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Background and aimsCAM photosynthesis is hypothesized to have evolved in atmospheres of low CO2 concentration in recent geological time because of its ability to concentrate CO2 around Rubisco and boost water use efficiency relative to C3 photosynthesis. We assess this hypothesis by compiling estimates of when CAM clades arose using phylogenetic chronograms for 73 CAM clades. We further consider evidence of how atmospheric CO2 affects CAM relative to C3 photosynthesis.ResultsWhere CAM origins can be inferred, strong CAM is estimated to have appeared in the past 30 million years in 46 of 48 examined clades, after atmospheric CO2 had declined from high (near 800 ppm) to lower (

Background and scopeThe growth of experimental studies of crassulacean acid metabolism (CAM) in diverse plant clades, coupled with recent advances in molecular systematics, presents an opportunity to re-assess the phylogenetic distribution and diversity of species capable of CAM. It has been more than two decades since the last comprehensive lists of CAM taxa were published, and an updated survey of the occurrence and distribution of CAM taxa is needed to facilitate and guide future CAM research. We aimed to survey the phylogenetic distribution of these taxa, their diverse morphology, physiology and ecology, and the likely number of evolutionary origins of CAM based on currently known lineages.Results and conclusionsWe found direct evidence (in the form of experimental or field observations of gas exchange, day-night fluctuations in organic acids, carbon isotope ratios and enzymatic activity) for CAM in 370 genera of vascular plants, representing 38 families. Further assumptions about the frequency of CAM species in CAM clades and the distribution of CAM in the Cactaceae and Crassulaceae bring the currently estimated number of CAM-capable species to nearly 7 % of all vascular plants. The phylogenetic distribution of these taxa suggests a minimum of 66 independent origins of CAM in vascular plants, possibly with dozens more. To achieve further insight into CAM origins, there is a need for more extensive and systematic surveys of previously unstudied lineages, particularly in living material to identify low-level CAM activity, and for denser sampling to increase phylogenetic resolution in CAM-evolving clades. This should allow further progress in understanding the functional significance of this pathway by integration with studies on the evolution and genomics of CAM in its many forms.

Process-based vegetation models attempt to represent the wide range of trait variation in biomes by grouping ecologically similar species into plant functional types (PFTs). This approach has been successful in representing many aspects of plant physiology and biophysics but struggles to capture biogeographic history and ecological dynamics that determine biome boundaries and plant distributions. Grass-dominated ecosystems are broadly distributed across all vegetated continents and harbour large functional diversity, yet most Land Surface Models (LSMs) summarise grasses into two generic PFTs based primarily on differences between temperate C3 grasses and (sub)tropical C4 grasses. Incorporation of species-level trait variation is an active area of research to enhance the ecological realism of PFTs, which form the basis for vegetation processes and dynamics in LSMs. Using reported measurements, we developed grass functional trait values (physiological, structural, biochemical, anatomical, phenological, and disturbance-related) of dominant lineages to improve LSM representations. Our method is fundamentally different from previous efforts, as it uses phylogenetic relatedness to create lineage-based functional types (LFTs), situated between species-level trait data and PFT-level abstractions, thus providing a realistic representation of functional diversity and opening the door to the development of new vegetation models.

This essay reviews the following works: Slavery Unseen: Sex, Power, and Violence in Brazilian History. By Lamonte Aidoo. Durham, NC: Duke University Press, 2018. Pp. 272. $26.95 paperback. IBSN: 9780822371298. [...]

The Textbook of Neonatal Resuscitation, seventh edition, does not suggest routine endotracheal suctioning for non-vigorous infants born through meconium-stained amniotic fluid. We compared 301,150 infants at ≥35 weeks' gestational age inborn at 311 Vermont Oxford Network member centers in the United States (U.S.) and admitted to neonatal intensive care units (NICU) who were born before (2013 to 2015) and after (2017) the guideline change. Logistic regression models adjusting for clustering of infants within centers were used to calculate risk ratios. NICU admissions for infants with a diagnosis of meconium aspiration syndrome (MAS) decreased from 1.8% to 1.5% (risk ratio: 0.82; 95% confidence interval: 0.68, 0.97) and delivery room endotracheal suctioning in this group decreased from 57.0% to 28.9% (0.51; 0.41, 0.62). Treatment with conventional or high frequency ventilation, inhaled nitric oxide, or extracorporeal membrane oxygenation remained unchanged 42.3% vs. 40.3% (0.95; 0.80, 1.13) among infants with MAS and 9.1% vs. 8.2% (0.91; 0.87, 0.95) among infants without MAS. The use of surfactant among infants with MAS increased from 24.6% to 30% (1.22; 1.02, 1.48). Mortality (2.6 to 2.9%, 1.12; 0.74, 1.69) and moderate/severe hypoxic-ischemic encephalopathy (5.4 to 6.8%, 1.24; 0.91, 1.69) increased slightly in 2017. Subgroup analyses of infants with 1 min Apgar scores of ≤3 found similar results. While NICU admissions for MAS and tracheal suctioning decreased after the introduction of the new guideline with no subsequent increase in severe respiratory distress among infants with and without a MAS diagnosis, limitations in our study preclude inferring that the new guideline is safe or effective.

OBJECTIVE: To provide contemporary data on infants inborn at 22 to 25 weeks' gestation and receiving care at level 3 and 4 neonatal intensive care units in the United States. METHODS: Vermont Oxford Network members submitted data on infants born at 22 to 25 weeks' gestation at a hospital with a level 3 or 4 NICU from 2020 to 2022. The primary outcome was survival to hospital discharge. Secondary outcomes included survival without severe complications, length of stay, and technology dependence. RESULTS: Overall, 22 953 infants at 636 US hospitals were included. Postnatal life support increased from 68.0% at 22 weeks to 99.8% at 25 weeks. The proportion of infants born at 22 weeks receiving postnatal life support increased from 61.6% in 2020 to 73.7% in 2022. For all infants, survival ranged from 24.9% at 22 weeks to 82.0% at 25 weeks. Among infants receiving postnatal life support, survival ranged from 35.4% at 22 weeks to 82.0% at 25 weeks. Survival without severe complications ranged from 6.3% at 22 weeks to 43.2% at 25 weeks. Median length of stay ranged from 160 days at 22 weeks to 110 days at 25 weeks. Among survivors, infants born at 22 weeks had higher rates of technology dependence at discharge home than infants born at later gestational ages. CONCLUSIONS: Survival ranged from 24.9% at 22 weeks to 82.1% at 25 weeks, with low proportions of infants surviving without complications, prolonged lengths of hospital stay, and frequent technology dependence at all gestational ages. [ABSTRACT FROM AUTHOR]

Background: Exercise reduces the odds of sadness and suicidality in bullied students, but the role of the bullying environment on this relationship remains unknown. Methods: Using combined data from the 2013 and 2015 Youth Risk Behavior Survey (N = 29,207), adjusted logistic regression models estimated odds ratios between exercise, sadness, and suicidal ideation and attempt, stratified by bullying exposure (electronically/at school). Results: Overall, 40.2% of students bullied at school and 48.3% of students bullied electronically reported feeling sad, compared to 22.6% of those not bullied. Bullied students were 2-3 times more likely to report suicidal ideation, and 3-4 times more likely to report suicidal attempt, regardless of bullying context. Students who were bullied at school and exercised 4-7 days per week had lower odds of sadness (adjusted odds ratio [AOR]: 0.64; 95% confidence interval [CI]: 0.51-0.81), suicidal ideation (AOR: 0.66; 95% CI: 0.53-82), and suicidal attempt (AOR: 0.69; 95% CI: 0.48-0.98) compared to those who exercised 0-3 days. There were no protective effects of exercise for students bullied electronically. Conclusions: Exercise reduced sadness and suicidality in adolescents bullied at school but not for students who were cyberbullied. Bullying environment should be a primary consideration in school mental health treatment and maintenance paradigms.

Understanding how plants survive drought and cold is increasingly important as plants worldwide experience dieback with drought in moist places and grow taller with warming in cold ones. Crucial in plant climate adaptation are the diameters of water-transporting conduits. Sampling 537 species across climate zones dominated by angiosperms, we find that plant size is unambiguously the main driver of conduit diameter variation. And because taller plants have wider conduits, and wider conduits within species are more vulnerable to conduction-blocking embolisms, taller conspecifics should be more vulnerable than shorter ones, a prediction we confirm with a plantation experiment. As a result, maximum plant size should be short under drought and cold, which cause embolism, or increase if these pressures relax. That conduit diameter and embolism vulnerability are inseparably related to plant size helps explain why factors that interact with conduit diameter, such as drought or warming, are altering plant heights worldwide.

Current morphometric methods that comprehensively measure shape cannot compare the disparate leaf shapes found in seed plants and are sensitive to processing artifacts. We explore the use of persistent homology, a topological method applied as a filtration across simplicial complexes (or more simply, a method to measure topological features of spaces across different spatial resolutions), to overcome these limitations. The described method isolates subsets of shape features and measures the spatial relationship of neighboring pixel densities in a shape. We apply the method to the analysis of 182,707 leaves, both published and unpublished, representing 141 plant families collected from 75 sites throughout the world. By measuring leaves from throughout the seed plants using persistent homology, a defined morphospace comparing all leaves is demarcated. Clear differences in shape between major phylogenetic groups are detected and estimates of leaf shape diversity within plant families are made. The approach predicts plant family above chance. The application of a persistent homology method, using topological features, to measure leaf shape allows for a unified morphometric framework to measure plant form, including shapes, textures, patterns, and branching architectures.