The recurrent evolution of extremely resistant xylem

International audienceAbstractKey messageHighly resistant xylem has evolved multiple times over the past 400 million years.ContextWater is transported under tension in xylem and consequently is vulnerable to invasion by air and the formation of embolism. A debate has raged over whether embolism formation is non-reversible occurring at low water potentials or a regular diurnal occurrence that is non-lethal because of a capacity to refill embolised conduits.AimsThis commentary is on a recent article, which utilised new non-invasive imaging techniques for assessing the formation of embolism in xylem, finding that the xylem of Laurus nobilis was highly resistant to the formation of embolism.MethodsThe recent results of this discovery are placed in the context knowledge from a diversity of species that has so far been identified with xylem similarly highly resistant to embolism formation.ResultsThe discovery that L. nobilis has xylem highly resistant to embolism formation adds to a body of literature suggesting that the resistance of xylem to embolism formation is a key adaptation utilised by many species native to seasonally dry environments. Highly resistant xylem has evolved numerous times across the angiosperm clade.ConclusionWith more studies utilising similar observational and direct methods of assessing embolism resistance, further insight into the ecological and evolutionary relevance of this trait is imminent

Temperaturas de armazenamento de sementes de Bowdichia virgilioides: uma espécie em extinção

Bowdichia virgilioides Kunth is a tree species native to the Brazilian Cerrado that has been listed as an endangered species due to its overexploitation in the last decades. Given its slow and difficult propagation in natural environments, propagation in plant nurseries appears as an interesting strategy to preserve this endangered species. Therefore, in this study we employed a wide range of temperatures (i.e. from -25°C to -196°C) to store seeds of B. virgilioides in the short-term, and evaluated its efficiency by assessing seed germination rate, speed index, time and synchrony, as well as seedling growth and quality. Germination percentage was only slightly negatively affected by storage time (up to 32 weeks) at 25°C. Despite that, after 32 weeks of storage, all storage temperatures resulted in similar seed germination parameters and seedling growth and quality. Overall, our results highlight that the seeds of this species can be stored in the short-term at a wide range of temperatures, facilitating large-scale propagation in plant nurseries.Bowdichia virgilioides Kunth es una especie arbórea nativa del bosque Cerrado brasileño que ha sido considerada en peligro de extinción debido a su sobreexplotación en las últimas décadas. Dada su lenta y difícil propagación en ambientes naturales, la propagación de plantas en viveros aparece como una estrategia interesante para preservar esta especie en peligro de extinción. Por lo tanto, en este estudio empleamos un amplio rango de temperaturas (es decir, desde -25 °C a -196 °C) para almacenar semillas de B. virgilioides en un corto plazo y evaluar su eficiencia a través de la tasa de germinación de semillas, el índice de velocidad, el tiempo y la sincronía, así como el crecimiento y la calidad de las plántulas. El porcentaje de germinación se vio afectado ligeramente por el tiempo de almacenamiento (de hasta 32 semanas) a una temperatura de 25 °C. A pesar de eso, después de 32 semanas de almacenamiento, todas las temperaturas de almacenamiento dieron como resultado la germinación de las semillas, con crecimiento y calidad de plántulas similares. En general, nuestros resultados destacan que las semillas de esta especie se pueden almacenar en un corto plazo en una amplia gama de temperaturas, facilitando así la propagación a gran escala en viveros.Bowdichia virgilioides Kunth é uma espécie arbórea nativa do Cerrado brasileiro que tem sido considerada ameaçada de extinção devido à sua superexploração nas últimas décadas. Por ter uma propagação lenta e dificultada em ambientes naturais, a propagação em viveiros de plantas surge como uma estratégia interessante para preservar esta espécie ameaçada de extinção. Portanto, neste estudo, empregamos uma ampla gama de temperaturas (i.e., de -25°C a -196°C) para armazenar sementes de B. virgilioides em curto prazo e avaliamos sua eficiência através da taxa de germinação de sementes, índice de velocidade, tempo e sincronia, bem como crescimento e qualidade da plântula. A porcentagem de germinação sofreu pequenas reduções com o tempo de armazenamento (de até 32 semanas) apenas na temperatura de 25°C. Apesar disso, após 32 semanas de armazenamento, todas as temperaturas de armazenamento resultaram em parâmetros de germinação de sementes, crescimento e qualidade de plântulas semelhantes. De forma geral, nossos resultados demonstram que as sementes dessa espécie podem ser armazenadas no curto prazo em uma ampla faixa de temperatura, facilitando a propagação da espécie em larga escala em viveiros

Graphene oxide and a GO/ZnO nanocomposite as catalysts for epoxy ring-opening of epoxidized soybean fatty acids methyl esters

In this work, the grapheme oxide (GO) and GO/ZnO nanocomposite were successfully obtained from the oxidation of graphite and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). In the GO/ZnO nanocomposite, the GO sheets were coated with aggregated ZnO nanoneedles with ca. 20 nm of diameter. The obtained materials were used as heterogeneous catalysts for acetylation of Soybean Fatty Acids Methyl Esters (FAME), promoting the epoxy ring-opening using acetic anhydride. The epoxy ring was almost completely opened in the presence of GO or GO/ZnO nanocomposites, with conversion rates up to 99% and selectivity of ca. 90%, and partially opened using only ZnO. The GO/Zn and GO catalysts were reused three times with conversion rates of ca. 85 and 74%, respectively

A T8.5 Brown Dwarf Member of the Xi Ursae Majoris System

The Wide-field Infrared Survey Explorer has revealed a T8.5 brown dwarf (WISE J111838.70+312537.9) that exhibits common proper motion with a solar-neighborhood (8 pc) quadruple star system - Xi Ursae Majoris. The angular separation is 8.5 arc-min, and the projected physical separation is about 4000 AU. The sub-solar metallicity and low chromospheric activity of Xi UMa A argue that the system has an age of at least 2 Gyr. The infrared luminosity and color of the brown dwarf suggests the mass of this companion ranges between 14 and 38 Jupiter masses for system ages of 2 and 8 Gyr respectively.Comment: AJ in press, 12 pages LaTeX with 6 figures. More astrometric data and a laser guide star adaptive optics image adde

Abscisic acid acts essentially on stomata, not on xylem, to improve drought resistance in tomato

Drought resistance is essential for plant production under water-limiting environments. Abscisic acid (ABA) plays a critical role in stomata but its impact on hydraulic function beyond the stomata is far less studied. We selected genotypes differing in their ability to accumulate ABA to investigate its role in drought-induced dysfunction. All genotypes exhibited similar leaf and stem embolism resistance regardless of differences in ABA levels. Their leaf hydraulic resistance was also similar. Differences were only observed between the two extreme genotypes: sitiens (sit; a strong ABA-deficient mutant) and sp12 (a transgenic line that constitutively overaccumulates ABA), where the water potential inducing 50% embolism was 0.25 MPa lower in sp12 than in sit. Maximum stomatal and minimum leaf conductances were considerably lower in plants with higher ABA (wild type [WT] and sp12) than in ABA-deficient mutants. Variations in gas exchange across genotypes were associated with ABA levels and differences in stomatal density and size. The lower water loss in plants with higher ABA meant that lethal water potentials associated with embolism occurred later during drought in sp12 plants, followed by WT, and then by the ABA-deficient mutants. Therefore, the primary pathway by which ABA enhances drought resistance is via declines in water loss, which delays dehydration and hydraulic dysfunction

A large‐scale assessment of plant dispersal mode and seed traits across human‐modified Amazonian forests

1. Quantifying the impact of habitat disturbance on ecosystem function is critical to understanding and predicting the future of tropical forests. Many studies have examined post-disturbance changes in animal traits related to mutualistic interactions with plants, but the effect of disturbance on plant traits in diverse forests has received much less attention. 2. Focusing on two study regions in the eastern Brazilian Amazon, we used a trait-based approach to examine how seed dispersal functionality within tropical plant communities changes across a landscape-scale gradient of human modification, including both regenerating secondary forests and primary forests disturbed by burning and selective logging. 3. Surveys of 230 forest plots recorded 26,533 live stems from 846 tree species. Using herbarium material and literature, we compiled trait information for each tree species, focusing on dispersal mode and seed size. 4. Disturbance reduced tree diversity and increased the proportion of lower wood density and small-seeded tree species in study plots. Disturbance also increased the proportion of stems with seeds that are ingested by animals and reduced those dispersed by other mechanisms (e.g. wind). Older secondary forests had function-ally similar plant communities to the most heavily disturbed primary forests. Mean seed size and wood density per plot were positively correlated for plant species with seeds ingested by animals. 5. Synthesis. Anthropogenic disturbance has major effects on the seed traits of tree communities, with implications for mutualistic interactions with animals. The important role of animal-mediated seed dispersal in disturbed and recovering forests highlights the need to avoid defaunation or promote faunal recovery. The changes in mean seed width suggest larger vertebrates hold especially important functional roles in these human-modified forests. Monitoring fruit and seed traits can provide a valuable indicator of ecosystem condition, emphasizing the importance of developing a comprehensive plant traits database for the Amazon and other biomes

DNAJC21 Mutations Link a Cancer-Prone Bone Marrow Failure Syndrome to Corruption in 60S Ribosome Subunit Maturation

This work was funded by The Medical Research Council UK (MR/K000292/1), Children with Cancer UK (2013/144), Barts and The London Charity (845/1796), and Leukaemia Lymphoma Research/Bloodwise (14032)