WATER POTENTIAL GRADIENTS AND RESISTANCES OF A SOIL-ROOT SYSTEM MEASURED WITH THE ROOT AND SOIL PSYCHROMETER

1979 ◽  
pp. 99-113 ◽  
Author(s):  
H.B. SO
Keyword(s):  
Water Potential ◽  
Root System ◽  
Potential Gradients

scholarly journals Evidence for root adaptation to a spatially discontinuous water availability in the absence of external water potential gradients

2020 ◽  
Vol 118 (1) ◽  
pp. e2012892118
Author(s):  
Kara R. Lind ◽  
Oskar Siemianowski ◽  
Bin Yuan ◽  
Tom Sizmur ◽  
Hannah VanEvery ◽  
...  
Keyword(s):  
Water Potential ◽  
Root System ◽  
Water Availability ◽  
Root Systems ◽  
Water Sources ◽  
Access To Water ◽  
Paper Microfluidic ◽  
Potential Gradients ◽  
External Water ◽  
Square Array

We hereby show that root systems adapt to a spatially discontinuous pattern of water availability even when the gradients of water potential across them are vanishingly small. A paper microfluidic approach allowed us to expose the entire root system ofBrassica rapaplants to a square array of water sources, separated by dry areas. Gradients in the concentration of water vapor across the root system were as small as 10−4⋅mM⋅m−1(∼4 orders of magnitude smaller than in conventional hydrotropism assays). Despite such minuscule gradients (which greatly limit the possible influence of the well-understood gradient-driven hydrotropic response), our results show that 1) individual roots as well as the root system as a whole adapt to the pattern of water availability to maximize access to water, and that 2) this adaptation increases as water sources become more rare. These results suggest that either plant roots are more sensitive to water gradients than humanmade water sensors by 3–5 orders of magnitude, or they might have developed, like other organisms, mechanisms for water foraging that allow them to find water in the absence of an external gradient in water potential.

Accuracy and Usefulness of Psychrometer and Pressure Chamber for Evaluating Water Potentials of Pinus radiata Needles

1982 ◽  
Vol 9 (5) ◽  
pp. 499 ◽  
Author(s):  
BD Millar
Keyword(s):  
Water Potential ◽  
Pinus Radiata ◽  
Xylem Sap ◽  
Pressure Chamber ◽  
Pressure Potential ◽  
Pine Trees ◽  
Average Water ◽  
Potential Gradients ◽  
Fundamental Uncertainty ◽  
The One

Pressure chamber evaluations of xylem sap pressure potential (P) and thermocouple psychrometric evaluations of average water potential (Ψl) in needles from both transpiring and non-transpiring pine trees (Pinus radiata D. Don) were compared in order to determine the relative accuracy and usefulness of these methods for assessing Ψl. Markedly different but linear P v. Ψl relationships were obtained for pine needles of different age and also for the case where resin exudation masked the xylem and led to a 'resin error'. Evidence suggests that these differences are mainly due to injection and resin errors in pressure chamber determinations totalling as much as 1 MPa (a 10 bar). The psychrometric method appears to be the much more accurate. Radial water potential gradients across leaves did not result in differences between evaluations of P and Ψl, at least in P. radiata. The need for multiple 'calibrations' of the pressure chamber and the fundamental uncertainty about the constancy of such calibrations on the one hand and the slowness of the excised-needle psychrometer on the other can restrict the usefulness of these methods.

Water relations of winter wheat. 5. The root system and osmotic adjustment in relation to crop evaporation

1984 ◽  
Vol 102 (2) ◽  
pp. 415-425 ◽  
Author(s):  
M. McGowan ◽  
P. Blanch ◽  
P. J. Gregory ◽  
D. Haycock
Keyword(s):  
Winter Wheat ◽  
Water Potential ◽  
Root System ◽  
Soil Water ◽  
Osmotic Adjustment ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Plant Water ◽  
Potential Evaporation ◽  
Plant Water Potential

SummaryShoot and root growth and associated leaf and soil water potential relations were compared in three consecutive crops of winter wheat grown in the same field. Despite a profuse root system the crop grown in the second drought year (1976) failed to dry the soil as throughly as the crops in 1975 and 1977. Measurements of plant water potential showed that the restricted utilization of soil water reserves by this crop was associated with failure to make any significant osmotic adjustment, leading to premature loss of leaf turgor and stomatal closure. The implications of these results for models to estimate actual crop evaporation from values of potential evaporation are discussed.

Comparative analysis reveals gravity is involved in the MIZ1-regulated root hydrotropism

2020 ◽  
Vol 71 (22) ◽  
pp. 7316-7330
Author(s):  
Ying Li ◽  
Wei Yuan ◽  
Luocheng Li ◽  
Hui Dai ◽  
Xiaolin Dang ◽  
...  
Keyword(s):  
Water Potential ◽  
Double Mutant ◽  
Root Elongation ◽  
Vertical Orientation ◽  
Tomato Plants ◽  
Oblique Orientation ◽  
Experimental Systems ◽  
Potential Gradients ◽  
Insight Into

Abstract Hydrotropism is the directed growth of roots toward the water found in the soil. However, mechanisms governing interactions between hydrotropism and gravitropism remain largely unclear. In this study, we found that an air system and an agar–sorbitol system induced only oblique water-potential gradients; an agar–glycerol system induced only vertical water-potential gradients; and a sand system established both oblique and vertical water-potential gradients. We employed obliquely oriented and vertically oriented experimental systems to study hydrotropism in Arabidopsis and tomato plants. Comparative analyses using different hydrotropic systems showed that gravity hindered the ability of roots to search for obliquely oriented water, whilst facilitating roots’ search for vertically oriented water. We found that the gravitropism-deficient mutant aux1 showed enhanced hydrotropism in the oblique orientation but impaired root elongation towards water in the vertical orientation. The miz1 mutant exhibited deficient hydrotropism in the oblique orientation but normal root elongation towards water in the vertical orientation. Importantly, in contrast to miz1, the miz1/aux1 double mutant exhibited hydrotropic bending in the oblique orientation and attenuated root elongation towards water in the vertical orientation. Our results suggest that gravitropism is required for MIZ1-regulated root hydrotropism in both the oblique orientation and the vertical orientation, providing further insight into the role of gravity in root hydrotropism.

scholarly journals Water Potential Gradients in Field Tobacco

1970 ◽  
Vol 46 (2) ◽  
pp. 343-346 ◽  
Author(s):  
John E. Begg ◽  
Neil C. Turner
Keyword(s):  
Water Potential ◽  
Potential Gradients

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 Rehydration rates and the prevalence of xylem-hydration of flowers

2018 ◽  
Author(s):  
Adam B. Roddy ◽  
Craig R. Brodersen
Keyword(s):  
Water Potential ◽  
Water Transport ◽  
Plant Canopy ◽  
Abiotic Conditions ◽  
Physiological Constraints ◽  
Diverse Species ◽  
Extant Species ◽  
Significant Difference ◽  
Potential Gradients ◽  
Floral Form

AbstractAngiosperm flowers are remarkably diverse anatomically and morphologically, yet they all must satisfy the physiological constraints of supplying sufficient amounts of water and carbon effectively promote pollination. Flowers often occur in the hottest, driest parts of the plant canopy and can face harsh abiotic conditions. Prior evidence suggests that extant species vary dramatically in how water is delivered to flowers, with some evidence that water may be imported into flowers by the phloem. Here we measured midday water potential gradients between flowers, leaves, and stems often phylogenetically diverse species. We further tested the likelihood of xylem-hydration by measuring rates of rehydration after experimentally induced desiccation. There was no significant difference in rehydration rates between leaves and flowers. These results are consistent with xylem-hydration of flowers and suggest that there has been little modification to the mechanisms of water transport despite the diversity of floral form.

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