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.

LEAF WATER CONTENT AND POTENTIAL IN CORN, SORGHUM, SOYBEAN, AND SUNFLOWER

1974 ◽  
Vol 54 (1) ◽  
pp. 185-195 ◽  
Author(s):  
H. H. NEUMANN ◽  
G. W. THURTELL ◽  
K. R. STEVENSON ◽  
C. L. BEADLE
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Leaf Water Potential ◽  
Leaf Water ◽  
Leaf Water Content ◽  
Relative Water ◽  
Helianthus Annus ◽  
Glycine Max L ◽  
Water Contents

The Peltier-cooled thermocouple dewpoint hygrometer technique of in situ measurement of leaf water potential was further developed. The observed response of the instrument agreed so well with theoretical analysis that calibration based on theory was within 1% of that obtained using salt solutions of known water potential. Simultaneous measurements with the hygrometer and a beta gauge were made to derive the leaf water content–potential relationships for several crop plants. Results showed relative water contents dropping only to near 0.95 for mature corn (Zea mays L.); sorghum (Sorghum vulgare Pers.); and sunflower (Helianthus annus L.) leaves, and to 0.90 for not quite mature soybean (Glycine max (L.) Merr.) leaves as potentials declined from near −1 bar to the plant wilting point (−8 to −14 bars). Further decline of leaf water potential resulted in relatively much greater loss of leaf water.

The relationship between steady-state transpiration rates and leaf water potential in cassava (Manihot esculenta cv. Llanera)

1978 ◽  
Vol 56 (13) ◽  
pp. 1537-1539 ◽  
Author(s):  
I. F. Ike ◽  
G. W. Thurtell ◽  
K. R. Stevenson
Keyword(s):  
Steady State ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Manihot Esculenta ◽  
Regression Line ◽  
Leaf Water ◽  
Dew Point ◽  
Manihot Esculenta Crantz ◽  
The Relationship

The relationship between leaf water potential (ψL) and transpiration rate (T) was investigated using indoor-grown cassava plants (Manihot esculenta Crantz cv. Llanera). Leaf water potentials were measured with in situ dew-point hygrometer and transpiration rates by gas exchange analysis technique.Regression analyses of the data showed that T was consistently linearly related to ψL (r2 = 0.94). This implies that the plant resistance to flow was constant and hence that an Ohm's Law analog is valid for the transpiration range studied. Extrapolated values of leaf water potential at zero transpiration were close to the osmotic potential of the nutrient solution. Calculated resistance values (slope of regression line for individual plants) varied between 2.90 and 3.05 bars dm2 h g−1 (1 bar = 100 kPa).

STEADY STATE RESISTANCE TO WATER FLOW IN CORN UNDER WELL WATERED CONDITIONS

1975 ◽  
Vol 55 (4) ◽  
pp. 941-948 ◽  
Author(s):  
P. A. DUBÉ ◽  
K. R. STEVENSON ◽  
G. W. THURTELL ◽  
H. H. NEUMANN
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Leaf Water Potential ◽  
Water Movement ◽  
Leaf Water ◽  
In Vivo Detection ◽  
Staining Techniques ◽  
Total Plant ◽  
Potential Gradients

Determinations of plant resistance to water flow from measurements of leaf water potential at steady transpiration rates were made on different lines of corn (Zea mays L.). Two inbreds, Q188, a wilting mutant, and DR1, an inbred line shown to have at least some heat and drought tolerance under field conditions, were compared to a commercial single-cross hybrid, United 106. The purpose of the experiment was to isolate the cause of the wilting characteristic of Q188. A linear relationship was found between leaf water potential and transpiration rate for all lines. No water potential gradients were found at zero transpiration. Low total plant resistances were observed in United 106 and DR1, with the major resistance being in the root system in both genotypes. Although the resistance to water movement through the roots and lower stalk in Q188 did not appear to differ from those of the other lines, a much larger resistance was found in the upper stalk of Q188; resistance to water movement through the lower stalk (up to node 5) decreased as the plants matured from 55 to 70 days of age but no comparable changes occurred in the upper portions of the stem. In vivo detection of the xylem vessels with staining techniques confirmed the observed differences in resistances.

scholarly journals A minimally disruptive method for measuring water potential in planta using hydrogel nanoreporters

2021 ◽  
Vol 118 (23) ◽  
pp. e2008276118
Author(s):  
Piyush Jain ◽  
Weizhen Liu ◽  
Siyu Zhu ◽  
Christine Yao-Yun Chang ◽  
Jeff Melkonian ◽  
...  
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Water Status ◽  
Resonance Energy ◽  
Field Measurements ◽  
Leaf Water ◽  
Plant Water Status ◽  
Plant Water ◽  
In Planta

Leaf water potential is a critical indicator of plant water status, integrating soil moisture status, plant physiology, and environmental conditions. There are few tools for measuring plant water status (water potential) in situ, presenting a critical barrier for developing appropriate phenotyping (measurement) methods for crop development and modeling efforts aimed at understanding water transport in plants. Here, we present the development of an in situ, minimally disruptive hydrogel nanoreporter (AquaDust) for measuring leaf water potential. The gel matrix responds to changes in water potential in its local environment by swelling; the distance between covalently linked dyes changes with the reconfiguration of the polymer, leading to changes in the emission spectrum via Förster Resonance Energy Transfer (FRET). Upon infiltration into leaves, the nanoparticles localize within the apoplastic space in the mesophyll; they do not enter the cytoplasm or the xylem. We characterize the physical basis for AquaDust’s response and demonstrate its function in intact maize (Zea mays L.) leaves as a reporter of leaf water potential. We use AquaDust to measure gradients of water potential along intact, actively transpiring leaves as a function of water status; the localized nature of the reporters allows us to define a hydraulic model that distinguishes resistances inside and outside the xylem. We also present field measurements with AquaDust through a full diurnal cycle to confirm the robustness of the technique and of our model. We conclude that AquaDust offers potential opportunities for high-throughput field measurements and spatially resolved studies of water relations within plant tissues.

Impact of soil water potential pattern on root water uptake distribution and leaf water potential

2021 ◽  
Author(s):  
Ali Mehmandoost Kotlar ◽  
Mathieu Javaux
Keyword(s):  
Water Potential ◽  
Root System ◽  
Soil Water ◽  
Water Flow ◽  
Water Uptake ◽  
Leaf Water Potential ◽  
Root Water Uptake ◽  
Leaf Water ◽  
Hydraulic Lift ◽  
Water Potentials

<p>Root water uptake is a major process controlling water balance and accounts for about 60% of global terrestrial evapotranspiration. The root system employs different strategies to better exploit available soil water, however, the regulation of water uptake under the spatiotemporal heterogeneous and uneven distribution of soil water is still a major question. To tackle this question, we need to understand how plants cope with this heterogeneity by adjustment of above ground responses to partial rhizosphere drying. Therefore, we use R-SWMS simulating soil water flow, flow towards the roots, and radial and the axial flow inside the root system to perform numerical experiments on a 9-cell gridded rhizotrone (50 cm×50 cm). The water potentials in each cell can be varied and fixed for the period of simulation and no water flow is allowed between cells while roots can pass over the boundaries. Then a static mature maize root architecture to different extents invaded in all cells is subjected to the various arrangements of cells' soil water potentials. R-SWMS allows determining possible hydraulic lift in drier areas. With these simulations, the variation of root water and leaf water potential will be determined and the role of root length density in each cell and corresponding average soil-root water potential will be statistically discussed.</p>

Effects of disrupting stem sapwood water conduction on the water status in Douglas-fir crowns

1985 ◽  
Vol 15 (5) ◽  
pp. 982-985 ◽  
Author(s):  
H. Brix ◽  
A. K. Mitchell
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Leaf Water Potential ◽  
Water Status ◽  
Soil Water Potential ◽  
Douglas Fir ◽  
Leaf Water ◽  
Cross Sectional ◽  
Breast Height ◽  
Water Conduction

The sapwood cross-sectional area at breast height was reduced by 0 (control), 42, 69, and 100%, in 36-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees to study treatment effects on the water status in the crowns. Only the complete removal of breast-height sapwood affected the leaf water potential which decreased rapidly the 1st day, but then changed little for the next 38 days varying only from −2.3 to −2.6 MPa. Water use for those trees was limited to that stored above breast height, primarily in stem sapwood, and amounted to approximately 45 L. This corresponded to 6.5 mm of precipitation or 4% of potential transpiration. The finding that leaf water potential was not affected by partial sapwood reduction but rather by changes in soil water potential suggests that resistance to water flow in stems was small compared with that in other parts of the water-flow pathways of soil and trees.

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