1,721,031 research outputs found
Three phylogenetically distant shade-tolerant temperate forest herbs have similar seed germination syndromes
No full textPlants growing in the same environment typically share ecophysiological characteristics enabling them to survive and reproduce when exposed to a common selection pressure. As such, seedlings establishing in temperate forest habitats cope with similar issues of low light availability and climate seasonality. We examined similarities in the germination syndromes in three shade-tolerant temperate forest herbs, Allium ursinum (Amaryllidaceae), Mercurialis perennis (Euphorbiaceae) and Dioscorea communis (Dioscoreaceae) with a distant phylogenetic affiliation. Seeds of M. perennis and A. ursinum are dispersed in spring and those of D. communis in autumn. Experiments on phenology of seed germination and seedling emergence in natural conditions revealed that seeds of all three species germinate in the following autumn. Seedlings do not emerge immediately but rather remain below the soil surface until late winter or early spring. Experiments in controlled laboratory conditions showed that seeds germinated best at intermediate autumn or spring temperatures (between 10 and 15°C) following a period at high summer temperatures (around 20°C). Seed germination of Allium ursinum is strongly photoinhibited, while moderate photoinhibition and no photoinhibition at all was observed in Dioscorea communis and Mercurialis perennis, respectively. Although seeds of all three species are endospermic at dispersal, no embryo growth prior to germination was observed. The cotyledons functioned as a haustorium, recuperating the nutrient reserves in the endosperm post-germination. It can be concluded that although phylogenetically unrelated, the three species studied show a remarkable similarity in germination and seedling emergence strategy that is commonly observed in plants adapted to growing in shady conditions
Photophobia in Lilioid monocots: photoinhibition of seed germination explained by seed traits, habitat adaptation and phylogenetic inertia
No full textPhotoinhibition of seed germination, known to occur notably in species growing in dry and hot habitats, is considered an adaptation to avoid germination at the soil surface after unpredictable rainfall events during the dry season. Hence, the association of this ecophysiological response with plant life histories and the natural environment was investigated in Lilioid monocots, a group of plants where photoinhibition has been pre-eminently observed
An evaluation of the taxonomic status of Musa viridis and Musa splendida using high-throughput sequencing data
No full textThe delimitation of species based on morphological traits can be challenging due to overlapping trait variation. The taxonomic identity of closely related sympatric species with individuals displaying intermediate phenotypes is particularly questionable. However, thorough morphological assessments or traditional molecular analyses often lack resolution to clarify if two species are truly separate taxonomic entities or should be merged. Interestingly, advances in high-throughput sequencing methods and data processing during the last decades enable the use of high-resolution data to tackle taxonomic problems. Several species with an unclear taxonomic status are found in the banana family (Musaceae). In Vietnam, the Musa species M. viridis and M. splendida have very similar morphological trait characteristics. The main difference between the two species is the colour of the male flower bud: M. splendida has red flower buds, whereas M. viridis has pink flower buds. Both species occur sympatrically, and individuals with red and pink male flower buds are found together in some populations. In this study, we used high-throughput (DArT) sequencing data from plants of nine populations to investigate the taxonomic status of these Musa species. Maximum likelihood phylogenetic trees were reconstructed for over 12,000 loci (< 120 base pairs) and one ASTRAL consensus tree was created from all locus trees. The individuals in the ASTRAL phylogenetic tree did not cluster by species identity, but by population, having individuals from different species in the same cluster. Consequently, we propose to merge the species M. viridis and M. splendida into one species named M. splendida according to nomenclatural conventions
Identifying coffee: development of a low-cost and robust barcoding assay for wild African Coffea species
No full textWith an estimated consumption of more than two billion cups a day, coffee is one of the most popular beverages in the world. Nearly all coffee is produced from the seeds of two species: Coffea arabica (Arabica coffee) and Coffea canephora (Robusta coffee). Both Arabica and Robusta coffee production is threatened by climate fluctuations and disease outbreaks, reducing yields and ravaging coffee plantations. To overcome these challenges, the potential of other wild Coffea species for the improvement of existing coffee varieties or for the development of new varieties has been studied. The Coffea genus consists of circa 130 described species that are mainly found in sub-Saharan Africa and Madagascar. Coffea species on the African continent are more closely related to Arabica and Robusta coffee. Nevertheless, the identification of African Coffea species at species level based on morphological traits can be challenging as several species seem to have overlapping trait characteristics. In this study, we developed a molecular barcoding assay consisting of eight nuclear markers between ca. 200 and 800 base pairs long that can be sequenced using Sanger sequencing. Marker regions were selected based on the output of publicly available genotyping-by-sequencing data, ensuring that each Coffea species included in this dataset had a unique allele for at least two out of eight markers. The resulting barcoding assay is a cost-efficient and accessible tool for the molecular identification of wild African Coffea species, facilitating their conservation and their application for the improvement of coffee cultivation
An evaluation of the taxonomic status of Musa viridis and Musa splendida using high-throughput sequencing data
No full textThe delimitation of species based on morphological traits can be challenging due to overlapping trait variation. The taxonomic identity of closely related sympatric species with individuals displaying intermediate phenotypes is particularly questionable. However, thorough morphological assessments or traditional molecular analyses often lack resolution to clarify if two species are truly separate taxonomic entities or should be merged. Interestingly, advances in high-throughput sequencing methods and data processing during the last decades enable the use of high-resolution data to tackle taxonomic problems. Several species with an unclear taxonomic status are found in the banana family (Musaceae). In Vietnam, the Musa species M. viridis and M. splendida have very similar morphological trait characteristics. The main difference between the two species is the colour of the male flower bud: M. splendida has red flower buds, whereas M. viridis has pink flower buds. Both species occur sympatrically, and individuals with red and pink male flower buds are found together in some populations. In this study, we used high-throughput (DArT) sequencing data from plants of nine populations to investigate the taxonomic status of these Musa species. Maximum likelihood phylogenetic trees were reconstructed for over 12,000 loci (< 120 base pairs) and one ASTRAL consensus tree was created from all locus trees. The individuals in the ASTRAL phylogenetic tree did not cluster by species identity, but by population, having individuals from different species in the same cluster. Consequently, we propose to merge the species M. viridis and M. splendida into one species named M. splendida according to nomenclatural conventions
Identifying coffee: development of a low-cost and robust barcoding assay for wild African Coffea species
No full textWith an estimated consumption of more than two billion cups a day, coffee is one of the most popular beverages in the world. Nearly all coffee is produced from the seeds of two species: Coffea arabica (Arabica coffee) and Coffea canephora (Robusta coffee). Both Arabica and Robusta coffee production is threatened by climate fluctuations and disease outbreaks, reducing yields and ravaging coffee plantations. To overcome these challenges, the potential of other wild Coffea species for the improvement of existing coffee varieties or for the development of new varieties has been studied. The Coffea genus consists of circa 130 described species that are mainly found in sub-Saharan Africa and Madagascar. Coffea species on the African continent are more closely related to Arabica and Robusta coffee. Nevertheless, the identification of African Coffea species at species level based on morphological traits can be challenging as several species seem to have overlapping trait characteristics. In this study, we developed a molecular barcoding assay consisting of eight nuclear markers between ca. 200 and 800 base pairs long that can be sequenced using Sanger sequencing. Marker regions were selected based on the output of publicly available genotyping-by-sequencing data, ensuring that each Coffea species included in this dataset had a unique allele for at least two out of eight markers. The resulting barcoding assay is a cost-efficient and accessible tool for the molecular identification of wild African Coffea species, facilitating their conservation and their application for the improvement of coffee cultivation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
OTIMIZAÇÃO DO PROTOCOLO DE GERMINAÇÃO DE SEMENTES DE BANANAS SELVAGENS (MUSA ACUMINATA COLLA)Implicações para a germinação de sementes inteiras e conservação ex situ de germoplasma de Variedades Selvagens de banana (Musa acuminata Colla)
No full textDissertação de Mestrado em Biodiversidade e Biotecnologia Vegetal apresentada à Faculdade de Ciências e TecnologiaBananas (Musa spp.) are nowadays the most produced and consumed fruit crop in the world. They comprise commercial dessert, plantain bananas and wild relatives (CWR). Despite many efforts, important commercial Banana varieties face the risk of disappearing as a consequence of pests and diseases, global monoculture production and the present climate crisis.Meise Botanic Garden, Belgium (MBG) and Leuven University, Belgium (KU Leuven), in association with international banana research centers (as INIBAP, ITC) and Musa Consortia investigate seed conservation, ex situ, in vitro and cryo- conservation of Musa resources. Regardless of past efforts, there is still little knowledge on Musa’s seed germination, dormancy strategy, and storage behavior. Actual germination protocols are not effective, and they require a long time (months to years) to yield results. Seed dormancy appears to be related to integument constraints, for this reason Embryo Rescue (ER) is the prevalent method to germinate banana seeds.I performed my research in the Seed Bank of MBG and KU Leuven with the goal of contributing to the research on conservation of Musa seed resources and developing a feasible germination protocol of CWR of Musa acuminata, for future implementation in seed banks. My focus was on quantifying initial viability through morphological analyses of seeds (stored and fresh) and testing combined effects of: 1) different dormancy breaking treatments, 2) temperature oscillation regimes and/or 3) substrates, on diverse seed germination protocols. At the end of the experiments, a Cut test followed by a Tetrazolium Chloride test (TTC) or ER test was made to determine the viability of non-germinated seeds; and TTC and ER results were compared to assess the eligibility of TTC as a reliable post-incubation viability test for M. acuminata.Our findings highlight the importance of considering seed morphology and maturity in the development of effective germination protocols for M. acuminata. Despite a substantial number of stored and fresh seeds, and the high number of treatments employed in germination testing, the dormancy-breaking and incubation factors tested proved to be insufficient to effectively overcome the dormancy of M. acuminata seeds. The low Final Germination Percentage and the high percentage of apparent viable seeds after incubation suggest that high dormancy levels are present in both dry and fresh seeds of M. acuminata. In both dry and fresh seeds, the ER technique alleviated dormancy constrains, and it revealed that the type of pre-treatment, substrate and temperature regime have a significant impact in embryo viability. I also concluded that the TTC procedure used in this study is not a reliable and precise test for assessing post-incubation viability of M. acuminata seeds.Despite the ineffectiveness demonstrated by the 18 treatments employed in germination testing, the work developed in this project is essential to understand the relationship between seed morphology and initial viability of seeds. Additionally, it contributes to understand the impact of various pre-treatment and incubation variables on post-incubation seed viability. This knowledge is crucial to design innovative germination tests, either by excluding the factors tested in this project or by incorporating them in alternative combinations.As bananas (Musa spp.) são atualmente o fruto mais produzido e consumido no mundo. Neste grupo estão incluídas as variedades comerciais de sobremesa, bananas-plantain, e as variedades selvagens (CWR). Apesar dos esforços, importantes variedades comerciais de banana enfrentam o risco de desaparecer como consequência de pragas e doenças, da produção global em monocultura e da atual crise climática.O Jardim Botânico de Meise (MBG) e a Universidade de Leuven (KU Leuven), ambos na Bélgica, em parceria com centros internacionais de investigação (INIBAP, ITC) e Consorcia em Musa, investigam a conservação de recursos genéticos de Musa em sementes, ex situ -, in vitro - e crio- conservação. Existe pouco conhecimento sobre a germinação de sementes de Musa, da sua dormência e do seu comportamento em Bancos de Sementes: os atuais protocolos de germinação são ineficientes e levam bastante tempo (meses a anos) a obter resultados. A dormência das sementes de banana aparenta estar relacionada com constrangimentos provocados pelos integumentos; por esta razão, Embryo Rescue (ER) (Resgate de Embriões) é o método prevalente de germinação.Realizado no Banco de Sementes do MBG e na KU Leuven, o meu projeto de tese teve como objetivo contribuir para a investigação na conservação de sementes de Musa e desenvolver um protocolo de germinação de CWR de Musa acuminata, com perspetivas futuras de implementação em bancos de sementes. O meu foco prendeu-se com a quantificação da viabilidade inicial através de análises morfológicas das sementes (armazenadas e frescas) e testar: 1) tratamentos de quebra de dormência, 2) regimes de oscilação de temperatura, e 3) substratos, em diversos protocolos de germinação. No final de cada experiência, foi executado um Cut test, seguido por um teste Tetrazolium Chloride (TTC) ou teste ER de forma a quantificar a viabilidade das sementes não-germinadas. Os resultados de TTC e ER foram comparados para verificar a elegibilidade do teste TTC como um teste de viabilidade pós-incubação para M. acuminata. As nossas descobertas sublinham a importância de considerar a morfologia e maturidade das sementes nos protocolos de germinação de M. acuminata. Apesar do elevado número de sementes e dos tratamentos utilizados nos testes de germinação, os fatores de quebra de dormência e de incubação testados revelaram-se insuficientes para superar a dormência das sementes de M. acuminata. A baixa Percentagem de Germinação Final e a elevada percentagem de sementes aparentemente viáveis após a incubação sugerem que as sementes secas e frescas de M. acuminata apresentam elevados níveis de dormência. A técnica de ER aliviou a dormência e revelou que o tipo de pré-tratamento, substrato e regime de temperatura tem um impacto significativo na viabilidade dos embriões. Concluímos ainda que o procedimento TTC utilizado neste estudo não é adequado para avaliar a viabilidade pós-incubação das sementes de ¬M. acuminata.Apesar da ineficácia dos 18 tratamentos aplicados no teste de germinação, o trabalho aqui desenvolvido é essencial para perceber o impacto dos vários fatores na viabilidade das sementes; e é crucial para desenhar novos testes de germinação, removendo os fatores testados ou implementando-os em combinações alternativas.Outro - Financial support from Erasmus plus traineeship mobility (EU funds
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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