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The photosynthetic gas exchange capacities of early angiosperms remain enigmatic. Nevertheless, many hypotheses about the causes of early angiosperm success and how angiosperms influenced Mesozoic ecosystem function hinge on understanding the maximum capacity for early angiosperm metabolism. We applied structure-functional analyses of leaf veins and stomatal pore geometry to determine the hydraulic and diffusive gas exchange capacities of Early Cretaceous fossil leaves. All of the late Aptian—early Albian angiosperms measured possessed low vein density and low maximal stomatal pore area, indicating low leaf gas exchange capacities in comparison to modern ecologically dominant angiosperms. Gas exchange capacities for Early Cretaceous angiosperms were equivalent or lower than ferns and gymnosperms. Fossil leaf taxa from Aptian to Paleocene sediments previously identified as putative stem-lineages to Austrobaileyales and Chloranthales had the same gas exchange capacities and possibly leaf water relations of their living relatives. Our results provide fossil evidence for the hypothesis that high leaf gas exchange capacity is a derived feature of later angiosperm evolution. In addition, the leaf gas exchange functions of austrobaileyoid and chloranthoid fossils support the hypothesis that comparative research on the biology of living basal angiosperm lineages reveals genuine signals of Early Cretaceous angiosperm ecophysiology.
In adults the prevalence of psychological distress varies in different ethnic groups, and this has been explained by differences in socio-economic status. Is this also the case in adolescents?
To examine whether ethnic differences in prevalence of psychological distress in adolescents are associated with social deprivation.
A cross-sectional questionnaire survey was used to assess 2790 male and female pupils, aged 11–14 years, from a representative sample of 28 east London secondary schools.
Rates of psychological distress were similar to rates in UK national samples in boys and girls. Bangladeshi pupils, although highly socially disadvantaged, had a lower risk of psychological distress (OR=0.63, 95% CI 0.4–0.9). Non-UK White girls had higher rates of depressive symptoms (OR=1.54, 95% C11.1–2.2).
High rates of depressive symptoms in non-UK White girls may be related to recent migration. Low rates of psychological distress in Bangladeshi pupils in this sample relative to White pupils, despite socio-economic disadvantage, could be associated with cultural protective factors that require further investigation.
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