Water relations and osmotic pressure in Biomphalaria pfeifferi (Krauss), Biomphalaria glabrata (Say) and Helisoma trivolvis (Say) (Gastropoda : Planorbidae) in response to cationic alterations of the medium

Hydrobiologia ◽  
1980 ◽  
Vol 68 (2) ◽  
pp. 139-144 ◽  
Author(s):  
W. K. Nduku ◽  
A. D. Harrison
Keyword(s):  
Osmotic Pressure ◽  
Water Relations ◽  
Biomphalaria Glabrata ◽  
Biomphalaria Pfeifferi ◽  
Helisoma Trivolvis

WATER RELATIONS OF ASEXUAL SPORES OF SPHAEROTHECA MACULARIS (WALLR. EX. FR.) COOKE AND ERYSIPHE POLYGONI DC.

1965 ◽  
Vol 11 (3) ◽  
pp. 531-538 ◽  
Author(s):  
J. S. Jhooty ◽  
W. E. McKeen
Keyword(s):  
Relative Humidity ◽  
Water Content ◽  
Osmotic Pressure ◽  
Water Relations ◽  
Erysiphe Polygoni ◽  
Significant Change ◽  
Sphaerotheca Macularis ◽  
Glass Surfaces

The conidia of Sphaerotheca macularis germinate best at a relative humidity (R.H.) of 99 and 100% on glass surfaces, and germination does not occur if the R.H. is below 93%. Conidia of Erysiphe polygoni DC. germinate at 3% R.H. The water content of conidia of S. macularis and E. polygoni is 53 and 69% respectively. The osmotic pressure of S. macularis conidia is about 18 atm and their density varies from 1.10 to 1.11 g/ml. There is no significant change in the diameter and length of the conidia during germination.

Turgor-Volume Regulation and Cellular Water Relations of Nicotiana tabacum Roots Grown in High Salinities

1989 ◽  
Vol 16 (6) ◽  
pp. 517 ◽  
Author(s):  
SD Tyerman ◽  
P Oats ◽  
J Gibbs ◽  
M Dracup ◽  
H Greenway
Keyword(s):  
Nicotiana Tabacum ◽  
Osmotic Pressure ◽  
Water Relations ◽  
Volume Regulation ◽  
Turgor Pressure ◽  
Root Hairs ◽  
Solution Culture ◽  
Pressure Probe ◽  
Initial Increase ◽  
Solute Permeability

Nicotiana tabacum plants were grown in solution culture with salinity treatments of 1, 100 and 200 mol m-3 [NaCl], in Hoagland solution. After several weeks, solute concentrations and osmotic pressure of cell sap from the roots were measured. Increases in cellular [Na+] and [Cl-] and a smaller reduction in [K+] accounted for the difference in sap osmotic pressure between the 200 mol m-3 and 1 mol m-3 treatments. Turgor pressure (P) of fully expanded cortex cells measured with the pressure probe were 0.48 MPa in 1 mol m-3, 0.24 MPa in 100 mol m-3, 0.20 MPa in 200 mol m-3, and these values agreed with those calculated by difference between internal and external osmotic pressure. Low values of volumetric elastic modulus (ε), ranging from 1.2 MPa to 3.0 MPa at P = 0.42 MPa were obtained, which accounted for long equilibration times to changes in water potential. There was no effect of high salinities on ε after accounting for the fact that ε was a function of P and neither was there an effect on hydraulic conductivity (Lp), which ranged between 1.9 × 10-8 and 24.1 × 10-8 m s-1 Mpa-1. At 200 mol m-3 [NaCl]o, and to a lesser degree at 100 mol m-3 [NaCl]o, root hairs became deformed to resemble spherical bladders (mean diameter = 88 �m) which displayed similar P and water relations to other epidermal cells and cortex cells. In other experiments the response to a sudden reduction in [NaCl], from 200 to 1 mol m-3 was studied. P of cortex cells first rapidly increased from about 0.15 MPa to 0.53 MPa and then slowly declined with a half time of about 35 min to a new steady state of 0.3 MPa. This level was maintained in intact roots for at least 48 h. The rate of the initial increase in P is limited by water flow into the cells while the slow decline is limited by solute efflux from the cells with water following osmotically. The efflux was mainly in response to reduced external osmotic pressure rather than [NaCl]o. Efflux of Na+, K+ and Cl- accounted for the decrease in internal osmotic pressure but it is possible that the membrane also became more permeable to sugars. With the exception of bladder hairs, the overall integrity of the cell membrane was maintained since Lp did not increase and P declined smoothly to the new level with no evidence of rupture and resealing of the membrane. It is argued that the loss of solutes after the step down in external osmotic pressure consists of turgor or volume regulation in which solute permeability increases steeply as turgor or volume goes above a threshold.

A comparison of systematic errors between the Richards and Hammel methods of measuring tissue – water relations parameters

1978 ◽  
Vol 56 (17) ◽  
pp. 2153-2161 ◽  
Author(s):  
M. T. Tyree ◽  
M. E. MacGregor ◽  
A. Petrov ◽  
M. I. Upenieks
Keyword(s):  
Cell Wall ◽  
Osmotic Pressure ◽  
Water Relations ◽  
Turgor Pressure ◽  
Systematic Errors ◽  
Tissue Water ◽  
Cell Wall Elasticity ◽  
Pressure Bomb ◽  
Bomb Method

The pressure bomb is being used to a much greater extent to measure some tissue – water relations parameters such as osmotic pressure, turgor pressure, and cell wall elasticity. Recently, Richards has developed a faster pressure-bomb method of obtaining these and other parameters than the method used by Hammel and modified by us. In this paper, we compare the two methods and conclude that Richards’ method should not be used when accuracy is deemed important. The Richards method usually overestimates osmotic pressure by 0.2 MPa (= 2 bars) and sometimes by 0.8 MPa (= 8 bars).

Differences in Water Relations Parameters for the Chlorenchyma and the Parenchyma of Opuntia ficus-indica Under Wet Versus Dry Conditions

1991 ◽  
Vol 18 (2) ◽  
pp. 95 ◽  
Author(s):  
G Goldstein ◽  
JL Andrade ◽  
PS Nobel
Keyword(s):  
Osmotic Pressure ◽  
Water Relations ◽  
Water Storage ◽  
Dry Weight ◽  
High Water ◽  
Opuntia Ficus Indica ◽  
Large Numbers ◽  
Parenchyma Cells ◽  
Storage Parenchyma ◽  
Dry Conditions

Water relations of the photosynthetic tissue (chlorenchyma) and of the water-storage parenchyma were studied for well watered and droughted Opuntia ficus-indica, a crassulacean acid metabolism plant cultivated worldwide for its fruits and cladodes. For well watered plants, die1 changes in osmotic pressure were evident in the chlorenchyma. Droughting the plants for 4 months resulted in a massive loss of water from the cladodes, particularly from the water-storage parenchyma, which could lose up to 82% of the water present at full turgor without irreversible tissue damage. Pressure-volume curves indicated a decrease in the osmotic pressure at full turgor of about 0.1 MPa for the water-storage parenchyma cells during drought; such a decrease of osmotically active solutes was consistent with the appearance of large numbers of starch grains. The bulk modulus of elasticity was 0.36 MPa for the water-storage parenchyma cells and 2.5-fold higher for the chlorenchyma cells, which were smaller with thicker cell walls than the former cells. Mucilage, a polysaccharide occurring extracellularly, constituted about 14% of the cladode dry weight; it could hold more than 30% of the total water content of the water-storage parenchyma. Polymerisation of sugars, large elastic cells in the water-storage parenchyma and mucilage with its high water-holding capacity helped maintain a positive turgor in the photosynthetic tissue, even after 4 months of drought.

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.

Sign in / Sign up

Export Citation Format

Share Document