Dependency of cI/ca and Leaf Transpiration Efficiency on the Vapour Pressure Deficit

1996 ◽  
Vol 23 (5) ◽  
pp. 561 ◽  
Author(s):  
Hehui Zhang ◽  
PS Nobel
Keyword(s):  
Vapour Pressure ◽  
Sonoran Desert ◽  
Vapour Pressure Deficit ◽  
Published Data ◽  
Plant Responses ◽  
Transpiration Efficiency ◽  
C4 Species ◽  
Leaf Transpiration ◽  
Proposed Model ◽  
C3 Species

The leaf transpiration efficiency (A/E, where A is the assimilation rate and E the transpiration rate) is widely used to evaluate plant responses to the environment, yet little attention has been paid to its relationship with vapour pressure deficit (D), the driving force for E. The proposed model is based on the increasingly recognised linear relationship between the ratio of intercellular to ambient CO2 partial pressures (cI/ca) and D. Unlike previous models for A/E, the proposed model does not assume that the leaf and air temperatures are the same or that ci/ca is constant. A/E predicted by the model agreed with that measured for the C3 Encelia farinosa and the C4 Pleuraphis rigida, common species in the north-westem Sonoran Desert, based on gas exchange measured in the field and in environmental chambers. The dependency of cI/ca and A/E on D was additionally evaluated using published data for five other C3 species and two other C4 species. Generally, ci/ca was more sensitive to changes in D for the C4 species than the C3 species. The predictions for A/E by the model were also compared with predictions using a constant ci/ca, either a general cI/ca (0.7 for C3 and 0.3 for C4) or a species-dependent mean cI/ca. Overall, the proposed model performed best for both the C3 and C4 species; using the general cI/ca always resulted in an over-prediction of A/E.

Effect of Temperature, Vapour-Pressure Deficit and Irradiance on Transpiration Rates of Maize, Paspalum, Westerwolds and Perennial Ryegrasses, Peas, White Clover and Lucerne

1977 ◽  
Vol 4 (6) ◽  
pp. 889 ◽  
Author(s):  
BJ Forde ◽  
KJ Mitchell ◽  
EA Edge
Keyword(s):  
Water Use ◽  
Transpiration Rate ◽  
White Clover ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Effect Of Temperature ◽  
Climate Conditions ◽  
Growth Environment ◽  
Temperature Regimes ◽  
C3 Species

Rates of water use [g H2O (g dry wt leaf)-1 h-1] of young plants of maize, paspalum, perennial ryegrass, Westerwolds ryegrass, peas, white clover and lucerne were measured during the day under controlled climate conditions with ample water available to the plant. Plants were grown and observations made with day/night temperatures of 32.5/27.5°C, 27.5/22.5°, 22.5/17.5°, and 17.5/12.5°C with a day/night vapour pressure deficit (VPD) of the air of 10/2mbar. Water use measurements were also made at 27.5/22.5° and 17.5/12.5°C under day/night VPD regimes of 5/2 and 15/2 mbar. Irradiance during the 12-h day was 170 W m-2 (400-700 nm). Further water use determinations were made at the four temperature regimes under 10/2 mbar VPD and an irradiance of 60 W m-2 (400-700 nm). For a given species, transpiration rates increased with temperature at constant VPD under both irradiance environments, by factors ranging from 1.4 to 2.3. Transpiration rates of maize and paspalum (C4) were lower at a given temperature than were the rates of the C3 species, while lucerne and clover had the highest rates. Water use by lucerne was 2.5 to 3.5 times that of maize. Transpiration rates of maize and paspalum were lower under 60 W m-2 than under 170 W m-2 but irradiance had little effect on transpiration rate of the C3 species. Though transpiration rate generally increased with increasing VPD, the difference in rates between plants at 5 mbar and 10 mbar VPD was much greater than between 10 mbar and 15 mbar. The physiological adaption of different species to their growth environment is discussed, and the implications of the results with reference to water loss by young, single-spaced plants in the field is outlined.

Correlation between carbon isotope discrimination and transpiration efficiency in lines of the C4 species Sorghum bicolor in the glasshouse and the field

1998 ◽  
Vol 25 (1) ◽  
pp. 111 ◽  
Author(s):  
S. Henderson ◽  
S. von Caemmerer ◽  
G.D. Farquhar ◽  
L. Wade ◽  
G. Hammer
Keyword(s):  
Sorghum Bicolor ◽  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Negative Slope ◽  
Environment Interaction ◽  
Transpiration Efficiency ◽  
Isotope Discrimination ◽  
C4 Species ◽  
C3 Species ◽  
The Mean

Transpiration efficiency, W, the ratio of plant carbon produced to water transpired and carbon isotope discrimination of leaf dry matter, Δd, were measured together on 30 lines of the C4 species, Sorghum bicolor, in the glasshouse and on eight lines grown in the field. In the glasshouse, the mean W observed was 4.9 mmol C mol-1 H2O and the range was 0.8 mmol C mol -1 H2O. The mean Δd was 3.0 and the observed range was 0.4‰. In the field, the mean W was lower at 2.8 mmol C mol-1 H2O and the mean Δd was 4.6‰. Significant positive correlations between W and Δd were observed for plants grown in the glasshouse and in the field. The observed correlations were consistent with theory, opposite to those for C3 species, and showed that variation in Δd was an integrated measure of long-term variation in the ratio of intercellular to ambient CO2 partial pressure, pi/pa. Detailed gas exchange measurements of carbon isotope discrimination during CO2 uptake, ΔA, and pi/pa were made on leaves of eight S. bicolorlines. The observed relationship between ΔA and pi/pa was linear with a negative slope of 3.7‰ in ΔA for a unit change in pi/pa. The slope of this linear relationship between ΔA and pi/pa in C4 species is dependent on the leakiness of the CO2 concentrating mechanism of the C4 pathway. We estimated the leakiness (defined as the fraction of CO2 released in the bundle sheath by C4 acid decarboxylations, which is lost by leakage) to be 0.2. We conclude that, although variation in Δd observed in the 30 lines of S. bicolor is smaller than that commonly observed in C3 species, it also reflects variation in transpiration efficiency, W. Among the eight lines examined in detail and in the environments used, there was considerable genotype × environment interaction.

Influence of Solar Radiation and Vapour Pressure Deficit on Transpiration Efficiency of Rainfed Sorghum

1993 ◽  
Vol 171 (5) ◽  
pp. 336-342 ◽  
Author(s):  
V. Bala Subramanian ◽  
S. Venkateswarlu ◽  
M. Maheswari ◽  
M. Narayana Reddy
Keyword(s):  
Solar Radiation ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Transpiration Efficiency

scholarly journals A record of vapour pressure deficit preserved in wood and soil across biomes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Adrian Broz ◽  
Gregory J. Retallack ◽  
Toby M. Maxwell ◽  
Lucas C. R. Silva
Keyword(s):  
Vapour Pressure ◽  
Atmospheric Carbon Dioxide ◽  
Plant Stress ◽  
Vapour Pressure Deficit ◽  
Climatic Conditions ◽  
Published Data ◽  
Pedogenic Carbonate ◽  
The Past ◽  
Important Measurement ◽  
Global Carbon

AbstractThe drying power of air, or vapour pressure deficit (VPD), is an important measurement of potential plant stress and productivity. Estimates of VPD values of the past are integral for understanding the link between rising modern atmospheric carbon dioxide (pCO2) and global water balance. A geological record of VPD is needed for paleoclimate studies of past greenhouse spikes which attempt to constrain future climate, but at present there are few quantitative atmospheric moisture proxies that can be applied to fossil material. Here we show that VPD leaves a permanent record in the slope (S) of least-squares regressions between stable isotope ratios of carbon and oxygen (13C and 18O) found in cellulose and pedogenic carbonate. Using previously published data collected across four continents we show that S can be used to reconstruct VPD within and across biomes. As one application, we used S to estimate VPD of 0.46 kPa ± 0.26 kPa for cellulose preserved tens of millions of years ago—in the Eocene (45 Ma) Metasequoia from Axel Heiberg Island, Canada—and 0.82 kPa ± 0.52 kPa—in the Oligocene (26 Ma) for pedogenic carbonate from Oregon, USA—both of which are consistent with existing records at those locations. Finally, we discuss mechanisms that contribute to the positive correlation observed between VPD and S, which could help reconstruct past climatic conditions and constrain future alterations of global carbon and water cycles resulting from modern climate change.

High vapour pressure deficit and low soil water availability enhance shoot growth responses of a C4 grass (Panicum coloratum cv. Bambatsi) to CO2 enrichment

1998 ◽  
Vol 25 (3) ◽  
pp. 287 ◽  
Author(s):  
Saman P. Seneweera ◽  
Oula Ghannoum ◽  
Jann Conroy
Keyword(s):  
Soil Water ◽  
Elevated Co2 ◽  
Vapour Pressure ◽  
Shoot Growth ◽  
Vapour Pressure Deficit ◽  
C4 Grasses ◽  
Growth Responses ◽  
High Co2 ◽  
C4 Grass ◽  
Shoot Mass

The hypothesis that shoot growth responses of C4 grasses to elevated CO2 are dependent on shoot water relations was tested using a C4 grass, Panicum coloratum (NAD-ME subtype). Plants were grown for 35 days at CO2 concentrations of 350 or 1000 µL CO2 L-1. Shoot water relations were altered by growing plants in soil which was brought daily to 65, 80 or 100% field capacity (FC) and by maintaining the vapour pressure deficit (VPD) at 0.9 or 2.1 kPa. At 350 µL CO2 L-1, high VPD and lower soil water content depressed shoot dry mass, which declined in parallel at each VPD with decreasing soil water content. The growth depression at high VPD was associated with increased shoot transpiration, whereas at low soil water, leaf water potential was reduced. Elevated CO2 ameliorated the impact of both stresses by decreasing transpiration rates and raising leaf water potential. Consequently, high CO2 approximately doubled shoot mass and leaf length at a VPD of 2.1 kPa and soil water contents of 65 and 80% FC but had no effect on unstressed plants. Water use efficiency was enhanced by elevated CO2 under conditions of stress but this was primarily due to increases in shoot mass. High CO2 had a greater effect on leaf growth parameters than on stem mass. Elevated CO2 increased specific leaf area and leaf area ratio, the latter at high VPD only. We conclude that high CO2 increases shoot growth of C4 grasses by ameliorating the effects of stress induced by either high VPD or low soil moisture. Since these factors limit growth of field-grown C4 grasses, it is likely that their biomass will be enhanced by rising atmospheric CO2 concentrations.

scholarly journals A psychrometric model to assess the biological decay of the SARS-CoV-2 virus in aerosols

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11024
Author(s):  
Clive B. Beggs ◽  
Eldad J. Avital
Keyword(s):  
Air Temperature ◽  
Vapour Pressure ◽  
Half Life ◽  
Analytical Study ◽  
Decay Constant ◽  
Meteorological Data ◽  
Environmental Parameters ◽  
Published Data ◽  
Reasonable Accuracy ◽  
The Impact

There is increasing evidence that the 2020 COVID-19 pandemic has been influenced by variations in air temperature and humidity. However, the impact that these environmental parameters have on survival of the SARS-CoV-2 virus has not been fully characterised. Therefore, an analytical study was undertaken using published data to develop a psychrometric model to assess the biological decay rate of the virus in aerosols. This revealed that it is possible to describe with reasonable accuracy (R2 = 0.718, p < 0.001) the biological decay constant for the SARS-CoV-2 virus using a regression model with enthalpy, vapour pressure and specific volume as predictors. Applying this to historical meteorological data from London, Paris and Milan over the pandemic period, produced results which indicate that the average half-life of the virus in aerosols outdoors was in the region 13–22 times longer in March 2020, when the outbreak was accelerating, than it was in August 2020 when epidemic in Europe was at its nadir. However, indoors, this variation is likely to be much less. As such, this suggests that changes in virus survivability due the variations in the psychrometric qualities of the air might influence the transmission of SARS-CoV-2.

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