CO2 EXCHANGE RATES AND STOMATAL DIFFUSIVE RESISTANCE IN SOYBEAN EXPOSED TO O3 AND SO2

1985 ◽  
Vol 65 (2) ◽  
pp. 267-274 ◽  
Author(s):  
B. I. CHEVONE ◽  
Y. S. YANG
Keyword(s):  
Exchange Rates ◽  
Net Photosynthesis ◽  
Stomatal Resistance ◽  
Co2 Exchange ◽  
Carbon Dioxide Exchange ◽  
Simultaneous Application ◽  
Diffusive Resistance ◽  
Before And After ◽  
Glycine Max L ◽  
Pollutant Mixtures

Soybean (Glycine max (L.) Merr. ’Essex’) plants, 21–24 days old, were exposed to 400 μg/m3 (0.20 μL/L) ozone (O3) and 1865 μg/m3 (0.70 μL/L) sulfur dioxide (SO2) in various combinations. Fumigation was administered for 2 h either as single pollutants (O3 and SO2), simultaneously (O3 + SO2), or in overlapping pollutant combinations (O3 for 1 h followed by O3 + SO2 or SO2 for 1 h followed by SO2 + O3). Carbon dioxide exchange rates (CER) of trifoliolate leaves were measured during the fumigations, and stomatal resistance to H2O was determined immediately before and after pollutant exposure. At the end of a 2-h exposure, O3 and SO2, administered separately, did not significantly affect CER. Exposure to O3 followed by O3 + SO2, SO2 followed by SO2 + O3, and continuous O3 + SO2 significantly reduced CER to 62, 41 and 33% of preexposure rates, respectively. Stomatal resistance was not significantly altered by pollutant fumigation except in the simultaneous application of O3 + SO2 where an 11% decrease occurred. Reductions in CER in response to fumigation were not attributed to changes in stomatal resistance, but appeared to result from changes in mesophyll resistance. A proposed mechanism for pollutant-induced reduction in CER is discussed.Key words: Air pollution, net photosynthesis, pollutant mixtures

CARBON DIOXIDE EXCHANGE RATES OF FRUITING SOYBEAN PLANTS EXPOSED TO OZONE AND SULPHUR DIOXIDE SINGLY OR IN COMBINATION

1984 ◽  
Vol 64 (1) ◽  
pp. 69-75 ◽  
Author(s):  
N. M. LE SUEUR-BRYMER ◽  
D. P. ORMROD
Keyword(s):  
Carbon Dioxide ◽  
Glycine Max ◽  
Exchange Rates ◽  
Sulphur Dioxide ◽  
Net Photosynthesis ◽  
Exposure Period ◽  
Carbon Dioxide Exchange ◽  
Continuous Stirred Tank Reactor ◽  
Glycine Max L ◽  
Soybean Plants

Carbon dioxide exchange rates (CER) of intact soybean (Glycine max (L.) Merr.) plants at the fruiting stage were measured in continuous stirred tank reactor (CSTR) chambers. Plants were exposed to clean air, 67 ppb ozone (O3), 300 ppb sulphur dioxide (SO2), or 67 ppb O3 plus 300 ppb SO2 for 7.5 h∙day−1 for 5 days. Carbon dioxide exchange rates were measured hourly during the last 6 h of each exposure period and decreased progressively during the first period of exposure to O3 plus SO2, dropping in hour 6 to 42% of the hour 1 rate, and to a lesser extent in the second daily exposure when the corresponding decline was to 70%. There was a declining trend in CER of SO2-treated but not O3-treated plants with increasing number of days of exposure. Carbon dioxide exchange rates of all plants generally peaked and declined during each exposure period.Key words: Air pollution, net photosynthesis, mixtures, Glycine max

Effect of Water Deficit on Carbon Dioxide Exchange and Leaf Elongation Rate of Panicum maximum Var. trichoglume

1976 ◽  
Vol 3 (3) ◽  
pp. 401 ◽  
Author(s):  
MM Ludlow ◽  
TT Ng
Keyword(s):  
Carbon Dioxide ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Net Photosynthesis ◽  
Stomatal Resistance ◽  
Leaf Water ◽  
Carbon Dioxide Exchange ◽  
Leaf Elongation ◽  
Water Deficits ◽  
Water Potentials

The responses of carbon dioxide exchange and leaf elongation of potted P. maximum var. trichoglume plants to water deficits were investigated in controlled environments and outdoors during drying cycles down to -92 bars leaf water potential, The sensitivities of net photosynthesis and leaf elongation to water deficits were similar. The leaf water potentials at which net photosynthesis and elongation ceased (c. -12 bars), and stomatal resistance increased substantially (- 6 bars), were relatively unaffected by nitrogen supply, environmental conditions during growth, and whether plants had previously experienced stress. However, these factors influenced the rate of net photosynthesis, at high leaf water potentials by affecting stomatal resistance and at moderate water potentials by affecting both stomatal and intracellular resistances. Stomata1 resistance was more sensitive than intracellular resistance to water deficits. Dark respiration rate decreased with leaf water potential, and was higher in plants receiving additional nitrogen. At moderate leaf water potentials (-7 to -9 bars), net photosynthesis of this C4 grass exhibited light saturation and rates similar to C3 plants. We suggest that the difference in behaviour of controlled-environment-grown and field-grown plants to water deficits observed with some species is unlikely to be due to differences in the aerial environment, but may result from differences in the rate at which stress develops. The ecological significance and evolution of the C4 syndrome are discussed briefly.

Alterations in the physiology of CO2 exchange in tomato plants grown in CO2-enriched atmospheres

1980 ◽  
Vol 58 (20) ◽  
pp. 2181-2189 ◽  
Author(s):  
Peter R. Hicklenton ◽  
Peter A. Jolliffe
Keyword(s):  
Growth Rate ◽  
Gas Exchange ◽  
Early Stage ◽  
Atmospheric Oxygen ◽  
Net Photosynthesis ◽  
Stomatal Resistance ◽  
Co2 Exchange ◽  
Acid Oxidase ◽  
Bisphosphate Carboxylase ◽  
Tomato Plants

Young, greenhouse-grown tomato plants were transferred to growth cabinets where they were maintained in normal air (0.03% CO2) or in air enriched to 0.1 or 0.5% CO2. CO2 enrichment increased net assimilation rate but decreased leaf area ratio. As a result, relative growth rate was greatest at 0.1% CO2 and was less in 0.5% CO2 than in 0.03% CO2. Gas exchange measurements were made on the third true leaf of plants from different CO2 regimes. They indicated that growth under conditions of CO2 enrichment affected photosynthesis at an early stage of leaf development (leaf plastochron index (PI) = 5) but not at a later stage (PI = 10.5). The effects were linked to changes in mesophyll resistance, not stomatal resistance. At PI = 5 and under equivalent test conditions of irradiance and CO2 concentration, net photosynthesis tended to be increased following growth in 0.1% CO2 but was decreased or unchanged by 0.5% CO2. Young leaves developed in 0.1% CO2 were less subject to photosynthetic inhibition by atmospheric oxygen and had low CO2 compensation points. CO2 enrichment also affected the activities of the enzymes ribulose-1,5-bisphosphate carboxylase and glycolic acid oxidase and the enzyme responses corresponded well with the gas exchange responses. The results indicate that photosynthetic adaptations may occur in response to the concentration of CO2 present during growth, and that enrichment to concentrations much above 0.1% CO2 may be detrimental to net photosynthesis and growth rate.

An Empirical Investigation of Factors Affecting Stock Prices in Vietnam

2014 ◽  
pp. 74-89 ◽  
Author(s):  
Vinh Vo Xuan
Keyword(s):  
Exchange Rates ◽  
Crude Oil ◽  
Foreign Exchange ◽  
Stock Prices ◽  
Global Financial Crisis ◽  
Oil Prices ◽  
Foreign Exchange Rates ◽  
Factors Affecting ◽  
Crude Oil Prices ◽  
Before And After

This paper investigates factors affecting Vietnam’s stock prices including US stock prices, foreign exchange rates, gold prices and crude oil prices. Using the daily data from 2005 to 2012, the results indicate that Vietnam’s stock prices are influenced by crude oil prices. In addition, Vietnam’s stock prices are also affected significantly by US stock prices, and foreign exchange rates over the period before the 2008 Global Financial Crisis. There is evidence that Vietnam’s stock prices are highly correlated with US stock prices, foreign exchange rates and gold prices for the same period. Furthermore, Vietnam’s stock prices were cointegrated with US stock prices both before and after the crisis, and with foreign exchange rates, gold prices and crude oil prices only during and after the crisis.

scholarly journals An airborne regional carbon balance for Central Amazonia

2007 ◽  
Vol 4 (1) ◽  
pp. 99-123 ◽  
Author(s):  
J. Lloyd ◽  
O. Kolle ◽  
H. Fritsch ◽  
S. R. de Freitas ◽  
M. A. F. Silva Dias ◽  
...  
Keyword(s):  
Exchange Rates ◽  
Eddy Covariance ◽  
Carbon Balance ◽  
Carbon Budget ◽  
Carbon Sink ◽  
Co2 Exchange ◽  
Night Time ◽  
Central Amazonia ◽  
Regional Estimates ◽  
Good Agreement

Abstract. We obtained regional estimates of surface CO2 exchange rates using atmospheric boundary layer budgeting techniques above tropical forest near Manaus, Brazil. Comparisons were made with simultaneous measurements from two eddy covariance towers below. Although there was good agreement for daytime measurements, large differences emerged for integrating periods dominated by the night-time fluxes. These results suggest that a systematic underestimation of night time respiratory effluxes may be responsible for the high Amazonian carbon sink suggested by several previous eddy covariance studies. Large CO2 fluxes from riverine sources or high respiratory losses from recently disturbed forests do not need to be invoked in order to balance the carbon budget of the Amazon. Our results do not, however, discount some contribution of these processes to the overall Amazon carbon budget.

Effects of Coppicing on Growth Rates, Stomatal Characteristics and Water Relations in Eucalyptus camaldulensis Dehn

1980 ◽  
Vol 7 (1) ◽  
pp. 81 ◽  
Author(s):  
T.J Blake
Keyword(s):  
Transpiration Rate ◽  
Stem Elongation ◽  
Eucalyptus Camaldulensis ◽  
Fold Increase ◽  
Lower Surface ◽  
Stomatal Resistance ◽  
Stomatal Characteristics ◽  
Unit Leaf ◽  
Diffusive Resistance ◽  
Stomatal Length

Stem elongation, transpiration rate, water potential, diffusive resistance and stomatal characteristics were compared in intact and coppiced (decapitated) seedlings of E. camaldulensis. Stump sprouts from coppiced seedlings showed a threefold increase in the rate of stem elongation, a doubling in transpiration rate per seedling and a 5–8-fold increase in transpiration per unit leaf area compared with intact seedlings. Reversion to more juvenile leaf morphology following decapitation was accompanied by decrease in leaf stomatal resistance. Increased stomatal length and higher stomatal frequency on the lower surface of coppice leaves appears to explain the increased transpiration rate following decapitation compared with intact seedlings.

scholarly journals Determination of the carbon budget of a pasture: effect of system boundaries and flux uncertainties

2016 ◽  
Vol 13 (10) ◽  
pp. 2959-2969 ◽  
Author(s):  
Raphael Felber ◽  
Daniel Bretscher ◽  
Andreas Münger ◽  
Albrecht Neftel ◽  
Christof Ammann
Keyword(s):  
Carbon Budget ◽  
Agricultural Sector ◽  
Ghg Emissions ◽  
C Sequestration ◽  
Co2 Exchange ◽  
System Boundaries ◽  
Simultaneous Application ◽  
Soil C ◽  
Ecosystem Carbon ◽  
Eddy Covariance Measurements

Abstract. Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECBtot for system boundaries including the grazing cows and NECBpast for system boundaries excluding the cows. CO2 and CH4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small near-neutral C budget: NECBtot −27 ± 62 and NECBpast 23 ± 76 g C m−2 yr−1. The considerable uncertainties, depending on the approach, were mainly due to errors in the CO2 exchange or in the animal-related fluxes. The comparison of the NECB results with the annual exchange of other GHG revealed CH4 emissions from the cows to be the major contributor in terms of CO2 equivalents, but with much lower uncertainty compared to NECB. Although only 1 year of data limit the representativeness of the carbon budget results, they demonstrate the important contribution of the non-CO2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

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