Combination Of Elevated CO Research Articles

Morphological mechanism of growth response in treeline species Minjiang fir to elevated CO2 and temperature

To test whether and how morphological traits are linked with growth responses of plants to temperature and CO is important for understanding the mechanism underlying how plant growth will respond to global warming. In this study, using closed-top chambers to mimic future elevated CO and temperature, the growth response, morphological traits of Minjiang fir (Abies faxoniana Rehd.et Wils.) and the relationship of the two were investigated after two years of exposure to the single and combined elevation of CO and temperature. The results showed that biomass of Minjiang fir was 21%, 31%, and 35% greater than the control in elevated CO, elevated temperature and the combination of elevated CO and temperature treatments, respectively. Elevated CO and temperature significantly affected the morphology of Minjiang fir, and a few morphological traits were highly correlated with growth responses. Larger branch angles at the upper layer, crown volume, and relative crown length contributed to positive growth responses to elevated CO, while decreased specific leaf area (SLA) constricted any further growth response. Leaf morphological traits were more closely correlated with the response ratio than crown did in the elevated temperature, while in the combination of elevated CO and temperature, crown was more correlated with the response ratio than the leaf morphological traits. Thus, our results indicate that morphological traits may contribute differently to growth responses under different experimental conditions.22222222

Effects of elevated CO 2 concentration, supplemental irrigation and nitrogenous fertilizer application on rain-fed spring wheat yield

It is expected that the CO 2 concentration of the Earth’s atmosphere will reach 600–1000 ppm by the end of the 21st century. Therefore, in this study, we evaluated the effects of elevated CO 2 concentrations on the development of rain-fed spring wheat in an attempt to identify a practical pathway to increase crop production. To accomplish this, a field experiment was conducted at Guyuan Experimental Station in a semiarid region of China during 2005–2007. During this experiment, the CO 2 concentration was increased to 40.0 ppm and supplemental irrigation and nitrogenous fertilizer (N fertilizer) were applied. The experimental results showed that the elevated CO 2 concentration significantly improved the thousand-grain weight and the grain number per spike. Furthermore, supplemental irrigation and N fertilizer application during the elongation and booting stage of rain-fed spring wheat in conjunction with an elevated CO 2 concentration improved the water use efficiency (WUE), nitrogen use efficiency (NUE), thousand-grain weight, and the yield by 14.6%, 39.6%, 9.3%, and 14.7%, respectively, when compared to groups subjected to the same treatment but not grown under elevated CO 2 concentrations. Furthermore, the spring wheat yield was improved by 81.8% in response to an elevated CO 2 concentration, 60 mm of supplemental irrigation and applied N fertilizer (37.5 g m −2 NH 4NO 3). However, the presence of an elevated CO 2 concentration without supplemental irrigation and N fertilizer only resulted in an increase in the wheat yield of 7.8%. Consequently, the combination of elevated CO 2 concentration, supplemental irrigation and N fertilizer application played an important role in the improvement of WUE, NUE, thousand-grain weight, and grain yield of rain-fed spring wheat in this region.

Leaf size and surface characteristics of Betula papyrifera exposed to elevated CO 2 and O 3

Betula papyrifera trees were exposed to elevated concentrations of CO 2 (1.4 × ambient), O 3 (1.2 × ambient) or CO 2 + O 3 at the Aspen Free-air CO 2 Enrichment Experiment. The treatment effects on leaf surface characteristics were studied after nine years of tree exposure. CO 2 and O 3 increased epidermal cell size and reduced epidermal cell density but leaf size was not altered. Stomatal density remained unaffected, but stomatal index increased under elevated CO 2. Cuticular ridges and epicuticular wax crystallites were less evident under CO 2 and CO 2 + O 3. The increase in amorphous deposits, particularly under CO 2 + O 3, was associated with the appearance of elongated plate crystallites in stomatal chambers. Increased proportions of alkyl esters resulted from increased esterification of fatty acids and alcohols under elevated CO 2 + O 3. The combination of elevated CO 2 and O 3 resulted in different responses than expected under exposure to CO 2 or O 3 alone.

Elevated carbon dioxide improves plant iron nutrition through enhancing the iron-deficiency-induced responses under iron-limited conditions in tomato.

The increases in atmospheric carbon dioxide (CO(2)) concentrations can enhance plant growth and change their nutrient demands. We report that when tomato (Lycopersicon esculentum 'Zheza 809') plants were grown in iron (Fe)-limited medium (with hydrous ferric iron oxide) and elevated CO(2) (800 microL L(-1)), their biomass and root-to-shoot ratio were greater than plants grown in ambient CO(2) (350 microL L(-1)). Furthermore, the associated increase in Fe concentrations in the shoots and roots alleviated Fe-deficiency-induced chlorosis. Despite the improved nutrient status of plants grown in Fe-limited medium under elevated CO(2), the Fe-deficiency-induced responses in roots, including ferric chelate reductase activity, proton secretion, subapical root hair development, and the expression of FER, FRO1, and IRT genes, were all greater than plants grown in the ambient CO(2). The biomass of plants grown in Fe-sufficient medium was also increased by the elevated CO(2) treatment, but changes in tissue Fe concentrations and Fe deficiency responses were not observed. These results suggest that the improved Fe nutrition and induction of Fe-deficient-induced responses in plants grown in Fe-limited medium under elevated CO(2) are caused by interactions between elevated CO(2) and Fe deprivation. Elevated CO(2) also increased the nitric oxide (NO) levels in roots, but treatment with the NO scavenger cPTIO inhibited ferric chelate reductase activity and prevented the accumulation of LeFRO1, LeIRT1, and FER transcripts in roots of the Fe-limited plants. These results implicate some involvement of NO in enhancing Fe-deficiency-induced responses when Fe limitation and elevated CO(2) occur together. We propose that the combination of elevated CO(2) and Fe limitation induces morphological, physiological, and molecular responses that enhance the capacity for plants to access and utilize Fe from sparingly soluble sources, such as Fe(III)-oxide.

Impact of Elevated CO2 and O3 Concentrations on Biogenic Volatile Organic Compounds Emissions from Ginkgo biloba

In natural environment with ambient air, ginkgo trees emitted volatile organic compounds 0.18 microg g(-1) h(-1) in July, and 0.92 microg g(-1) h(-1) in September. Isoprene and limonene were the most abundant detected compounds. In September, alpha-pinene accounted for 22.5% of the total. Elevated CO(2) concentration in OTCs increased isoprene emission significantly in July (p<0.05) and September (p<0.05), while the total monoterpenes emission was enhanced in July and decreased in September by elevated CO(2). Exposed to elevated O(3) increased the isoprene and monoterpenes emissions in July and September, and the total volatile organic compounds emission rates were 0.48 microg g(-1) h(-1) (in July) and 2.24 microg g(-1) h(-1) (in September), respectively. The combination of elevated CO(2) and O(3) did not have any effect on biogenic volatile organic compounds emissions, except increases of isoprene and Delta3-carene in September.

Fine‐root respiration in a loblolly pine (Pinus taeda L.) forest exposed to elevated CO2 and N fertilization

Forest ecosystems release large amounts of carbon to the atmosphere from fine-root respiration (R(r)), but the control of this flux and its temperature sensitivity (Q(10)) are poorly understood. We attempted to: (1) identify the factors limiting this flux using additions of glucose and an electron transport uncoupler (carbonyl cyanide m-chlorophenylhydrazone); and (2) improve yearly estimates of R(r) by directly measuring its Q(10)in situ using temperature-controlled cuvettes buried around intact, attached roots. The proximal limits of R(r) of loblolly pine (Pinus taeda L.) trees exposed to free-air CO(2) enrichment (FACE) and N fertilization were seasonally variable; enzyme capacity limited R(r) in the winter, and a combination of substrate supply and adenylate availability limited R(r) in summer months. The limiting factors of R(r) were not affected by elevated CO(2) or N fertilization. Elevated CO(2 )increased annual stand-level R(r) by 34% whereas the combination of elevated CO(2) and N fertilization reduced R(r) by 40%. Measurements of in situ R(r) with high temporal resolution detected diel patterns that were correlated with canopy photosynthesis with a lag of 1 d or less as measured by eddy covariance, indicating a dynamic link between canopy photosynthesis and root respiration. These results suggest that R(r) is coupled to daily canopy photosynthesis and increases with carbon allocation below ground.

An ABA inducible WRKY gene integrates responses of creosote bush ( Larrea tridentata) to elevated CO 2 and abiotic stresses

The physiological and molecular responses of Larrea tridentata, an evergreen desert shrub, to elevated CO 2, and abiotic stresses were examined to enhance our understanding of the crosstalk of hormones, stresses, and elevated CO 2 in signaling. Under nonlimiting conditions of water and nutrients, elevated CO 2 increased both ABA and starch concentrations in leaves by two-fold. Combinations of elevated CO 2 and water deficit treatments further increased the concentrations of ABA, but not starch. A transcription factor, LtWRKY21, was cloned from Larrea tridentata to address questions regarding crosstalk at the molecular level. The expression of LtWRKY21 was enhanced by elevated CO 2, water deficit, high salinity, and wounding. In addition, ABA, jasmonic acid (JA), and glucose induced the expression of LtWRKY21. However, cold and heat treatments decreased the wounding-induced LtWRKY21 mRNA level. Transient expression of LtWRKY21 suggests that this transcription factor acts as an activator of ABA signaling and as a repressor of gibberellin (GA) signaling. These results suggest that LtWRKY21 might function as a key regulator of signaling networks in Larrea tridentata.

Growth responses of Populus tremuloides clones to interacting elevated carbon dioxide and tropospheric ozone

The Intergovernmental Panel of Climate Change (IPCC) has concluded that the greenhouse gases carbon dioxide (CO 2) and tropospheric ozone (O 3) are increasing concomitantly globally. Little is known about the effect of these interacting gases on growth, survival, and productivity of forest ecosystems. In this study we assess the effects of three successive years of exposure to combinations of elevated CO 2 and O 3 on growth responses in a five trembling aspen ( Populus tremuloides) clonal mixture in a regenerating stand. The experiment is located in Rhinelander, Wisconsin, USA (45°N 89°W) and employs free air carbon dioxide and ozone enrichment (FACE) technology. The aspen stand was exposed to a factorial combination of four treatments consisting of elevated CO 2 (560 ppm), elevated O 3 (episodic exposure-90 μ1 1 −1 hour −1), a combination of elevated CO 2 and O 3, and ambient control in 30 m treatment rings with three replications. Our overall results showed that our three growth parameters including height, diameter and volume were increased by elevated CO 2, decreased by elevated O 3, and were not significantly different from the ambient control under elevated CO 2+O 3. However, there were significant clonal differences in the responses; all five clones exhibited increased growth with elevated CO 2, one clone showed an increase with elevated O 3, and two clones showed an increase over the control with elevated CO 2+O 3, two clones showed a decrease, and one was not significantly different from the control. Notably, there was a significant increase in current terminal shoot dieback with elevated CO 2 during the 1999–2000 dormant season. Dieback was especially prominent in two of the five clones, and was attributed to those clones growing longer into the autumnal season where they were subject to frost. Our results show that elevated O 3 negates expected positive growth effects of elevated CO 2 in Populus tremuloides in the field, and suggest that future climate model predictions should take into account the offsetting effects of elevated O 3 on CO 2 enrichment when estimating future growth of trembling aspen stands.

Influence of elevated CO 2 on the sensitivity of two soybean cultivars to sulphur dioxide

Two cultivars of soybean ( Glycine max cv. Bragg and PK 472) were subjected to elevated concentrations of CO 2 (600 μl l −1) and/or SO 2 (0.06 μl l −1), for 8 h from germination to grain maturity in open top chambers under field conditions to assess the modification in response to SO 2 exposure resulting form CO 2 enrichment. Exposure to SO 2 alone resulted in reductions in plant growth, biomass and yield, as well as declines in foliar starch and protein content in both the cultivars of soybean. Elevated CO 2 stimulated plant growth, yield and enhanced foliar starch content, photosynthesis and WUE in both the cultivars. In plants exposed to the combination of elevated CO 2+SO 2, the adverse influence of SO 2 was mitigated by CO 2 enrichment. This effect was considered to result from the provision of extra carbon sources required for repair and detoxification processes and a reduction in SO 2 uptake through reduction in stomatal conductance. PK 472 exhibited greater sensitivity to SO 2 than Bragg. PK 472 also showed greater stimulation of yield under CO 2+SO 2 treatment than Bragg.

Net primary production and carbon stocks in differently managed grasslands: simulation of site-specific sensitivity to an increase in atmospheric CO 2 and to climate change

Elevated atmospheric CO 2 and climate changes are expected to influence managed grassland ecosystems. The mechanistic pasture simulation model (PaSim) was used to quantify effects on net primary productivity (NPP) and carbon (C) stocks at three locations differing in climate and soil type. An earlier model version was modified to enable long-term simulations at different altitudes, and to consider management in the form of either cutting or grazing by lactating cows. Results from simulations under current conditions agreed favourably with measured data for yield and C stocks, and model behaviour appeared to be plausible. Elevated CO 2 alone or in combination with increased temperature stimulated NPP at all sites. The stimulation was positively related to increasing precipitation at dry sites, but negatively at cool sites. Climate change scenarios in combination with elevated CO 2 led to increase C stocks. The sensitivity of C stocks to changes in temperature and precipitation was similar, and much larger than to management. Grazing led to higher C stocks compared with cutting, depending mainly on the difference in NPP between the management options. Grazing had a positive effect on C stocks under cool conditions, but the effect tended to become negative with increasing temperature. Comparing different sites revealed that local conditions affect system behaviour qualitatively. In quantitative terms, the results confirm that the combination of elevated CO 2 and climate change affects NPP and C stocks, and that the influence of management is site-specific.

QUALITY OF MUSCADINE GRAPES AS INFLUENCED BY ELEVATED CO2 AND REDUCED O2 ATMOSPHERE

Berries of muscadine grapes (Vitis rotundifolia Michx cv. 'Higgin') were hand-harvested at late maturity and early ripening stage. After precooling, the berries were kept for four weeks in 20% CO 2 and 3% O 2 atmosphere in glass jars at 1-2 °C and 90-95% relative humidity. Samples were withdrawn weekly to determine fruit quality attributes. Shelf-life extension could be obtained for muscadine grapes using a combination of elevated CO 2 and reduced O 2 concentrations in the atmosphere (CA) under cold storage. Muscadine grapes can be stored for 2.5 to 3 weeks under cold CA with no appreciable damage.

Effects of long-term CO 2 and temperature elevation on crown nitrogen distribution and daily photosynthetic performance of Scots pine

Single Scots pines ( Pinus sylvestris L.), aged 20–25 years, were grown in open-top chambers and exposed to elevated temperature (Elev. T), elevated CO 2 (Elev. C) and a combination of elevated CO 2 and temperature (Elev. C + T) for 4 years. The vertical distribution of needle nitrogen concentration was measured simultaneously with gas exchange of attached shoots. Based on the measurements, the dependencies on needle nitrogen concentrations of four photosynthetic parameters, i.e., RuP 2 (ribulose 1,5-bisphosphate)-saturated rate of carboxylation ( V cmax), maximum potential electron transport ( J max), the rate of respiration in the light ( R d) and light-use-efficiency factor (δ), were determined. Using a crown multilayer model, the performance of daily crown photosynthesis in Scots pine was predicted. Compared to the control treatment, the mean concentration of nitrogen in the foliage decreased by 20% and by 17% for trees grown under Elev. C and under Elev. C + T, respectively, but increased by 4% for trees grown under Elev. T. However, the total content of foliage nitrogen per unit ground area increased by 25% for trees grown under Elev. C, by 19% for trees grown under Elev. C + T and by 6% for trees grown under Elev. T; these were due to the increase in the total needle area index. Regressions showed that the foliage grown under Elev. C and Elev. C + T had steeper slopes representing the responses of V cmax, R d and δ to leaf nitrogen concentrations, while Elev. C + T and Elev. T had steeper slopes representing the response of J max to needle nitrogen concentrations. Predictions showed that, on a typical sunny day, the daily total of crown photosynthesis increased 22% and 27%, separately for Elev. C and Elev. C + T, and by only 9% for Elev. T alone. Furthermore, the increased daily crown photosynthesis, resulting from treatments involving elevated CO 2, can be attributed mainly to an increase in the ambient CO 2 concentration and the needle area index, while modification of the intrinsic photosynthetic capacity had only a marginal effect. Based on the current pattern of crown nitrogen allocation, the prediction showed also that the relationship between daily crown photosynthesis and crown nitrogen content was strongly dependent on the daily incident PAR and air temperature. The CO 2-elevated treatments led to an increase in the sensitivity of daily crown photosynthesis to changes in crown nitrogen content, daily incident PAR and temperature, while the temperature-elevated treatment had the opposite effect on the sensitivity.

Effects of elevated CO 2 on gas exchange characteristics of alpine grassland

The ecosystem-level gas exchange characteristics of an alpine grassland treated with a combination of elevated CO 2 and moderate additions of NPK fertilizer during the third season of experimental treatments are described. Mid-season maximum daytime net ecosystem CO 2 flux (NEC max) increased significantly under elevated CO 2 (+45%), whereas nighttime NEC was unaffected by the CO 2 treatment. Since daytimke NEC under elevated CO 2 underwent a seasonal decline, only moderate carbon surpluses accumulated under elevated CO 2. The observed seasonal decline in daytime NEC may be due to reduced sink strength once maximum aboveground biomass is attained and appears to be a regulatory mechanism of ecosystem carbon accumulation. Moderate additions of NPK fertilizer stimulated both day-(+39%) and nighttime NEC (+29%) due to increased plant biomass, independent of CO 2 treatment. Yet there is no indication that enhanced mineral nutrient status will increase ecosystem responsiveness to elevated CO 2.

Below-Ground Microbial and Microfaunal Responses to Artemisia tridentata Grown Under Elevated Atmospheric Co 2

1. Soil microbes are fed primarily by root-derived substrates, fulfil functions such as mineralization, immobilization, decomposition, pathogeneity and improvement of plant nutrition, and form the basis of the below-ground food web. Hitherto, below-ground processes have generally been monitored using a 'black-box' approach, thereby ignoring effects of global change at a finer level of resolution. We describe shifts in the activity between microbial functional groups associated with roots of Artemisia tridentata, and the influence of this change on higher trophic levels. 2. We tested the hypothesis that elevated atmospheric CO 2 causes the soil community to change qualitatively. We measured the responses of several soil microbe and soil microfaunal parameters to a double-ambient CO 2 concentration and nutrient additions. The soil community, as measured by those parameters, showed great changes in response to the treatments. There was a very strong interaction between elevated CO 2 and the nutrient addition. 3. Under low nutrient conditions, total microbial biomass did not change under elevated atmospheric CO 2 , but doubled under conditions of elevated CO 2 and added nutrients. As we increased the resolution of our analysis, however, results shifted. Under low nutrient conditions, mycorrhizal fungi responded positively to elevated CO 2 , whereas with added soil nutrients they responded negatively to the same elevated CO 2 concentration. Bacteria and non-mycorrhizal fungi did not respond under the former conditions but more than doubled in biomass under conditions of elevated CO 2 and added nutrients. Soil fauna was also affected by the treatments. Overall, elevated CO 2 shifted carbon flow in the plant-soil system to a more mutualistic-closed, mycorrhizal-dominated system, whereas the combination of elevated CO 2 and nutrient addition shifted carbon flow to a more opportunistic-open, saprobe/pathogen-dominated one. 4. This indicates that elevated atmospheric CO 2 may lead to far less predictable feedback patterns than previously thought and that qualitative shifts in the soil community may be far more important than mere changes in total C sink strength.

Environmental physiology of the banner-tailed kangaroo rat—II. Influences of the burrow environment on metabolism and water loss

1. 1. Oxygen consumption and evaporative water loss were measured in response to burrow and control temperature, water vapor pressure and inspired CO 2 concentration for Dipodomys spectabilis. 2. 2. Oxygen uptake of banner-tail kangaroo rats increased in response to increased inspired CO 2 and decreased temperature. 3. 3. Oxygen consumption of the kangaroo rats decreased in response to a combination of elevated CO 2 and water vapor pressure, relative to elevated CO 2 in dry air. but there was no consistent response to increased water vapor pressure, alone or in combination with temperature. 4. 4. Evaporative water loss and heat loss decreased with decreasing temperature and/or increasing water vapor pressure, but water loss increased at elevated inspired CO 2 concentrations and decreased in response to the combination of elevated CO 2 and water vapor. 5. 5. Seasonal acclimatization of oxygen consumption was evident when data were plotted as responses to control exposures by month. 6. 6. Oxygen uptake and heat loss measured under burrow conditions were related to the seasonal thermal cycle, in that metabolism decreased and heat loss increased during the months of highest burrow temperatures. 7. 7. Evaporative water loss showed little seasonal change under either control or burrow conditions, but had a slight increase in September and October, months in which burrow water vapor pressure was reduced .