1.
Rising Atmospheric CO2 Lowers Concentrations of Plant Carotenoids Essential to Human Health: A Meta-Analysis.
Loladze, I, Nolan, JM, Ziska, LH, Knobbe, AR
Molecular nutrition & food research. 2019;(15):e1801047
Abstract
Plant and human tissues (e.g., leaves, retina) share the need for carotenoids to protect against light-induced and other oxidative stresses. While plants synthesize carotenoids de novo, humans must obtain them primarily through plant-based foods. In plants, elevated levels of atmospheric carbon dioxide (eCO2 ) decrease the concentrations of essential minerals, including magnesium and zinc (essential for brain and eye health), but the overall effect of globally rising CO2 levels on carotenoids is unknown. Here, investigation is sought on how eCO2 affects carotenoids in plants. A meta-analysis of 1026 experimental observations from 37 studies shows that eCO2 decreases plant carotenoid concentrations by 15% (95% CI: -26% to -6%). The meta-analysis of available gene expression data for Arabidopsis thaliana points to a potential CO2 -induced downregulation of carotenoid biosynthesis (Log2 fold-change -13%, 95% CI: -17% to -9%). Some other stoichiometric and biochemical mechanisms related to CO2 -induced changes in carotenoids are also highlighted. While overall eCO2 decreases carotenoid concentrations, individual CO2 studies report variable responses, including increases in carotenoid levels, especially in abiotically stressed plants. The initial assessment raises a novel question about the potential effects of rising CO2 on human health through its global effect on plant carotenoids.
2.
Effect of environmental changes on vegetable and legume yields and nutritional quality.
Scheelbeek, PFD, Bird, FA, Tuomisto, HL, Green, R, Harris, FB, Joy, EJM, Chalabi, Z, Allen, E, Haines, A, Dangour, AD
Proceedings of the National Academy of Sciences of the United States of America. 2018;(26):6804-6809
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Abstract
Environmental changes threaten agricultural production, food security, and health. Previous reviews suggest that environmental changes will substantially affect future yields of starchy dietary staples. To date, no comprehensive global analysis of the impacts of environmental change on (nonstaple) vegetables and legumes-important constituents of healthy diets-has been reported. We systematically searched for articles published between 1975 and 2016 on the effects of ambient temperature, tropospheric carbon dioxide (CO2), and ozone (O3) concentrations, water availability, and salinization on yields and nutritional quality of vegetables and legumes. We estimated mean effects of standardized environmental changes using observed exposure-response relationships and conducted meta-analyses where possible. We identified 174 relevant papers reporting 1,540 experiments. The mean (95% CI) reported yield changes for all vegetables and legumes combined were +22.0% (+11.6% to +32.5%) for a 250-ppm increase in CO2 concentration, -8.9% (-15.6% to -2.2%) for a 25% increase in O3 concentration,-34.7% (-44.6% to -24.9%) for a 50% reduction in water availability, and -2.3% (-3.7% to -0.9%) for a 25% increase in salinity. In papers with baseline temperatures >20 °C, a 4 °C increase in temperature reduced mean yields by -31.5% (-41.4% to -21.5%). Impacts of environmental changes on nutritional quality were mixed. In a business-as-usual scenario, predicted changes in environmental exposures would lead to reductions in yields of nonstaple vegetables and legumes. Where adaptation possibilities are limited, this may substantially change their global availability, affordability, and consumption in the mid to long term. Our results stress the importance of prioritizing agricultural developments, to minimize potential reductions in vegetable and legume yields and associated negative health effects.
3.
Reproductive allocation in plants as affected by elevated carbon dioxide and other environmental changes: a synthesis using meta-analysis and graphical vector analysis.
Wang, X, Taub, DR, Jablonski, LM
Oecologia. 2015;(4):1075-87
Abstract
Reproduction is an important life history trait that strongly affects dynamics of plant populations. Although it has been well documented that elevated carbon dioxide (CO2) in the atmosphere greatly enhances biomass production in plants, the overall effect of elevated CO2 on reproductive allocation (RA), i.e., the proportion of biomass allocated to reproductive structures, is little understood. We combined meta-analysis with graphical vector analysis to examine the overall effect of elevated CO2 on RA and how other environmental factors, such as low nutrients, drought and elevated atmospheric ozone (O3), interacted with elevated CO2 in affecting RA in herbaceous plants. Averaged across all species of different functional groups and environmental conditions, elevated CO2 had little effect on RA (-0.9%). RA in plants of different reproductive strategies and functional groups, however, differed in response to elevated CO2. For example, RA in iteroparous wild species decreased by 8%, while RA in iteroparous crops increased significantly (+14%) at elevated CO2. RA was unaffected by CO2 in plants grown with no stress or in low-nutrient soils. RA decreased at elevated CO2 and elevated O3, but increased in response to elevated CO2 in drought-stressed plants, suggesting that elevated CO2 could ameliorate the adverse effect of drought on crop production to some extent. Our results demonstrate that elevated CO2 and other global environmental changes have the potential to greatly alter plant community composition through differential effects on RA of different plant species and thus affect the dynamics of natural and agricultural ecosystems in the future.
4.
Systematic Review and Meta-Analysis of End-Tidal Carbon Dioxide Values Associated With Return of Spontaneous Circulation During Cardiopulmonary Resuscitation.
Hartmann, SM, Farris, RW, Di Gennaro, JL, Roberts, JS
Journal of intensive care medicine. 2015;(7):426-35
Abstract
OBJECTIVE End-tidal carbon dioxide (ETCO(2)) measurements during cardiopulmonary resuscitation (CPR) reflect variable cardiac output over time, and low values have been associated with decreased survival. The goals of this review are to confirm and quantify this relationship and to determine the mean ETCO(2) value among patients with return of spontaneous circulation (ROSC) as an initial step toward determining an appropriate target for intervention during resuscitation in the absence of prospective data. DATA SOURCES AND STUDY SELECTION The PubMed database was searched for the key words "end-tidal carbon dioxide" or "capnometry" or "capnography" and "resuscitation" or "return of spontaneous circulation." Randomized controlled trials, cohort studies, or case-control studies that reported ETCO(2) values for participants with and without ROSC were included. DATA EXTRACTION AND SYNTHESIS Twenty-seven studies met the inclusion criteria for qualitative synthesis. Twenty studies were included in determination of average ETCO(2) values. The mean ETCO(2) in participants with ROSC was 25.8 ± 9.8 mm Hg versus 13.1 ± 8.2 mm Hg (P = .001) in those without ROSC. Nineteen studies were included in a meta-analysis. The mean difference in ETCO(2) was 12.7 mm Hg (95% confidence interval: 10.3-15.1) between participants with and without ROSC (P < .001). The mean difference in ETCO(2) was not modified by the receipt of sodium bicarbonate, uncontrolled minute ventilation, or era of resuscitation guidelines. The overall quality of data by Grades of Recommendations, Assessment, Development and Evaluation criteria is very low, but no prospective data are currently available. CONCLUSIONS Participants with ROSC after CPR have statistically higher levels of ETCO(2). The average ETCO(2) level of 25 mm Hg in participants with ROSC is notably higher than the threshold of 10 to 20 mm Hg to improve delivery of chest compressions. The ETCO(2) goals during resuscitation may be higher than previously suggested and further investigation into appropriate targets during resuscitation is needed to diminish morbidity and mortality after cardiorespiratory arrest.
5.
Reduction of transpiration and altered nutrient allocation contribute to nutrient decline of crops grown in elevated CO(2) concentrations.
McGrath, JM, Lobell, DB
Plant, cell & environment. 2013;(3):697-705
Abstract
Plants grown in elevated [CO(2) ] have lower protein and mineral concentrations compared with plants grown in ambient [CO(2) ]. Dilution by enhanced production of carbohydrates is a likely cause, but it cannot explain all of the reductions. Two proposed, but untested, hypotheses are that (1) reduced canopy transpiration reduces mass flow of nutrients to the roots thus reducing nutrient uptake and (2) changes in metabolite or enzyme concentrations caused by physiological changes alter requirements for minerals as protein cofactors or in other organic complexes, shifting allocation between tissues and possibly altering uptake. Here, we use the meta-analysis of previous studies in crops to test these hypotheses. Nutrients acquired mostly by mass flow were decreased significantly more by elevated [CO(2) ] than nutrients acquired by diffusion to the roots through the soil, supporting the first hypothesis. Similarly, Mg showed large concentration declines in leaves and wheat stems, but smaller decreases in other tissues. Because chlorophyll requires a large fraction of total plant Mg, and chlorophyll concentration is reduced by growth in elevated [CO(2) ], this supports the second hypothesis. Understanding these mechanisms may guide efforts to improve nutrient content, and allow modeling of nutrient changes and health impacts under future climate change scenarios.