Some notes concerning the measurement of water potentials of leaf tissue with specific reference to Tsuga canadensis and Picea abies

1975 ◽  
Vol 53 (8) ◽  
pp. 784-788 ◽  
Author(s):  
A. J. B. Talbot ◽  
M. T. Tyree ◽  
J. Dainty
Keyword(s):  
Picea Abies ◽  
Water Potential ◽  
Leaf Tissue ◽  
Tsuga Canadensis ◽  
Specific Reference ◽  
Wound Area ◽  
Tissue Volume ◽  
Water Potentials ◽  
Detached Leaves ◽  
Pressure Bomb

Psychrometric measurements of the water potentials of leaves of Tsuga canadensis (L.) Carr. and Picea abies L. are compared with the water potentials of the shoots from which they came as measured by the pressure-bomb technique. Agreement between the two techniques is good when whole leaves are used in the psychrometer chamber, but deviations occur when bisected leaves are used in which the wound area to tissue volume is very small (1 to 2 cm2/cm3 of leaf tissue). Psychrometer determinations of water potential of these detached leaves are much more sensitive to cutting than in other species, e.g., sunflower and pepper (2). A more reliable means of measuring turgor and osmotic pressures in leaves is proposed.

The water relations of hemlock (Tsuga canadensis). IV. The dependence of the balance pressure on temperature as measured by the pressure-bomb technique

1974 ◽  
Vol 52 (5) ◽  
pp. 973-978 ◽  
Author(s):  
M. T. Tyree ◽  
J. Dainty ◽  
D. M. Hunter
Keyword(s):  
Temperature Dependence ◽  
Water Potential ◽  
Osmotic Pressure ◽  
Water Relations ◽  
Turgor Pressure ◽  
Tsuga Canadensis ◽  
Constant Volume ◽  
Pressure Bomb

The temperature dependence of the balance pressure is reported for shoots of Tsuga canadensis at constant volume, i.e., when water is neither added to nor removed from the shoot. Since the balance pressure closely equals minus the water potential, the temperature dependence of the balance pressure should reflect the combined temperature dependence of the osmotic and turgor pressures. Both the osmotic and the turgor pressures decline with decreasing temperature; frequently the turgor pressure declines 2 to 3 times more rapidly than the osmotic pressure, causing the balance pressure to rise with decreasing temperature. Only when the turgor pressure is zero (only beyond incipient plasmolysis) does the temperature dependence of the balance pressure closely follow the temperature dependence of the osmotic pressure; this occurs when the balance pressure equals or exceeds 24 bars.

Influence of temperature and water potential on growth of Botrytis allii

1984 ◽  
Vol 62 (8) ◽  
pp. 1567-1570 ◽  
Author(s):  
S. C. Alderman ◽  
M. L. Lacy
Keyword(s):  
Water Potential ◽  
Growth Rates ◽  
Radial Growth ◽  
Leaf Tissue ◽  
Dead Leaf ◽  
Salt Solutions ◽  
Influence Of Temperature ◽  
Water Potentials ◽  
Botrytis Allii ◽  
Peg 8000

Water potentials for optimum growth varied with temperature and with the material used to alter water potential. On prune extract – lactose – yeast extract (PLY) agar adjusted with KCl, sucrose, NaCl, or polyethylene glycol (PEG) 8000, growth rates were optimal at 20 or 25 °C and at water potentials of −5 to −10 bars (1 bar = 100 kPa). At 30 °C growth rates were optimal at −35 to −45 bars in the presence of KCl or sucrose and at −10 to −20 bars with NaCl or PEG 8000. Radial growth rates in dried onion leaves, adjusted to various water potentials over salt solutions in sealed chambers, corresponded to those on PLY media adjusted to the same water potentials with KCl or sucrose. Growth was halted at water potentials below −95 to −100 bars in onion leaves or in PLY agar containing KCl or sucrose osmotica, but it was halted at −50 to −60 bars in the presence of NaCl or PEG 8000. Growth of Botrytis allii in onion bulb tissue was optimal at 20 °C. Extent of bulb colonization increased linearly with the logarithm of increasing inoculum concentrations applied to small wounds in bulbs. Survival of B. allii in dead leaf tissue declined rapidly after 3 and 9 days at 37 and 32 °C, respectively.

NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

Photosynthesis Response of Sunlit and Shade Pepper (Capsicum annuum) Leaves at Different Positions in the Canopy Under Two Water Regimes

1994 ◽  
Vol 21 (3) ◽  
pp. 377 ◽  
Author(s):  
A Alvino ◽  
M Centritto ◽  
FD Lorenzi
Keyword(s):  
Water Potential ◽  
Capsicum Annuum ◽  
Leaf Water Potential ◽  
Co2 Exchange ◽  
Leaf Water ◽  
Predawn Leaf Water Potential ◽  
Water Regimes ◽  
Water Potentials ◽  
Sun And Shade ◽  
Shade Leaves

Pepper (Capsicum annuum L.) plants were grown in 1 m2 lysimeters under two different water regimes in order to investigate differences in the spatial arrangements of the leaves and to relate this to daily assimilation rates of leaves of the canopy. The control regime (well-watered (W) treatment) was irrigated whenever the accumulated 'A' pan evaporation reached 4 cm, whereas the water-stressed (S) treatment was watered whenever the predawn leaf water potential fell below -1 MPa. During the growing cycle, equal numbers of sun and shade leaves were chosen from the apical, middle and basal parts of the canopy, corresponding to groups of leaves of increasing age. The CO2 exchange rate (CER) was measured at 0830, 1230 and 1530 hours on 8 days along the crop cycle, on leaves in their natural inclination and orientation. Leaf water potentials were measured on apical leaves before dawn and concurrently with gas exchange measurements. Control plants maintained predawn leaf water potential at -0.3 MPa, but S plants reached values lower than -1.2 MPa. Midday leaf water potentials were about twice as low in the S plants as in the controls. Water stress reduced LA1 during the period of crop growth, and dry matter production at harvest. Stressed apical leaves appeared to reduce stress by changing their inclination. They were paraheliotropic around midday and diaheliotropic at 0830 and 1530 hours. The CER values of the S treatment were significantly lower than those of the W treatment in apical and middle leaves, whereas the CER of basal leaves did not differ in either treatments. In the S treatment, reduction in the CER values of sunlit apical leaves was more evident in the afternoon than at midday or early in the morning, whereas basal leaves were less affected by water than basal stress leaves if sunlit, and negligibly in shaded conditions.

scholarly journals Dehydration of Macromolecules I. Effect of Dehydration-Rehydration on Indoleacetic Acid Oxidase, Ribonuclease, Ribulosediphosphate Carboxylase, and Ketose-1-Phosphate Aldolase

1973 ◽  
Vol 26 (3) ◽  
pp. 591 ◽  
Author(s):  
B Darbyshire ◽  
BT Steer
Keyword(s):  
Water Potential ◽  
Indoleacetic Acid ◽  
Acid Oxidase ◽  
Enzyme Preparations ◽  
Water Potentials ◽  
Membrane Technique ◽  
Indoleacetic Acid Oxidase

A pressure-membrane technique has been developed to physically manipulate the water potential of in vitro enzyme preparations. Enzyme preparations were subjected to a range of water potentials using this technique.

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.

Evaluation of the hydraulic press for measurement of leaf water potentials in cassava

1983 ◽  
Vol 101 (2) ◽  
pp. 407-410 ◽  
Author(s):  
J. A. Palta
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Hydraulic Press ◽  
Pressure Chamber ◽  
Leaf Water ◽  
Moisture Loss ◽  
Total Leaf Area ◽  
Water Potentials ◽  
Wide Range ◽  
Poor Relationship

SUMMARYIn the application of the Scholander pressure chamber technique to cassava water relations studies, the leaf water potential measured on central lobules was initially compared with that measured on entire leaves (including petiole). Measurements made using both a Campbell-Brewster hydraulic press and a pressure chamber of the leaf water potential in six different cassava clones were also compared. Although the central lobules showed a greater sensitivity to moisture loss after sampling than entire leaves, their leaf water potential was in close agreement with those measured on the entire leaves (r3 = 0·96). Therefore, for routine and field estimates in cassava, measurements made on the central lobules may be used to avoid the large reduction in total leaf area. The Campbell-Brewster hydraulic press satisfactorily estimated leaf water potential in M.Col. 1684 clone, which had the longest and narrowest lobules, but in other clones the leaf water potential was overestimated at high leaf potential (> -12·5) and underestimated at low water potentials (< -12·5). Over a wide range of leaf water potentials, a poor relationship between leaf water potentials estimated with hydraulic press and with the pressure chamber was observed for cassava because press estimates are influenced by lobule length and lobule width.

Dehydration tolerance of five bur oak (Quercusmacrocarpa) seed sources from Texas, Nebraska, Minnesota, and New York

1993 ◽  
Vol 23 (3) ◽  
pp. 387-393 ◽  
Author(s):  
Michael R. Kuhns ◽  
Walter W. Stroup ◽  
G. Michael Gebre
Keyword(s):  
New York ◽  
Water Potential ◽  
Electrolyte Leakage ◽  
Dry Period ◽  
Membrane Injury ◽  
North Central ◽  
Dehydration Tolerance ◽  
Seed Sources ◽  
Water Potentials ◽  
Bur Oak

Dehydration tolerance was studied in saplings of five widely distributed sources of Quercusmacrocarpa Michx. growing together in an outdoor plot in Lincoln, Nebraska. Membrane electrolyte leakage, expressed as percent injury, was used as a measure of dehydration tolerance. Leaves were excised from several plants of each source on July 16 after a long dry period and on August 26 after a long moist period. Leaves were allowed to dry for various times in a laboratory, their water potential was measured, and membrane injury was determined. Regressions were calculated for percent injury versus leaf water potential, so sources could be compared at selected water potentials. All sources showed increased leakage at lower water potentials, with most leakage occurring below a water potential of −3 MPa. A source from Texas had the highest leakage, 23% at −6 MPa in August, while a source from a more xeric site in north central Nebraska generally had the lowest leakage. Stress preconditioning appeared to affect leakage, with leakage often significantly lower in July than in August.

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