Uptake of gaseous sulphur dioxide by the lichen Cladina rangiferina

1985 ◽  
Vol 63 (4) ◽  
pp. 797-805 ◽  
Author(s):  
B. Grace ◽  
T. J. Gillespie ◽  
K. J. Puckett
Keyword(s):  
Sulphur Dioxide ◽  
Analog Model ◽  
Potassium Efflux ◽  
Flow Rates ◽  
Lichen Sample ◽  
Potassium Release ◽  
Layer Resistance ◽  
Release Curve ◽  
Boundary Layer Resistance ◽  
Cladina Rangiferina

Samples of the lichen Cladina rangiferina were exposed to various concentrations of sulphur dioxide in a fumigation cuvette system for time periods ranging from 1 to 18 h. The cuvette system provided airstreams which, within the limits of measurement, had identical flow rates, temperatures, and relative humidities. Sulphur dioxide was added to one airstream as a treatment, while the other remained free of sulphur dioxide for control purposes. In some experiments, wind speed could be varied from 8 to 250 cm∙s−1 in a small wind tunnel placed in the fumigation cuvette. The system allowed for the calculation of sulphur dioxide uptake by the lichen sample. Potassium release was shown to increase with an increasing uptake of sulphur dioxide (time-integrated flux), but was not uniquely related to sulphur dioxide concentration alone. Extrapolation of a linear transformation of the potassium release curve to zero potassium efflux resulted in a threshold uptake value of 240 μg SO2∙g lichen−1. Internal lichen resistance and lichen boundary-layer resistance were experimentally determined for later use in an electrical analog model for the calculation of sulphur dioxide uptake.

Sulphur dioxide threshold concentration values for Cladina rangiferina in the Mackenzie Valley, N.W.T.

1985 ◽  
Vol 63 (4) ◽  
pp. 806-812 ◽  
Author(s):  
B. Grace ◽  
T. J. Gillespie ◽  
K. J. Puckett
Keyword(s):  
Water Content ◽  
Sulphur Dioxide ◽  
Threshold Concentration ◽  
Initial Value ◽  
Near Surface ◽  
Wind Speeds ◽  
Air Temperatures ◽  
Layer Resistance ◽  
Boundary Layer Resistance ◽  
Cladina Rangiferina

A simulation model for the prediction of threshold concentration values of gaseous sulphur dioxide for damage to Cladina rangiferina over a 24-h period is presented. The model requires inputs of near surface relative humidities and air temperatures as well as lichen surface temperatures, and nearby airport wind speeds. An initial value of percent lichen water content must also be specified. Studies of lichen water relationships provided expressions utilized in the model for the calculation of the percent lichen water content. The model was applied to four microclimatically different days for an open lichen–spruce woodland near Inuvik, N.W.T. Boundary-layer resistance was found to be not as important as internal thallus resistance to sulphur dioxide uptake. For all days examined, threshold gaseous concentration values of sulphur dioxide for a 24-h period ranged from 20 to 30 μg∙m−3.

Genotypic Variation in Carbon Isotope Discrimination and Transpiration Efficiency in Wheat. Leaf Gas Exchange and Whole Plant Studies

1990 ◽  
Vol 17 (1) ◽  
pp. 9 ◽  
Author(s):  
AG Condon ◽  
GD Farquhar ◽  
RA Richards
Keyword(s):  
Boundary Layer ◽  
Water Loss ◽  
Dry Matter ◽  
Carbon Isotope Discrimination ◽  
Genotypic Variation ◽  
Transpiration Efficiency ◽  
Layer Resistance ◽  
Boundary Layer Resistance ◽  
The Relationship ◽  
Canopy Water

The relationship between carbon isotope discrimination, Δ, measured in plant dry matter and the ratio of intercellular to atmospheric partial pressures of CO2, pi/pa, in leaves was examined in two glasshouse experiments using 14 wheat genotypes selected on the basis of variation in Δ of dry matter. Genotypic variation in Δ was similar in both experiments, with an average range of 1.8 x 10-3. Variation in pi/pa was significant but the range in pi/pa was relatively small, averaging 0.075. In both experiments, Δ measured in dry matter and pi/pa measured in flag leaves were positively correlated. Variation among genotypes in pi/pa was attributed, approximately equally, to variation in leaf conductance and in photosynthetic capacity. The relationship between plant transpiration efficiency, W* (the amount of above-ground dry matter produced per unit water transpired) and � was also examined. There was a negative correlation between W * and Δ; under well watered conditions and under gradually increasing terminal water stress. The relationship between W* of stressed plants and Δ measured in well watered plants was also negative. These results indicate that genotypic variation in Δ measured in dry matter should provide a reasonable measure of genotypic variation in long-term mean leaf pi/pa in wheat. Further, selection for improved plant transpiration efficiency in wheat under both well watered and terminally water- stressed conditions should be possible based on Δ measured in well watered plants. The extent to which such selection will be effective in improving transpiration efficiency at the field canopy level may depend on the influence of boundary layer resistance on transpirationsal water loss. Under well watered conditions and at full canopy closure, the influence of boundary layer resistance on canopy water loss may be relatively large and stomatal control of water loss may be limited. Under water stress, stomatal control of canopy water loss will be greater.

Relationship of hepatic potassium efflux to phosphorylase activation induced by glucagon

1964 ◽  
Vol 206 (4) ◽  
pp. 738-742 ◽  
Author(s):  
Anthony G. Finder ◽  
Theodore Boyme ◽  
William C. Shoemaker
Keyword(s):  
Time Course ◽  
Potassium Concentration ◽  
Plasma Potassium ◽  
Potassium Efflux ◽  
Blood Samples ◽  
Potassium Release ◽  
Anesthetized Dogs ◽  
Relationship Of ◽  
Primary Action ◽  
Made In

Hepatic biopsies were obtained from intact, anesthetized dogs before and at 6- to 15-sec intervals after intravenous administration of glucagon. Simultaneously, blood samples were taken from the hepatic vein at 3-sec intervals and the plasma potassium concentration measured. The time course of phosphorylase activation in hepatic biopsies was observed and compared with the time course of potassium release into the hepatic efflux. Measurements were made in normothermic (38 C) animals and in animals subjected to hypothermia (21–25 C). Maximum phosphorylase activation was reached in an average of 79 sec in normothermia and in 144 sec in hypothermia. Maximum hepatic venous potassium concentrations were observed in an average of 41 sec in normothermia and 108 sec in hypothermia. The increased hepatic potassium release which preceded the activation of phosphorylase suggested that electrolyte shifts may be involved in the primary action of glucagon upon hepatic glycogenolytic systems.

Sign in / Sign up

Export Citation Format

Share Document