Effects of repeated stress on turgor pressure and cell elasticity changes in black spruce seedlings

1991 ◽  
Vol 21 (9) ◽  
pp. 1329-1333 ◽  
Author(s):  
T. J. Blake ◽  
E. Bevilacqua ◽  
Janusz J. Zwiazek
Keyword(s):  
Polyethylene Glycol ◽  
Black Spruce ◽  
Turgor Pressure ◽  
Stress Relief ◽  
Tissue Elasticity ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Relative Water ◽  
One Year ◽  
Osmotic Potentials

One-year-old black spruce (Piceamariana (Mill.) B.S.P.) seedlings were preconditioned by exposing them to either one or two dehydration–rehydration cycles by using the osmoticum polyethylene glycol 3350. Preconditioned and unconditioned seedlings were then subjected to a more severe osmotic (water) stress by exposing them to a higher concentration of polyethylene glycol. Effects of repeated dehydration–rehydration cycles on cell-water relations were studied after 3, 7, and 13 days of stress relief using pressure–volume curve analysis. Repeated dehydration–rehydration cycles caused a cumulative increase in turgor potentials at full saturation. In these preconditioned plants there was also a progressive lowering of osmotic potentials and relative water contents at zero turgor, which increased over time with stress relief. The decline in osmotic potentials at zero turgor in osmotically stressed black spruce was associated with increased cell wall relaxation, followed by increased turgor potentials, in preconditioned but not in unconditioned seedlings. Saturated osmotic potentials were not altered by repeated, short-term conditioning stresses, suggesting that tissue elasticity was more important for turgor regulation than osmotic adjustment.

Seasonal changes in leaf water potential components in two almond cultivars

1993 ◽  
Vol 120 (3) ◽  
pp. 347-351 ◽  
Author(s):  
M. C. Ruíz-Sánchez ◽  
M. J. Sánchez-Blanco ◽  
J. Planes ◽  
J. J. Alarcón ◽  
A. Torrecillas
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Leaf Water Potential ◽  
Leaf Water ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Leaf Osmotic Potential ◽  
Relative Water ◽  
Almond Trees ◽  
Amygdalus Communis

SUMMARYAlmond trees (Amygdalus communis L. cvs Garrigues and Ramillete) were grown in the field under non-irrigated conditions in Murcia, Spain. Seasonal variations in leaf water potential components were studied in 1989. Predawn leaf water potential showed high values in both cultivars, due to the absence of soil water stress. Pressure-volume curve analysis indicated that the leaf osmotic potential at full saturation (Ψo(sat)) for cv. Garrigues remained fairly constant throughout the season. Bulk modulus of elasticity (E) showed, in both cultivars, a tendency to decrease as the season progressed. E values were higher in Ramillete than in Garrigues. The relative water content at the turgor loss point (RWCtlp) seemed to be controlled by E values. The larger relative apoplastic water content (RWCa found in Ramillete might have allowed it to retain more water at low leaf water potentials than Garrigues. These facts would support the suggestion that Ramillete is a more drought-resistant cultivar than Garrigues.

Water relations of cassava: water content, water, osmotic and turgor potential relationships

1981 ◽  
Vol 59 (6) ◽  
pp. 956-964 ◽  
Author(s):  
I. F. Ike ◽  
G. W. Thurtell
Keyword(s):  
Water Content ◽  
Turgor Pressure ◽  
Pressure Chamber ◽  
Dew Point ◽  
Time Intervals ◽  
Water Potentials ◽  
Relative Water ◽  
High Starch ◽  
Short Time ◽  
Osmotic Potentials

The water content, water potential, osmotic potential, and turgor pressure relationships of two cultivars of indoor-grown cassava (Manihot esculenta) were examined. The two cultivars (CMC9 and MCOL113) represent low and high starch yielding varieties, respectively.Leaf water potentials were measured insitu with a dew-point hygrometer. A pressure chamber was used to estimate ψL in excised leaves. Relative water content (RWC) of intact leaves was measured with a beta-gauge but was calculated from the pressure chamber data for excised leaves. Osmotic potentials at water contents between 0 and 100% were calculated and the corresponding turgor pressures were obtained by difference.At low soil moisture tension, RWC and ψL dropped to minimum values during the day but recovered considerably at night. Osmotic potentials of turgid leaves were −970 kPa in cv. CMC9 and −1000 kPa in cv. MCOL113. Diurnal variations ψπ were small in both cultivars. However, daily fluctuations in ψP were larger and paralleled changes in ψL. A marked hysteresis was evident in the water content-potential and the water content-turgor pressure data obtained during the drying cycle. However, when water potentials and turgor pressures were changed rapidly by switching the lights off and on at short-time intervals, no hysteresis was observed in the data.

Effects of preconditioning on carbohydrate and amino acid composition of osmotically stressed black spruce (Piceamariana) cuttings

1990 ◽  
Vol 20 (1) ◽  
pp. 108-112 ◽  
Author(s):  
J. J. Zwiazek ◽  
T. J. Blake
Keyword(s):  
Amino Acids ◽  
Polyethylene Glycol ◽  
Amino Acid ◽  
Free Amino Acids ◽  
Free Amino ◽  
Black Spruce ◽  
Solution Culture ◽  
Soluble Carbohydrates ◽  
Carbohydrate Levels ◽  
Osmotic Potentials

The effects of preconditioning on osmotic potentials and the composition of soluble carbohydrates and free amino acids were studied in ramets of black spruce (Piceamariana Mill. B.S.P.). Plants were grown in solution culture and preconditioned by exposure to increasing concentrations of polyethylene glycol, and their osmotic potentials and composition of free amino acids and soluble carbohydrates were determined. Preconditioning increased levels of soluble carbohydrates compared with unconditioned plants. When the preconditioned and unconditioned plants were subjected to a subsequent, more severe osmotic stress with polyethylene glycol, high levels of monosaccharides and certain amino acids were observed in both preconditioned and unconditioned plants. During stress, preconditioned plants had lower (more negative) osmotic potentials and contained slightly higher levels of amino acids, but carbohydrate levels did not significantly differ from unconditioned plants. The increase in free amino acids and carbohydrates was insufficient to explain the drop in osmotic potentials resulting from preconditioning treatment.

Changes in osmotic potential, cell elasticity, and turgor relationships of 2nd-year black spruce container seedlings

1987 ◽  
Vol 17 (5) ◽  
pp. 365-369 ◽  
Author(s):  
S. J. Colombo
Keyword(s):  
Water Potential ◽  
Black Spruce ◽  
Turgor Pressure ◽  
Shoot Elongation ◽  
Growth Potential ◽  
Tree Seedlings ◽  
Tissue Water ◽  
Turgor Loss Point ◽  
Container Seedlings ◽  
Relative Water

Components of tissue water potential and shoot apical activity of black spruce (Piceamariana (Mill.) B.S.P.) container seedlings were evaluated during the 2nd-year cycle of shoot elongation. Water potential components estimated using the pressure–volume technique included osmotic potentials at full turgor (ψπ100) and the turgor loss point (ψπTLP) and their difference (Δψπ), relative water content at the turgor loss point (RWCTLP), total turgor pressure (ψPTOTAL), maximum bulk modulus of elasticity (Σmax), and elasticity near full turgor (ΣFT). All parameters changed in concert with the morphology of shoot elongation; ψπ100, ψπTLP, RWCTLP, and Σ were at minimum values prior to bud swelling, increasing to a maximum during rapid shoot elongation and decreasing slowly following bud initiation and needle primordia development. Δψπ and ψPTOTAL in contrast were at minimums during shoot elongation. The relationship between Σ and ψP varied with shoot phenology. Total turgor pressure over the range of naturally occurring relative water contents is proposed as an indicator of the survival and growth potential of out planted tree seedlings.

Changes of lung surfactant and pressure-volume curve in bleomycin-induced pulmonary fibrosis

1991 ◽  
Vol 70 (3) ◽  
pp. 1300-1308 ◽  
Author(s):  
K. Osanai ◽  
K. Takahashi ◽  
S. Sato ◽  
K. Iwabuchi ◽  
K. Ohtake ◽  
...  
Keyword(s):  
Pulmonary Fibrosis ◽  
Lung Volume ◽  
Lung Surfactant ◽  
Control Level ◽  
Surface Force ◽  
Lung Mechanics ◽  
Tissue Elasticity ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Alveolar Surface

We investigated whether alveolar surface force increased and participated in the lung pressure-volume relationship in bleomycin-induced pulmonary fibrosis in hamsters and, if so, whether lung surfactant was hampered in the lungs. On the air-filled pressure-volume curve, decreases of lung volume from control level were significantly higher at 3-8 cmH2O pressure on day 10 than on day 30. Because the change of lung tissue elasticity evaluated from the saline-filled pressure-volume curve was equal for the 2 days, the higher decrease of air volume on day 10 was due primarily to contribution of alveolar surface force. Pressure differences between deflation limbs of air-filled and saline-filled pressure-volume curves, which represented net alveolar surface force, were significantly higher at any lung volume between 50 and 90% total lung capacity on day 10, but almost no significance was observed on day 30. Phospholipid concentration in bronchoalveolar lavage fluid significantly decreased on day 10 but had improved by day 30. Analysis of phospholipid species in purified lung surfactant showed decreased fractions of disaturated phosphatidylcholine and phosphatidylglycerol on day 10. Surface-active properties of the surfactant, measured by a modified Wilhelmy balance, were remarkably hampered on day 10, but most of them had improved by day 30. We consider that the quantitative and functional abnormalities of lung surfactant have a part in the aggravation of lung mechanics in the acute phase of pulmonary fibrosis.

Mechanisms for drought tolerance in two Mediterranean seasonal dimorphic shrubs

1999 ◽  
Vol 26 (6) ◽  
pp. 587 ◽  
Author(s):  
G. Grammatikopoulos
Keyword(s):  
Drought Tolerance ◽  
Water Content ◽  
Relative Water Content ◽  
Turgor Pressure ◽  
Tissue Elasticity ◽  
Dry Period ◽  
Turgor Loss Point ◽  
Relative Water ◽  
Seasonal Basis ◽  
Cistus Creticus

Pressure-volume curves were constructed on a seasonal basis in two malacophyllous, drought semi-deciduous Mediterranean species (Phlomis fruticosa L. and Cistus creticus L.). Summer reduction of water potential at the turgor loss point in both species was less pronounced than corresponding changes in relative water content (RWC) at the turgor loss point, implying the existence of turgor maintenance mechanisms. However, actual summer leaf water potentials and RWCs in the field indicate that plants may experience zero or negative turgor pressure during the dry period. In both species, gradual decreases in osmotic potential and apoplastic relative water content, as well as increases in tissue elasticity, were observed during the summer. In particular, P. fruticosa exhibited a remarkable elasticity throughout the year. Indications for osmotic adjustment processes were also recorded. Critical (sublethal) RWCs measured during the winter and summer were lower not only from the corresponding RWCs at turgor loss point but also from the actual midday RWCs usually observed in the field. Both species seem to use a combination of elastic and osmotic adjustments in order to maintain their turgidity during the dry period. However, even though turgor may be lost during part of the summer, water deficits do not usually surpass critical levels under field conditions. This is probably achieved through the occurrence of two leaf populations (summer and winter leaves) with differential physiological drought tolerance.

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