Water relations and drought resistance of young Pinusbanksiana and P. resinosa plantation trees

1977 ◽  
Vol 7 (1) ◽  
pp. 132-137 ◽  
Author(s):  
J. S. Pereira ◽  
T. T. Kozlowski
Keyword(s):  
Water Potential ◽  
Drought Resistance ◽  
Stomatal Closure ◽  
Growing Season ◽  
Early Morning ◽  
Diffusion Resistance ◽  
Soil Water Depletion ◽  
Water Potentials ◽  
Needle Water Potential ◽  
Better Than

Daytime changes in needle water potential and needle diffusion resistance of young Pinusbanksiana and P. resinosa plantation trees were determined at various times throughout the 1974 growing season in northern Wisconsin. Early in the growing season, early-morning water potential and daytime needle diffusion resistance varied little between the two species. However, midday water potentials generally were higher in P. banksiana than in P. resinosa. As the season progressed, water potentials in the early morning were lower, and they decreased more during the day in P. resinosa than in P. banksiana. In addition, stomata of P. banksiana usually closed earlier in the day. Pinusbanksiana appeared to avoid drought better than P. resinosa because the former maintained a higher needle water potential throughout most of the growing season. This reflected lower transpiration and slower soil water depletion associated with lower leaf area and stomatal closure at higher needle water potential in P. banksiana.

Effect of Water Stress on Stomatal Conductance and Leaf Water Relations of Leaves Along Current-Year Branches of Peach

1989 ◽  
Vol 16 (6) ◽  
pp. 549 ◽  
Author(s):  
SL Steinberg ◽  
MJ Mcfarland ◽  
JC Miller
Keyword(s):  
Water Stress ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Water Status ◽  
Stomatal Closure ◽  
Water Flux ◽  
Leaf Water ◽  
Leaf Water Status ◽  
Mature Leaves ◽  
Water Potentials

A gradation, that reflects the maturity of the leaves, exists in the leaf water, osmotic and turgor potential and stomatal conductance of leaves along current and 1-year-old branches of peach. Predawn leaf water potentials of immature folded leaves were approximately 0.24 MPa lower than mature leaves under both well-watered and dry conditions. During the daytime the leaf water potential of immature leaves reflected the water potential produced by water flux for transpiration. In well- watered trees, mature and immature unfolded leaves had a solute potential at least 0.5 MPa lower than immature folded leaves, resulting in a turgor potential that was approximately 0.8 MPa higher. The turgor requirement for growth appeared to be much less than that maintained in mature leaves. As water stress developed and leaf water potentials decreased, the osmotic potential of immature folded leaves declined to the level found in mature leaves, thus maintaining turgor. In contrast, mature leaves showed little evidence of turgor maintenance. Stomatal conductance was lower in immature leaves than in fully mature leaves. With the onset of water stress, conductance of mature leaves declined to a level near that of immature leaves. Loss of turgor in mature leaves may be a major factor in early stomatal closure. It was concluded that osmotic adjustment played a role in maintenance of a leaf water status favorable for some growth in water-stressed immature peach leaves.

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.

COMPARISON BETWEEN TWO INBRED CORN LINES FOR DIFFUSIVE RESISTANCES, PHOTOSYNTHESIS AND TRANSPIRATION AS A FUNCTION OF LEAF WATER POTENTIAL

1974 ◽  
Vol 54 (4) ◽  
pp. 765-770 ◽  
Author(s):  
P. A. DUBÉ ◽  
K. R. STEVENSON ◽  
G. W. THURTELL
Keyword(s):  
Water Vapor ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Zea Mays L ◽  
Stomatal Closure ◽  
Leaf Water ◽  
Water Potentials ◽  
Diffusive Resistance ◽  
Response To Water ◽  
Mesophyll Resistance

Relationships between (1) photosynthesis (2) transpiration (3) total diffusive resistance to water vapor and (4) mesophyll resistance and leaf water potential were examined in two lines of corn (Zea mays L.) differing in phenotypic response to water stress. One line (Q-188) was a wilting inbred and the other (DR-1) was an inbred known to have at least some heat and drought resistance under field conditions. No differences were found between inbred lines in net photosynthetic rate, transpiration rate and total diffusive resistance to water vapor at high or low leaf water potentials in the light. In both lines, stomatal closure began to occur between − 8.5 to − 9.5 bars. Similarly, rapid increases in both total resistance to water vapor diffusion and mesophyll resistance to carbon dioxide diffusion occurred within a narrow range of water potentials. However, leaf water potential, and thus all other parameters, differed markedly between lines when considered on a time scale. The early wilting of Q-188 suggested that high resistances to water flow were present in the xylem system.

Transpiration and leaf water potentials of wheat in relation to changing soil water potential

1977 ◽  
Vol 28 (3) ◽  
pp. 355 ◽  
Author(s):  
KA Seaton ◽  
JJ Landsberg ◽  
RH Sedgley
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Transpiration Rate ◽  
Water Conservation ◽  
Root Zone ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Stomatal Resistance ◽  
Leaf Water ◽  
Water Potentials

Changes in the transpiration rate of wheat in drying soils were followed in experiments in which plants were grown in two small weighable lysimeters in a glasshouse. Hourly measurements of soil water potential (Ψs) were made at three depths in each lysimeter. The water potential of flag leaves was measured with a pressure chamber, and stomatal resistance with a pressure drop porometer. Data on root densities and distribution were also obtained. Transpiration rates fell below estimated potential levels when the average value of Ψs in the root zone was reduced to –1 to –5 bars, depending on soil storage, root distribution and potential transpiration rate. From this point Ψs fell rapidly in the surface layers, more slowly at depth. It was found that accurate calculations of daily water uptake could be made from changes in soil water content. The minimum value of leaf water potential (�1 )attained each day declined progressively through the drying cycle, but there was evidence that stomatal resistance (rs) is not uniquely related to Ψ1; initial stomatal closure occurred at Ψ1, values which decreased from –11 to –25 bars as drying progressed. This adaptive mechanism is related to changes in osmotic potential of the leaves. Whole plant resistances (Rp), derived from leaf water potentials and fluxes through individual stems, increased as stem populations increased. In the high population lysimeter Rp decreased from 300 to 100 bar sec mm-3 as canopy transpiration rates increased from 1.5 to 4.5 x 10-4 mm sec-1. In the low population lysimeter Rp decreased from 70 to 30 bar sec mm-3 as transpiration increased from about 2.2 to 4.5 x 10-4 mm sec-1. The higher resistances appear to confer significant advantages in terms of water conservation and adaptation to drought.

Influence of light intensity, temperature, and leaf area on stomatal aperture and water potential of woody plants

1977 ◽  
Vol 7 (1) ◽  
pp. 145-153 ◽  
Author(s):  
J. S. Pereira ◽  
T. T. Kozlowski
Keyword(s):  
Light Intensity ◽  
Water Potential ◽  
Leaf Area ◽  
Stomatal Closure ◽  
Time Of Day ◽  
Diffusion Resistance ◽  
Leaf Resistance ◽  
Increasing Temperature ◽  
Opening And Closing ◽  
Temperature Time

Leaf diffusion resistance and shoot water potential of seedlings of six species of woody angiosperms were studied in a 4 × 4 design of crossed gradients of light intensity (1507, 4306, 10 764, and 21 528 lx) and temperature (18, 22.5, 26, and 30 °C). In all species, leaf diffusion resistance generally increased with decreasing light intensity and increasing temperature, but the effects of light intensity were much greater. Highly significant differences on leaf diffusion resistance were found for light intensity, temperature, time of day, and various interactions of these. Shoot water potential of all species decreased with increasing light intensity and temperature. Both leaf resistance and water potential under light and temperature stress varied among species. Despite high leaf resistance under environmental stress, indicating rapid stomatal closure, Acersaccharum with an extensive leaf area developed high shoot water deficits. Stomatal opening and closing in responses to changes in light intensity varied among five species of woody angiosperms but were not consistently correlated with species shade tolerance.

Drought resistance of cotton (Gossypium hirsutum) is promoted by early stomatal closure and leaf shedding

2020 ◽  
Vol 47 (2) ◽  
pp. 91 ◽  
Author(s):  
Ximeng Li ◽  
Renee Smith ◽  
Brendan Choat ◽  
David T. Tissue
Keyword(s):  
Gossypium Hirsutum ◽  
Water Potential ◽  
Drought Resistance ◽  
Leaf Gas Exchange ◽  
Stomatal Closure ◽  
Water Shortage ◽  
Drought Avoidance ◽  
Xylem Vulnerability ◽  
Leaf Shedding

Water relations have been well documented in tree species, but relatively little is known about the hydraulic characteristics of crops. Here, we report on the hydraulic strategy of cotton (Gossypium hirsutum L.). Leaf gas exchange and in vivo embolism formation were monitored simultaneously on plants that were dried down in situ under controlled environment conditions, and xylem vulnerability to embolism of leaves, stems and roots was measured using intact plants. Water potential inducing 50% embolised vessels (P50) in leaves was significantly higher (less negative) than P50 of stems and roots, suggesting that leaves were the most vulnerable organ to embolism. Furthermore, the water potential generating stomatal closure (Pgs) was higher than required to generate embolism formation, and complete stomatal closure always preceded the onset of embolism with declining soil water content. Although protracted drought resulted in massive leaf shedding, stem embolism remained minimal even after ~90% leaf area was lost. Overall, cotton maintained hydraulic integrity during long-term drought stress through early stomatal closure and leaf shedding, thus exhibiting a drought avoidance strategy. Given that water potentials triggering xylem embolism are uncommon under field conditions, cotton is unlikely to experience hydraulic dysfunction except under extreme climates. Results of this study provide physiological evidence for drought resistance in cotton with regard to hydraulics, and may provide guidance in developing irrigation schedules during periods of water shortage.

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

2021 ◽  
Vol 18 (2) ◽  
pp. 739-753
Author(s):  
Nataniel M. 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 05:00 eastern daylight time (UTC−4). 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.

NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

scholarly journals Arabidopsis MADS-box factor AGL16 negatively regulates drought resistance via stomatal density and stomatal movement

2020 ◽  
Vol 71 (19) ◽  
pp. 6092-6106 ◽  
Author(s):  
Ping-Xia Zhao ◽  
Zi-Qing Miao ◽  
Jing Zhang ◽  
Si-Yan Chen ◽  
Qian-Qian Liu ◽  
...  
Keyword(s):  
Drought Stress ◽  
Drought Resistance ◽  
Molecular Mechanisms ◽  
Stomatal Density ◽  
Stomatal Closure ◽  
Negative Regulator ◽  
Stomatal Development ◽  
Mads Box ◽  
Mobility Shift ◽  
Aba Metabolism

Abstract Drought is one of the most important environmental factors limiting plant growth and productivity. The molecular mechanisms underlying plant drought resistance are complex and not yet fully understood. Here, we show that the Arabidopsis MADS-box transcription factor AGL16 acts as a negative regulator in drought resistance by regulating stomatal density and movement. Loss-of-AGL16 mutants were more resistant to drought stress and had higher relative water content, which was attributed to lower leaf stomatal density and more sensitive stomatal closure due to higher leaf ABA levels compared with the wild type. AGL16-overexpressing lines displayed the opposite phenotypes. AGL16 is preferentially expressed in guard cells and down-regulated in response to drought stress. The expression of CYP707A3 and AAO3 in ABA metabolism and SDD1 in stomatal development was altered in agl16 and overexpression lines, making them potential targets of AGL16. Using chromatin immunoprecipitation, transient transactivation, yeast one-hybrid, and electrophoretic mobility shift assays, we demonstrated that AGL16 was able to bind the CArG motifs in the promoters of the CYP707A3, AAO3, and SDD1 and regulate their transcription, leading to altered leaf stomatal density and ABA levels. Taking our findings together, AGL16 acts as a negative regulator of drought resistance by modulating leaf stomatal density and ABA accumulation.

Photosynthesis Response of Sunlit and Shade Pepper (Capsicum annuum) Leaves at Different Positions in the Canopy Under Two Water Regimes

1994 ◽  
Vol 21 (3) ◽  
pp. 377 ◽  
Author(s):  
A Alvino ◽  
M Centritto ◽  
FD Lorenzi
Keyword(s):  
Water Potential ◽  
Capsicum Annuum ◽  
Leaf Water Potential ◽  
Co2 Exchange ◽  
Leaf Water ◽  
Predawn Leaf Water Potential ◽  
Water Regimes ◽  
Water Potentials ◽  
Sun And Shade ◽  
Shade Leaves

Pepper (Capsicum annuum L.) plants were grown in 1 m2 lysimeters under two different water regimes in order to investigate differences in the spatial arrangements of the leaves and to relate this to daily assimilation rates of leaves of the canopy. The control regime (well-watered (W) treatment) was irrigated whenever the accumulated 'A' pan evaporation reached 4 cm, whereas the water-stressed (S) treatment was watered whenever the predawn leaf water potential fell below -1 MPa. During the growing cycle, equal numbers of sun and shade leaves were chosen from the apical, middle and basal parts of the canopy, corresponding to groups of leaves of increasing age. The CO2 exchange rate (CER) was measured at 0830, 1230 and 1530 hours on 8 days along the crop cycle, on leaves in their natural inclination and orientation. Leaf water potentials were measured on apical leaves before dawn and concurrently with gas exchange measurements. Control plants maintained predawn leaf water potential at -0.3 MPa, but S plants reached values lower than -1.2 MPa. Midday leaf water potentials were about twice as low in the S plants as in the controls. Water stress reduced LA1 during the period of crop growth, and dry matter production at harvest. Stressed apical leaves appeared to reduce stress by changing their inclination. They were paraheliotropic around midday and diaheliotropic at 0830 and 1530 hours. The CER values of the S treatment were significantly lower than those of the W treatment in apical and middle leaves, whereas the CER of basal leaves did not differ in either treatments. In the S treatment, reduction in the CER values of sunlit apical leaves was more evident in the afternoon than at midday or early in the morning, whereas basal leaves were less affected by water than basal stress leaves if sunlit, and negligibly in shaded conditions.

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