Electrical resistance measurements of water potential in avocado and white spruce

1978 ◽  
Vol 8 (1) ◽  
pp. 73-80 ◽  
Author(s):  
M. A. Dixon ◽  
R. G. Thompson ◽  
D. S. Fensom
Keyword(s):  
Water Potential ◽  
Linear Correlation ◽  
Electrical Resistance ◽  
Measurement Techniques ◽  
White Spruce ◽  
Nondestructive Method ◽  
Fixed Position ◽  
Thermocouple Psychrometer ◽  
Daily Cycles ◽  
Pressure Bomb

Simultaneous measurements of electrical resistance (or impedance (Z)) and water potential have been made on avocado Perseaamericana Mill. in the laboratory and on white spruce Piceaglauca (Moench) Voss in the field.A significant correlation was found between electrical impedance (corrected to standard temperature of 20 °C) and water potential of nearby leaves as measured by either pressure bomb or thermocouple psychrometer. When the resistance measurements were expressed as a percent of the measured maximum resistance reading the correlation with water potential was very nearly linear (correlation coefficient: Perseaamericana Mill., 0.98; Piceaglauca (Moench) Voss, 0.94). This relationship also seems to hold in Helianthusannuus L.The application of electrical resistance measurement techniques to these two plant systems has been shown to be a simple, nondestructive method of monitoring the water potential of such systems. The linear correlation between water potential and electrical resistance held whether the technique was applied on a tree at a fixed position through daily cycles, at different positions vertically up a tree, or under various degrees of hydration in a pressure bomb.

Relation between air water potential and cambial electrical resistance of balsam fir and white spruce after budbreak

1987 ◽  
Vol 17 (2) ◽  
pp. 105-108 ◽  
Author(s):  
Robert R. Gagnon ◽  
Eric Bauce ◽  
Marius Pineau
Keyword(s):  
Relative Humidity ◽  
Water Potential ◽  
Correlation Coefficient ◽  
Electrical Resistance ◽  
White Spruce ◽  
The Other ◽  
Balsam Fir ◽  
Simultaneous Measurements ◽  
Electrical Resistance Measurements ◽  
Made In

Cambial electrical resistance in 10 balsam fir (Abiesbalsamea (L.) Mill.) and 10 white spruce (Piceaglauca (Moench) Voss) trees in Québec was measured 42 times during July and August 1985. Simultaneous measurements of relative humidity and temperature were also taken so that water potential in air (ψa) could be determined. In both species, cambial electrical resistance, corrected to a constant temperature of 15 °C (CERCOR), was negatively correlated with ψa. On the other hand, 10 measurements on 14 balsam fir trees that had been severely defoliated by the spruce budworm (Choristoneurafumiferana (Clem.)) in 1983 and 1984, and 12 measurements on 14 protected trees showed that the correlation was stronger for sprayed trees than for those that had been defoliated. We propose that the correlation coefficient between cercor and ψa may be a useful index of tree vigor. However, in situations where plots can be visited only once during the season, cambial electrical resistance measurements should be made in the morning when the relative humidity is high.

Corrigenda - Measurement of the total water potential of aqueous solutions of polyethylene glycol - A comparison between osmometer, thermocouple psychrometer and equilibrated soil cores

Soil Research ◽  
1993 ◽  
Vol 31 (1) ◽  
pp. 1
Author(s):  
IM Wood ◽  
IK Dart ◽  
HB So
Keyword(s):  
Polyethylene Glycol ◽  
Water Potential ◽  
Close Correlation ◽  
Ease Of Use ◽  
Effect Of Temperature ◽  
Soil Cores ◽  
Total Water ◽  
Matric Potential ◽  
Thermocouple Psychrometer ◽  
Water Potentials

This study examined two polyethylene glycol (PEG) polymers (PEG 6000 and PEG 10000) and compared measurements of water potential obtained with a thermocouple osmometer and thermocouple psychrometers at three temperatures (15, 25 and 35�C) and five osmdalities (50, 100, 200, 300 and 400 g/1000 g water). These were then compared with estimates of matric potential of three soils brought to equilibrium with PEG solutions of the same osmolalities. At the same osmolality and temperature the two PEG polymers gave essentially the same water potential. There was a significant effect of temperature on water potential which corresponded closely with changes in specific gravity of the PEG solution. There was a close correlation between the measurements of water potential of the PEG solutions obtained with the osmometer and the psychrometers (R = 0.99). However, the psychrometer gave increasingly lower values than the osmometer as water potential decreased. The differences in the measurements between the two methods are thought to be the result of design and calibration differences. The ease of use of the osmometer is such that it is recommended for routine use. The water potentials of the soil cores brought to equilibrium with the PEG 10 000 solution were linearly related to the water potentials of the PEG solutions estimated from both the osmometer and psychrometers (R2 = 0.84). However, there were clear deviations from a 1:l relationship. It was concluded that the results from the soil cores could not be used to determine which of the two instruments gave the more accurate measurement of water potential of PEG solutions.

Viewpoint: Consideration of apoplastic water in plant organs: a reminder

2005 ◽  
Vol 32 (6) ◽  
pp. 561 ◽  
Author(s):  
Ian F. Wardlaw
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Solute Concentration ◽  
Pressure Chamber ◽  
Dilution Method ◽  
Water Fraction ◽  
Thermocouple Psychrometer ◽  
Relative Water ◽  
Cell Turgor ◽  
The Difference

The importance of apoplastic water was confirmed for the leaves of a range of species by a comparison of tissue solute concentrations determined by the extrapolation of water potential isotherms to 100% relative water content (symplastic solute concentration at full turgor) and concentrations derived more directly from frozen / thawed tissue, where there is dilution of the symplastic water fraction by the apoplastic water fraction. A thermocouple psychrometer was used for both water potential and solute potential measurements. Parallel measurements of the apoplastic water content, estimated by the extrapolation of pressure–volume curves to zero (1 / water potential) with a pressure chamber and measurements based on the dilution method, with a thermocouple psychrometer, showed that the two methods gave similar results. This lends support to the conclusion that water is lost from the symplast and not from the apoplast of leaves when these are subjected to increasing pressure in a pressure chamber. However, where tissues or organs are air-dried the loss of water occurs from both the symplast and apoplast. The overall data support the conclusion that the apoplastic water should not be ignored in plant water relations studies, particularly when estimating cell turgor indirectly from the difference between water potential and cell solute concentration based on the analysis of frozen / thawed tissue.

Water relations parameters on single leaves obtained in a pressure bomb and some ecological interpretations

1975 ◽  
Vol 53 (13) ◽  
pp. 1342-1346 ◽  
Author(s):  
Y. N. S. Cheung ◽  
M. T. Tyree ◽  
J. Dainty
Keyword(s):  
Cell Wall ◽  
Water Potential ◽  
Osmotic Pressure ◽  
Water Loss ◽  
Ecological Significance ◽  
Cell Wall Elasticity ◽  
Use Of Data ◽  
Adaptive Value ◽  
Pressure Bomb ◽  
Volume Relation

The physical implications of the various parameters obtained from a pressure-bomb study are explored and related to their possible ecological significance. Our analysis suggests that the original bulk osmotic pressure, the bulk osmotic pressure at incipient plasmolysis, and cell wall elasticity are closely associated with the extent to which a leaf can osmoregulate or conserve water within a certain range of water potential change in the environment and might therefore have certain adaptive value. The pressure–volume relation could be applied to predict changes in leaf water potential at various degrees of water loss in the field. The values of these various parameters were obtained from a pressure-bomb study on single leaves from a wide variety of species. The use of data from single leaves as compared with whole shoots is discussed.

The ecophysiological and growth responses of Aleppo pine (Pinushalepensis) to controlled heating applied to the base of the trunk

1996 ◽  
Vol 26 (8) ◽  
pp. 1366-1374 ◽  
Author(s):  
Michel Ducrey ◽  
Fabrice Duhoux ◽  
Roland Huc ◽  
Eric Rigolot
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Flux Density ◽  
Electrical Resistance ◽  
Aleppo Pine ◽  
Sap Flux ◽  
Growth Responses ◽  
Tree Physiology ◽  
Sap Flux Density ◽  
Trunk Diameter

Controlled, localized heating was applied to the trunks of young Aleppo pines (Pinushalepensis Mill.) during the winter. Three levels of burning were applied to the circumference of the trunks (zero, partial, or total), and the effects on tree physiology and growth were monitored during the 7 months following heating. Effects of the heat treatment on tree physiology were assessed by measuring predawn water potential, sap flux density, microvariations in trunk diameter, electrical resistance of the cambium, and gas exchanges from the needles (photosynthesis and stomatal conductance). Morphological response measurements included height and radial growth of the trees and morphological characteristics of the needles. The amount of chlorotic foliage was also measured. Aleppo pine was highly resistant to trunk injury, surviving when 80% of the trunk circumference was destroyed by fire. The behaviour of partially burnt pines was not significantly different from that of controls, for all variables studied. Trees whose trunks were totally burnt died from 1 to 5 months after treatment. Sap flux density of totally burnt trees was already significantly lower than that of other trees in the first week following the treatment. A decrease in net photosynthesis and stomatal conductance in the still surviving totally burnt trees was also recorded during the first measurements made in July. Treatment differences in predawn water potential, microvariations in trunk diameter, and electrical resistance of the cambium only appeared a few days before death of the totally burnt trees.

MEASUREMENT OF INTERNAL WATER STRESS IN WHEAT PLANTS

1968 ◽  
Vol 48 (1) ◽  
pp. 89-95 ◽  
Author(s):  
S. J. Yang ◽  
E. de Jong
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Great Promise ◽  
Plant Water ◽  
Thermocouple Psychrometer ◽  
Water Potentials ◽  
Plant Water Potential ◽  
Highly Correlated ◽  
The Many ◽  
Non Destructive

The thermocouple psychrometer technique was used to measure plant water stresses of wheat. The usefulness of this technique is limited due to the many precautions that must be taken. The β-ray absorption and relative turgidity were highly correlated (P = 0.01) with plant water potential, but the correlation changed with age. Relative turgidity gave a slightly better estimate of leaf water potential than β-ray absorption (r2 of 0.88 to 0.99 and 0.81 to 0.96 respectively). The β-ray technique has great promise because of its non-destructive nature.At soil water potentials higher than −10 atm, plant water potentials remained nearly constant, indicating that soil water was equally available. Temporary wilting occurred at soil water potentials of −35 to −40 atm.

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