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Although the respiratory response of native and agricultural plants to atmospheric CO2 enrichment has been reported over the past 75 years, only recently have these effects emerged as prominent measures of plant and ecosystem response to the earth's changing climate. In this review we discuss this rapidly expanding field of study and propose that both increasing and decreasing rates of leaf and whole-plant respiration are likely to occur in response to rising CO2 concentrations. While the stimulatory effects of CO2 on respiration are consistent with our knowledge of leaf carbohydrate status and plant metabolism, we wish to emphasize the rather surprising short-term inhibition of leaf respiration by elevated CO2 and the reported effects of long-term CO2 exposure on growth and maintenance respiration. As is being found in many studies, it is easier to document the respiratory response of higher plants to elevated CO2 than it is to assign a mechanistic basis for the observed effects. Despite this gap in our understanding of how respiration is affected by CO2 enrichment, data are sufficient to suggest that changes in leaf and whole-plant respiration may be important considerations in the carbon dynamics of terrestrial ecosystems as global CO2 continues to rise. Suggestions for future research that would enable these and other effects of CO2 on respiration to be unravelled are presented.

Light and electron microscopy was used to relate histological and ultrastructural differences of cotton (Gossypium hirsutum L.) leaves, bracts, and capsule walls to their different photosynthetic activities. Light microscopy revealed that the leaf thickness was approximately 152 μm, had a well-defined internal organization with elongated palisade mesophyll cells and loosely packed spongy mesophyll cells. In contrast, the bract was thinner (111 μm), lacked a defined palisade layer, and was largely composed of internal air spaces. The capsule wall was very thick (1013 μm) and composed of numerous tightly packed, parenchymatous cortical cells with little or no intercellular air space

Estimates of the net exchange of carbon between the terrestrial biosphere and the atmosphere may be too large because the models of carbon release from changes in land use do not allow for enhanced carbon assimilation by the terrestrial biosphere in response to increasing atmospheric CO2. We address this deficiency with a model of terrestrial biosphere that includes both ecosystem response to land-use perturbation and vegetation response to atmospheric CO2. Model inputs specify the areas affected by land-use change since 1700. The carbon dynamics of the affected areas are described by an area distribution function for vegetation carbon density and a compartment model of carbon in vegetation, litter, and soil. Vegetation growth is modeled as the difference between net primary production (NPP) and mortality. NPP, the net flux of carbon from atmosphere to vegetation, is a logistic function of vegetation carbon density. The response of NPP to atmospheric CO2 is modeled with three response functions: a logarithmic, a rectangular-hyperbolic, and a response function derived from a biochemical model of C3 photosynthesis. The response functions are parameterized by ecosystem type with data from CO2 exposure experiments. Elevated CO2 affects the NPP of both undisturbed and recovering ecosystems. We use the model to test the hypothesis that the CO2 enhancement of terrestrial NPP explains the historical missing carbon sink of the global carbon cycle budget. Our estimates of the biosphere's CO2 enhanced carbon flux are much smaller than the reconstructed missing carbon sink. We conclude that our model results do not support the hypothesis.DOI: 10.1034/j.1600-0889.47.issue4.9.x

The rising prices, declining supplies, and concerns about environmental safety and energy security associated with the use of fossil fuels are driving the development and use of biofuels (Gonzalez-Garcia et al., 2010; Markevicius et al., 2010; Singh et al., 2010; Sahin, 2011). Biofuels in general can be defined as liquid, gas and solid fuels predominantly produced from biomass (Demirbas, 2008). In this chapter, we will specifically focus on liquid biofuels which have attracted world-wide attention due to their renewability, sustainability, common availability, reduction of greenhouse gas (GHG) emissions, and biodegradability (Demirbas, 2009; Gonzalez-Garcia et al., 2010; Balat, 2011). Currently there are two major types of liquid biofuels, bioalcohol and biodiesel, as alternatives to gasoline and diesel fuel, respectively. Among the various bioalcohols, bioethanol is currently the most widely used and biobutanol has great growth potential in the future due to its significant properties including high energy content, hydrophobicity, blending ability, compatibility with combustion engines, and octane rating (Kumar & Gayen, 2011). To date, liquid biofuels have been mainly produced in the U.S., Brazil and several European countries (Fig. 1A). Furthermore, there is a regional difference in the preference for biofuels types, with bioethanol preferentially produced in the American and Asian countries (e.g., U.S., Brazil, China, and Canada) while biodiesel is preferentially produced in European countries (e.g., Germany, France) (Fig. 1B). Bioethanol can be produced from three categories of raw materials: simple sugars, starch, and lignocelluloses (Balat, 2011). Biomass feedstock for biodiesel production is under active development worldwide, with rapeseed and sunflower oils predominating in Europe, palm oil in tropical countries, and soybean oil and animal fats in the United States; and development of additional feedstocks such as Jatropha oil and algae for biodiesel is also underway (Dyer et al., 2008; Knothe et al., 2009). In particular, microalgal oil is one of the major renewable biofuels with great potential for replacing petroleum-based liquid fuels (Cooper et al., 2010).

A variety of thermal approaches are used to estimate sap flux density in stems of woody plants. Models have proved valuable tools for interpreting the behavior of heat pulse, heat balance and heat field deformation techniques, but have seldom been used to describe heat transfer dynamics for the heat dissipation method. Therefore, to better understand the behavior of heat dissipation probes, a model was developed that takes into account the thermal properties of wood, the physical dimensions and thermal characteristics of the probes, and the conductive and convective heat transfer that occurs due to water flow in the sapwood. Probes were simulated as aluminum tubes 20 mm in length and 2 mm in diameter, whereas sapwood, heartwood and bark each had a density and water fraction that determined their thermal properties. Base simulations assumed a constant sap flux density with sapwood depth and no wounding or physical disruption of xylem beyond the 2 mm diameter hole drilled for probe installation. Simulations across a range of sap flux densities showed that the dimensionless quantity k [defined as (ΔT(m) -ΔT)/ΔT, where ΔT(m) is the temperature differential (ΔT) between the heated and unheated probe under zero-flow conditions] was dependent on the thermal conductivity of the sapwood. The relationship between sap flux density and k was also sensitive to radial gradients in sap flux density and to xylem disruption near the probe. Monte Carlo analysis in which 1000 simulations were conducted while simultaneously varying thermal conductivity and wound diameter revealed that sap flux density and k showed considerable departure from the original calibration equation used with this technique. The departure was greatest for variation in sap flux density typical of ring-porous species. Depending on the specific combination of thermal conductivity and wound diameter, use of the original calibration equation resulted in an 81% under- to 48% overestimation of sap flux density at modest flux rates. Future studies should verify these simulations and assess their utility in estimating sap flux density for this widely used technique.

The heat shock response continues to be layered with additional complexity as interactions and crosstalk among heat shock proteins (HSPs), the reactive oxygen network and hormonal signalling are discovered. However, comparative analyses exploring variation in each of these processes among species remain relatively unexplored. In controlled environment experiments, photosynthetic response curves were conducted from 22 to 42 °C and indicated that temperature optimum of light-saturated photosynthesis was greater for Glycine max relative to Arabidopsis thaliana or Populus trichocarpa. Transcript profiles were taken at defined states along the temperature response curves, and inferred pathway analysis revealed species-specific variation in the abiotic stress and the minor carbohydrate raffinose/galactinol pathways. A weighted gene co-expression network approach was used to group individual genes into network modules linking biochemical measures of the antioxidant system to leaf-level photosynthesis among P. trichocarpa, G. max and A. thaliana. Network-enabled results revealed an expansion in the G. max HSP17 protein family and divergence in the regulation of the antioxidant and heat shock modules relative to P. trichocarpa and A. thaliana. These results indicate that although the heat shock response is highly conserved, there is considerable species-specific variation in its regulation.

In 2007, an extreme drought and acute heat wave impacted ecosystems across the southeastern USA, including a 19-year-old Liquidambar styraciflua L. (sweetgum) tree plantation exposed to long-term elevated (E(CO(2))) or ambient (A(CO(2))) CO(2) treatments. Stem sap velocities were analyzed to assess plant response to potential interactions between CO(2) and these weather extremes. Canopy conductance and net carbon assimilation (A(net)) were modeled based on patterns of sap velocity to estimate indirect impacts of observed reductions in transpiration under E(CO(2)) on premature leaf senescence. Elevated CO(2) reduced sap flow by 28% during early summer, and by up to 45% late in the drought during record-setting temperatures. Modeled canopy conductance declined more rapidly in E(CO(2)) plots during this period, thereby directly reducing carbon gain at a greater rate than in A(CO(2)) plots. Indeed, pre-drought canopy A(net) was similar across treatment plots, but declined to ∼40% less than A(net) in A(CO(2)) as the drought progressed, likely leading to negative net carbon balance. Consequently, premature leaf senescence and abscission increased rapidly during this period, and was 30% greater for E(CO(2)). While E(CO(2)) can reduce leaf-level water use under droughty conditions, acute drought may induce excessive stomatal closure that could offset benefits of E(CO(2)) to temperate forest species during extreme weather events.

We present the case of a patient with treatment-refractory mania. The patient had been tried on numerous medications, to which she either did not respond well or on which she developed severe side effects, However, the patient improved rapidly when treated with unilateral electropercussive therapy (ECT) following a court order. We outline the legal barriers that have been raised against the use of ECT in patients with mania, who often refuse treatment, and the irony that ECT can be safer than medications for some patients. ECT is underutilized in mania but deserves more frequent consideration. (Journal of Psychiatric Practice. 2011;17:61-66).

Osmotic adjustment of loblolly pine (Pinus taeda L.) seedlings to fluctuating water supply in elevated CO(2) was investigated. Seedlings were grown in controlled-environment chambers in either 350 or 700 micro l l(-1) CO(2) with weekly watering for four months, after which they were either watered weekly (well-watered treatment) or every two weeks (water-stress treatment) for 59 days. Osmotic adjustment was assessed by pressure-volume analysis of shoots and by analysis of soluble carbohydrates and free amino acids in roots during the last drying cycle. In well-watered seedlings, elevated CO(2) increased the concentration of soluble sugars in roots by 68%. Water stress reduced the soluble sugar concentration in roots of seedling growing in ambient CO(2) to 26% of that in roots of well-watered seedlings. Elevated CO(2) mitigated the water stress-induced decrease in the concentration of soluble sugars in roots. However, this was probably due, in part, to carbohydrate loading during the first four months when all seedlings were grown in the presence of a high water supply, rather than to osmotic adjustment to water stress. Water stress caused a doubling in the concentration of free primary amino acids in roots, whereas elevated CO(2) reduced primary amino acid and nitrogen concentrations to 32 and 74%, respectively, of those in roots of seedlings grown in ambient CO(2). There was no indication of large-scale osmotic adjustment to water stress or that elevated CO(2) enhanced osmotic adjustment in loblolly pine.

Forest floor CO(2) efflux (FF(cer)) is an important component of global carbon budgets, but the spatial variability of forest floor respiration within a forest type is not well documented. Measurements of FF(cer) were initiated in mid-March of 1991 and continued at biweekly to monthly intervals until mid-November. Observations were made at 45 sites along topographic gradients of the Walker Branch Watershed, Tennessee including northeast and southwest facing slopes, valley-bottoms, and exposed ridge-top locations. The FF(cer) measurements were made with a portable gas-exchange system, and all observations were accompanied by soil temperature and soil water content measurements. As expected, FF(cer) exhibited a distinct seasonal trend following patterns of soil temperature, but soil water content and the volume percent of the soil's coarse fraction were also correlated with observed rates. Over the entire measurement period, FF(cer) ranged from a typical minimum of 0.8 micro mol m(-2) s(-1) to an average maximum near 5.7 micro mol m(-2) s(-1). No significant differences in FF(cer) were observed among the ridge-top and slope positions, but FF(cer) in the valley-bottom locations was lower on several occasions. An empirical model of FF(cer) based on these observations is suggested for application to whole-stand estimates of forest carbon sequestration.

differences in the assimilation of atmospheric CO2 depends upon differences in the capacities for the biochemical reactions that regulate the gas-exchange process. Quantifying these differences for more than a few species, however, has proven difficult. Therefore, to understand better how species differ in their capacity for CO2 assimilation, a widely used model, capable of partitioning limitations to the activity of ribulose-l,5-W.sphosphate carboxylase-oxygenase, to the rate of ribulose 1,5-tophosphate regeneration via electron transport, and to the rate of triose phosphate utilization was used to analyse 164 previously published A/C, curves for 109 C3 plant species. Based on this analysis, the maximum rate of carboxylation, Vcmax, ranged from 6/umol m~2 s"1 for the coniferous species Picea abies to 194jj,mol m" 2 s"1 for the agricultural species Beta vulgaris, and averaged 64^mol m" 2 s"1 across all species. The maximum rate of electron transport, Jmx, ranged from 17/^mol m~2 s"1 again for Picea abies to 372/j.mol m~2 s"1 for the desert annual Mahastrum rotundifolium, and averaged 134fxmol m~2 s"1 across all species. A strong positive correlation between Vc^x and Jmax indicated that the assimilation of CO2 was regulated in a co-ordinated manner by these two component processes. Of the AjC{ curves analysed, 23 showed either an insensitivity or reversed-sensitivity to increasing CO2 concentration, indicating that CO2 assimilation was limited by the utilization of triose phosphates. The rate of triose phosphate utilization ranged from 4-9/xtnol m" 2 s"1 for the tropical perennial Tabebuia rosea to 20-1 /xmol m~2 s"1 for the weedy annual Xanthium strumarium, and averaged 101 ftmol m" 2 s"1 across all species. Despite what at first glance would appear to be a wide range of estimates for the biochemical capacities that regulate CO2 assimilation, separating these species-specific results into those of broad plant categories revealed that Vcmax and Jmax were in general higher for herbaceous annuals than they were for woody perennials. For annuals, Vc^^ and Jmax averaged 75 and 154ftmol m~2 s"1, while for perennials these same two parameters averaged only 44 and 97/xmol m~2 s"1, respectively. Although these differences between groups may be coincidental, such an observation points to differences between annuals and perennials in either the availability or allocation of resources to the gas-exchange process.

In this study, we established a comprehensive genetic map with a large number of progeny from a three-generation hybrid Populus intercross, and phenotyped the lignin content, S/G ratio and 28 cell wall subcomponents both in stems and roots for the mapping individuals. Phenotypic analysis revealed that lignin content and syringyl-to-guaiacyl (S/G) ratio using pyrolysis molecular beam mass spectroscopy (pyMBMS) varied among mapping individuals. Phenotypic analysis revealed that stem lignin content is significantly higher than that in root and the quantified traits can be classified into four distinct groups, with strong correlations observed among components within organs. Altogether, 179 coordinating QTLs were detected, and they were co-localized into 49 genetic loci, 27 of which appear to be pleiotropic. Many of the detected genetic loci were detected differentially in stem and root. This is the first report of separate genetic loci controlling cell wall phenotypes above and below ground. These results suggest that it may be possible to modify lignin content and composition via breed and/or engineer as a means of simultaneously improving Populus for cellulosic ethanol production and carbon sequestration.

A new pad conditioning arm design enables the use of closed-loop control (CLC) to improve conditioning performance throughout the life of a pad and disk pair. Measured pad conditioner torque is used to monitor and control the conditioning and polish processes in situ and in real time. The CLC system maintains process performance throughout pad life by adjusting the conditioner down force to compensate for process drift, such as the loss of diamond aggressiveness as the disk ages.

Chemical mechanical planarization (CMP) pads require conditioning to maintain the surfaces yielding optimal performance. However, conditioning not only regenerates the pad surface but also wears away the pad material and slurry transport grooves. Non-optimized conditioning may result in non-uniform pad profiles, limiting the productive lifetimes of pads. A new approach to conditioning uses closed-loop control (CLC) of conditioning sweep to enable uniform groove depth removal across the pad, throughout pad life. A sensor integrated into the conditioning arm enables the pad stack thickness to be monitored in situ and in real time. Feedback from the thickness sensor is used to modify pad conditioner dwell times across the pad surface, correcting for drifts in the pad profile that may arise as the pad and disk age. Pad profile CLC enables uniform reduction in groove depth with continued conditioning, providing longer consumables lifetimes and reduced operating costs.

Atmospheric CO2 enrichment reportedly reduces respiration of mature leaves in a number of woody and herbaceous perennials. It has yet to be determined, however, whether these reductions reflect changes in maintenance respiration alone or whether CO2 might affect growth respiration as well. This possibility was examined in white oak (Quercusalba L.) seedlings that had been planted directly into the ground within open-top chambers and exposed to ambient, ambient +150 μL•L−1, and ambient +300 μL•L−1 CO2 concentrations over a 3-year period. In the spring of 1992, respiration rates were measured repeatedly during leaf expansion, and the growth and maintenance coefficients were determined using a two-component model. Specific respiration rates (mg CO2•g−1•h−1) were consistently lower for leaves of CO2-enriched saplings than for leaves of ambient-grown saplings. Partitioning these reductions in leaf respiration to either the growth or maintenance coefficients indicated a strong effect of CO2 on both components. The growth coefficient for leaves exposed to the ambient CO2 treatment was 964 mg CO2•g−1 compared with 849 and 664 mg CO2•g−1•for leaves from the two elevated CO2 concentrations, respectively. The maintenance coefficient was similarly reduced from a control rate of 114 mg CO2•g−1•d−1 to below 65 mg CO2•g−1•d−1 for leaves exposed to CO2 enrichment. Our results quantitatively describe the magnitude by which growth and maintenance respiration are affected by CO2 enrichment and as such should provide useful information for the future modeling of this phenomenon.

We conducted a series of modeling exercises designed to re-evaluate the light-response and CO 2 -response curves of Taylor and Gunderson ( Pl. Physiol. 86, 85–92, 1988) and to examine further their conclusion that ethylene-induced inhibition of electron transport may contribute to reduced CO 2 assimilation in leaves of Glycine max . By partitioning the response of CO 2 assimilation to either electron transport-limited or Rubisco-limited rates of carboxylation, we calculated that the electron transport capacity ( J max ) of ethylene-treated leaves decreased by over 30% following a 4-hr exposure to 10 μl/l ethylene and noted that ethylene-induced reductions in CO 2 assimilation could be explained without a decrease in Rubisco activity ( Vc max ). Measurements of in vivo Chl fluorescence supported these observations and indicated that the efficiency by which excitation energy was captured in PSII (i.e. ( F m − F o / F m ) was reduced from 0.80 to 0.73 after a 4-hr exposure to 10 μl/l ethylene. This reduction was also accompanied by a 12% decrease in steady-state photochemical quenching ( q p ), indicating that a lower proportion of open or oxidized PSII reaction centers were participating in light-dependent processes. Effects of ethylene on Chl fluorescence were amplified at increased irradiance, suggesting that photoinhibition may play a role in the ethylene-induced inhibition of CO 2 assimilation.

Simulation models are increasingly being used to describe physiological processes in the plant sciences. These models, while useful for research purposes, also offer tremendous potential for demonstrating a wide array of scientific concepts to students. We have developed an educational software package that illustrates the stomatal and biochemical control of transpiration and photosynthesis. The simulation program uses a biochemical model of C assimilation that, when coupled to an empirical submodel describing stomatal conductance, can be solved iteratively for leaf photosynthesis, stomatal conductance, and transpiration. Graphic and tabular presentations, combined with on-screen requests for student input, serve to effectively convey the basic fundamentals of plant gas-exchange, and the diurnal patterns of photosynthesis and transpiration in response to fluctuating environmental conditions. More advanced topics focus on the biochemical limitations imposed on photosynthesis by Rubisco activity, electron transport capacity, and the regeneration of inorganic P. Also included is an exercise that challenges students to use the lessons learned to optimize C assimilation, while minimizing water losses, over a 3-d simulation period. Application of the program can assist instructors in illustrating important concepts regarding stomatal and biochemical control of plant gas-exchange.

summary Specific respiration rate (SRR) was mathematically partitioned into its growth and maintenance components for leaves of yellow-poplar (Liriodendron tulipifera L.) after 3 yr of CO2 enrichment in open-top field chambers. Despite the absence of a CO2 effect on individual leaf expansion or specific growth rate (SGR), increasing the CO2 concentration to ambient +150 or +300 cm3 m−3 decreased SRR by 28 to 45% compared with ambient-grown controls. These lower leaf respiration rates were correlated with reduced leaf nitrogen concentrations. As described by the two-component model of growth and maintenance respiration, SRR was a linear function of SGR. Ambient-grown leaves had a growth respiration coefficient of 704 mg CO2 g−1 dry mass compared with 572 and 570 mg CO2 g−1 for leaves grown at the two higher CO2 concentrations. Leaves from the elevated CO2 treatments had an average maintenance respiration coefficient of 88 mg CO2 g−1 dry mass d−1 compared with 135 mg CO2 g−1 d −1 for leaves from the ambient treatment. Incorporating these growth and maintenance coefficients into a leaf growth simulation model indicated that total respiration would be reduced by 21 to 26 % for a leaf exposed to + 150 or + 300 cm3 m−3 CO2 throughout its 50-d lifespan compared with one grown at ambient CO2 conditions. Reductions in total respiration were dominated by a lower rate of maintenance respiration, while the contribution of a lower specific rate of growth respiration was largely offset by a greater dry mass for leaves grown at elevated CO2 concentrations. Although reductions in the respiratory loss of carbon could be beneficial, respiration is unlikely to decrease without a concomitant decrease in other metabolic processes. Whether these reductions are beneficial or detrimental to the long-term growth of plants exposed to elevated CO2 remains unresolved.

Aerial and overhead center-pivot irrigation system (chemigated) applica- tions of chlorpyrifos 4 emulsifiable concentrate (EC) and fenvalerate 2.4EC significantly reduced numbers of first- and second-generation European corn borer, Ostrinia nubilalis Hubner, larvae in field corn, Zea mays L. The number of first-generation O. nubilalis larvae, pupae, or cavities per plant in plots chemigated with chlorpyrifos in 1984 was significantly less than in plots where chlorpyrifos was applied aerially. A similar trend was observed for fenvalerate in 1985. No significant differences among application methods were observed for second-generation O. nubilalis treatments. Chlorpyrifos and fenvalerate were effective O. nubilalis control agents but efficacy differences between these two insecticides were variable. Corn yields did not vary significantly among application meth- ods.

Leaf senescence contributes to reduced canopy photosynthesis when new leaf initiation cannot compensate for increased leaf aging after canopy closure. However, since leaf aging is seldom addressed in whole plant investigations, it is difficult to evaluate how age-class composition influences crop productivity. Field studies were conducted to examine leaf area development in cotton (Gossypium hirsutum L.) and to incorporate this information into a simulation model for assessing canopy age-class dynamics. Simulated results indicated that leaf area produced during rapid canopy expansion (60 DAP [days after planting], LAI [leaf area index] = 2.3) was largely composed of young leaves, with >35% of the LAI being 29 d old increased to 75%. This shift in ageclass composition toward progressively older leaves altered the relative contribution of C from differing layers within the canopy. The middle portion of the canopy was the most important contributor of C early in crop growth, supplemented by roughly equal contributions from the lower and upper canopies. However, after 90 DAP the supply of assimilate from the upper canopy rapidly increased to >45% and that of the lower canopy decreased dramatically. Towards the end of the season (120 DAP), the middle and upper portions of the canopy were about equally divided in their importance to late-season C production. These results highlight the dynamic nature of age-related processes within the cotton canopy and the importance of leaf area development in sustaining whole-plant C production. Publicatin no. 3769, Environmental Sciences Division, Oak Ridge Natl. Lab. Oak Ridge Natl. Lab is managed by Martin Marietta Energy Systems, under contract DE-AC05-840R21400 with the U.S. Dept. of Energy.

Seedlings of yellow-poplar (Liriodendron tulipifera L.) and white oak (Quercus alba L.) were exposed continuously to one of three CO(2) concentrations in open-top chambers under field conditions and evaluated after 24 weeks with respect to carbon exchange rates (CER), chlorophyll (Chl) content, and diurnal carbohydrate status. Increasing the CO(2) concentration from ambient to +150 or +300 microl l(-1) stimulated CER of yellow-poplar and white oak seedlings by 60 and over 35%, respectively, compared to ambient-grown seedlings. The increases in CER were not associated with a significant change in stomatal conductance and occurred despite a reduction in the amounts of Chl and accessory pigments in the leaves of plants grown in CO(2)-enriched air. Total Chl contents of yellow-poplar and white oak seedlings grown at +300 microl l(-1) were reduced by 27 and over 55%, respectively, compared with ambient-grown seedlings. Yellow-poplar and white oak seedlings grown at +300 microl l(-1) contained 72 and 67% more morning starch, respectively, than did ambient-grown plants. In contrast, yellow-poplar and white oak seedlings grown at +300 microl l(-1) contained 17 and 27% less evening sucrose, respectively, than did plants grown at ambient CO(2) concentration. Diurnal starch accumulation and the subsequent depletion of sucrose contributed to a pronounced increase in the starch/sucrose ratio of plants grown in CO(2)-enriched air. All seedlings exhibited a substantial reduction in dark respiration as CO(2) concentration increased, but the significance of this increase to the carbohydrate status and carbon economy of plants grown in CO(2)-enriched air remains unclear.

TDP-43 is a DNA/RNA-binding protein implicated in multiple steps of transcriptional and post-transcriptional regulation of gene expression. Alteration of this multifunctional protein is associated with a number of neurodegenerative diseases including amyotrophic lateral sclerosis and frontotemporal lobar degeneration with ubiquitin positive inclusions. Whereas a pathological link to neurodegenerative disorders has been established, the cellular and physiological functions of TDP-43 remain unknown. In this study, we show that TDP-43 is a nuclear protein with persistent high-level expression during embryonic development and with progressively decreased protein levels during postnatal development. In mice where the TDP-43 gene (Tardbp) was disrupted using a gene trap that carries a beta-galactosidase marker gene, heterozygous (Tardbp(+/-)) mice are fertile and healthy, but intercrosses of Tardbp(+/-) mice yielded no viable homozygotic null (Tardbp(-/-)) mice. Indeed, Tardbp(-/-) embryos die between 3.5 and 8.5 days of development. Tardbp(-/-) blastocysts grown in cell culture display abnormal expansion of their inner cell mass. The pattern of beta-galactosidase staining at E9.5 Tardbp(+/-) embryos is predominantly restricted to the neuroepithelium and remains prominent in neural progenitors at E10.5-12.5. TDP-43 is detected in spinal cord progenitors and in differentiated motor neurons as well as in the dorsal root ganglia at E12.5. Beta-galactosidase staining of tissues from adult Tardbp(+/-) mice shows widespread expression of TDP-43, including prominent levels in various regions of the central nervous system afflicted in neurodegenerative disorders. These results indicate that TDP-43 is developmentally regulated and indispensible for early embryonic development.

Current at-sea calibrations of ship mounted echosounders are based on the method of standard target calibration, which involves deploying one or more standard targets, or calibration spheres, to depths that are in the farfield of the transducers. The spheres are tethered with three lines fed through three downriggers which are mounted on the Port and Starboard sides of the vessel bracketing the centerboard, and controlled manually by an operator. The efficiency of the calibration depends heavily on the experience of the operator, especially when calibration of a hull-mounted multi-beam sonar is involved. To more effectively conduct the acoustic system calibration at sea, an automated calibration system has been built which includes three highly modified commercially available fishing downriggers, with each downrigger containing an integrated mechanical, electrical, and electronics control system. The mechanical component includes the commercial downrigger gear motor, line spool, and custom sensing head (line length in centimeters and line tension in fractions of kilograms). The electrical component consists of forward and reverse power relays, high power pulse width modulation motor speed control, and protection circuitry. The electronics control system consists of a microcontroller based panel with display, manual control buttons, RS-232 interface, and custom software. The microcontroller software allows the remote laptop computer to control the downrigger line movement at variable speeds in both the forward and reverse directions, keeps track of line length in centimeters, and observes line tension. The control software is written in MATLAB, with an easy-to-use Graphic User Interface (GUI). The control and response commands are sent and received from the laptop to the micro-controller via a USB to serial link RS232 port expander. The software can control each of the three downriggers independently to within one centimeter of accuracy. The locations of the spheres can be determined by the software so that the calibration spheres can be moved to any desired locations in three dimensions within the acoustically insonified volume. The MATLAB control software calculates the desired line movement for each of the downriggers to control the sphere movement horizontally while maintaining proper depth under the transducers of the ship. Line tension is constantly monitored to prevent line fouling, excessive strain on the components, and to detect possible line snagging on the ship's hull. Such an automated system can: 1) improve the efficiency of the calibration, especially for mapping the beampattern of transducers mounted on the ship's centerboard; 2) be operated by an inexperienced staff; and 3) control the positions of standard calibration spheres more precisely and with much less fluctuation compared with the conventional manually operated at-sea calibration. This allows for more repeatable measurements and maintains the sphere positions to approximately the same ranges.

Fossil-fuel combustion and land-use change have elevated atmospheric CO2 concentrations from 280 ppmv at the beginning of the industrial era to more than 381 ppmv in 2006. Carbon dioxide emissions from fossil fuels and cement rose 71% during 1970–2000 to a rate of 7.0 PgC/y (1). Canadell et al. (2) estimated that CO2 emissions rose at a rate at 1.3% per year during 1990–1999, but since 2000 it has been growing at 3.3% per year. Emissions reached 8.4 PgC/y in 2006. It is likely that the current 2-ppm annual increase will accelerate as the global economy expands, increasing the risk of climate system impacts. There is good agreement that photosynthetic CO2 capture from the atmosphere and storage of the C in above- and belowground biomass and in soil organic and inorganic forms could be exploited for safe and affordable greenhouse gas (GHG) mitigation (3). Nevertheless, C sequestration in the terrestrial biosphere has been a source of contention before and since the drafting of the Kyoto Protocol in 1997. Concerns have been raised that C sequestration in the biosphere is not permanent, that it is difficult to measure and monitor, that there would be “carbon leakage” outside of the mitigation activity,more » and that any attention paid to environmental sequestration would be a distraction from the central issue of reducing GHG emissions from energy production and use. A decade after drafting the Kyoto Protocol, it is clear that international accord and success in reducing emissions from the energy system are not coming easily and concerns about climate change are growing. It is time to re-evaluate all available options that might not be permanent yet have the potential to buy time, bridging to a future when new energy system technologies and a transformed energy infrastructure can fully address the climate challenge. Terrestrial sequestration is one option large enough to make a contribution in the coming decades using proven land-management methods and with the possibility that new technologies could significantly enhance the opportunity. Here we review progress on key scientific, economic, and social issues; postulate the extent to which new technologies might significantly enhance terrestrial sequestration potential; and address remaining research needs.« less

Conservation of respired CO 2 by an efficient recycling mechanism in fruit could provide a significant source of C for yield productivity. However, the extent to which such a mechanism operates in cotton ( Gossypium hirsutum L.) is unknown. Therefore, a combination of CO 2 exchange, stable C isotope, and chlorophyll (Chl) fluorescence techniques were used to examine the recycling of respired CO 2 in cotton fruit. Respiratory CO 2 losses of illuminated fruit were reduced 15 to 20% compared with losses for dark-incubated fruit. This light-dependent reduction in CO 2 efflux occurred almost exclusively via the fruit9s outer capsule wall. Compared with the photosynthetic activity of leaves, CO 2 recycling by the outer capsule wall was 35 to 40% as efficient. Calculation of 14 CO 2 fixation on a per Chl basis revealed that the rate of CO 2 recycling for the capsule wall was 62.2 micromoles 14 CO 2 per millimole Chl per second compared with an assimilation rate of 64.6 micromoles 14 CO 2 per millimole Chl per second for leaves. During fruit development, CO 2 recycling contributed more than 10% of that C necessary for fruit dry weight growth. Carbon isotope analyses (δ 13 C) showed significant differences among the organs examined, but the observed isotopic compositions were consistent with a C 3 pathway of photosynthesis. Pulse-modulated Chl fluorescence indicated that leaves and fruit were equally efficient in photochemical and nonphotochemical dissipation of light energy. These studies demonstrated that the cotton fruit possesses a highly efficient, light-dependent CO 2 recovery mechanism that aids in the net retention of plant C and, therein, contributes to yield productivity.

In response to concerns about oil dependency and the contributions of fossil fuel use to climatic change, the U.S. Department of Energy has begun a research initiative to make 20% of motor fuels biofuel based in 10 years, and make 30% of fuels bio-based by 2030. Fundamental to this objective is developing an understanding of feedstock dynamics of crops suitable for cellulosic ethanol production. This report focuses on switchgrass, reviewing the existing literature from field trials across the United States, and compiling it for the first time into a single database. Data available from the literature included cultivar and crop management information, and location of the field trial. For each location we determined latitude and longitude, and used this information to add temperature and precipitation records from the nearest weather station. Within this broad database we were able to identify the major sources of variation in biomass yield, and to characterize yield as a function of some of the more influential factors, e.g., stand age, ecotype, precipitation and temperature in the year of harvest, site latitude, and fertilization regime. We then used a modeling approach, based chiefly on climatic factors and ecotype, to predict potential yields for a given temperaturemore » and weather pattern (based on 95th percentile response curves), assuming the choice of optimal cultivars and harvest schedules. For upland ecotype varieties, potential yields were as high as 18 to 20 Mg/ha, given ideal growing conditions, whereas yields in lowland ecotype varieties could reach 23 to 27 Mg/ha. The predictive equations were used to produce maps of potential yield across the continental United States, based on precipitation and temperature in the long term climate record, using the Parameter-elevation Regressions on Independent Slopes Model (PRISM) in a Geographic Information System (GIS). Potential yields calculated via this characterization were subsequently compared to the Oak Ridge Energy Crop County Level data base (ORECCL), which was created at Oak Ridge National Laboratory (Graham et al. 1996) to predict biofuel crop yields at the county level within a limited geographic area. Mapped output using the model was relatively consistent with known switchgrass distribution. It correctly showed higher yields for lowland switchgrass when compared with upland varieties at most locations. Projections for the most northern parts of the range suggest comparable yields for the two ecotypes, but inadequate data for lowland ecotypes grown at high latitudes make it difficult to fully assess this projection. The final model is a predictor of optimal yields for a given climate scenario, but does not attempt to identify or account for other limiting or interacting factors. The statistical model is nevertheless an improvement over historical efforts, in that it is based on quantifiable climatic differences, and it can be used to extrapolate beyond the historic range of switchgrass. Additional refinement of the current statistical model, or the use of different empirical or process-based models, might improve the prediction of switchgrass yields with respect to climate and interactions with cultivar and management practices, assisting growers in choosing high-yielding cultivars within the context of local environmental growing conditions.« less

SUMMARY Seven ectomycorrhizal fungi were screened by a soybean cell division bioassay to determine their potential for cytokinin synthesis. Fungal isolates of Rhizopogon roseolus (Corda) Hollos and Suillus punctipes (Peck) Sing, released significant quantities of cytokinin-like substances into the culture medium. In contrast, Cenococcum geophilum (Fr.), Hebeloma crustuliniforme (Bull. ex. St. Amans) Qual., Pisolithus tinctorius (Pers.) Coker and Couch, Suillus granulatus (L. ex. Fr.) O. Kuntze, and Thelephora terrestris (Ehrh.) Fr. failed to elicit a positive cytokinin response in the soybean bioassay. Purification of S. punctipes culture filtrates by cation exchange, organic solvent partitioning, and separation on Sephadex LH-20 revealed the presence of compounds with the same retention volume as zeatin and zeatin riboside. Greenhouse studies with loblolly pine (Pinus taeda L.) indicated that, together with improved plant growth and enhanced mineral nutrition, P. tinctorius mediated a significant effect on host cytokinin relations. Cytokinin activity of extracted needles increased 44 and 30% for 12- and 14-month-old seedings, respectively, following ectomycorrhizal establishment. Axenically grown seedlings colonized by 5. punctipes showed no alterations in growth, nutrition, or cytokinin concentration, compared to non-inoculated controls, even though mycorrhizal formation exceeded 30%. The ability of ectomycorrhizal fungi to affect host cytokinins was not dependent upon an ability to synthesize cytokinins in pure culture. Results are discussed in relation to improved mineral nutrition, enhanced root growth, and increased short-root proliferation in the ectomycorrhizal association.

Growth chamber experiments were conducted to elucidate the morphological and physiological responses of rice to postemergence application of fenox- aprop. Two rice cultivars, 'Newbonnet' and 'Mars', and barnyardgrass were treated with 0.17 kg ai ha-l fenox- aprop at the five-leaf stage. Within 2 days of fenoxaprop application, rice cultivars developed a white chlorotic band across leaves that were in direct contact with spray droplets. Leaf elongation rates for the two rice cultivars were inhibited by 40% after 4 days and by over 50% after 14 days. Inhibition of leaf elongation by fenoxaprop contributed to an overall decrease in leaf area and shoot dry weight. Net photosynthesis was reduced by 35% in fenoxaprop-treated plants 11 days after application, although stomatal conductance was not affected. Nitrogen fertilization prior to fenoxaprop application increased foliar injury of both rice cultivars. Visible injury symptoms showed the following order of susceptibility to foliar-applied fenoxaprop: barnyardgrass > Mars rice > Newbonnet rice. Nomenclature: Barnyardgrass, Echinoch- loa crus-galli (L.) Beauv. #3 ECHCG; fenoxaprop, (?)- 2 - (4 - ((6 - chloro-2-benzoxazolyl)oxy)phenoxy)propanoic acid; rice, Oryza sativa L. 'Mars' and 'Newbonnet'. Additional index words. Crop injury, epicuticular wax, growth analysis, photosynthesis, stomatal conductance, Echinochloa crus-galli, ECHCG.