with Struthanthus and Cladocolea. Flowering material was collected in February and August 2012, in Santa María, Boyacá, Colombia. Histological sections were prepared and stained with astrablue-fuchsin and floral dissections were performed under a stereomicroscope. Peristethium leptostachyum shares inflorescence characters with Cladocolea (determinate inflorescence, ebracteate terminal flower), but also with Struthanthus (pairs of triads along the axis, deciduous bracts and actinomorphic flowers). The flowers of P. leptostachyum from Santa María are clearly hermaphrodites with androecium and gynoecium fully developed. This observation contradicts the description by Kuijt who reported this species to be dioecious. The androecium was observed to be similar to that of Struthanthus vulgaris, with a glandular tapetum and simultaneous microsporogenesis; in contrast, Cladocolea loniceroides has a periplasmodial tapetum and successive microsporogenesis. The gynoecium of P. leptostachyum, like that of Cladocolea, Struthanthus and Phthirusa, has a unilocular ovary with a mamelon and arquesporial tissue isoriented towards the style, which in turn is solid and amyliferous. Peristethium leptostachyum is similar to Cladocolea loniceroides and differs from Strutanthus vulgaris in presenting multiple embryo sacs and an unlignified pelvis (hipostase). The presence of a solid stylar canal is proposed as a synapomorphy of the tribe Psittacanthinae. Given that P. leptostachyum shares characters with both Cladocolea and Struthanthus generic placement cannot be clearly determined on the basis of anatomical evidence. Phylogenetic studies that include representative species of all three genera are desirable to test hypotheses of monophyly. The sexual system observed here in P. leptostachyum is different from that reported by Kuijt and more studies are needed to identify the factors (geographic, ecological, etc.) that influence this variation.

[Structure, ontogeny and vascularization of the flowers and inflorescences of Drimys granadensis (Winteraceae)]. / Estructura, ontogenia y vascularización de las flores e inflorescencias de Drimys granadensis (Winteraceae).

Structure, ontogeny and vascularization of the flowers and inflorescences of Drimys granadensis (Winteraceae). Drimys granadensis is a widespread species in montane forests of South and Central America. In this research, the structure, ontogeny, phyllotaxis and vascularization of the flowers and inflorescences of this species was studied in a population from the Eastern hills of Sabana de Bogota, Colombia. The methods used applied both optical microscopy, with astra blue-fuchsin staining, and scanning electron microscopy, using critical point dryed and gold-paladium metallized samples. Besides, results were compared with those of Drimys winteri, a widely studied species distributed in Chile and Argentina. Additionally, we studied the detail of the floral anatomy to determine the bracteal or calicine identity of the caliptra. I confirmed the proliferative status of the monothelic inflorescence, discarding alternative explanations of the terminal flower identity. I found that uniflorescences have an acropetal development until the terminal meristem becomes the terminal flower, then this flower develops rapidly resulting in a determined uniflorescence. I found pseudosyphonosthelic vascularization in peduncles and pedicels. Besides, I discovered some evidence in the vascular and anatomical structures, to consider the caliptra as the fusion product of various structures and therefore of calicine origin. The caliptra showed a whorled phyllotaxis, but the petals, stamens and carpels presented a spiral condition; phyllotaxis change was explained by the long time lapse between the initiation of the calyx and the corolla. I found great similarities among the inflorescences of D. granadensis and D. winteri; they were different in the proliferation start time, and in the frequent presence of nomophylls in D. granadensis, in contrast to the presence of reduced bracts and bracteoles in D. winteri inflorescences.

Estructura, ontogenia y vascularización de las flores e inflorescencias de Drimys granadensis (Winteraceae) / Structure, ontogeny and vascularization of the flowers and inflorescences of Drimys granadensis (Winteraceae)

Drimys granadensis is a widespread species in montane forests of South and Central America. In this research, the structure, ontogeny, phyllotaxis and vascularization of the flowers and inflorescences of this species was studied in a population from the Eastern hills of Sabana de Bogota, Colombia. The methods used applied both optical microscopy, with astra blue-fuchsin staining, and scanning electron microscopy, using critical point dryed and gold-paladium metallized samples. Besides, results were compared with those of Drimys winteri, a widely studied species distributed in Chile and Argentina. Additionally, we studied the detail of the floral anatomy to determine the bracteal or calicine identity of the caliptra. I confirmed the proliferative status of the monothelic inflorescence, discarding alternative explanations of the terminal flower identity. I found that uniflorescences have an acropetal development until the terminal meristem becomes the terminal flower, then this flower develops rapidly resulting in a determined uniflorescence. I found pseudosyphonosthelic vascularization in peduncles and pedicels. Besides, I discovered some evidence in the vascular and anatomical structures, to consider the caliptra as the fusion product of various structures and therefore of calicine origin. The caliptra showed a whorled phyllotaxis, but the petals, stamens and carpels presented a spiral condition; phyllotaxis change was explained by the long time lapse between the initiation of the calyx and the corolla. I found great similarities among the inflorescences of D. granadensis and D. winteri; they were different in the proliferation start time, and in the frequent presence of nomophylls in D. granadensis, in contrast to the presence of reduced bracts and bracteoles in D. winteri inflorescences.

Drimys granadensis es una especie de amplia distribución en los bosques montanos de Sur y Centro América. En esta investigación se estudiaron, mediante microscopía óptica y electrónica de barrido, la estructura, ontogenia, filotaxis y vascularización de sus flores e inflorescencias, y fueron comparadas con las de Drimys winteri, especie distribuida en Chile y Argentina. Adicionalmente, se buscó evidencia para determinar la identidad bracteal o calicina de la caliptra de sus flores. Se confirmó la condición monotélica proliferante de la inflorescencia, descartando explicaciones alternativas de identidad de la flor terminal. Las uniflorescencias presentan un desarrollo acrópeto, hasta que el meristemo terminal se transforma en flor terminal, entonces esta flor se desarrolla rápidamente dando lugar a una uniflorescencia determinada. La vascularización es pseudosifonostélica para pedúnculos y pedicelos. Se encontró evidencia en la vascularización y estructura anatómica para considerar la caliptra como el producto de fusión de varias estructuras y, por tanto, de origen calicino. La caliptra presentó una filotaxis verticilada, pero los pétalos, estambres y carpelos presentaron una filotaxis espiralada; el cambio se explicó por el tiempo prolongado entre la iniciación de cáliz y corola. Las inflorescencias de D. granadensis y D. winteri son muy similares; siendo diferente el tiempo de inicio de la proliferación y la frecuente presencia de nomófilos en las inflorescencias de D. granadensis, en contraste con la presencia de brácteas y bracteolas reducidas en D. winteri.

Floral structure and development in the monoecious palm Gaussia attenuata (Arecaceae; Arecoideae).

BACKGROUND AND AIMS: Sexual dimorphism, at both the flower and plant level, is widespread in the palm family (Arecaceae), in contrast to the situation in angiosperms as a whole. The tribe Chamaedoreeae is of special interest for studies of the evolution of sexual expression since dioecy appears to have evolved independently twice in this group from a monoecious ancestor. In order to understand the underlying evolutionary pathways, it is important to obtain detailed information on flower structure and development in each of the main clades. METHODS: Dissection and light and scanning electron microscopy were performed on developing flowers of Gaussia attenuata, a neotropical species belonging to one of the three monoecious genera of the tribe. KEY RESULTS: Like species of the other monoecious genera of the Chamaedoreeae (namely Hyophorbe and Synechanthus), G. attenuata produces a bisexual flower cluster known as an acervulus, consisting of a row of male flowers with a basal female flower. Whereas the sterile androecium of female flowers terminated its development at an early stage of floral ontogeny, the pistillode of male flowers was large in size but with no recognizable ovule, developing for a longer period of time. Conspicuous nectary differentiation in the pistillode suggested a possible role in pollinator attraction. CONCLUSIONS: Gaussia attenuata displays a number of floral characters that are likely to be ancestral to the tribe, notably the acervulus flower cluster, which is conserved in the other monoecious genera and also (albeit in a unisexual male form) in the dioecious genera (Wendlandiella and a few species of Chamaedorea). Comparison with earlier data from other genera suggests that large nectariferous pistillodes and early arrest in staminode development might also be regarded as ancestral characters in this tribe.

FENOLOGÍA FLORAL Y VISITANTES FLORALES EN Drimys granadensis L.f. (WINTERACEAE) / Floral Phenology And Flower Visitors In Drimys granadensis L.f. (Winteraceae)

El propósito de este trabajo fue caracterizar las fases fenológicas florales y determinar los visitantes florales en una población natural de Drimys granadensis (nombre común: canelo; Winteraceae) ubicada en Altos de Yerbabuena ( 2.850 m ), cerros orientales de la Sabana de Bogotá, (Colombia). El desarrollo fenológico floral duró 9,5 días cuando la floración ocurrió en época soleada, 12,5 días en época lluviosa y 16 días cuando se excluyeron a los visitantes florales mediante embolsado. Se realizaron observaciones del recurso utilizado, fase fenólogica de la flor visitada y cargas polínicas en los visitante florales, los cuales correspondieron a seis órdenes, 21 familias y 29 morfoespecies de insectos. Cuatro especies de coleópteros y dos de dípteros fueron considerados posibles polinizadores por su abundancia y carga de polen. Los resultados obtenidos se discuten en relación con aquellos reportados en otras especies del género Drimys y de la familia Winteraceae.

The purpose of this research was to characterize the flowering phenological phases and to determine the flower visitors in a natural population of Drimys granadensis (common name: canelo; Winteraceae) in Altos de Yerbabuena, eastern mountains of Sabana de Bogotá ( Colombia ). Floral phenology development lasted 9.5 days when flowering occurred under sunny conditions, 12.5 days under rainy conditions and 16 days when flower visitors were excluded using cloth bags. It was done observations related with the resources used, the phenological phases of visited flowers and the pollen load on the flower visitors. Visitors corresponded with 29 morphospecies, 6 orders y 21 families of insects. Four species of coleoptera and two species of diptera were considered as possible pollinators taking in account abundance and pollen load. The results are analyzed in relation with those reported for other species in the genus Drimys and in the family Winteraceae.

Generic relationships and dating of lineages in Winteraceae based on nuclear (ITS) and plastid (rpS16 and psbA-trnH) sequence data.

Phylogenetic analyses of representative species from the five genera of Winteraceae (Drimys, Pseudowintera, Takhtajania, Tasmannia, and Zygogynum s.l.) were performed using ITS nuclear sequences and a combined data-set of ITS+psbA-trnH+rpS16 sequences (sampling of 30 and 15 species, respectively). Indel informativity using simple gap coding or gaps as a fifth character was examined in both data-sets. Parsimony and Bayesian analyses support the monophyly of Drimys, Tasmannia, and Zygogynum s.l., but do not support the monophyly of Belliolum, Zygogynum s.s., and Bubbia. Within Drimys, the combined data-set recovers two subclades. Divergence time estimates suggest that the splitting between Drimys and its sister clade (Pseudowintera+Zygogynum s.l.) occurred around the end of the Cretaceous; in contrast, the divergence between the two subclades within Drimys is more recent (15.5-18.5MY) and coincides in time with the Andean uplift. Estimates suggest that the earliest divergences within Winteraceae could have predated the first events of Gondwana fragmentation.