scholarly journals Dynamic aspects of plant water potential revealed by a microtensiometer

2021 ◽  
Author(s):  
Vinay V Pagay
Keyword(s):  
Water Potential ◽  
Water Status ◽  
Vapour Pressure Deficit ◽  
Irrigation Scheduling ◽  
Field Conditions ◽  
Plant Water ◽  
Water Potentials ◽  
Cross Correlation Analysis ◽  
Plant Water Potential ◽  
Long Time

Water potential is a fundamental thermodynamic parameter that describes the activity of water. In this paper, we describe the continuous measurement of plant water potential, a reliable indicator of its water status, using a novel in situ sensor known as a microtensiometer in mature grapevines under field conditions. The microtensiometer operates on the principle of equilibration of water potentials of internal liquid water with an external vapour or liquid phase. We characterised the seasonal and diurnal dynamics of trunk water potentials (Ψtrunk) obtained from microtensiometers installed in two grapevine cultivars, Shiraz and Cabernet Sauvignon, and compared these values to pressure chamber-derived stem (Ψstem) and leaf (Ψleaf) water potentials as well as leaf stomatal conductance. Diurnal patterns of Ψtrunk matched those of Ψstem and Ψleaf under low vapour pressure deficit (VPD) conditions, but diverged under high VPD conditions. The highest diurnal values of Ψtrunk were observed shortly after dawn, while the lowest values were typically observed in the late afternoon. Differential responses of Ψtrunk to VPD were observed between cultivars, with Shiraz more sensitive than Cabernet to increasing VPD over long time scales, and both cultivars had a stronger VPD response than soil moisture response. On a diurnal basis, however, time cross correlation analysis revealed that Shiraz Ψtrunk lagged Cabernet Ψtrunk in response to changing VPD. Microtensiometers were shown to operate reliably under field conditions over several months. To be useful for irrigation scheduling of woody crops, new thresholds of Ψtrunk need to be developed.

A Hydrological Study of a Subtropical Semiarid Forest of Acacia harpophylla F. Muell. Ex Benth. (Brigalow)

1981 ◽  
Vol 29 (3) ◽  
pp. 311 ◽  
Author(s):  
BR Tunstall ◽  
DJ Connor
Keyword(s):  
Soil Water ◽  
Water Status ◽  
Water Storage ◽  
Soil Water Storage ◽  
Severe Drought ◽  
Plant Water ◽  
Evaporative Demand ◽  
Water Potentials ◽  
Plant Water Potential ◽  
Stem Flow

Water input, soil water storage and plant water status were measured at monthly intervals over 2� years In a mature brigalow (Acacla harpophylla) forest. Redistribution of rainfall by the canopy was slight and stem flow averaged only 1.8%, but the direct loss of intercepted water accounted for 15% of the Annual ramfall In the wettest condltlon the soil stored 890 mm of water to a depth of 3 m The minimum sod water store measured under severe drought conditions was 840 mm when the dawn values of plant water potential were -6.8 MPa The soil water potentials below 1 m were consistently around -3.5 MPa due largely to high salt concentrations The tendency in a drying soil was towards a uniform profile of soil water potentlal, and soil water at depths below 1 m was extracted only when dawn plant water potentials were less than - 3.5 MPa Over monthly Intervals the maximum and minimum rates of evapotransplratlon were 3.3 and 0 .46 mm/d respectively, and the pattern of community water use was related to rainfall and not to potentlal evaporation. To survive in such an environment the plants develop and withstand extremely low water potentials associated wlth the low availability of water and the high evaporative demand.

Internal Water Balance of Brigalow (Acacia harpophylla F. Muell.) Under Natural Conditions

1975 ◽  
Vol 2 (4) ◽  
pp. 489 ◽  
Author(s):  
BR Tunstall ◽  
DJ Connor
Keyword(s):  
Water Potential ◽  
Water Status ◽  
Carbon Uptake ◽  
Diurnal Changes ◽  
Plant Water ◽  
Litter Fall ◽  
Tissue Water ◽  
Diffusive Resistance ◽  
Plant Water Potential ◽  
Water Contents

On one day each month over a period of 2½ years, diurnal measurements of plant water status, leaf diffusive resistance, carbon uptake, irradiance, ambient temperature and humidity were made in a brigalow community. Diurnal changes in leaf diffusive resistance, osmotic potential, plant water potential, and carbon uptake are shown to follow general patterns and the changes in plant water potential were related to the dawn value of plant water potential. The data suggest the development of negative turgor in brigalow and demonstrate the capacity of the plant to maintain high tissue water contents at low water potentials. Measurements of shoot extension and litter fall showed that litter fall occurred principally following shoot extension.

scholarly journals L-band vegetation optical depth as an indicator of plant water potential in a temperate deciduous forest stand

2020 ◽  
Author(s):  
Nataniel Holtzman ◽  
Leander D. L. Anderegg ◽  
Simon Kraatz ◽  
Alex Mavrovic ◽  
Oliver Sonnentag ◽  
...  
Keyword(s):  
Water Potential ◽  
Optical Depth ◽  
Growing Season ◽  
Forest Stand ◽  
Plant Water ◽  
Stem Water Potential ◽  
Water Potentials ◽  
Plant Water Potential ◽  
Stem Water ◽  
L Band

Abstract. Vegetation optical depth (VOD) retrieved from microwave radiometry correlates with the total amount of water in vegetation, based on theoretical and empirical evidence. Because the total amount of water in vegetation varies with relative water content (as well as with biomass), this correlation further suggests a possible relationship between VOD and plant water potential, a quantity that drives plant hydraulic behavior. Previous studies have found evidence for that relationship on the scale of satellite pixels tens of kilometers across, but these comparisons suffer from significant scaling error. Here we used small-scale remote sensing to test the link between remotely sensed VOD and plant water potential. We placed an L-band radiometer on a tower above the canopy looking down at red oak forest stand during the 2019 growing season in central Massachusetts, United States. We measured stem xylem and leaf water potentials of trees within the stand, and retrieved VOD with a single-channel algorithm based on continuous radiometer measurements and measured soil moisture. VOD exhibited a diurnal cycle similar to that of leaf and stem water potential, with a peak at approximately 5 AM. VOD was also positively correlated with both the measured dielectric constant and water potentials of stem xylem over the growing season. The presence of moisture on the leaves did not affect the observed relationship between VOD and stem water potential. We used our observed VOD-water potential relationship to estimate stand-level values for a radiative transfer parameter and a plant hydraulic parameter, which compared well with the published literature. Our findings support the use of VOD for plant hydraulic studies in temperate forests.

Soil Moisture as Predictor of Plant Water Status

2021 ◽  
Vol 47 (3) ◽  
pp. 110-115
Author(s):  
Johannes Hertzler ◽  
Steffen Rust
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Status ◽  
Soil Water Potential ◽  
Irrigation Scheduling ◽  
Plant Water Status ◽  
Plant Water ◽  
Estimation Errors ◽  
Plant Available Water ◽  
The Relationship

Soil water potential can be used as a proxy for plant available water in irrigation scheduling. This study investigated the relationship between soil water potential and plant water status of pines (Pinus sylvestris L.) planted into two different substrates. Predawn leaf water potential as a well-established measure of the plant water status and soil water potential correlated very well. However, estimating the plant water status from individual sensor readings is subject to significant estimation errors. Furthermore, it was shown that heterogeneous soil/root ball combinations can lead to critical effects on the soil water balance, and that sensors installed outside of the root balls cannot estimate the plant water status without site-specific calibration.

MEASUREMENT OF INTERNAL WATER STRESS IN WHEAT PLANTS

1968 ◽  
Vol 48 (1) ◽  
pp. 89-95 ◽  
Author(s):  
S. J. Yang ◽  
E. de Jong
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Great Promise ◽  
Plant Water ◽  
Thermocouple Psychrometer ◽  
Water Potentials ◽  
Plant Water Potential ◽  
Highly Correlated ◽  
The Many ◽  
Non Destructive

The thermocouple psychrometer technique was used to measure plant water stresses of wheat. The usefulness of this technique is limited due to the many precautions that must be taken. The β-ray absorption and relative turgidity were highly correlated (P = 0.01) with plant water potential, but the correlation changed with age. Relative turgidity gave a slightly better estimate of leaf water potential than β-ray absorption (r2 of 0.88 to 0.99 and 0.81 to 0.96 respectively). The β-ray technique has great promise because of its non-destructive nature.At soil water potentials higher than −10 atm, plant water potentials remained nearly constant, indicating that soil water was equally available. Temporary wilting occurred at soil water potentials of −35 to −40 atm.

scholarly journals 593 A Lightweight, Hand-operated Pressure Chamber for Determining Plant Water Status

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 499B-499
Author(s):  
Ken Shackel ◽  
David Paige
Keyword(s):  
Water Potential ◽  
Water Status ◽  
Irrigation Management ◽  
Nitrogen Pressure ◽  
Irrigation Scheduling ◽  
Pressure Chamber ◽  
Plant Water ◽  
Stem Water Potential ◽  
Stem Water ◽  
Time Required

In a number of tree crops, we have found that the water potential of lower canopy, nontranspiring leaves, measured with the pressure chamber at midday (midday stem water potential), is an excellent index of plant water stress and can be used for irrigation scheduling. Because stem water potential is typically much higher than transpiring leaf water potential, a lower pressure is required for the measurement, allowing us to design and build a lightweight device that could be easily operated by hand. The prototype was designed for pressures up to 2 MPa, which is sufficient for most irrigation conditions. A number of design features were incorporated into the sealing gland to eliminate the need for retightening during the pressurization process, reduce the amount of tissue external to the pressure chamber, and allow a greater visibility of the petiole. Identical values to those obtained with the standard, compressed nitrogen pressure chamber were obtained over the entire 2-MPa range, and the time required using either device under field conditions was the same (about 1 min per measurement). A number of alternative protocols were tested, and we found that even substantial recutting of the petiole had no influence on the measured water potential, contrary to popular belief. We also found that the same sample could be remeasured multiple times (five), with no net change in the water potential, allowing the measurement to be checked if necessary. This device should be of great utility in field irrigation management.

scholarly journals Rapid Equilibration of Leaf and Stem Water Potential under Field Conditions in Almonds, Walnuts, and Prunes

2001 ◽  
Vol 11 (4) ◽  
pp. 609-615 ◽  
Author(s):  
Allan Fulton ◽  
Richard Buchner ◽  
Cyndi Gilles ◽  
Bill Olson ◽  
Nick Bertagna ◽  
...  
Keyword(s):  
Sample Size ◽  
Water Potential ◽  
Water Status ◽  
Irrigation Management ◽  
Irrigation Scheduling ◽  
Field Conditions ◽  
Equilibration Time ◽  
Diurnal Changes ◽  
Stem Water Potential ◽  
Stem Water

Covering a plant leaf with a reflective, water impervious bag ensures that equilibrium is reached between the nontranspiring leaf and the stem, and appears to improve the accuracy of determining plant water status under field conditions. However, the inconvenience of covering the leaf for 1 to 2 hours before measuring stem water potential (SWP) has constrained on-farm adoption of this irrigation management technique. A second constraint has been that the requirement of midafternoon determinations limits the area that can be monitored by one person with a pressure chamber. This paper reports findings from field studies in almonds (Prunus dulcis),prunes (P. domestica), and walnuts (Juglans regia) demonstrating modified procedures to measure midday SWP, making it a more convenient and practical tool for irrigation management. For routine monitoring and irrigation scheduling, an equilibration period of 10 min or longer appears to be suitable to provide accurate SWP measurements. Based on the large sample sizes in this study, we estimate that measurement error related to equilibration time for SWP can be reduced to an acceptable level [0.05 MPa (0.5 bar)] with a sample size of about 10 leaves when using a 10-min equilibration period. Under orchard conditions where tree growth and health appears uniform, a sample of one leaf per tree and 10 trees per irrigation management unit should give an accurate mean indicator of orchard water status. Under more variable orchard conditions a larger sample size may be needed. Midmorning and midday SWP both exhibited similar seasonal patterns and responded alike to irrigation events. On some occasions, midday SWP was accurately predicted from midmorning SWP and the change in air vapor pressure deficit (VPD) from midmorning to midday, but both over- and underestimate errors [to 0.3 MPa (3.0 bar)] appeared to be associated with unusually low or high diurnal changes in VPD, respectively. Hence, direct measurement of SWP under midday conditions (about 1300 to 1500 hr) is still recommended.

The influences of temperature and soil water on growth, photosynthesis, and nitrogen fixation of red alder (Alnusrubra) seedlings

1994 ◽  
Vol 24 (5) ◽  
pp. 1029-1032 ◽  
Author(s):  
B.J. Hawkins ◽  
S. McDonald
Keyword(s):  
Nitrogen Fixation ◽  
Water Potential ◽  
Soil Water ◽  
Water Status ◽  
Net Photosynthesis ◽  
Field Capacity ◽  
Plant Water ◽  
Red Alder ◽  
Plant Water Potential ◽  
The Difference

A 3 × 2 factorial experiment was conducted to investigate the interaction of temperature and soil water status on the growth, photosynthetic, transpiration, and nitrogen fixation rates of 2-month-old red alder (Alnusrubra Bong.) seedlings. Three day: night temperature treatments, 15:10 °C, 20:10 °C, and 25:10 °C were used. Two soil-water treatments kept pots between 85 and 100% of field capacity (wet) and 70–85% of field capacity (dry). Treatment effects on growth, net photosynthetic, transpiration and nitrogen fixation rates, plant water potential, and foliar nutrient concentration were measured over a 9-week period. The greatest seedling growth occurred at 25 °C day temperatures, while 20 and 25 °C days produced the greatest nodule growth. The allocation of biomass to roots increased with decreasing temperature. The highest rates of net photosynthesis occurred at 15 and 20 °C whereas transpiration was greatest at 25 °C. Plant water stress was greatest at 25 °C. The difference in plant water potential between the wet and dry treatments was only 0.04 MPa, which was not great enough to produce significant effects on growth or photosynthesis. Nitrogen fixation rates were highest in the wet treatment seedlings at 20 and 25 °C.

Branch water potential; a useful indicator of plant water potential in comparison to leaf water potential in canola

2000 ◽  
Vol 40 (5) ◽  
pp. 687 ◽  
Author(s):  
A. L. Bernardi
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Water Status ◽  
Source Material ◽  
Leaf Water ◽  
Moisture Loss ◽  
Plant Water ◽  
Portable Equipment ◽  
Plant Water Potential ◽  
Main Growth

The water potentials of canola branches and leaves were compared using a pressure chamber to determine whether they produced similar results. This study also investigated the magnitude of errors in the water status of canola resulting from re-cutting the branches, and the effects of delaying readings. The use of branches containing pods or pods and flowers/buds gave very good correlation with leaves. As this is the area of greatest photosynthesis and transpiration from mid-flowering, it provides an easily obtainable source material close to the main growth areas to measure plant water potential. Storage of both leaves and stems before measurement is an acceptable procedure if a large number of samples are required to be completed or portable equipment is not available provided precautions are taken to prevent moisture loss. Re-cutting the branch leads to lower water potential and should be avoided.

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