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.

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.

Evaluation of the pressure chamber technique for measurement of leaf water potential in cassava (Manihot species)

1978 ◽  
Vol 56 (14) ◽  
pp. 1638-1641 ◽  
Author(s):  
I. F. Ike ◽  
G. W. Thurtell ◽  
K. R. Stevenson
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Pressure Chamber ◽  
Leaf Water ◽  
Dew Point ◽  
Manihot Esculenta Crantz ◽  
Osmotic Potentials ◽  
Chamber Technique ◽  
Cassava Varieties

The pressure chamber technique was evaluated as a method for estimating leaf water potential in cassava (Manihot esculenta Crantz). Xylem pressure potentials (ψP) measured with the pressure chamber were compared with leaf water potential (ψL) obtained for the same leaf with the in situ dew-point hygrometer.In both cassava varieties studied, ψL and ψP were linearly related (r2 = 0.87 and 0.98 for CMC9 and CMC40 respectively). The length of petiole exposed outside the chamber affects the relation between ψL and ψP and should be kept at between 1 and 3 cm for better agreement. In CMC40, ψP was consistently lower (drier) than ψL by about 1.0 bar (1 bar = 100 kPa) in the entire range of water potential studied, but was not the case in CMC9. The reason for this difference is unclear but may be due to a filling of tissues other than xylem tissues (Boyer 1967) during the measurement of ψP in CMC40. Average xylem osmotic potentials (ψS) were low (−1.0 ± 0.2 bars and −1.0 ± 0.4 bars for CMC9 and CMC40 respectively). It is, therefore, unnecessary to correct for ψS when using the pressure chamber to estimate leaf water potentials in cassava.

Pressure–volume curves of shoots and roots of normal and drought conditioned western hemlock seedlings

1980 ◽  
Vol 10 (1) ◽  
pp. 10-16 ◽  
Author(s):  
R. A. Kandiko ◽  
R. Timmis ◽  
J. Worrall
Keyword(s):  
Drought Stress ◽  
Water Content ◽  
Water Deficit ◽  
Western Hemlock ◽  
Relative Water ◽  
Osmotic Potentials ◽  
Water Contents

Pressure–volume curves for western hemlock (Tsugaheterophylla (Raf.) Sarg.) seedlings showed roots to have lower osmotic potentials, at both full turgor and incipient plasmolysis, and lower relative water contents at incipient plasmolysis than shoots. Roots remained turgid under mild water deficit, whereas shoots lost turgor exponentially with water content. Shoots of seedlings given a 2-week drought stress had lower osmotic potentials at full turgor and incipient plasmolysis than shoots of unstressed seedlings; roots showed a similar trend.

scholarly journals Turgor Maintenance in Rosa rugosa Grown at Three Levels of Nitrogen and Subjected to Drought

1990 ◽  
Vol 8 (3) ◽  
pp. 108-112 ◽  
Author(s):  
R.M. Augé ◽  
A.J.W. Stodola ◽  
D.M. Gealy
Keyword(s):  
Water Content ◽  
Turgor Pressure ◽  
N Fertilization ◽  
Leaf Water ◽  
Leaf Water Content ◽  
Rosa Rugosa ◽  
Turgor Maintenance ◽  
Relative Water ◽  
Complete Fertilizer ◽  
Water Contents

Abstract The influence of N fertilization on turgor maintenance was determined in leaves from well-watered and droughted Rosa rugosa L. Plants were fertilized for 60 days with a complete fertilizer with N at levels of 0, 200 or 500 ppm and then subjected to several drought cycles for 22 days. Plants receivmg no N were stunted and chlorotic, but had the greatest full saturation turgor pressure and symplastic osmolality, and the lowest full saturation osmotic potential, after drought. These plants also maintained higher turgor across a range of leaf water potentials and relative water contents. Leaf water content at full turgor and relative water content at the turgor loss point were also lower in plants without N. N treatments of 200 and 500 ppm had similar water relations under both well-watered and drought conditions.

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.

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.

Osmotic adjustment leads to anomalously low estimates of relative water content in wheat and barley

2008 ◽  
Vol 35 (11) ◽  
pp. 1172 ◽  
Author(s):  
John S. Boyer ◽  
Richard A. James ◽  
Rana Munns ◽  
Tony (A. G.) Condon ◽  
John B. Passioura
Keyword(s):  
Water Content ◽  
Osmotic Adjustment ◽  
Relative Water Content ◽  
Triticum Turgidum ◽  
Water Status ◽  
Turgor Pressure ◽  
Excess Water ◽  
Direct Measurements ◽  
Relative Water ◽  
Definition Of

Relative water content (RWC) is used extensively to determine the water status of plants relative to their fully turgid condition. However, plants often adjust osmotically to salinity or water deficit, which maintains turgor pressure and obscures the definition of ‘full turgidity’. To explore this problem, turgor was measured by isopiestic psychrometry in mature leaf blades of barley (Hordeum vulgare) and durum wheat (Triticum turgidum ssp. durum) salinised to 150 mm NaCl, or bread wheat (Triticum aestivum) grown in soil dehydrated to varying degrees. Osmotic adjustment maintained turgor in all the plants but despite full maintenance in some of the salinised plants, their leaf RWC decreased substantially. This occurred because excess water was absorbed while the samples were floated on water as part of the RWC measurement. The absorption falsely increased the weight of the ‘fully turgid’ condition, causing RWC to be anomalously low by 10–15%. Cell solution was secreted into intercellular spaces and was seen under a microscope, which is a test encouraged for all RWC measurements. Several alternate methods are suggested for rehydrating tissues while minimising excess water absorption, but no simple definition of ‘full turgidity’ seems possible. In general, direct measurements of osmotic adjustment and turgor are preferred.

Proposal of PV Output Estimate Method in Short Time Intervals

2016 ◽  
Vol 136 (12) ◽  
pp. 891-897 ◽  
Author(s):  
Katsuhiro Matsuda ◽  
Kazuhiro Misawa ◽  
Hirotaka Takahashi ◽  
Kenta Furukawa ◽  
Satoshi Uemura
Keyword(s):  
Time Intervals ◽  
Estimate Method ◽  
Short Time
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