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.

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.

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.

Response of the components of sugar beet leaf water potential to a drying soil profile

1987 ◽  
Vol 109 (3) ◽  
pp. 437-444 ◽  
Author(s):  
Kay F. Brown ◽  
M. McGowan ◽  
M. J. Armstrong
Keyword(s):  
Sugar Beet ◽  
Water Potential ◽  
Soil Water ◽  
Leaf Water Potential ◽  
Osmotic Potential ◽  
Seasonal Changes ◽  
Water Movement ◽  
Soil Water Potential ◽  
Leaf Water ◽  
Leaf Osmotic Potential

SummaryFor many field-grown crops, including sugar beet, there is little information on the seasonal changes in leaf water potential and its components as the soil dries. Therefore, seasonal changes in leaf water, osmotic and turgor potentials of sugar beet were measured in two seasons, in crops that experienced differing degrees of soil moisture stress. In 1983 potentials of crops exposed to early and late droughts were compared with those of irrigated crops, and in 1984 measurements were made in a non-irrigated crop. In the irrigated crop the midday leaf water potential changed little during the season, except in response to fluctuating evaporative demand. In the drought and non-irrigated treatments there was a sharp fall in leaf water potential as soon as the soil water potential decreased. The size of the midday leaf water potential was primarily determined by soil dryness. However, the leaf water potential did not decrease below about — 1·5 MPa in either year. The leaf osmotic potential declined at the same time as the leaf water potential, but the extent to which this happened differed in the two years. Only in the 1984 non-irrigated crop did the osmotic potential continue to decrease as the soil dried, suggesting that osmotic adjustment had taken place in 1984 but not in 1983. Thus higher turgor was maintained in the 1984 crop than in the 1983 drought-affected crops. Some turgors were recorded as apparently negative in 1983.Since the leaf water potential declined to a minimum of about — 1·5 MPa, the soil water potential minima were also about — 1·5 MPa. However, deeper soil was not dried to this extent, suggesting that the extra resistance for water uptake from deep soil was limiting or the rooting density was too low.The pattern of recovery of leaf water potential overnight suggested that the rhizosphere resistance to water movement was small, even as the soil dried. However, measurement of stem water potentials in 1984 indicated that a significant resistance to water flow existed within the aerial part of sugar beet plants. This shows that the use of the water potential in leaves as an estimate of that in stems or roots can be misleading.

Water Relations of the Mistletoe, Amyema miquelii, and Its Host Eucalyptus fasciculosa

1988 ◽  
Vol 36 (3) ◽  
pp. 239 ◽  
Author(s):  
J Whittington ◽  
R Sinclair
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Water Relations ◽  
Leaf Water Potential ◽  
Transpiration Rate ◽  
Water Status ◽  
Leaf Water ◽  
Tissue Water ◽  
The Relationship ◽  
Seasonal Data

Mistletoes have frequently been found to transpire more rapidly than their hosts, and usually maintain a more negative water potential. Leaf water potential and diffusive conductance were monitored from the end of a dry summer (March) through a wet winter (to August) on the mistletoe Amyema miquelii (Lehm. ex Miq.) Tieghem and its host Eucalyptus fasciculosa F. Muell. The calculated transpiration rate of the mistletoe was greater than that of its host, but water potential data showed two unusual features. Firstly, the parasite pre-dawn water potential always remained lower than that of the host, regardless of the host's water status. Secondly, the parasite water potential during the day was on one occasion less negative than that of the host, i.e. a reverse gradient. Tissue water relations studies showed that A. miquelii leaves had more negative solute potential and a larger water capacitance than E. fasciculosa leaves. The unusual features of the seasonal data were explained in terms of a large haustorial resistance to water flow and hysteresis in the relationship between transpiration and water potential in the mistletoe leaf. This hysteresis was thought to be due to the contribution of stored leaf water to transpiration.

The Influence of the Lignotuber on Hydraulic Conductance and Leaf Conductance in Eucalyptus behriana Seedlings

1995 ◽  
Vol 22 (5) ◽  
pp. 857 ◽  
Author(s):  
BA Myers
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Leaf Water Potential ◽  
Hydraulic Conductance ◽  
Leaf Conductance ◽  
Leaf Water ◽  
Mature Trees ◽  
Flow Through ◽  
Transpirational Flow ◽  
Stem Segments

Hydraulic conductances of stem segments and stem-plus-lignotuber segments were estimated for 3-year-old seedlings of the mallee eucalypt Eucalyptus behriana F. Muell. Stems of seedlings were cut underwater and either above or below the lignotuber. Cutting the stem of intact seedlings underwater and above the lignotuber resulted in rapid increases in leaf water potential (Ψ); 1.1 MPa in 10-15 min with a concomitant decrease in leaf conductance. Cutting the stem below the lignotuber did not significantly affect leaf Ψ or leaf conductance. Transpirational flow through whole seedlings and segments of seedlings was about 10-9 m3 s-1. The hydraulic conductance of the lignotuber (2.27 × 10-9 m3 s-1 Mpa-1) was about half that of the stem. This work suggests that resistance to water flow through the lignotuber accounts, in part, for the persistently low dawn Ψ of the foliage of mature trees of E. behriana.

Sign in / Sign up

Export Citation Format

Share Document