Protein Profiling of Psittacanthus calyculatus during Mesquite Infection.

Psittacanthus calyculatus is a hemiparasite mistletoe that represents an ecological problem due to the impacts caused to various tree species of ecological and commercial interest. Although the life cycle for the Psittacanthus genus is well established in the literature, the development stages and molecular mechanism implicated in P. calyculatus host infection are poorly understood. In this study, we used a manageable infestation of P. laevigata with P. calyculatus to clearly trace the infection, which allowed us to describe five phenological infective stages of mistletoe on host tree branches: mature seed (T1), holdfast formation (T2), haustorium activation (T3), haustorium penetration (T4), and haustorium connection (T5) with the host tree. Proteomic analyses revealed proteins with a different accumulation and cellular processes in infective stages. Activities of the cell wall-degrading enzymes cellulase and ß-1,4-glucosidase were primarily active in haustorium development (T3), while xylanase, endo-glucanase, and peptidase were highly active in the haustorium penetration (T4) and xylem connection (T5). Patterns of auxins and cytokinin showed spatial concentrations in infective stages and moreover were involved in haustorium development. These results are the first evidence of proteins, cell wall-degrading enzymes, and phytohormones that are involved in early infection for the Psittacanthus genus, and thus represent a general infection mechanism for other mistletoe species. These results could help to understand the molecular dialogue in the establishment of P. calyculatus parasitism.

Transcripts Expressed during Germination Sensu Stricto Are Associated with Vigor in Soybean Seeds.

The rapid and uniform establishment of crop plants in the field underpins food security through uniform mechanical crop harvesting. In order to achieve this, seeds with greater vigor should be used. Vigor is a component of physiological quality related to seed resilience. Despite this importance, there is little knowledge of the association between events at the molecular level and seed vigor. In this study, we investigated the relationship between gene expression during germination and seed vigor in soybean. The expression level of twenty genes related to growth at the beginning of the germination process was correlated with vigor. In this paper, vigor was evaluated by different tests. Then we reported the identification of the genes Expansin-like A1, Xyloglucan endotransglucosylase/hydrolase 22, 65-kDa microtubule-associated protein, Xyloglucan endotransglucosylase/hydrolase 2, N-glycosylase/DNA lyase OGG1 and Cellulose synthase A catalytic subunit 2, which are expressed during germination, that correlated with several vigor tests commonly used in routine analysis of soybean seed quality. The identification of these transcripts provides tools to study vigor in soybean seeds at the molecular level.

The distinct roles of water table depth and soil properties in controlling alternative woodland-grassland states in the Cerrado.

Open grassy vegetation and forests share riparian zones across the Neotropical savannas, characterizing alternative stable states. However, factors determining the occurrence and maintenance of each vegetation type are yet to be elucidated. To disentangle the role of environmental factors (soil properties and groundwater depth) constraining tree colonization of wet grasslands in the Cerrado, we assessed tree establishment during the early seedling and sapling stages and the influence of these factors on leaf gas exchange and leaf water potential of tree saplings. Three functionally distinct tree species were studied: (1) flood-tolerant species characteristic of gallery forests, (2) flood-intolerant species characteristic of seasonally dry savannas, and (3) generalist species found in both gallery forests and seasonally dry savannas. Savanna species was constrained by waterlogging, especially at the sapling stage, with restricted stomatal conductance and leaf water potential, resulting in low carbon assimilation, decreased plant size, and high mortality (above 80%). The gallery forest and the generalist species, however, were able to colonize the wet grasslands and survive, despite the low seedling emergence (below 30%) and sapling growth constrained by low gas exchange rates. Soil waterlogging is, therefore, an effective environmental filter that prevents savanna trees from expanding over wet grasslands. However, colonization by trees adapted to a shallow water table cannot be constrained by this or other soil properties, turning the wet grasslands dependent on natural disturbances to persist as an alternative state, sharing the waterlogged environments with the gallery forests in the Cerrado region.

Seed-to-seedling transitions exhibit distance-dependent mortality but no strong spacing effects in a Neotropical forest.

Patterns of seed dispersal and seed mortality influence the spatial structure of plant communities and the local coexistence of competing species. Most seeds are dispersed in proximity to the parent tree, where mortality is also expected to be the highest, because of competition with siblings or the attraction of natural enemies. Whereas distance-dependent mortality in the seed-to-seedling transition was often observed in tropical forests, few studies have attempted to estimate the shape of the survival-distance curves, which determines whether the peak of seedling establishment occurs away from the parent tree (Janzen-Connell pattern) or if the peak attenuates but remains at the parent location (Hubbell pattern). In this study, we inferred the probability density of seed dispersal and two stages of seedling establishment (new recruits, and seedlings 20 cm or taller) with distance for 24 tree species present in the 50-ha Forest Dynamics Plot of Barro Colorado Island, Panama. Using data from seed traps, seedling survey quadrats, and tree-census records spanning the 1988-2014 period, we fit hierarchical Bayesian models including parameters for tree fecundity, the shape of the dispersal kernel, and overdispersion of seed or seedling counts. We combined predictions from multiple dispersal kernels to obtain more robust inferences. We find that Hubbell patterns are the most common and Janzen-Connell patterns are very rare among those species; that distance-dependent mortality may be stronger in the seed stage, in the early recruit stage, or comparable in both; and that species with larger seeds experience less overall mortality and less distance-dependent mortality. Finally, we describe how this modeling approach could be extended at a community scale to include less abundant species.

Limitations to recovery following wildfire in dry forests of southern Colorado and northern New Mexico, USA.

Climate warming is contributing to increases in wildfire activity throughout the western United States, leading to potentially long-lasting shifts in vegetation. The response of forest ecosystems to wildfire is thus a crucial indicator of future vegetation trajectories, and these responses are contingent upon factors such as seed availability, interannual climate variability, average climate, and other components of the physical environment. To better understand variation in resilience to wildfire across vulnerable dry forests, we surveyed conifer seedling densities in 15 recent (1988-2010) wildfires and characterized temporal variation in seed cone production and seedling establishment. We then predicted postfire seedling densities at a 30-m resolution within each fire perimeter using downscaled climate data, monthly water balance models, and maps of surviving forest cover. Widespread ponderosa pine (Pinus ponderosa) seed cone production occurred at least twice following each fire surveyed, and pulses of conifer seedling establishment coincided with years of above-average moisture availability. Ponderosa pine and Douglas-fir (Pseudotsuga menziesii) seedling densities were higher on more mesic sites and adjacent to surviving trees, though there were also important interspecific differences, likely attributable to drought and shade tolerance. We estimated that postfire seedling densities in 42% (for ponderosa pine) and 69% (for Douglas-fir) of the total burned area were below the lowest reported historical tree densities in these forests. Spatial models demonstrated that an absence of mature conifers (particularly in the interior of large, high-severity patches) limited seedling densities in many areas, but 30-yr average actual evapotranspiration and climatic water deficit limited densities on marginal sites. A better understanding of the limitations to postfire forest recovery will refine models of vegetation dynamics and will help to improve strategies of adaptation to a warming climate and shifting fire activity.

Seed local adaptation and seedling plasticity account for Gleditsia triacanthos tree invasion across biomes.

BACKGROUND AND AIMS: Phenotypic plasticity and local adaption can contribute to the success of invasive species. While the former is an environmentally induced trait, the latter involves a selection process to filter the best genotype for a location. We examined the evidence for phenotypic plasticity and local adaptation for seed and seedling traits of the invasive tree Gleditsia triacanthos, with three origins distributed along an approx. 10° latitude gradient across three biomes. METHODS: In sub-tropical forests, dry woodlands and secondary temperate grasslands in Argentina, we harvested seeds from clusters of neighbouring trees (i.e. families) distributed within 15-20 km in each origin (biome). We manipulated the environmental conditions relevant to each biome, assuming that propagule availability did not represent an ecological barrier. In growth chambers, we evaluated seed imbibition and seed germination under different light, temperature and water potential. In a 2 year common garden, we evaluated the impact of resident vegetation removal on seedling survival and growth. KEY RESULTS: Mean time to complete seed imbibition differed among origins; seeds from temperate grasslands reached full imbibition before seeds from dry woodlands and sub-tropical forests. Germination was always >70 %, but was differentially affected by water potential, and light quantity (dark-light) and quality (red-far red) among origins, suggesting local adaptation. In the common garden, vegetation removal rather than origin negatively affected seedling survival and enhanced seedling growth. Vegetation removal increased basal diameter, leaves per plant and spine number, and reduced the height:basal diameter ratio. CONCLUSIONS: We conclude that local adaptation in seed germination traits and plastic changes in seedling allometry (e.g. height:diameter) may allow this tree to respond over the short and long term to changes in environmental conditions, and to contribute to shape G. triacanthos as a successful woody invader. Overall, our study revealed how local adaptation and plasticity can explain different aspects of tree invasion capacity across biomes.

Context-dependent effects of fire and browsing on woody alien invasion in mountain ecosystems.

Anthropogenic activities have increased disturbances and alien woody invasion in mountain ecosystems worldwide. Whether disturbances promote or counteract upward movement of woody aliens is poorly understood. We assessed if the most successful woody invader of low mountains of central Argentina (Gleditsia triacanthos) might expand its elevational distribution in response to the principal disturbances of these ecosystems (fire and livestock browsing) across increasing climatic severity. We assessed seedling emergence, growth and mycorrhizal colonization on sown plots distributed in burned and unburned sites, with and without browsing at the lower and upper elevation belts (i.e. 1000 and 2400 m a.s.l.). Additionally, several abiotic variables were measured to relate their influence on the seedling establishment. Disturbances reduced seedling emergence at both elevations. Burned conditions increased seedling growth and arbuscular colonization only in the lower belt. Seedling success (total seedling biomass per plot) was not modified by disturbances at the upper elevation, but was reduced by browsing and enhanced by fire in the lower elevation. The overall reduction in seedling emergence and growth in the upper elevation despite the higher soil nutrient content places climate as the strongest regulator of G. triacanthos seedling establishment. Accordingly, climate rather than disturbances would be the main limiting factor of upward expansion of this woody alien. Our findings differ from general patterns described for mountain invasion by herbaceous species, highlighting that mountain invasibility is highly growth-form dependent, and that upper range expansion by woody aliens interacting with multiple disturbances should be assessed worldwide.

Conspecific plants are better 'nurses' than rocks: consistent results revealing intraspecific facilitation as a process that promotes establishment in a hyper-arid environment.

Harsh environmental conditions in arid ecosystems limit seedling recruitment to microhabitats under nurse structures, such as shrubs or rocks. These structures, however, do not necessarily afford the same benefits to plants because nurse rocks provide only physical nurse effects, whereas nurse plants can provide both physical and biological nurse effects. Nevertheless, if the nurse plant is a conspecific, the benefits it provides may be outweighed by higher mortality due to negative density-dependent processes; consequently, negative density-dependence is expected to limit plants from acting as nurses to their own seedlings. The degree to which an abiotic nurse may be more beneficial than a conspecific one remains largely unexplored. Here, we examine the role and elucidate the mechanisms by which conspecific plants and rocks promote plant establishment in a hyper-arid desert. For 4 years, we examined establishment patterns of Myrcianthes coquimbensis (Myrtaceae), a threatened desert shrub that recruits solely in rock cavities and under conspecific shrubs. Specifically, we characterized these microhabitats, as well as open interspaces for comparison, and conducted germination, seed removal and seedling survival experiments. Our results revealed that conspecific shrubs and nurse rocks modified environmental conditions in similar ways; soil and air temperatures were lower, and water availability was higher than in open interspaces. We found no evidence on negative density-dependent recruitment: seed removal was lowest and seedling emergence highest under conspecific plants, moreover seedling survival probabilities were similar in rock cavities and under conspecific plants. We conclude that the probability of establishment was highest under conspecific plants than in other microhabitats, contrasting what is expected under the Janzen-Connell recruitment model. We suggest that for species living in stressful environments, population regulation may be a function of positive density-dependence and intraspecific facilitation may be a process that promotes the persistence of some plant species within a community.

Seed vigor and amount of soybean straw on seedling emergence and productive performance of wheat / Vigor de sementes e quantidades de palhada de soja na emergência de plântulas e desempenho produtivo do trigo

The use of high-quality seeds is essential to minimize the possible suppressive effect of straw on seedling emergence, contributing to stand establishment and high grain yield. The aim of this study was to assess the influence of seed vigor associated with soil cover with different amounts of soybean straw on seedling emergence and productive performance of wheat. The experiment was conducted in a greenhouse using two wheat cultivars (CD 150 and BRS Gralha Azul) under a completely randomized design in a 2 × 5 factorial scheme with four replications. Factors consisted of two seed vigor levels (high and low) and five amounts of soybean straw (0, 3, 6, 9, and 12 t ha?1). The following assessments were performed: seedling emergence, dry mass of seedling shoot, number of tillers, plant height, yield components (number of spikes per plant, number of grains per spike, and mass of one thousand seeds), grain yield, and harvest index. The use of high vigor seeds favors the emergence and dry mass production of seedling shoot for both cultivars. The increased amount of soybean straw reduces seedling emergence in both cultivars. In the cultivars CD 150 and BRS Gralha Azul, the amounts of soybean straw of 2.45 and 5.40 t ha?1, respectively, result in a higher wheat grain yield.(AU)

O uso de sementes de elevada qualidade é fundamental para minimizar o possível efeito supressor da palhada sobre a emergência de plântulas, contribuindo para o estabelecimento do estande e a obtenção de altos rendimentos de grãos. O objetivo foi avaliar a influência do vigor de sementes associado à cobertura do solo com diferentes quantidades de palhada de soja, sobre a emergência de plântulas e o desempenho produtivo da cultura do trigo. O experimento foi conduzido em casa de vegetação, utilizando duas cultivares de trigo (CD 150 e BRS Gralha Azul), sob o delineamento inteiramente casualizado, em esquema fatorial 2x5, com quatro repetições. Os fatores foram constituídos por dois níveis de vigor de sementes (alto e baixo) e cinco quantidades de palhada de soja (0, 3, 6, 9 e 12 t ha-1). As avaliações efetuadas foram: emergência de plântulas, massa seca da parte aérea de plântulas, número de perfilhos, altura de plantas, componentes do rendimento (número de espigas por planta, número de grãos por espiga e massa de mil sementes), produtividade de grãos e índice de colheita. A utilização de sementes de alto vigor favorece a emergência e a produção de massa seca da parte aérea das plântulas, para ambas cultivares. O aumento da quantidade de palhada de soja reduz a emergência de plântulas, nas duas cultivares. Nas cultivares CD 150 e BRS Gralha Azul, as quantidades de palhada de soja reduz a emergência de plântulas, nas duas cultivares. Nas cultivares CD 150 e BRS Gralha Azul, as quantidades de palhada de soja de 2,45 e 5,40 t ha-1, respectivamente, resultam em maior produtividade de grãos de trigo.(AU)

An active Mitochondrial Complex II Present in Mature Seeds Contains an Embryo-Specific Iron-Sulfur Subunit Regulated by ABA and bZIP53 and Is Involved in Germination and Seedling Establishment.

Complex II (succinate dehydrogenase) is an essential mitochondrial enzyme involved in both the tricarboxylic acid cycle and the respiratory chain. In Arabidopsis thaliana, its iron-sulfur subunit (SDH2) is encoded by three genes, one of them (SDH2.3) being specifically expressed during seed maturation in the embryo. Here we show that seed SDH2.3 expression is regulated by abscisic acid (ABA) and we define the promoter region (-114 to +49) possessing all the cis-elements necessary and sufficient for high expression in seeds. This region includes between -114 and -32 three ABRE (ABA-responsive) elements and one RY-enhancer like element, and we demonstrate that these elements, although necessary, are not sufficient for seed expression, our results supporting a role for the region encoding the 5' untranslated region (+1 to +49). The SDH2.3 promoter is activated in leaf protoplasts by heterodimers between the basic leucine zipper transcription factors bZIP53 (group S1) and bZIP10 (group C) acting through the ABRE elements, and by the B3 domain transcription factor ABA insensitive 3 (ABI3). The in vivo role of bZIP53 is further supported by decreased SDH2.3 expression in a knockdown bzip53 mutant. By using the protein synthesis inhibitor cycloheximide and sdh2 mutants we have been able to conclusively show that complex II is already present in mature embryos before imbibition, and contains mainly SDH2.3 as iron-sulfur subunit. This complex plays a role during seed germination sensu-stricto since we have previously shown that seeds lacking SDH2.3 show retarded germination and now we demonstrate that low concentrations of thenoyltrifluoroacetone, a complex II inhibitor, also delay germination. Furthermore, complex II inhibitors completely block hypocotyl elongation in the dark and seedling establishment in the light, highlighting an essential role of complex II in the acquisition of photosynthetic competence and the transition from heterotrophy to autotrophy.

Seed vigor and amount of soybean straw on seedling emergence and productive performance of wheat / Vigor de sementes e quantidades de palhada de soja na emergência de plântulas e desempenho produtivo do trigo

The use of high-quality seeds is essential to minimize the possible suppressive effect of straw on seedling emergence, contributing to stand establishment and high grain yield. The aim of this study was to assess the influence of seed vigor associated with soil cover with different amounts of soybean straw on seedling emergence and productive performance of wheat. The experiment was conducted in a greenhouse using two wheat cultivars (CD 150 and BRS Gralha Azul) under a completely randomized design in a 2 × 5 factorial scheme with four replications. Factors consisted of two seed vigor levels (high and low) and five amounts of soybean straw (0, 3, 6, 9, and 12 t ha?1). The following assessments were performed: seedling emergence, dry mass of seedling shoot, number of tillers, plant height, yield components (number of spikes per plant, number of grains per spike, and mass of one thousand seeds), grain yield, and harvest index. The use of high vigor seeds favors the emergence and dry mass production of seedling shoot for both cultivars. The increased amount of soybean straw reduces seedling emergence in both cultivars. In the cultivars CD 150 and BRS Gralha Azul, the amounts of soybean straw of 2.45 and 5.40 t ha?1, respectively, result in a higher wheat grain yield.

O uso de sementes de elevada qualidade é fundamental para minimizar o possível efeito supressor da palhada sobre a emergência de plântulas, contribuindo para o estabelecimento do estande e a obtenção de altos rendimentos de grãos. O objetivo foi avaliar a influência do vigor de sementes associado à cobertura do solo com diferentes quantidades de palhada de soja, sobre a emergência de plântulas e o desempenho produtivo da cultura do trigo. O experimento foi conduzido em casa de vegetação, utilizando duas cultivares de trigo (CD 150 e BRS Gralha Azul), sob o delineamento inteiramente casualizado, em esquema fatorial 2x5, com quatro repetições. Os fatores foram constituídos por dois níveis de vigor de sementes (alto e baixo) e cinco quantidades de palhada de soja (0, 3, 6, 9 e 12 t ha-1). As avaliações efetuadas foram: emergência de plântulas, massa seca da parte aérea de plântulas, número de perfilhos, altura de plantas, componentes do rendimento (número de espigas por planta, número de grãos por espiga e massa de mil sementes), produtividade de grãos e índice de colheita. A utilização de sementes de alto vigor favorece a emergência e a produção de massa seca da parte aérea das plântulas, para ambas cultivares. O aumento da quantidade de palhada de soja reduz a emergência de plântulas, nas duas cultivares. Nas cultivares CD 150 e BRS Gralha Azul, as quantidades de palhada de soja

Seed vigor and amount of soybean straw on seedling emergence and productive performance of wheat / Vigor de sementes e quantidades de palhada de soja na emergência de plântulas e desempenho produtivo do trigo

The use of high-quality seeds is essential to minimize the possible suppressive effect of straw on seedling emergence, contributing to stand establishment and high grain yield. The aim of this study was to assess the influence of seed vigor associated with soil cover with different amounts of soybean straw on seedling emergence and productive performance of wheat. The experiment was conducted in a greenhouse using two wheat cultivars (CD 150 and BRS Gralha Azul) under a completely randomized design in a 2 × 5 factorial scheme with four replications. Factors consisted of two seed vigor levels (high and low) and five amounts of soybean straw (0, 3, 6, 9, and 12 t ha?1). The following assessments were performed: seedling emergence, dry mass of seedling shoot, number of tillers, plant height, yield components (number of spikes per plant, number of grains per spike, and mass of one thousand seeds), grain yield, and harvest index. The use of high vigor seeds favors the emergence and dry mass production of seedling shoot for both cultivars. The increased amount of soybean straw reduces seedling emergence in both cultivars. In the cultivars CD 150 and BRS Gralha Azul, the amounts of soybean straw of 2.45 and 5.40 t ha?1, respectively, result in a higher wheat grain yield.

O uso de sementes de elevada qualidade é fundamental para minimizar o possível efeito supressor da palhada sobre a emergência de plântulas, contribuindo para o estabelecimento do estande e a obtenção de altos rendimentos de grãos. O objetivo foi avaliar a influência do vigor de sementes associado à cobertura do solo com diferentes quantidades de palhada de soja, sobre a emergência de plântulas e o desempenho produtivo da cultura do trigo. O experimento foi conduzido em casa de vegetação, utilizando duas cultivares de trigo (CD 150 e BRS Gralha Azul), sob o delineamento inteiramente casualizado, em esquema fatorial 2x5, com quatro repetições. Os fatores foram constituídos por dois níveis de vigor de sementes (alto e baixo) e cinco quantidades de palhada de soja (0, 3, 6, 9 e 12 t ha-1). As avaliações efetuadas foram: emergência de plântulas, massa seca da parte aérea de plântulas, número de perfilhos, altura de plantas, componentes do rendimento (número de espigas por planta, número de grãos por espiga e massa de mil sementes), produtividade de grãos e índice de colheita. A utilização de sementes de alto vigor favorece a emergência e a produção de massa seca da parte aérea das plântulas, para ambas cultivares. O aumento da quantidade de palhada de soja reduz a emergência de plântulas, nas duas cultivares. Nas cultivares CD 150 e BRS Gralha Azul, as quantidades de palhada de soja reduz a emergência de plântulas, nas duas cultivares. Nas cultivares CD 150 e BRS Gralha Azul, as quantidades de palhada de soja de 2,45 e 5,40 t ha-1, respectivamente, resultam em maior produtividade de grãos de trigo.

Metabolite profiling of Ricinus communis germination at different temperatures provides new insights into thermo-mediated requirements for successful seedling establishment.

Ricinus communis seeds germinate to a high percentage and faster at 35 °C than at lower temperatures, but with compromised seedling establishment. However, seedlings are able to cope with high temperatures at later stages of seedling establishment if germination occurred at lower temperatures. Our objective was to assess the biochemical and molecular requirements of R. communis germination for successful seedling establishment at varying temperatures. For that, we performed metabolite profiling (GC-TOF-MS) and measured transcript levels of key genes involved in several energy-generating pathways, such as storage oil mobilization, ß-oxidation and gluconeogenesis of seeds germinated at three different temperatures. We identified a thermo-sensitive window during seed germination in which high temperatures compromise seedling development, most likely by down-regulating some energy-generating pathways. Overexpression of malate synthase (MLS) and glycerol kinase (GK) genes resulted in higher starch levels in Nicotiana benthamiana leaves, which highlights the importance of these genes in energy-generating pathways for seedling establishment. Additionally, we showed that GABA, which is a stress-responsive metabolite, accumulated in response to the water content of the seeds during the initial phase of imbibition. Herewith, we provide new insights into the molecular requirements for vigorous seedling growth of R. communis under different environmental conditions.

Seed size-number trade-off in Euterpe edulis in plant communities of the Atlantic Forest

Investigations of seed size and number differences among plant populations growing in contrasting habitats can provide relevant information about ecological strategies that optimize reproductive effort. This may imply important consequences for biodiversity conservation and restoration. Therefore, we sought to investigate seed size-number trade-off in Euterpe edulis populations growing in plant communities in the Brazilian Atlantic Forest. Seed dry mass and seed number per bunch were evaluated in 2008 and 2009 in large remnants of the Seasonally Dry Forest, Restinga Forest and Atlantic Rainforest in southeastern Brazil, in 20 individuals per site and year. Seed size and seed number varied among forest types, but a seed size-number trade-off was neither observed within nor among populations. Positive association between seed size and number was found in the Atlantic Rainforest, and reduced seed crop was not accompanied by heavier seeds in the Restinga Forest. Seed dry mass declined in 2009 in all three forest types. Compared to seed number in 2008, palms of both the Restinga Forest and the Atlantic Rainforest produced in 2009 higher yields of smaller seeds - evidence of between years seed size-number trade-off -, while the Seasonally Dry Forest population produced a reduced number of smaller seeds. Such a flexible reproductive strategy, involving neutral, positive, and negative associations between seed size and number could enhance the ecological amplitude of this species and their potential to adapt to different environment conditions.(AU)

Seed size-number trade-off in Euterpe edulis in plant communities of the Atlantic Forest

Investigations of seed size and number differences among plant populations growing in contrasting habitats can provide relevant information about ecological strategies that optimize reproductive effort. This may imply important consequences for biodiversity conservation and restoration. Therefore, we sought to investigate seed size-number trade-off in Euterpe edulis populations growing in plant communities in the Brazilian Atlantic Forest. Seed dry mass and seed number per bunch were evaluated in 2008 and 2009 in large remnants of the Seasonally Dry Forest, Restinga Forest and Atlantic Rainforest in southeastern Brazil, in 20 individuals per site and year. Seed size and seed number varied among forest types, but a seed size-number trade-off was neither observed within nor among populations. Positive association between seed size and number was found in the Atlantic Rainforest, and reduced seed crop was not accompanied by heavier seeds in the Restinga Forest. Seed dry mass declined in 2009 in all three forest types. Compared to seed number in 2008, palms of both the Restinga Forest and the Atlantic Rainforest produced in 2009 higher yields of smaller seeds - evidence of between years seed size-number trade-off -, while the Seasonally Dry Forest population produced a reduced number of smaller seeds. Such a flexible reproductive strategy, involving neutral, positive, and negative associations between seed size and number could enhance the ecological amplitude of this species and their potential to adapt to different environment conditions.

Evaluación de sustratos para el establecimiento en laboratorio de plántulas de Puya raimondii Harms (Bromeliaceae)

Puya raimondii Harms (Bromeliaceae) es una planta monocárpica que puede producir entre 6 y 12 millones de semillas, sin embargo es muy raro encontrar plántulas en su hábitat natural, lo que significaría la existencia de factores limitantes en el proceso de establecimiento. En el presente trabajo muestra los resultados de experimentos para determinar el sustrato más adecuado para el establecimiento de P. raimondii bajo condiciones de laboratorio. Se comparó la sobrevivencia y vigor de plántulas de P. raimondii en los substratos de turba, musgo, turba-tierra y musgo-tierra. El sustrato turba presentó la mayor supervivencia, mostrando que es el más adecuado para el establecimiento de las plántulas, porque mantiene una humedad adecuada y pH estable lo que permitiría que las plántulas presenten un mayor vigor; los sustratos con muy poca (caso turbatierra) o demasiada (caso musgo) retención de humedad afectan negativamente su vigor y desarrollo.

Puya raimondii Harms (Bromeliaceae) is a monocarpic plant, that can produce about 6 to 12 million seeds, nevertheless is very rare to find seedlings in their natural habitat, indicating difficulties for its establishment. In this work, the conditions for establishment of P. raimondii under laboratory conditions were determined carrying out experiments to determine the better substrate. It was compared the survival and vigour of P. raimondii seedling that were transplanted in peat, moss, peat-soil and moss-soil substrates. The peat substrate showed high survival and was better for establishment of seedlings because it maintains steady and suitable humidity and pH conditions, this allowed that seedlings presents a good vigour. Substrates with very little (case peat-earth) or too much (case moss) humidity retention had a negative effect over vigour and development.

Seed size and establishment conditions in tropical trees : On the use of taxonomic relatedness in determining ecological patterns.

Within a multi-species study, species do not necessarily represent independent data points. The data set used by Foster and Janson (1985) to look at the relationship between seed size and establishment conditions for naturally occurring tropical trees was re-analyzed, to take into account the effect of relatedness among species. The re-analysis showed that 1) this data set does not support the hypothesis that large-seeded species are more likely to establish in small gaps or shade than are small-seeded species, and 2) more than 1/3 (16 of 39) of the data points were extraneous to the test of the hypothesis. It is recommended that all ecologists, and not just those interested in evolutionary questions, consider species relatedness prior to inception of any multi-species study.