Modelling diurnal patterns of leaf water potential in field conditions

1986 ◽  
Vol 33 (2-4) ◽  
pp. 185-203 ◽  
Author(s):  
Nader Katerji ◽  
Marc Hallaire ◽  
Yvette Menoux-Boyer ◽  
Brigitte Durand
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Leaf Water ◽  
Field Conditions ◽  
Diurnal Patterns

Seasonal and Diurnal Patterns of Carbon Assimilation, Stomatal Conductance and Leaf Water Potential in Eucalyptus tetrodonta Saplings in a Wet - Dry Savanna in Northern Australia

1997 ◽  
Vol 45 (2) ◽  
pp. 241 ◽  
Author(s):  
L. D. Prior ◽  
D. Eamus ◽  
G. A. Duff
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Linear Relationship ◽  
Leaf Water Potential ◽  
Stomatal Closure ◽  
Carbon Assimilation ◽  
Leaf Water ◽  
Daily Maximum ◽  
Diurnal Patterns ◽  
Log Linear

Seasonal and diurnal trends in carbon assimilation, stomatal conductance and leaf water potential were studied using 1–3 m tall saplings of Eucalyptus tetrodonta (F.Muell.). The study site was in an unburnt savanna near Darwin, where rainfall is strongly seasonal. Mean daily maximum assimilation rates ranged from 14.5 µmol m-2 s-1 in May to 4.8 µmol m-2 s-1 in October. There was a linear relationship between daily maximum assimilation rates and pre-dawn leaf water potential (r = 0.62, n = 508) and a log–log linear relationship between daily maximum stomatal conductance and pre-dawn leaf water potential (r = 0.68, n = 508). Assimilation rates and stomatal conductance were always higher in the morning than in the afternoon, irrespective of season. Stomatal conductance responded more strongly to leaf-to-air vapour pressure difference when pre-dawn leaf water potentials were moderately low (–0.5 to –1.5 MPa) than when they were very low (< –1.5 MPa) or high (> –0.5 MPa). Assimilation decreased sharply when temperature exceeded 35˚C. Seasonal trends in assimilation rate could be attributed primarily to stomatal closure, but diurnal trends could not. High leaf temperatures were a major cause of lower assimilation rates in the afternoon. Approximately 90% of leaves were lost by the end of the dry season, and above-ground growth was very slow. It is hypothesised that E. tetrodonta saplings allocate most photosynthate to root and lignotuber growth in order to tolerate seasonal drought and the high frequency of fire in northern Australian savannas.

Stomatal Responses and Whole-Tree Hydraulic Conductivity of Orchard Macadamia integrifolia Under Irrigated and Non-Irrigated Conditions

1991 ◽  
Vol 18 (6) ◽  
pp. 661 ◽  
Author(s):  
J Lloyd ◽  
T Trochoulias ◽  
R Ensbey
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Water Status ◽  
Simple Expression ◽  
Leaf Water ◽  
Leaf Water Status ◽  
Diurnal Patterns ◽  
Macadamia Integrifolia ◽  
Independent Variable

Diurnal patterns of stomatal conductance (gs) and leaf water potential (Ψ1) were determined for leaves on irrigated and non-irrigated 5-year-old Macadamia integrifolia trees over a 4-month period from September to December 1989. An empirical model for stomatal conductance was developed for irrigated trees using relationships to photon irradiance (I), leaf temperature (T1) and vapour mole fraction difference (D). This model accounted for 69% of the variance in gs, and was not improved by the inclusion of Ψ1 as an independent variable. Fitted parameters led to the effective prediction of gs for untried combinations of environmental variables. By using a simple expression to link leaf water potential to transpiration rate (E), the model was extended to prediction of Ψ1 from measurements of I, T1 and D. Stornatal conductances were significantly lower on non-irrigated trees after a 2-month dry period. Lower stornatal conductances were not accompanied by more negative Ψ1 indicating that soil rather than leaf water status may control gs in macadamia trees under non-irrigated conditions.

scholarly journals Behaviour study of "Danlas" grapevines grown under plastic cover

OENO One ◽  
2003 ◽  
Vol 37 (2) ◽  
pp. 117
Author(s):  
Aziz Ezzahouani
Keyword(s):  
Ambient Temperature ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Atlantic Coast ◽  
Canopy Temperature ◽  
Titratable Acidity ◽  
Climatic Conditions ◽  
Leaf Water ◽  
Field Conditions ◽  
Soluble Solids

<p style="text-align: justify;">The aim of this study is to determine the behaviour of ‘Danlas’ grapevines conducted under plastic cover, near atlantic coast, known for its early table grape production. Measurements included climatic conditions, leaf water potential, canopy temperature and production components. The use of plastic cover resulted in an increase of midday ambient temperature and vapor pressure deficit, with a maximum of 5. 7 °C and 1.28 kPa, respectively. Midday canopy temperature under field conditions were lower than ambient temperature by an average of 2.5 °C. The most negative leaf water potential values were recoded for grapevines under plastic cover relatively to field conditions, ranging from –7.2 to –17.0 bars and from –7.0 to –14.0 bars, respectively. Harvest date was advanced by more than one month after the use of plastic cover. Results showed that crop weight, cluster weight and number per vine were not significantly affected. However, the number of berries per cluster was significantly reduced. Plastic cover promoted fruit quality, berry weight and soluble solids concentration were increased by 2.23 g and 1.0 °Brix, respectively. While titratable acidity was decreased by 1.20 g/l.</p>

INDICATORS OF WATER STRESS IN CORN (Zea mays L.)

1984 ◽  
Vol 64 (3) ◽  
pp. 537-546 ◽  
Author(s):  
L. M. DWYER ◽  
D. W. STEWART
Keyword(s):  
Zea Mays ◽  
Water Stress ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Zea Mays L ◽  
Stomatal Resistance ◽  
Leaf Water ◽  
Predawn Leaf Water Potential ◽  
Diurnal Patterns ◽  
Potential Transpiration

Greenhouse experiments were conducted to monitor the response of corn (Zea mays L.) to water stress conditions during and following tasselling, and to compare several indicators of water stress. Daily measurements of soil water content and of evaporative demand were made. The degree of plant water stress was indicated by estimates of minimum daily stomatal resistance, comparison of estimated actual and potential transpiration rates, diurnal patterns of leaf water potential and predawn leaf water potentials taken on lower leaves. Analysis of the series of measurements necessary to estimate minimum daily stomatal resistance, actual to potential transpiration rate ratios, and diurnal patterns of leaf water potential identified periods of relative water stress. The simpler and less time-consuming measurement of predawn leaf water potential compared favorably with these other indicators of water stress. We therefore suggest that predawn leaf water potential is an appropriate diagnostic measurement of water stress with promise for irrigation scheduling, particularly for crops in which irrigation is important for a short but critical period.Key words: Leaf water potential, stomatal resistance, transpiration, vapor pressure deficit, soil water deficit

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