ORCID Profile
0000-0002-1197-8800
Current Organisations
Colorado State University
,
USDA Agricultural Research Service
,
University of Oklahoma
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Publisher: Wiley
Date: 23-11-2018
DOI: 10.1111/NPH.15562
Abstract: Atmospheric CO
Publisher: Proceedings of the National Academy of Sciences
Date: 21-12-2020
Abstract: Understanding ecosystem carbon-cycling responses to atmospheric CO 2 enrichment is critical to preserve bio ersity and maintain vital ecosystem services in grasslands impacted by global change. We conducted an 8-y experiment enriching CO 2 concentrations from preindustrial to midtwenty-first century levels on grassland plant communities on upland, lowland, and alluvial soils. CO 2 enrichment increased the CO 2 efflux from soils to atmosphere in amounts depending on whether the dominant limitation was CO 2 or feedbacks (net positive or negative) from soil moisture and plant species turnover. These findings highlight how multiple concurrent limitations, not single limitations in sequence, regulate the impacts of global change drivers in erse grasslands. Incorporating multiple limitations will improve forecasts of terrestrial carbon sequestration and ecosystem services.
Publisher: Wiley
Date: 03-06-2013
DOI: 10.1111/NPH.12339
Abstract: Plant gas exchange is regulated by stomata, which coordinate leaf‐level water loss with xylem transport. Stomatal opening responds to internal concentrations of CO 2 in the leaf, but changing CO 2 can also lead to changes in stomatal density that influence transpiration. Given that stomatal conductance increases under subambient concentrations of CO 2 and, conversely, that plants lose less water at elevated concentrations, can downstream effects of atmospheric CO 2 be observed in xylem tissue? We approached this problem by evaluating leaf stomatal density, xylem transport, xylem anatomy and resistance to cavitation in Helianthus annuus plants grown under three CO 2 regimes ranging from pre‐industrial to elevated concentrations. Xylem transport, conduit size and stomatal density all increased at 290 ppm relative to ambient and elevated CO 2 concentrations. The shoots of the 290‐ppm‐grown plants were most vulnerable to cavitation, whereas xylem cavitation resistance did not differ in 390‐ and 480‐ppm‐grown plants. Our data indicate that, even as an indirect driver of water loss, CO 2 can affect xylem structure and water transport by coupling stomatal and xylem hydraulic functions during plant development. This plastic response has implications for plant water use under variable concentrations of CO 2 , as well as the evolution of efficient xylem transport.
Publisher: Wiley
Date: 28-01-2018
DOI: 10.1111/GCB.14032
Abstract: Continuing enrichment of atmospheric CO 2 may change plant community composition, in part by altering the availability of other limiting resources including soil water, nutrients, or light. The combined effects of CO 2 enrichment and altered resource availability on species flowering remain poorly understood. We quantified flowering culm and ramet production and biomass allocation to flowering culms/ramets for 10 years in C 4 ‐dominated grassland communities on contrasting soils along a CO 2 concentration gradient spanning pre‐industrial to expected mid‐21st century levels (250–500 μl/L). CO 2 enrichment explained up to 77% of the variation in flowering culm count across soils for three of the five species, and was correlated with flowering culm count on at least one soil for four of five species. In contrast, allocation to flowering culms was only weakly correlated with CO 2 enrichment for two species. Flowering culm counts were strongly correlated with species aboveground biomass (AGB R 2 = .34–.74), a measure of species abundance. CO 2 enrichment also increased soil moisture and decreased light levels within the canopy but did not affect soil inorganic nitrogen availability. Structural equation models fit across the soils suggested species‐specific controls on flowering in two general forms: (1) CO 2 effects on flowering culm count mediated by canopy light level and relative species AGB (species AGB/total AGB) or by soil moisture effects on flowering culm count (2) effects of canopy light level or soil inorganic nitrogen on flowering and/or relative species AGB, but with no significant CO 2 effect. Understanding the heterogeneity in species responses to CO 2 enrichment in plant communities across soils in edaphically variable landscapes is critical to predict CO 2 effects on flowering and other plant fitness components, and species potential to adapt to future environmental changes.
Publisher: Oxford University Press (OUP)
Date: 16-03-2012
DOI: 10.1093/JPE/RTS007
Publisher: Springer Science and Business Media LLC
Date: 30-01-2020
DOI: 10.1038/S41467-020-14360-7
Abstract: Developmental epileptic encephalopathies are devastating disorders characterized by intractable epileptic seizures and developmental delay. Here, we report an allelic series of germline recessive mutations in UGDH in 36 cases from 25 families presenting with epileptic encephalopathy with developmental delay and hypotonia. UGDH encodes an oxidoreductase that converts UDP-glucose to UDP-glucuronic acid, a key component of specific proteoglycans and glycolipids. Consistent with being loss-of-function alleles, we show using patients’ primary fibroblasts and biochemical assays, that these mutations either impair UGDH stability, oligomerization, or enzymatic activity. In vitro, patient-derived cerebral organoids are smaller with a reduced number of proliferating neuronal progenitors while mutant ugdh zebrafish do not phenocopy the human disease. Our study defines UGDH as a key player for the production of extracellular matrix components that are essential for human brain development. Based on the incidence of variants observed, UGDH mutations are likely to be a frequent cause of recessive epileptic encephalopathy.
Location: United States of America
No related grants have been discovered for Herbert Polley.