Not just females and males: Unravelling the complex sex determinism of the hemp palm, Trachycarpus fortunei.

PREMISE: The ornamental Asian palm Trachycarpus fortunei (Arecaceae: Coryphoideae) is widely planted in temperate regions. In Europe, it has spread outside of gardens, particularly on the southern side of the Alps. Sexual expression in the species is complex, varying from dioecy to polygamy. This study investigated (1) sexual floral development and (2) genetic markers implicated in sex determinism. METHODS: The morphology and anatomy of floral organs at different developmental stages were studied using SEM observations and anatomical section. Sex determinism was explored using a genome-wide association study approach, searching for correlations between 31,000 single-nucleotide polymorphisms and sex affiliation of 122 palms from 21 wild populations. RESULTS: We observed that sexual differentiation appears late in floral development of T. fortunei. Morpho-anatomical characters of flowers conducive to panmixia were observed, such as well-differentiated septal nectaries that are thought to promote cross-pollination. At the molecular level, homozygous and heterozygous allelic systems with closely linked regions were found for sex determinism in individuals with female and "dominant-male" phenotypes, respectively. Through our wide sampling in the southern Alps, the closely linked genetic regions in males suggest that at least fifteen percent of wild palms are the direct offspring of "males" that can also produce fertile pistillate flowers. CONCLUSIONS: Trachycarpus fortunei is a further example of unstable sexual expression found in the family Arecaceae and represents an evolutionary path towards an XY genetic system. Our structural and genetic results may explain the high species dispersal ability in the southern Alps.

Morphological and molecular characterization of an Elaeis oleifera (H.B.K) Cortes germplasm collection located in Ucayali, Peru.

The African oil palm (Elaeis guineensis Jacq) is a crop that is widely distributed in tropical regions around the world; however, this crop is subject to limitations such as rapid trunk growth and susceptibility to bud rot and red ring diseases particularly in South America. To overcome these limitations, national breeding and conservation programs have been established, and there is a need to identify parental palms from natural populations of the American oil palm (E. oleifera H.B.K. Cortes) with desirable yield and morphological traits (i.e., yield production and bunch number) and with high genetic diversity. However, in Peru the morphological and genetic data related to this important crop is limited. In this study, we characterized the morphological and yield and estimated the genetic diversity using 12 neutral microsatellite markers (simple sequence repeats, SSRs) across 72 oil palm individuals belonging to the E. oleifera germplasm collection located in the tropical region of Ucayali, Peru. Our results showed that morphological and yield traits explained approximately 40.39% of the variability within the Peruvian germplasm. Furthermore, Yield Production was highly correlated with two yield traits: Bunch Number (0.67) and Average weight per bunch (0.78). Based on the yield and morphological traits, a clustering analysis was performed and three phenotypic groups were identified (1, 2 and 3) in which groups 1 and 3 showed high scores associated primarily with yield traits. Microsatellite markers revealed 143 alleles, 11.92 ± 4.72 alleles per locus (A) and an expected heterozygosity (He) of 0.69 ± 0.045. A structural analysis identified three populations (k = 3), that were not related to the phenotypic groups. Interestingly, a multiple allele background was identified within the groups using multilocus and phylogenetic relationship analyses. This is the first Peruvian report regarding E. oleifera that shows preliminary data of the morphological and yield traits and genetic data, and highlight the importance of this information to set up future steps to national breeding strategies and improve the conservation of genetic material of E. oleifera. Overall, these novel findings could contribute to the development of the local oil palm industry in Peru.

Frugivore-fruit size relationships between palms and mammals reveal past and future defaunation impacts.

Mammalian frugivores are critical seed dispersers, but many are under threat of extinction. Futhermore, the impact of past and future defaunation on plant assemblages has yet to be quantified at the global scale. Here, we integrate palm and mammalian frugivore trait and occurrence data and reveal a global positive relationship between fruit size and frugivore body size. Global variation in fruit size is better explained by present-day frugivore assemblages than by Late Pleistocene assemblages, suggesting ecological and evolutionary reorganization after end-Pleistocene extinctions, except in the Neotropics, where some large-fruited palm species may have outlived their main seed dispersers by thousands of years. Our simulations of frugivore extinction over the next 100 years suggest that the impact of defaunation will be highest in the Old World tropics, and an up to 4% assemblage-level decrease in fruit size would be required to maintain the global body size-fruit size relationship. Overall, our results suggest that while some palm species may be able to keep pace with future defaunation through evolutionary changes in fruit size, large-fruited species may be especially vulnerable to continued defaunation.

Associated evolution of fruit size, fruit colour and spines in Neotropical palms.

Understanding how ecological interactions have shaped the evolutionary dynamics of species traits remains a challenge in evolutionary ecology. Combining trait evolution models and phylogenies, we analysed the evolution of characters associated with seed dispersal (fruit size and colour) and herbivory (spines) in Neotropical palms to infer the role of these opposing animal-plant interactions in driving evolutionary patterns. We found that the evolution of fruit colour and fruit size was associated in Neotropical palms, supporting the adaptive interpretation of seed-dispersal syndromes and highlighting the role of frugivores in shaping plant evolution. Furthermore, we revealed a positive association between fruit size and the presence of spines on palm leaves, bracteas and stems. We hypothesize that interactions between palms and large-bodied frugivores/herbivores may explain the evolutionary relationship between fruit size and spines. Large-bodied frugivores, such as extinct megafauna, besides consuming the fruits and dispersing large seeds, may also have consumed the leaves or damaged the plants, thus simultaneously favouring the evolution of large fruits and defensive structures. Our findings show how current trait patterns can be understood as the result of the interplay between antagonistic and mutualistic interactions that have happened throughout the evolutionary history of a clade.

Genome-wide association study (GWAS) for morphological and yield-related traits in an oil palm hybrid (Elaeis oleifera x Elaeis guineensis) population.

BACKGROUND: The genus Elaeis has two species of economic importance for the oil palm agroindustry: Elaeis oleifera (O), native to the Americas, and Elaeis guineensis (G), native to Africa. This work provides to our knowledge, the first association mapping study in an interspecific OxG oil palm population, which shows tolerance to pests and diseases, high oil quality, and acceptable fruit bunch production. RESULTS: Using genotyping-by-sequencing (GBS), we identified a total of 3776 single nucleotide polymorphisms (SNPs) that were used to perform a genome-wide association analysis (GWAS) in 378 OxG hybrid population for 10 agronomic traits. Twelve genomic regions (SNPs) were located near candidate genes implicated in multiple functional categories, such as tissue growth, cellular trafficking, and physiological processes. CONCLUSIONS: We provide new insights on genomic regions that mapped on candidate genes involved in plant architecture and yield. These potential candidate genes need to be confirmed for future targeted functional analyses. Associated markers to the traits of interest may be valuable resources for the development of marker-assisted selection in oil palm breeding.

Genome-wide association study for leaf area, rachis length and total dry weight in oil palm (Eleaeisguineensis) using genotyping by sequencing.

The marker-trait association for complex traits using genotyping by sequencing (GBS) method is being widely spread in plants. The study aimed to identify significant single nucleotide polymorphism (SNP) associations for rachis length (RL), leaf area (LA) and total dry weight (TrDW) in oil palm among diverse African germplasm. The Illumina NextSeq platform has been used for SNP genotyping and retained 4031 fully informative SNPs after applying the filter criterion. These 4031 SNPs were used for genome wide association study for the above three traits. The LD decay rates of the African germplasm using GBS data of SNP is observed to be 25 Kb at 0.45 of average pair wise correlation coefficient (r2). Association mapping led to the identification of seven significant associations for three traits using MLM approach at a P value of ≤ 0.001. Three associations were identified for total dry weight, two each for leaf area index and rachis length. The qtlLA1 was found to be highly significant at a P value of 7.39E-05 (18.4% phenotypic variance) which is located on chromosome 4. Two QTLs (qtlLA2 and qtlRL1) were located on chromosome 1, which explained 11.9% and 12.4% of phenotypic variance respectively. Three QTLs for total dry weight were located on chromosome 2, 14 and 16, all-together explained 40% phenotypic variance. The results showed that the SNP-trait associations identified in the present study could be used in selection of elite oil palm germplasm for higher yields.

Chronic leaf harvesting reduces reproductive success of a tropical dry forest palm in northern Mexico.

Palm leaves represent one of the most important non-timber forest products in tropical and subtropical regions. Brahea aculeata is an endemic palm of northwest Mexico, whose leaves are intensively exploited for roof thatch and handcrafts. As part of a long-term defoliation experiment, we evaluated the effects of different leaf harvest on foliar and reproductive traits of adults and attributes of their progeny. We conducted a six-year manipulative experiment and applied three harvesting treatments to adults: high harvest, low harvest and no harvest (control). We recorded leaf production and size, flower and fruit production, seed germination and seedling growth. We also explored trade-offs among foliar and reproductive traits. Harvested palms exhibited drastically reduced reproductive activity, producing fewer flowers and fruits (up to 80 and 90% fewer than unharvested palms). However, individuals in both harvest treatments had larger leaves and increased leaf production rates, compared to control palms. For harvested palms, we registered first a slight increase in leaf traits and a decline in reproductive attributes. These traits showed a gradual reduction and for six period attained very low proportional values compared to control palms (~0.10), however individuals in the harvested treatments maintained the greatest leaf lengths and leaf production rates. Seed germination and seedling growth rates of progeny from harvested palms were significantly lower than control palms, with seeds from the high harvest treatment having the lowest seed production and germination rates. Relationships among leaf (size/production) and reproductive traits (flower/fruit production) were positive during the fourth year, but showed negative relationships for the fifth year suggesting a trade-off between reproduction and growth functions. Leaf harvesting in B. aculeata seems to alter patterns of resource allocation away from reproduction as reflected in a decrease in the probability of reproduction, seed number, germination, and vigor, causing a strong decrease in the reproductive success of this species. Results showed that the consequences of long-term leaf harvest not only affect harvested individuals, but also the fitness and vigor of progeny. This type of long-term studies is essential to understand the population dynamics of non-timber forest products and helps inform sustainable harvesting programs considering intensity, frequencies and periods for recovery from defoliation. Also results may help to explain how intensive and non-planned management schemes may negatively affect vital rates and long-term dynamics of populations from non-timber forest products and other components of the ecosystem.

Anatomical modifications of Butia capitata propagated under colored shade nets.

The jelly palm plant [Butia capitata (Martius) Beccari] is a native palm of the Cerrado biome used for many purposes in northern Minas Gerais State, Brazil. Dormancy is common in palm seeds, resulting in slow and uneven germination that may take years to complete. Modification in the growth pattern, anatomical parameters, physiological and biochemical characteristics of the plant can be verified due to changes in the light spectrum transmitted through colored shade nets used. Therefore, the objective of this study is to evaluate the effect of colored shade nets on the leaf and root anatomy of the jelly palm plant. The experiment was performed in a completely randomized design, with five treatments, ten replicates and eight plants per replicate, totaling 400 plants. Four colored photo-converter nets with 50% shading and different radiation proportions were employed: white (985 µmol.m-2.s-1), red (327 µmol.m-2.s-1), black (433 µmol.m-2.s-1) and silver (405 µmol.m-2.s-1). The plants cultivated under direct sunlight (1000 µmol.m-2.s-1) were considered as the control group. Leaf and root anatomical analysis was performed on 10 plants per treatment. It is possible to conclude that the colored shade nets caused changes in leaf and root anatomy of the jelly palm plant (Butia capitata).

To adapt or go extinct? The fate of megafaunal palm fruits under past global change.

Past global change may have forced animal-dispersed plants with megafaunal fruits to adapt or go extinct, but these processes have remained unexplored at broad spatio-temporal scales. Here, we combine phylogenetic, distributional and fruit size data for more than 2500 palm (Arecaceae) species in a time-slice diversification analysis to quantify how extinction and adaptation have changed over deep time. Our results indicate that extinction rates of palms with megafaunal fruits have increased in the New World since the onset of the Quaternary (2.6 million years ago). In contrast, Old World palms show a Quaternary increase in transition rates towards evolving small fruits from megafaunal fruits. We suggest that Quaternary climate oscillations and concurrent habitat fragmentation and defaunation of megafaunal frugivores in the New World have reduced seed dispersal distances and geographical ranges of palms with megafaunal fruits, resulting in their extinction. The increasing adaptation to smaller fruits in the Old World could reflect selection for seed dispersal by ocean-crossing frugivores (e.g. medium-sized birds and bats) to colonize Indo-Pacific islands against a background of Quaternary sea-level fluctuations. Our macro-evolutionary results suggest that megafaunal fruits are increasingly being lost from tropical ecosystems, either due to extinctions or by adapting to smaller fruit sizes.

Haustorium-endosperm relationships and the integration between developmental pathways during reserve mobilization in Butia capitata (Arecaceae) seeds.

Background and Aims: Palm seeds are interesting models for studying seed reserve mobilization at the tissue level due to the abundance and complexity of reserves stored in their living endosperm cells and the development of a highly specialized haustorium. We studied structural and physiological aspects of the initial phases of reserve mobilization in seeds of a neotropical palm, Butia capitata, and sought to characterize the interactions between the different developmental pathways of the haustorium and endosperm. Methods: Morphological and histochemical evaluations of the haustorium, the endosperm adjacent to the embryo, and the peripheral endosperm of dry, imbibed, dormant seeds and seeds geminating for 2, 5 and 10 d were performed. Biochemical analyses included determinations of endo-ß-mannanase activity, hormonal profiling (20 hormones belonging to eight classes) and H2O2 quantification in various tissues. Key Results: The mobilization of haustorium reserves was associated with germination and involved distinct hormonal alterations in the endosperm related to H2O2 production. The mobilization of endosperm reserves occurred as a post-germination event controlled by the seedling and involved major structural changes in the haustorium, including growth (which increased contact with, and pressure on, the endosperm) and the formation of an aerenchyma (thus facilitating O2 diffusion). The flow of O2 to the endosperm and changes in endogenous contents of H2O2 and hormones (cytokinins, auxins, brassinosteroids and ethylene) induced the establishment of an endosperm digestion zone and the translocation of reserves to the haustorium. Conclusions: The haustorium-endosperm relationship during reserve mobilization plays a pivotal role in signal integration between growth and degradation pathways in germinating seeds of Butia capitata.

DigR: a generic model and its open source simulation software to mimic three-dimensional root-system architecture diversity.

Background and Aims: Many studies exist in the literature dealing with mathematical representations of root systems, categorized, for example, as pure structure description, partial derivative equations or functional-structural plant models. However, in these studies, root architecture modelling has seldom been carried out at the organ level with the inclusion of environmental influences that can be integrated into a whole plant characterization. Methods: We have conducted a multidisciplinary study on root systems including field observations, architectural analysis, and formal and mathematical modelling. This integrative and coherent approach leads to a generic model (DigR) and its software simulator. Architecture analysis applied to root systems helps at root type classification and architectural unit design for each species. Roots belonging to a particular type share dynamic and morphological characteristics which consist of topological and geometric features. The DigR simulator is integrated into the Xplo environment, with a user interface to input parameter values and make output ready for dynamic 3-D visualization, statistical analysis and saving to standard formats. DigR is simulated in a quasi-parallel computing algorithm and may be used either as a standalone tool or integrated into other simulation platforms. The software is open-source and free to download at http://amapstudio.cirad.fr/soft/xplo/download. Key Results: DigR is based on three key points: (1) a root-system architectural analysis, (2) root type classification and modelling and (3) a restricted set of 23 root type parameters with flexible values indexed in terms of root position. Genericity and botanical accuracy of the model is demonstrated for growth, branching, mortality and reiteration processes, and for different root architectures. Plugin examples demonstrate the model's versatility at simulating plastic responses to environmental constraints. Outputs of the model include diverse root system structures such as tap-root, fasciculate, tuberous, nodulated and clustered root systems. Conclusions: DigR is based on plant architecture analysis which leads to specific root type classification and organization that are directly linked to field measurements. The open source simulator of the model has been included within a friendly user environment. DigR accuracy and versatility are demonstrated for growth simulations of complex root systems for both annual and perennial plants.

Designing oil palm architectural ideotypes for optimal light interception and carbon assimilation through a sensitivity analysis of leaf traits.

Background and Aims: Enhancement of light harvesting in annual crops has successfully led to yield increases since the green revolution. Such an improvement has mainly been achieved by selecting plants with optimal canopy architecture for specific agronomic practices. For perennials such as oil palm, breeding programmes were focused more on fruit yield, but now aim at exploring more complex traits. The aim of the present study is to investigate potential improvements in light interception and carbon assimilation in the study case of oil palm, by manipulating leaf traits and proposing architectural ideotypes. Methods: Sensitivity analyses (Morris method and metamodel) were performed on a functional-structural plant model recently developed for oil palm which takes into account genetic variability, in order to virtually assess the impact of plant architecture on light interception efficiency and potential carbon acquisition. Key Results: The most sensitive parameters found over plant development were those related to leaf area (rachis length, number of leaflets, leaflet morphology), although fine attributes related to leaf geometry showed increasing influence when the canopy became closed. In adult stands, optimized carbon assimilation was estimated on plants with a leaf area index between 3.2 and 5.5 m2 m-2 (corresponding to usual agronomic conditions), with erect leaves, short rachis and petiole, and high number of leaflets on the rachis. Four architectural ideotypes for carbon assimilation are proposed based on specific combinations of organ dimensions and arrangement that limit mutual shading and optimize light distribution within the plant crown. Conclusions: A rapid set-up of leaf area is critical at young age to optimize light interception and subsequently carbon acquisition. At the adult stage, optimization of carbon assimilation could be achieved through specific combinations of architectural traits. The proposition of multiple morphotypes with comparable level of carbon assimilation opens the way to further investigate ideotypes carrying an optimal trade-off between carbon assimilation, plant transpiration and biomass partitioning.

Leaf histology of greenhouse plants, in vitro cultured and somaticembryo-derived plants of Bactris gasipaes Kunth / Histologia de folhas de Bactris gasipaes Kunth de plantas de casa-de-vegetação, cultivadasin vitro e obtidas por embriogênese somática

In vitro cultures of peach palm (Bactris gasipaes Kunth) were established by somatic embryogenesis but some improvements in maturation and conversion steps are still needed. The aim of this study was to analyze morpho-anatomical differences in peach palm leaves from greenhouse cultured plants, in vitro plants developed from in vitro germinated seeds and somatic embryo-derived plants. Expanded leaves were prepared for histological analyses and scanning electron microscopy. No significant difference was found between ex vitro and in vitro cultured plants, but the somatic embryo-derived plants showed structural alterations of the leaves. The epidermal cells were elongated in shape, the mesophyll cells were thicker and the vascular bundle was not very developed. In somatic embryo-derived leaves the cuticle was thinner than in other leaves and epicuticular wax was present but poorly deposited. In in vitro cultured plants, the deposition of epicuticular wax on the leaves was irregular while in the greenhouse plants it was regular and abundant. These alterations in somatic embryo-derived leaves could hinder the acclimatization and development of peach palm plants so it is necessary to improve the protocol for somatic embryogenesis to produce better plants.

O cultivo de pupunha (Bactris gasipaes Kunth) in vitro foi estabelecido através de embriogênese somática; alguns melhoramentos nas fases de maturação e conversão, contudo, ainda são necessários. O objetivo deste trabalho foi analisar diferenças morfoanatômicas em suas folhas, cultivadas em casa de vegetação, germinadas in vitro e provenientes de embriogênese somática. Folhas expandidas foram preparadas para análise histológica e microscopia eletrônica. Houve diferenças significativas entre as plantas da casa de vegetação e as plantas obtidas por embriogênese somática. As células epidérmicas eram alongadas; a espessura da folha e do clorênquima era menor que nas outras; a cutícula era menos espessa, com baixa deposição de ceras. Os feixes vasculares estavam menos desenvolvidos. As folhas das plantas cultivadas in vitro e de embriogênese somática apresentavam estruturas pouco desenvolvidas, o que sugere a necessidade de uma melhoria na fase de conversão durante a embriogênese somática.

High endemism and stem density distinguish New Caledonian from other high-diversity rainforests in the Southwest Pacific.

Background and Aims: The biodiversity hotspot of New Caledonia is globally renowned for the diversity and endemism of its flora. New Caledonia's tropical rainforests have been reported to have higher stem densities, higher concentrations of relictual lineages and higher endemism than other rainforests. This study investigates whether these aspects differ in New Caledonian rainforests compared to other high-diversity rainforests in the Southwest Pacific. Methods: Plants (with a diameter at breast height ≥10 cm) were surveyed in nine 1-ha rainforest plots across the main island of New Caledonia and compared with 14 1-ha plots in high-diversity rainforests of the Southwest Pacific (in Australia, Fiji, Papua New Guinea and the Solomon Islands). This facilitated a comparison of stem densities, taxonomic composition and diversity, and species turnover among plots and countries. Key Results: The study inventoried 11 280 stems belonging to 335 species (93 species ha-1 on average) in New Caledonia. In comparison with other rainforests in the Southwest Pacific, New Caledonian rainforests exhibited higher stem density (1253 stems ha-1 on average) including abundant palms and tree ferns, with the high abundance of the latter being unparalleled outside New Caledonia. In all plots, the density of relictual species was ≥10 % for both stems and species, with no discernible differences among countries. Species endemism, reaching 89 % on average, was significantly higher in New Caledonia. Overall, species turnover increased with geographical distance, but not among New Caledonian plots. Conclusions: High stem density, high endemism and a high abundance of tree ferns with stem diameters ≥10 cm are therefore unique characteristics of New Caledonian rainforests. High endemism and high spatial species turnover imply that the current system consisting of a few protected areas is inadequate, and that the spatial distribution of plant species needs to be considered to adequately protect the exceptional flora of New Caledonian rainforests.

Frugivory-related traits promote speciation of tropical palms.

Animal-mediated seed dispersal by frugivorous birds and mammals is central to the ecology and functioning of ecosystems, but whether and how frugivory-related traits have affected plant speciation remains little explored. Fruit size is directly linked to plant dispersal capacity and therefore influences gene flow and genetic divergence of plant populations. Using a global species-level phylogeny with comprehensive data on fruit sizes and plant species distributions, we test whether fruit size has affected speciation rates of palms (Arecaceae), a plant family characteristic of tropical rainforests. Globally, the results reveal that palms with small fruit sizes have increased speciation rates compared with those with large (megafaunal) fruits. Speciation of small-fruited palms is particularly high in the understory of tropical rainforests in the New World, and on islands in the Old World. This suggests that frugivory-related traits in combination with geography and the movement behaviour of frugivores can influence the speciation of fleshy-fruited plants.

Transcriptome-based investigation of cirrus development and identifying microsatellite markers in rattan (Daemonorops jenkinsiana).

Rattan is an important group of regenerating non-wood climbing palm in tropical forests. The cirrus is an essential climbing organ and provides morphological evidence for evolutionary and taxonomic studies. However, limited data are available on the molecular mechanisms underlying the development of the cirrus. Thus, we performed in-depth transcriptomic sequencing analyses to characterize the cirrus development at different developmental stages of Daemonorops jenkinsiana. The result showed 404,875 transcripts were assembled, including 61,569 high-quality unigenes were identified, of which approximately 76.16% were annotated and classified by seven authorized databases. Moreover, a comprehensive analysis of the gene expression profiles identified differentially expressed genes (DEGs) concentrated in developmental pathways, cell wall metabolism, and hook formation between the different stages of the cirri. Among them, 37 DEGs were validated by qRT-PCR. Furthermore, 14,693 transcriptome-based microsatellites were identified. Of the 168 designed SSR primer pairs, 153 were validated and 16 pairs were utilized for the polymorphic analysis of 25 rattan accessions. These findings can be used to interpret the molecular mechanisms of cirrus development, and the developed microsatellites markers provide valuable data for assisting rattan taxonomy and expanding the understanding of genomic study in rattan.

Endemic palm species shed light on habitat shifts and the assembly of the Cerrado and Restinga floras.

Species expansions into new habitats are often associated with physiological adaptations, for instance when rain forest lineages colonize dry habitats. Although such shifts have been documented for the Brazilian savanna (Cerrado), little is known about the biogeographic origin of species occupying an extreme South American habitat type, the coastal dunes (Restinga). We examined the formation of this poorly known, endangered habitat by reconstructing the evolutionary history of two endemic species. Due to the proposed recency and uniqueness of this habitat, we hypothesized that Restinga species of the palm genus Allagoptera to be recently evolved and to present derived morphological characters. To detect habit shifts in absolute time, we used one plastid and nine nuclear genes to reconstruct the phylogenetic and biogeographic history of Allagoptera. We used light microscopy and stable isotope analysis to explore whether morphological adaptations occurred concomitantly with habitat shifts. Phylogenetic relationships were well supported and we found ancestral lineages of Allagoptera to be widely distributed throughout habitats that are currently occupied by extant species. Over the last ca. 7Ma Allagoptera has shifted its preference to increasingly dry habitats. Coincident with the colonization of the Cerrado and Restinga, morphological adaptations also evolved, including subterranean stems that are fire-resistant and long underground stem and root systems that facilitate water access. We did not find differences in metabolic pathway or modifications to pollen morphology when compared to other palm lineages. Assuming that the evolutionary history of Allagoptera is indicative of the habitat in which it occurs, our results infer a recent origin for Cerrado species. Although little is known about the formation of the Restinga habitat, our results also suggest a longer history than currently proposed; with an origin of Restinga habitats dating back to the Late Pliocene.

Ontogenesis and functions of saxophone stem in Acrocomia aculeata (Arecaceae).

BACKGROUND AND AIMS: The underground saxophone stem systems produced by seedlings of certain palm species show peculiar growth patterns and distinctive morphologies, although little information is available concerning their development and function. We studied the ontogenesis of the saxophone stem in Acrocomia aculeata, an important neotropical oleaginous palm, and sought to experimentally define its function. METHODS: Morpho-anatomical evaluations were performed during 240 d on seedlings using traditional methodologies. The tuberous region of the structure was submitted to histochemical tests and evaluated by transmission electron microscopy. The aerial portions of 130 1- to 3-year-old greenhouse plants were removed and their continuous growth capacity was evaluated after 30 d. Severed saxophone stems were also stored at room temperature (average 25 °C) for up to 90 d and then cultured for 60 d to evaluate root and shoot emission. KEY RESULTS: The development of the saxophone stem is distinct from other underground systems previously described, and involves three processes: growth and curvature of the cotyledonary petiole, expansion and curvature of the hypocotyl, and expansion of the plumule internodes. The tuberous region stores water and starch, as well as lesser amounts of mucilage and oil. Growth of the aerial portion occurred in 84 % of the separated saxophone stems and in 53 % of the stems held in storage. CONCLUSIONS: The saxophone stem represents an important adaptation of A. aculeata to anthropogenically impacted and/or dry environments by promoting the burial of both the shoot meristem and storage reserves, which allows the continuous growth of aerial organs.

Micromorfología de los foliolos de pejibaye Bactris gasipaes (Arecaceae) var. Diamantes-10 / Micromorphology of pejibaye leaflets Bactris gasipaes (Arecaceae) var. diamonds-10

ResumenBactris gasipaes se cultiva ampliamente para el aprovechamiento del palmito y el consumo de los frutos En este trabajo se realizó una descripción de las características micro morfológicas de los foliolos de plantas adultas de la variedad sin espinas Diamantes-10 de B. gasipaes, recolectadas en la Estación Experimental Diamantes en Guápiles, Costa Rica. Se utilizó microscopía de luz, electrónica de barrido y de transmisión. Para el estudio se recolectaron 25 foliolos y se evidenció abundante cera epicuticular en la superficie adaxial y abaxial. La epidermis está compuesta de células isodiamétricas y las células de la hipodermis tienen forma rectangular y son de mayor tamaño que las de la epidermis, también se observaron células buliformes. Los foliolos son anfiestomáticos en las áreas intercostales y alternan con bandas de células epidérmicas. El mayor número de estomas se encuentra en la superficie abaxial. Estos foliolos presentan tres tipos de tricomas. El parénquima presenta varios estratos no muy bien definidos con presencia de astroesclereidas. También se observan haces de fibras entre el parénquima que forman grupos de células muy compactas. La vena central presenta varios haces vasculares, algunos dispuestos de forma continua y todos ellos se encuentran rodeados de una vaina de tejido esclerotizado, algunas de estas fibras presentaron protoplastos vivos. Todas las venas menores presentan la misma anatomía de los haces vasculares de la vena central. Los vasos del protoxilema y metaxilema tienen paredes laterales con ornamentaciones escalariformes. El floema se ubica hacia la superficie adaxial de la vena y en el corte se observaron las células cribosas y células compañeras rodeadas de células de parénquima y fibras. Las células compañeras presentaron plasmodesmatas ramificados unidos a un elemento criboso y en ellos se evidenció cuerpos de proteína, llamada proteína-P. La diferencia principal en la anatomía de los foliolos de la var. Diamantes-10 radica en la ausencia de espinas, pero en el resto de la morfología no parece presentar cambios morfológicos con el resto de las variedades de B. gasipaes K.

Abstract:Bactris gasipaes is widely cultivated for the consumption of palm hearts and fruits. The present work describes the micro morphological characteristics of leaflets from adult plants of B. gasipaes, thornless variety Diamantes-10, collected in the Diamantes Experimental Station in Guápiles, Costa Rica. We collected 25 leaflets and analyses were performed with a combination of microscopy techniques: light microscopy, scanning electron microscopy and transmission electron microscopy to study their structure. Our results showed that leaflets have abundant epicuticular wax on adaxial and abaxial surfaces. Analyses from the epidermis indicated that it is composed of isodiametric cells, and it is also evident that hypodermis cells have rectangular shape and are larger than the other epidermal cells. We observed stomata on both surfaces, but they were more abundant in the abaxial surface. On the other hand, the epidermis showed the presence of trichomes with three different morphologies. In the parenchyma, cells are large and not well defined, and we observed the presence of astroesclereids, and compact groups of fiber bundles between parenchyma cells. The central vein has several vascular bundles, arranged in a continuous manner, and they are surrounded by sclerotic tissue; some of these fibers presented live protoplasts. All minor veins showed the same anatomy as the central vein. In these veins, the vessel elements of protoxylem and metaxylem showed scalariform ornaments on their walls. Phloem is located towards the adaxial surface of the vein and we observed sieve and companion cells surrounded by fibers and parenchyma cells. The companion cells presented branched plasmodesmata attached to a sieve element, and in these elements we found protein bodies called P-protein. The main anatomical difference in the leaflets of the var. Diamantes-10, compared to the other varieties of B. gasipaes K, is the lack of thorns; the other morphological features seem to be conserved. Rev. Biol. Trop. 64 (3): 1273-1285. Epub 2016 September 01.