Effects of Osmotica Around the Roots on Water Uptake by Maize Plants

1980 ◽  
Vol 7 (1) ◽  
pp. 27 ◽  
Author(s):  
RA Nulsen ◽  
GW Thurtell
Keyword(s):  
Polyethylene Glycol ◽  
Water Potential ◽  
Nutrient Solution ◽  
Leaf Water Potential ◽  
Flow Rate ◽  
Osmotic Potential ◽  
Leaf Water ◽  
Maize Plants ◽  
The Difference ◽  
Osmotic Potentials

Nutrient solutions with osmotic potentials of -70, -190 and -380 kPa were supplied to maize plants whose roots were enclosed in a pressure chamber. The plants were stressed and then rewatered with the same nutrient solution. Sap flow rate from the detopped root system was measured at 400 kPa applied pressure. The lower was the osmotic potential of the pretreatment solution, the lower was the initial flow rate. Flow rates rapidly decreased to zero and did not recover for up to 90 min. Different responses in leaf water potential of unstressed, intact plants occurred when the nutrient solution bathing the root was replaced by either a more concentrated nutrient solution or a solution of sucrose or polyethylene glycol 6000. For nutrient solution replacement the change in leaf water potential was less than the difference in solution osmotic potentials; for sucrose the difference was greater, and for polyethylene glycol the change was equal to the osmotic potential difference. Osmotic effects observed were due to differential accumulations at different barriers in the root. The zero-flow periods seen during recovery of severely stressed plants may have been due to a decrease in the osmotic potential of the solution external to the plasmalemma of root cortical cells.

Osmotic Adjustment in Expanding and Fully Expanded Leaves of Sunflower in Response to Water Deficits

1980 ◽  
Vol 7 (2) ◽  
pp. 181 ◽  
Author(s):  
MM Jones ◽  
NC Turner
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Leaf Water ◽  
Similar Degree ◽  
Tissue Water ◽  
Predawn Leaf Water Potential ◽  
Leaf Osmotic Potential ◽  
Osmotic Potentials

Sunflower plants were grown in large volumes of soil and slowly water-stressed by withholding water. The tissue water relationships of leaves at various stages of stress and of leaves of equivalent well watered controls were studied by the pressure chamber technique. Plants were stressed either when leaf 17 was expanding or when it was fully expanded. When expanding leaves reached a moderate level of stress (predawn leaf water potential of -0.9 MPa), the osmotic potentials at full turgor and zero turgor were lower than the control values by 0.1 MPa and 0.2 MPa, respectively. When fully expanded leaves were stressed to a similar degree (predawn leaf water potential of - 1.1 MPa), the osmotic potentials at full turgor and zero turgor were lower than the control values by 0.2 MPa and 0.3 MPa, respectively. The development of more severe stress in the fully expanded leaves was not accompanied by any further osmotic adjustment. However, when the expanding leaves reached a predawn leaf water potential of -2.3 MPa, the values of leaf osmotic potential at full turgor and zero turgor were lower than the values for the well watered plants by 0.4 MPa and 0.6 MPa, respectively. In expanding leaves prestressed to a predawn leaf water potential of -2.3 MPa, the osmotic potential at full turgor was significantly less than the control values for at least 7 days after rewatering. Stress had no effect on the bulk modulus of elasticity. It is concluded that both expanding and fully expanded sunflower leaves show osmotic adjustment.

Carbon dioxide enrichment and water stress interaction on growth of two tomato cultivars

1984 ◽  
Vol 102 (3) ◽  
pp. 687-693 ◽  
Author(s):  
Alejandra Paez ◽  
H. Hellmers ◽  
B. R. Strain
Keyword(s):  
Carbon Dioxide ◽  
Water Stress ◽  
Plant Growth ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Osmotic Potential ◽  
Water Status ◽  
Carbon Dioxide Concentration ◽  
Leaf Water ◽  
Total Leaf

SummaryIf atmospheric carbon dioxide concentration continues to increase, plant growth and crop yield could be affected. New Yorker and Better Boy cultivars of tomato (Lycopersicon esculentum) were used to investigate possible intraspecific variation in the response of crop species to increased CO2. Because precipitation and temperature are predicted to change with the increasing atmospheric CO2 concentration, the response of the two cultivars to the interaction between CO2 and water stress was also examined. Seeds of the two cultivars were germinated and grown under controlled environmental conditions, in either 350 or 675 μ1 CO2/1.The plant water status of the two cultivars was inherently different but was little affected by the CO2 concentration when the plants were well watered. When water was withheld for 5 days the total leaf water potential and osmotic potential decreased in both CO2 treatments but less rapidly in high CO2 than in low. Under low CO2 total leaf water potential decreased to a lower value than osmotic potential. The differences were due, at least in part, to the reduced stomatal conductance and transpiration rate under high CO2.Increased CO2 ameliorated the detrimental effects of drought stress on plant growth. The results indicate that increased CO2 could differentially affect the relative drought resistance of species cultivars.

Divergence in plant water-use strategies in semiarid woody species

2017 ◽  
Vol 44 (11) ◽  
pp. 1134 ◽  
Author(s):  
Rachael H. Nolan ◽  
Kendal A. Fairweather ◽  
Tonantzin Tarin ◽  
Nadia S. Santini ◽  
James Cleverly ◽  
...  
Keyword(s):  
Water Potential ◽  
Leaf Area ◽  
Leaf Water Potential ◽  
Specific Leaf Area ◽  
Osmotic Potential ◽  
Water Status ◽  
Stomatal Closure ◽  
Woody Species ◽  
Leaf Water ◽  
Leaf Water Status

Partitioning of water resources amongst plant species within a single climate envelope is possible if the species differ in key hydraulic traits. We examined 11 bivariate trait relationships across nine woody species found in the Ti-Tree basin of central Australia. We found that species with limited access to soil moisture, evidenced by low pre-dawn leaf water potential, displayed anisohydric behaviour (e.g. large seasonal fluctuations in minimum leaf water potential), had greater sapwood density and lower osmotic potential at full turgor. Osmotic potential at full turgor was positively correlated with the leaf water potential at turgor loss, which was, in turn, positively correlated with the water potential at incipient stomatal closure. We also observed divergent behaviour in two species of Mulga, a complex of closely related Acacia species which range from tall shrubs to low trees and dominate large areas of arid and semiarid Australia. These Mulga species had much lower minimum leaf water potentials and lower specific leaf area compared with the other seven species. Finally, one species, Hakea macrocarpa A.Cunn ex.R.Br., had traits that may allow it to tolerate seasonal dryness (through possession of small specific leaf area and cavitation resistant xylem) despite exhibiting cellular water relations that were similar to groundwater-dependent species. We conclude that traits related to water transport and leaf water status differ across species that experience differences in soil water availability and that this enables a diversity of species to exist in this low rainfall environment.

Genotypic variation in osmotic adjustment in grain sorghum. I. Development of variation in osmotic adjustment under water-limited conditions

1991 ◽  
Vol 42 (5) ◽  
pp. 747 ◽  
Author(s):  
T Tangpremsri ◽  
S Fukai ◽  
KS Fischer ◽  
RG Henzell
Keyword(s):  
Water Potential ◽  
Water Deficit ◽  
Leaf Water Potential ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Genotypic Variation ◽  
Genetic Material ◽  
Covariance Analysis ◽  
Leaf Water ◽  
The Other

Development of genotypic variation in osmotic adjustment was examined in two glasshouse experiments using two sets of sorghum material. In the first experiment, 47 S2 lines extracted from a randomly mated population were used, whereas in the other, inbred parents and their 15 hybrids were compared. In both experiments, water deficit was induced in two periods, one before anthesis and the other after anthesis for most genotypes. In both experiments osmotic potential at the beginning of the first drying period was similar among genotypes and therefore osmotic potential obtained under water deficit was used for the comparison of osmotic adjustment among genotypes. In the first drying period of both experiments, when stress was milder, about 40% of the variation in osmotic adjustment was accounted for by difference in leaf water potential. When the effect of water potential was removed by covariance analysis, there was significant genotypic variation in osmotic adjustment in the second experiment, but not in the first experiment. On the other hand, in the second drying period, when stress was more severe, the effect of leaf water potential on osmotic adjustment was small. There was significant genotypic variation in osmotic adjustment in both experiments after the water potential effect was removed by covariance analysis. Osmotic adjustment in the second drying period was also negatively correlated with grain sink/source ratio (number of grains/leaf area) in the first set of materials. The comparison of osmotic adjustment among hybrids and their parents showed that, in this particular set of genotypes, the female parents were more important than the male in determining osmotic adjustment of the hybrids. The genotypic variation was associated with performance under water deficit in the field. It is concluded that there is considerable genotypic variation in osmotic adjustment in the genetic material examined. Osmotic adjustment is, however, correlated with water potential and grain sink/source balance, and hence the selection for osmotic adjustment needs to ensure that high value is not due simply to low water potential or small head size.

IN SITU MEASUREMENTS OF LEAF WATER POTENTIAL AND RESISTANCE TO WATER FLOW IN CORN, SOYBEAN, AND SUNFLOWER AT SEVERAL TRANSPIRATION RATES

1974 ◽  
Vol 54 (1) ◽  
pp. 175-184 ◽  
Author(s):  
H. H. NEUMANN ◽  
G. W. THURTELL ◽  
K. R. STEVENSON
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Nutrient Solution ◽  
Leaf Water Potential ◽  
Correlation Coefficients ◽  
Leaf Water ◽  
Silica Sand ◽  
Helianthus Annus ◽  
Glycine Max L

Peltier-cooled thermocouple dewpoint hygrometers were used to measure leaf water potentials at several transpiration rates on intact corn (Zea mays L.), soybean (Glycine max (L.) Merr.), and sunflower (Helianthus annus L.), grown in a controlled environment in silica sand rooting media frequently watered with nutrient solution. Hygrometers were left in position for the duration of measurements on each plant, but tests showed this to have little effect on measured potentials. Measured potentials were found to be linearly related to the transpiration rates (correlation coefficients greater than 0.98). Extrapolated values of leaf water potential at zero transpiration were within a few tenths bar of measured nutrient-solution potentials. These results indicated that plant resistances to water flow remained constant from near zero transpiration up to the maximum obtained average rates of 1.8–3.0 g dm−2 h−1. The magnitude of the resistance varied considerably from plant to plant even within a single cultivar of one species and definite conclusions as to interspecies differences in resistance were not made. Estimates of the relative resistance in the root, stalk, and the leaf that were made for a few plants were similar to previously published results.

Growth and yield of rice cultivars under sprinkler irrigation in south-eastern Queensland. 3. Water extraction and plant water relations dash comparison with maize and grain sorghum

1988 ◽  
Vol 28 (2) ◽  
pp. 249 ◽  
Author(s):  
S Fukai ◽  
P Inthapan
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Leaf Water Potential ◽  
Osmotic Potential ◽  
Root Length ◽  
Dry Matter ◽  
Root Length Density ◽  
Leaf Water

Several physiological responses were compared, under irrigated and water-stressed conditions, in an attempt to explain the reasons for the greater reduction in dry matter production of rice compared with maize and sorghum in a water-limiting environment. Leaf water potential and leaf rolling were determined weekly, soil water profiles and root length density twice, and leaf osmotic potential once during a long dry period. Root length density of rice was at least as high as that of maize and sorghum in the top 0.6 m layer of soil in both the wet and dry trials. There was no difference in water extraction among the 3 species from this layer, while rice extracted less water than did the other species from below 0.6 m. High variability among replicates precluded any conclusion being drawn regarding root length in the deeper layer. Leaf water potential, measured in the early afternoon, was consistently lower in rice than in maize and sorghum, even when soil water content was high, indicating high internal resistance to the flow of water in the rice plants. The low leaf water potential in rice was accompanied by low osmotic potential, and this assisted in maintenance of turgor and dry matter growth when soil water content was relatively high. As soil water content decreased, however, leaf water potential became very low (less than - 2.5 MPa) and, for rice, leaves rolled tightly.

Osmotic Adjustment of Sorghum and Sunflower Crops in Response to Water Deficits and Its Influence on the Water Potential at Which Stomata Close

1978 ◽  
Vol 5 (5) ◽  
pp. 597 ◽  
Author(s):  
NC Turner ◽  
JE Begg ◽  
ML Tonnet
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Stomatal Closure ◽  
Leaf Water ◽  
Water Deficits ◽  
Rate Of Increase ◽  
Leaf Osmotic Potential ◽  
Response To Water

The soil and plant water status of irrigated and unirrigated sorghum [Sorghum bicolor (L.) Moench cv. TX610] and sunflower (Helianthus annuus L. cv. Hysun 30) crops were compared on several days from the late vegetative to the early grain-filling stages of development. Additionally, the stems of plants from the irrigated and unirrigated plots of both species were cut near their base; this caused the plants to quickly dry until the stomata closed. The leaf water potential and leaf osmotic potential were measured when the stomatal resistance reached 6 s cm-� to give the water potential for stomatal closure and to provide osmotic potentials at equal turgor. Carbohydrate and potassium levels of leaves were also monitored. The mean daily minimum leaf water potentials in the irrigated sorghum and sunflower did not decrease below - 1 7 MPa and - 2.0 MPa, respectively, but decreased to - 2.1 MPa in the unirrigated sorghum and -2.6 MPa in the unirrigated sunflower. The osmotic potential at stomatal closure in the rapidly dried plants decreased with increasing leaf water deficit in both sunflower and sorghum: in both species the osmotic potential decreased approximately 0.6 MPa for each megapascal decrease in leaf water potential. The results indicate that both sorghum and sunflower adjusted osmotically in response to water deficits and that adjustment occurred at a rate of at least 0.1 MPa per day. The lowering of osmotic potential persisted less than 9 days after the relief of stress in both sunflower and sorghum. The soluble sugar concentration increased linearly in both sunflower and sorghum with osmotic adjustment: the rate of increase of soluble sugars was significantly greater in sunflower than sorghum. No changes in potassium concentration were observed during osmotic adjustment. The water potential at which the stomata closed varied from - 1.5 to -2.6 MPa in sorghum and - 1.7 to -2.7 MPa in sunflower: the water potential that induced stomatal closure decreased as the osmotic potential decreased. Stomatal closure occurred at a mean turgor of -0-5 MPa in both species: systematic error in the measurement of osmotic potential on frozen and thawed leaf tissue is considered the reason for the low turgor potentials at stomatal closure. The adaxial stomatal closed before the abaxial stomata in the sorghum and unirrigated sunflower but, since the leaf water potential initially fell rapidly and then became stable before the adaxial stomata closed, both the adaxial and abaxial stomata closed at the same leaf water potential.

Measurement of Total and Osmotic Potentials in Lucerne and Sunflower Tissues using Thermocouple Psychrometers

1988 ◽  
Vol 24 (4) ◽  
pp. 481-487
Author(s):  
G. C. Wright ◽  
D. M. Whitfield
Keyword(s):  
Time Delay ◽  
Water Potential ◽  
Water Loss ◽  
Osmotic Potential ◽  
Vapour Pressure ◽  
Leaf Water ◽  
Leaf Sample ◽  
Pressure Equilibrium ◽  
Osmotic Potentials ◽  
Chamber Size

SummaryThe measurement of leaf water and osmotic potential using thermocouple psychrometry was investigated in field grown stands of sunflower and lucerne. For the chamber size and tissue dimensions used, vapour pressure equilibrium was achieved after 4 to 6 h for leaf water and osmotic potential samples. In lucerne, as the time delay between excising the leaf and sealing it in the chamber was increased from 30 s to 8 min, water apparently evaporated from the leaf sample and leaf water and osmotic potential markedly decreased. For routine psychrometer determinations of leaf water and osmotic potential in lucerne (and presumably other species) leaf samples should therefore be sealed in the chambers as quickly as possible to minimize rapid water loss and associated errors in water potential determination. Vapour pressure equilibration for sunflower capitulum and root water and osmotic potential samples was achieved only after 6 and 24 h, respectively.G. C. Wright y D. M. Whitfield: Medición de los potentiates totales y osmóticos en tejidos de alfalfa y girasol usando psicrómetros termopar.

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.

Seasonal changes in leaf water relations and cell membrane stability in orchardgrass (Dactylis glomerata)

1993 ◽  
Vol 121 (2) ◽  
pp. 169-175 ◽  
Author(s):  
G. S. Premachandra ◽  
H. Saneoka ◽  
K. Fujita ◽  
S. Ogata
Keyword(s):  
Cell Membrane ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Osmotic Potential ◽  
Seasonal Changes ◽  
Membrane Stability ◽  
Leaf Water ◽  
Leaf Water Relations ◽  
Cold Temperatures ◽  
Cell Membrane Stability

SUMMARYFifteen cultivars of orchardgrass (Dactylis glomerata L.) were grown in the field at Hiroshima University, Japan, to investigate seasonal changes in leaf water relations and cell membrane stability (CMS) measured by the polyethylene glycol (PEG) test. Leaf water potential and osmotic potential were measured from August 1988 to August 1989. Solute concentration in leaf cell sap was also estimated.Cell membrane stability increased, leaf water potential and osmotic potential decreased and turgor potential increased with decreasing environmental temperatures during autumn and winter. The significant increases observed in CMS may enable plants to tolerate freezing temperatures during winter. Decrease in leaf water potential may be a result of water-deficit effects due to soil freezing at low temperatures and the decrease in osmotic potential may help plants to maintain turgor and tolerate freezing conditions. Plants maintained higher turgor as the osmotic potential decreased to values as low as – 3·98 MPa during winter; the maintenance of turgor helps to maintain water uptake under water deficit conditions at low temperatures.Sugar and K were the major osmotic contributors in orchardgrass leaves. Sugar and Ca concentrations increased and Mg and P concentrations decreased at cold temperatures. K concentration increased in six cultivars and decreased in nine others at cold temperatures. Sugar concentration in cell sap was negatively correlated with osmotic potential. It was concluded that seasonal changes in CMS may be mainly associated with the osmotic potential of the leaf tissues.

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