The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Kim C. Steiner - One of the best experts on this subject based on the ideXlab platform.
-
Ashes to ashes: Large Fraxinus germplasm collections and their fates
2010Co-Authors: Kim C. Steiner, Paul. LupoAbstract:As the emerald ash borer (EAB) threatens the survival of our ash species, measures should be taken to preserve their genetic variability in the event that we discover a way to restore populations destroyed by the beetle. As it happens, large germplasm collections exist for our most important and widely distributed eastern species of the genus, white ash (Fraxinus Americana L.) and green ash (F. pennsylvanica Marsh.).
-
Physiological and foliar symptom response in the crowns of Prunus serotina, Fraxinus Americana, and Acer rubrum canopy trees to ambient ozone under forest conditions
Environmental Pollution, 2005Co-Authors: Marcus Schaub, John M. Skelly, Donald D. Davis, Jianwei Zhang, J.a. Ferdinand, James E. Savage, R. E. Stevenson, Kim C. SteinerAbstract:Abstract The crowns of five canopy dominant black cherry ( Prunus serotina Ehrh.), five white ash ( Fraxinus Americana L.), and six red maple ( Acer rubrum L.) trees on naturally differing environmental conditions were accessed with scaffold towers within a mixed hardwood forest stand in central Pennsylvania. Ambient ozone concentrations, meteorological parameters, leaf gas exchange and leaf water potential were measured at the sites during the growing seasons of 1998 and 1999. Visible ozone-induced foliar injury was assessed on leaves within the upper and lower crown branches of each tree. Ambient ozone exposures were sufficient to induce typical symptoms on cherry (0–5% total affected leaf area, LAA), whereas foliar injury was not observed on ash or maple. There was a positive correlation between increasing cumulative ozone uptake ( U ) and increasing percent of LAA for cherry grown under drier site conditions. The lower crown leaves of cherry showed more severe foliar injury than the upper crown leaves. No significant differences in predawn leaf water potential ( ψ L ) were detected for all three species indicating no differing soil moisture conditions across the sites. Significant variation in stomatal conductance for water vapor ( g wv ) was found among species, soil moisture, time of day and sample date. When comparing cumulative ozone uptake and decreased photosynthetic activity ( P n ), red maple was the only species to show higher gas exchange under mesic vs. drier soil conditions ( P g wv and P n demonstrate the strong influence of heterogeneous environmental conditions within forest canopies.
-
Physiological and foliar injury responses of Prunus serotina, Fraxinus Americana, and Acer rubrum seedlings to varying soil moisture and ozone
Environmental Pollution, 2003Co-Authors: Marcus Schaub, John M. Skelly, Kim C. Steiner, Donald D. Davis, S. P. Pennypacker, Jianwei Zhang, J.a. Ferdinand, James E. Savage, R. E. StevensonAbstract:Sixteen black cherry (Prunus serotina, Ehrh.), 10 white ash (Fraxinus Americana, L.) and 10 red maple (Acer rubrum, L.) 1-year old seedlings were planted per plot in 1997 on a former nursery bed within 12 open-top chambers and six open plots. Seedlings were exposed to three different ozone scenarios (ambient air: 100% O3; non-filtered air: 98% ambient O3; charcoal-filtered air: 50% ambient O3) within each of two different water regimes (nine plots irrigated, nine plots non-irrigated) during three growing seasons. During the 1998 and 1999 growing season, leaf gas exchange, plant water relations, and foliar injury were measured. Climatic data, ambient- and chamber-ozone-concentrations were monitored. We found that seedlings grown under irrigated conditions had similar (in 1998) but significantly higher gas exchange rates (in 1999) than seedlings grown within non-irrigated plots among similar ozone exposures. Cherry and ash had similar ozone uptake but cherry developed more ozone-induced injury (< 34% affected leaf area, LAA) than ash (
-
physiological and foliar injury responses of prunus serotina Fraxinus Americana and acer rubrum seedlings to varying soil moisture and ozone
Environmental Pollution, 2003Co-Authors: Marcus Schaub, John M. Skelly, Kim C. Steiner, Donald D. Davis, S. P. Pennypacker, Jianwei Zhang, J.a. Ferdinand, James E. Savage, R. E. StevensonAbstract:Sixteen black cherry (Prunus serotina, Ehrh.), 10 white ash (Fraxinus Americana, L.) and 10 red maple (Acer rubrum, L.) 1-year old seedlings were planted per plot in 1997 on a former nursery bed within 12 open-top chambers and six open plots. Seedlings were exposed to three different ozone scenarios (ambient air: 100% O3; non-filtered air: 98% ambient O3; charcoal-filtered air: 50% ambient O3) within each of two different water regimes (nine plots irrigated, nine plots non-irrigated) during three growing seasons. During the 1998 and 1999 growing season, leaf gas exchange, plant water relations, and foliar injury were measured. Climatic data, ambient- and chamber-ozone-concentrations were monitored. We found that seedlings grown under irrigated conditions had similar (in 1998) but significantly higher gas exchange rates (in 1999) than seedlings grown within non-irrigated plots among similar ozone exposures. Cherry and ash had similar ozone uptake but cherry developed more ozone-induced injury (< 34% affected leaf area, LAA) than ash (<5% LAA), while maple rarely showed foliar injury, indicating the species differed in ozone sensitivity. Significantly more severe injury on seedlings grown under irrigated conditions than seedlings grown under non-irrigated conditions demonstrated that soil moisture altered seedling responses to ambient ozone exposures. # 2003 Elsevier Science Ltd. All rights reserved.
-
Systematic variation in xylem hydraulic capacity within the crown of white ash (Fraxinus Americana).
Tree Physiology, 1995Co-Authors: Brian J. Joyce, Kim C. SteinerAbstract:A 7-m tall white ash tree (Fraxinus Americana Marsh.) was dissected, and hydraulic parameters of the xylem were determined by inducing a steady-state flow of water through the stem segments and monitoring volume and velocity flow rates. Leaf-specific conductivity (LSC) was highest in the main stem and lowest in some of the leaf-bearing lateral shoots. The LSC was higher in the main stem than in branches and higher in primary than in secondary branch axes. Terminal leaf-bearing shoots were larger and had a significantly greater mean LSC than subjacent lateral shoots. A significant reduction in LSC was associated with the transition between 1- and 2-year-old growth. In branches of the same age, there was a close correspondence among LSC, branch position and branch size. The average LSC of leaf-bearing shoots from south-facing branches was 43% greater than that of shoots from north-facing branches. Within-crown variation in LSC was associated with variation in velocity flow rate (V). By contrast, the ratio of potentially functional xylem area to supported leaf area (A(pf)/A(l)) was relatively stable throughout the crown. Stratification of stems by Strahler order accounted for approximately 70% of the total variation in LSC. These results suggest that (1) there exists a systematic pattern of variation in LSC distribution within the crown of white ash, (2) within-crown variability in LSC is primarily the result of variation in mean vessel diameter, and (3) there is a physiological linkage between LSC and crown morphology that is maintained through a positive feedback mechanism during branch ontogeny.
Maciej A Zwieniecki - One of the best experts on this subject based on the ideXlab platform.
-
hydraulic properties of individual xylem vessels of Fraxinus Americana
Journal of Experimental Botany, 2001Co-Authors: Maciej A Zwieniecki, Peter J Melcher, Michele N HolbrookAbstract:: Studies of the hydraulic properties of xylem vessels have been limited to measurements of whole plant or whole stem segments. This approach allows the longitudinal transport properties of the ensemble of vessels within a stem to be determined, but provides little information on radial transport. Here the xylem of Fraxinus Americana L. has been examined using a new method that allows the transport properties of individual vessels to be examined. One goal of this study was to quantify transport parameters relevant to embolism repair. The longitudinal conductivity of vessel segments open at both ends (i.e. no end walls) agreed with values predicted by the Poiseuille equation. Radial specific conductance (conductance per unit area) was approximately six orders of magnitude lower than the longitudinal conductance of the vessel segment normalized by the cross-sectional area of the vessel lumen. There was a step increase in the radial specific conductance of previously gas-filled vessels when the delivery pressure exceeded 0.4 MPa. This is consistent with the idea that positive pressure, required for embolism repair, can be compartmentalized within a vessel if the bordered pit chambers are gas-filled. The diffusion coefficient for the movement of gas from a pressurized air-filled vessel was of the same order of magnitude as that for air diffusing through water (1.95 e(-9) m(2) s(-1)). Estimates of the time needed to displace all of the gas from an air-filled vessel were in the order of 20 min, suggesting that gas removal may not be a major limitation in embolism repair.
-
diurnal variation in xylem hydraulic conductivity in white ash Fraxinus Americana l red maple acer rubrum l and red spruce picea rubens sarg
Plant Cell and Environment, 1998Co-Authors: Maciej A Zwieniecki, N M HolbrookAbstract:Xylem hydraulic conductivity and percentage loss of conductivity (PLC) were measured on a ring-porous (Fraxinus Americana L., white ash), a diffuse porous (Acer rubrum L., red maple) and a coniferous (Picea rubens Sarg., red spruce) tree species in a temperate deciduous forest in central Massachusetts, USA. Measurements were made on current and 1-year-old branch segments in the afternoon and on the following morning. Afternoon PLC was 45 to 70% for the current year's extension growth in both white ash and red maple. Morning PLC was significantly lower (10–40%). Conductivity also varied diurnally suggesting, on average, a 50% recovery from cavitation overnight. Red spruce showed lower PLC and conductivity and a less pronounced night-time recovery. Diurnal variation in hydraulic conductivity and PLC suggests that embolism removal occurred in all three species despite the existence of tension within the xylem. Further evidence for embolism removal was observed with an in situ double-staining experiment in which dyes were fed to a transpiring branch during the late afternoon and the following morning. Examination of stem cross-sections showed that a larger number of vessels were conductive in the morning than on the preceding afternoon. Results of this study suggest that hydraulic capacity is highly dynamic and that conductivity measurements reflect a balance between two processes: cavitation and embolism removal.
F. A. Bazzaz - One of the best experts on this subject based on the ideXlab platform.
-
TREE SEEDLING EMERGENCE ON INTERACTIVE TEMPERATURE AND MOISTURE GRADIENTS AND IN PATCHES OF OLD‐FIELD VEGETATION
American Journal of Botany, 1991Co-Authors: Philip J. Burton, F. A. BazzazAbstract:Seeds of tree species commonly invading old-fields (Fraxinus Americana, Gleditsia triacanthos, Morus rubra, Platanus occidentalis, and Prunus serotina) were germinated at eight temperatures from 5 C to 40 C, with six moisture levels (2% to 18% gravimetric moisture content) at each temperature. For most species, total seedling emergence and emergence rat exhibited approximate bivariate Gaussian response surfaces. (...)
Sharon A. Bates - One of the best experts on this subject based on the ideXlab platform.
-
Somatic embryogenesis in white ash ( Fraxinus Americana L.)
Somatic Embryogenesis in Woody Plants, 1995Co-Authors: John E. Preece, Sharon A. BatesAbstract:White ash (Fraxinus Americana L.), a member of the Oleaceae, is an important hardwood tree species and the most common native ash found in North America. The fast growing dioecious trees can attain heights of more than 30 meters and trunk diameters of up to 1.3 meters. Younger trees have a pyramidal or ovoid shape and mature trees have rounded tops. In landscaping, white ash is well suited for large yards and open areas such as parks and along roadsides. The wood is excellent for tool handles and sporting equipment because it is hard, strong, stiff, shock resistant, and lightweight.
-
Thidiazuron stimulates shoot organogenesis and somatic embryogenesis in white ash (Fraxinus Americana L.)
Plant Cell Tissue and Organ Culture, 1992Co-Authors: Sharon A. Bates, John E. Preece, Nadia E. Navarrete, J. W. Van Sambeek, Gerald R. GaffneyAbstract:Immature and mature nonstratified seeds of white ash (Fraxinus Americana L.) were dissected transversely and 2/3 of each seed was placed onto agar-solidified Murashige and Skoog medium. Adventitious buds, shoots, and somatic embryos formed on callus, cotyledons, and hypocotyls of the resulting seedlings. Shoot organogenesis was induced on explants cultured on medium with 10 μM thidiazuron but not on explants on media with benzyladenine (BA) or isopentenyladenine. Not all seed sources were equally capable of shoot organogenesis and embryogenesis. Atypical of adventitious regeneration of other woody plants, mature seed explants of white ash were more organogenic with shoots that elongated better than explants from immature seeds. Somatic embryogenesis was observed in cultures where mature seeds were first cultured for 4 weeks on a medium containing 10 μM adenine 2,4-dichlorophenoxyacetic acid in combination with 0.1 and 1.0 μM thidiazuron, followed by transfer to a medium containing 0.05 μM 6-benzyladenine and 0.5 μM naphthaleneacetic acid. Adventitious shoots and epicotyls from both seedlings and germinated somatic embryos were rooted under intermittent mist and acclimatized to the greenhouse.
-
In vitro studies with white ash (Fraxinus Americana) nodules
Woody Plant Biotechnology, 1991Co-Authors: John E. Preece, Sharon A. BatesAbstract:Calli were obtained from cotyledonary tissue of cut zygotic seeds that had been cultured in vitro on agarsolidified MS medium with 5 μM 2,4-D and 5 μM BA for four weeks. Seedlings were subcultured onto MS with 0.5 μM NAA and 0.5 μM BA. After two to four months, callus tissue was excised and placed into liquid MS with 1 μM NAA and 1 μM BA on a shaker at 100 rpm. Within four weeks, spherical clusters (nodules) formed that regularly sloughed-off and produced additional clusters. To speed multiplication, nodule clusters could be physically broken-up with forceps and the pieces subcultured. Nodules had a distinct morphology compared to callus clumps. Scanning electron microscopy (SEM) studies of nodule cross sections revealed a cortical region composed of parenchyma cells surrounded by a layer of closely packed cells (possibly epidermis). Areas of vascularization containing xylem and a cambium-like tissue were evident within the cortical region. Nodules exposed to moderately high levels of thidiazuron produced large amounts of callus. Nodule clusters could be removed aseptically from liquid medium and dehydrated for up to 14 days. After desiccation for various times, the nodules were placed on agar-solidified medium where they rehydrated and grew as callus. Thidiazuron in the rehydration medium stimulated callus growth. Nodules showed sensitivity to glyphosate herbicide on agar-solidified and liquid media. On solidified medium, glyphosate at 0.1 and 1 mM was not lethal, and nodules remained green; 10 mM glyphosate resulted in nodules with areas of green and brown, and 0.1 and 1 M glyphosate were lethal. In liquid medium, nodules exposed to 1 mM herbicide became brown and died, at lower concentrations, both green and brown sectors were evident.
Amy E Zanne - One of the best experts on this subject based on the ideXlab platform.
-
dissecting the effects of diameter on wood decay emphasizes the importance of cross stem conductivity in Fraxinus Americana
Ecosystems, 2018Co-Authors: Brad Oberle, Kristofer R Covey, Kevin M Dunham, Edgar J Hernandez, Maranda L Walton, Darcy F Young, Amy E ZanneAbstract:Pest outbreaks are driving tree dieback and major influxes of deadwood into forest ecosystems. Understanding how pulses of deadwood impact the climate system requires understanding which factors influence greenhouse gas production during wood decay. Recent analyses identify stem diameter as an important control, but report effects that vary in magnitude and direction. This complexity may reflect interacting effects of soil contact, geometry and variable tissue properties. To dissect these effects, we implemented a three-way factorial experiment in Fraxinus Americana, (white ash), an iconic North American species threatened by an invasive beetle. Soil contact accelerated decay rates by an order of magnitude with an effect that varied with stem diameter, not bark presence. After experimentally controlling surface area-to-volume ratio, half-buried wide stems decayed more slowly than half-buried narrow stems but more quickly than the aggregate decay rate of buried and suspended stems. These results closely matched variation in moisture content within and among samples, suggesting that limited vertical conduction of soil moisture through deadwood mediates the effect of stem diameter on wood decay. Soil contact also influenced greenhouse gas concentrations reinforcing recent evidence that deadwood acts as a source for CO2 and CH4 while acting as a sink for N2O. Our results suggest that managing tree species affected by pest outbreaks, including F. Americana, for biomass salvage and greenhouse gas mitigation requires understanding traits that mediate wood permeability and diffusivity to soil moisture and greenhouse gases.
