How do climbing palms climb and why are they so long?

Climbing plants require a combination of mechanical properties during their growth that differs radically from self-supporting trees and shrubs. This mechanical requirement appears to be the same across many major groups of plants including monocots and dicots. One of the main trends in mechanical properties during development in climbers is the shift from relatively stiff to highly flexible stem properties. Whereas most woody dicotyledons produce this kind of change via elaborate secondary growth, climbing palms must produce stiffness, then flexibility by other means. The appearance of a very similar climbing habit in both the Arecoideae and Calamoideae has fascinated botanists for many years, especially since true rattans have some of the longest plant stems known. We investigated the developmental and biomechanical traits that are linked to attachment and stem biomechanics in both groups. The developmental constraints existing in palms including the lack of secondary growth have a profound influence on the kind of mechanical strategy adopted by climbing palms. The shift from high stiffness to high flexibility is made possible by the development of a stiff outer leaf sheath in early growth and then its senescence and loss during later development. Furthermore, when axes possessing a leaf sheath are submitted to overwhelming bending forces - such as during tree-falls - shattering of the leaf sheath releases the critical strains and fracture surfaces are not propagated across the internal stem. A major developmental constraint in palms linked to the continuous production of leaves at the stem apex, has a particularly profound effect on the climbing life histories. Whereas senescence of the leaf sheath provides a “cheap” way of producing high flexibility – compared with woody lianas, that same senescence also removes the mode of attachment on which the plant relies on to maintain its position and survival. Rattans are famous for their extremely long stems that can be several times longer than the height of the forest canopy in which they grow. More specifically, the extreme lengths of rattans and some arecoid climbers such as Desmoncus, result from a positive feed-back loop between attachment and the necessary stem mechanics. First, slender stems of canopy climbers must become flexible or they will be liable to fail. Second, to remain attached in the forest canopy, climbing palms must continue to produce more cirri or flagella and more stiff lengths of young stem/leaf sheath to access new supports as the established attachments fail. The positive feed-back between traits in climbing palms can be likened to a Red Queen dynamic whereby climbing palms must keep growing to stay in the same place. (Résumé d'auteur

Evolution of Plant Architecture, Functional Diversification and Divergent Evolution in the Genus Atractocarpus (Rubiaceae) for New Caledonia

The diversification of ecological roles and related adaptations in closely related species within a lineage is one of the most important processes linking plant evolution and ecology. Plant architecture offers a robust framework to study these processes as it can highlight how plant structure influences plant diversification and ecological strategies. We investigated a case of gradual evolution of branching architecture in Atractocarpus spp. (Rubiaceae), forming a monophyletic group in New Caledonia that has diversified rapidly, predominantly in rainforest understory habitats. We used a transdisciplinary approach to depict architectural variations and revealed multiple evolutionary transitions from a branched (Stone's architectural model) to a monocaulous habit (Corner's architectural model), which involved the functional reduction of branches into inflorescences. We propose an integrative functional index that assesses branching incidence on functional traits influencing both assimilation and exploration functions. We showed that architectural transitions correlate with ecologically important functional traits. Variation in ecologically important traits among closely relatives, as supported by the architectural analysis, is suggestive of intense competition that favored divergence among locally coexisting species. We propose that Pleistocene climatic fluctuations causing expansion and contraction of rainforest could also have offered ecological opportunities for colonizers in addition to the process of divergent evolution

Imidazole propionate is increased in diabetes and associated with dietary patterns and altered microbial ecology

Microbiota-host-diet interactions contribute to the development of metabolic diseases. Imidazole propionate is a novel microbially produced metabolite from histidine, which impairs glucose metabolism. Here, we show that subjects with prediabetes and diabetes in the MetaCardis cohort from three European countries have elevated serum imidazole propionate levels. Furthermore, imidazole propionate levels were increased in subjects with low bacterial gene richness and Bacteroides 2 enterotype, which have previously been associated with obesity. The Bacteroides 2 enterotype was also associated with increased abundance of the genes involved in imidazole propionate biosynthesis from dietary histidine. Since patients and controls did not differ in their histidine dietary intake, the elevated levels of imidazole propionate in type 2 diabetes likely reflects altered microbial metabolism of histidine, rather than histidine intake per se. Thus the microbiota may contribute to type 2 diabetes by generating imidazole propionate that can modulate host inflammation and metabolism

Neurological manifestations of COVID-19 in adults and children

Different neurological manifestations of coronavirus disease 2019 (COVID-19) in adults and children and their impact have not been well characterized. We aimed to determine the prevalence of neurological manifestations and in-hospital complications among hospitalized COVID-19 patients and ascertain differences between adults and children. We conducted a prospective multicentre observational study using the International Severe Acute Respiratory and emerging Infection Consortium (ISARIC) cohort across 1507 sites worldwide from 30 January 2020 to 25 May 2021. Analyses of neurological manifestations and neurological complications considered unadjusted prevalence estimates for predefined patient subgroups, and adjusted estimates as a function of patient age and time of hospitalization using generalized linear models. Overall, 161 239 patients (158 267 adults; 2972 children) hospitalized with COVID-19 and assessed for neurological manifestations and complications were included. In adults and children, the most frequent neurological manifestations at admission were fatigue (adults: 37.4%; children: 20.4%), altered consciousness (20.9%; 6.8%), myalgia (16.9%; 7.6%), dysgeusia (7.4%; 1.9%), anosmia (6.0%; 2.2%) and seizure (1.1%; 5.2%). In adults, the most frequent in-hospital neurological complications were stroke (1.5%), seizure (1%) and CNS infection (0.2%). Each occurred more frequently in intensive care unit (ICU) than in non-ICU patients. In children, seizure was the only neurological complication to occur more frequently in ICU versus non-ICU (7.1% versus 2.3%, P < 0.001). Stroke prevalence increased with increasing age, while CNS infection and seizure steadily decreased with age. There was a dramatic decrease in stroke over time during the pandemic. Hypertension, chronic neurological disease and the use of extracorporeal membrane oxygenation were associated with increased risk of stroke. Altered consciousness was associated with CNS infection, seizure and stroke. All in-hospital neurological complications were associated with increased odds of death. The likelihood of death rose with increasing age, especially after 25 years of age. In conclusion, adults and children have different neurological manifestations and in-hospital complications associated with COVID-19. Stroke risk increased with increasing age, while CNS infection and seizure risk decreased with age

What Makes New Caledonia’s Flora So Outstanding?

International audienceThis chapter explores the main characteristics of New Caledonian plant biodiversity, and provides a condensed picture of the major unique elements of its flora. We present the results of recent research conducted in a territory that has much to contribute to science and society. We explore the original and unique representation of some plant lineages and functional groups, as well as the rich and diversified vegetation