Relative sensitivity of leaf elongation and stomatal conductance of cucumber plants to changes in leaf and soil water potentials

1995 ◽  
Vol 75 (4) ◽  
pp. 909-915 ◽  
Author(s):  
Jeffrey Melkonian ◽  
David W. Wolfe
Keyword(s):  
Stomatal Conductance ◽  
Root System ◽  
Soil Water ◽  
Water Relations ◽  
Osmotic Adjustment ◽  
Soil Water Potential ◽  
Irrigation Scheduling ◽  
Leaf Water ◽  
Leaf Elongation ◽  
Split Root

Identification of drought-resistant cucumber genotypes and optimization of irrigation scheduling require an improved understanding of cucumber plant water relations. Stomatal conductance (ks), relative leaf elongation rate (RLER), and leaf water relations were examined on greenhouse-grown cucumber (Cucumis sativus L. 'Marketmore 80') over two drought cycles. Water was withheld from the entire root system of cucumber plants and ks, leaf length, leaf water (ΨL) and osmotic potential, and soil matric potential were measured periodically. In both drought cycles, ks decreased before, and RLER decreased after predawn ΨL began to decline. No osmotic adjustment was found after one drought cycle and slight osmotic adjustment (−0.14 MPa) was observed in expanding leaves after a second drought cycle. Evidence for a nonhydraulic root signal in cucumber was examined in split-root experiments. ΨL was similar in plants which received water to one (stress treatment) or to both halves (control treatment) of the root system. Stomatal conductance and RLER remained at control levels as soil water potential (Ψ soil) around half the root system declined to −0.25 to −0.30 MPa. No convincing evidence for effects of root signals on ks and RLER at lower Ψ soil was observed. Key words:Cucumis sativus L., leaf elongation, osmotic adjustment, split root, stomatal conductance, water stress

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.

scholarly journals SOIL AND LEAF WATER POTENTIAL OF QUERCUS SEMECARPIFOLIA AT PHULCHOWKI HILL, NEPAL

2014 ◽  
Vol 20 ◽  
pp. 115-121
Author(s):  
K. Poudyal
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Leaf Water Potential ◽  
Soil Water Potential ◽  
Adaptation Strategy ◽  
Leaf Water ◽  
Pure Stand ◽  
Natural Ecosystem ◽  
Quercus Semecarpifolia

Quercus semecarpifolia is a high altitude oak and dominant species of central Himalayan vegetation.In the central Himalaya, plants are subjected to a prolonged dry period, thus developing moisturestress. Soil water potential at 15 cm and 30 cm depth, predawn and midday leaf water potential andtheir relationship with stomatal conductance and phenological behaviour was studied at PhulchowkiHill, Kathmandu to evaluate the drought adaptation strategy of Q. semecarpifolia in a pure stand at2130 m elevation. The natural ecosystem of Himalayan region has a characteristic climatic pattern ofconcentrated rainfall and a prolonged dry season which have a strong effect on the adaptability of thisspecies. It maintained a high predawn leaf water potential (ΨL pd) and stomatal conductance (gw)despite low soil water Ψ and ΨL pd . Lowest Ψs and ΨL pd were observed in March 1999, when therewas almost no rain for five months. Mean ΨL pd and ΨL md were (–1.79 and –2.29 MPa, respectively).Patterns of ΨL pd and ΨL md correlated significantly with soil Ψ, and phenology as ΨL pd oftenincreased during leafing but not with gw.DOI: http://dx.doi.org/10.3126/eco.v20i0.11473ECOPRINT An International Journal of EcologyVol. 20, 2013page: 115-121

Potential role of soil moisture deficit in the distribution of Cakile edentula

1986 ◽  
Vol 64 (11) ◽  
pp. 2789-2791 ◽  
Author(s):  
R. Wayne Tyndall ◽  
Alan H. Teramura ◽  
Larry W. Douglass
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Leaf Water Potential ◽  
Soil Water Potential ◽  
Leaf Water ◽  
Moisture Deficit ◽  
Cakile Edentula ◽  
Survival And Growth

Soil water potential, leaf water potential, and stomatal conductance of Cakile edentula (Bigelow) Hooker were compared between beach and foredune habitats on Currituck Bank, North Carolina. All three variables were significantly lower on the foredune than on the beach. Low soil water potential on the foredune may contribute to low survival and growth inhibition by lowering leaf water potential and stomatal conductance.

Water Relations of Winter Wheat: the Root System, Petiolar Resistance and Development of a Root Abstraction Equation

1985 ◽  
Vol 21 (4) ◽  
pp. 377-388 ◽  
Author(s):  
M. McGowan ◽  
E. Tzimas
Keyword(s):  
Winter Wheat ◽  
Root System ◽  
Soil Water ◽  
Water Uptake ◽  
Water Relations ◽  
Field Experiments ◽  
Soil Water Potential ◽  
Root Systems ◽  
Wheat Crop ◽  
Winter Wheat Crop

SUMMARYThe vertical distribution of water potentials within the leaf canopy, along the stem and within the soil profile of a winter wheat crop was analysed and it is concluded the failure by previous workers to recognize the significance of petiolar resistance has probably resulted in over-estimates of the resistance of the soil to water uptake by root systems of field crops.From an analysis of the water relations of several winter wheat crops an equation is developed to describe the extraction of soil water reserves by crop root systems, based upon values of soil water potential, root xylem potential and ‘effective’ resistance to water uptake which can be obtained from field experiments. The equation provides an empirical basis to specify the minimum desirable root system for efficient capture of soil water reserves, to analyse the effects of differing root distributions and thus to help identify situations where it would be profitable to modify rooting either by tillage or by plant breeding.

Alternation of wet and dry sides during partial rootzone drying irrigation alters root-to-shoot signalling of abscisic acid

2006 ◽  
Vol 33 (12) ◽  
pp. 1081 ◽  
Author(s):  
Ian C. Dodd ◽  
Julian C. Theobald ◽  
Mark A. Bacon ◽  
William J. Davies
Keyword(s):  
Stomatal Conductance ◽  
Root System ◽  
Soil Water ◽  
Water Status ◽  
Leaf Water ◽  
Transpiration Stream ◽  
The Difference ◽  
Partial Rootzone Drying ◽  
Negative Impacts ◽  
Leaf Water Deficit

Partial rootzone drying (PRD) is an irrigation technique where water is distributed unevenly to the root system such that part is irrigated while the remainder is allowed to dry the soil. Tomato (Lycopersicon esculentum Mill.) plants were grown with their roots in two soil columns to compare the physiological consequences of alternation of wet and dry columns during PRD irrigation (alternate PRD, PRD-A) with retention of the same wet and dry columns (fixed PRD, PRD-F). When PRD plants received 50% less water than well-watered (WW) plants, xylem ABA concentration ([X-ABA]) increased and stomatal conductance decreased relative to WW plants. Although both sets of PRD plants received the same amount of water, [X-ABA] of PRD-A plants increased up to 2-fold above that of PRD-F plants, which further decreased stomatal conductance. Differences in [X-ABA] were detected within an hour of alternation, but did not persist beyond the photoperiod of alternation. [X-ABA] increased linearly as whole-pot soil water content (θpot) and leaf water potential (Ψleaf) declined, but the difference in [X-ABA] between the two sets of PRD plants was not due to differences in either θpot or Ψleaf. In PRD-F plants, the unwatered part of the root system contributes proportionally less to the transpiration stream as the soil progressively dries (Yao et al. 2001, Plant, Cell & Environment 24, 227–235). In PRD-A plants, we hypothesise that re-watering the dry part of the root system allows these roots to contribute proportionally more to total sap flux, thus liberating a pulse of ABA to the transpiration stream as the root ABA pool accumulated during soil drying is depleted. Since the enhancement of [X-ABA] caused by PRD-A increased as θpot and Ψleaf declined, an optimal frequency of alternation to maximise the cumulative physiological effects of this ABA pulse must consider possible negative impacts of leaf water deficit as soil water status declines.

Biomass allocation in tomato (Lycopersicon esculentum) plants grown under partial rootzone drying: enhancement of root growth

2004 ◽  
Vol 31 (10) ◽  
pp. 971 ◽  
Author(s):  
Darren M. Mingo ◽  
Julian C. Theobald ◽  
Mark A. Bacon ◽  
William J. Davies ◽  
Ian C. Dodd
Keyword(s):  
Lycopersicon Esculentum ◽  
Root System ◽  
Biomass Allocation ◽  
Root Biomass ◽  
Leaf Water ◽  
Total Biomass ◽  
Split Root ◽  
Split Root System ◽  
Partial Rootzone Drying ◽  
And Control

Tomato (Lycopersicon esculentum Mill.) plants were grown in either a glasshouse (GH) or a controlled environment cabinet (CEC) to assess the effects of partial rootzone drying (PRD) on biomass allocation. Control and PRD plants received the same amounts of water. In control plants, water was equally distributed between two compartments of a split-root system. In PRD plants, only one compartment was watered while the other was allowed to dry. At the end of each drying cycle, wet and dry compartments were alternated. In the GH, total biomass did not differ between PRD and control plants after four cycles of PRD, but PRD increased root biomass by 55% as resources were partitioned away from shoot organs. In the CEC, leaf water potential did not differ between treatments at the end of either of two cycles of PRD, but stomatal conductance of PRD plants was 20% less at the end of the first cycle than at the beginning. After two cycles of PRD in the CEC, biomass did not differ between PRD and control plants, but PRD increased root biomass by 19% over the control plants. The promotion of root biomass in PRD plants was associated with the alternation of wet and dry compartments, with increased root biomass occurring in the re-watered compartment after previous exposure to soil drying. Promotion of root biomass in field-grown PRD plants may allow the root system to access resources (water and nutrients) that would otherwise be unavailable to control plants. This may contribute to the ability of PRD plants to maintain similar leaf water potentials to conventionally irrigated plants, even when smaller irrigation volumes are supplied.

scholarly journals Stem girth changes in response to soil water potential in lowland dipterocarp forest in Borneo: a time-series analysis

2020 ◽  
Author(s):  
D. M. Newbery ◽  
M. Lingenfelder
Keyword(s):  
Time Series ◽  
Soil Water ◽  
Water Relations ◽  
Time Series Data ◽  
Soil Water Potential ◽  
Series Data ◽  
Relative Depth ◽  
Ecological Processes ◽  
Flux Dynamics ◽  
Negative Relationships

AbstractTime series data offer a way of investigating the causes driving ecological processes. To test for possible differences in water relations between species of different forest structural guilds, daily stem girth increments (gthi), of 18 trees across six species were regressed individually on soil moisture potential (SMP) and temperature (TEMP), accounting for temporal autocorrelation (in GLS-arima models), and compared between a wet and a dry period. Coefficients were estimates of response in gthi to increasing SMP or TEMP. The best-fitting significant variables were SMP the day before and TEMP the same day. The first resulted in a mix of positive and negative coefficients, the second largely positive ones. Negative relationships for large canopy trees can be interpreted in a reversed causal sense: fast transporting stems depleted soil water and lowered SMP. Positive relationships for understorey trees meant they took up most water at high SMP. The unexpected negative relationships for these understorey trees may have been due to their roots accessing deeper water supplies (SMP being inversely related to that of the surface layer), this influenced by competition with larger neighbour trees. A tree-soil flux dynamics manifold may have been operating. Patterns of mean diurnal girth variation were more consistent among species than, but weakly related to, time-series coefficients, suggesting no simple trait-based differentiation of responses. Expected differences in response to SMP in the wet and dry periods did not support a previous hypothesis for drought and non-drought tolerant understorey guilds. Trees within species showed highly individual responses. Time-series gthi-SMP regressions might be applied as indicators of relative depth of access to water for small trees. Obtaining detailed information on individual tree’s root systems and recording SMP at many depths and locations are needed to get closer to the mechanisms that underlie complex tree-soil water relations in tropical forests.

scholarly journals Stomatal conductance and root-to-shoot signalling in chestnut saplings exposed to Phytophthora cinnamomi or partial soil drying

2004 ◽  
Vol 31 (1) ◽  
pp. 41 ◽  
Author(s):  
Marion Maurel ◽  
Cécile Robin ◽  
Thierry Simonneau ◽  
Denis Loustau ◽  
Erwin Dreyer ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Potential Role ◽  
Phytophthora Cinnamomi ◽  
Castanea Sativa ◽  
Hydraulic Conductance ◽  
Leaf Water ◽  
Split Root

The effects of root infection by Phytophthora cinnamomi on stomatal conductance in Castanea sativa L. saplings were investigated to determine the potential role of root-derived chemical signals. A split-root experiment was carried out, in which inoculation of the pathogen or drought was applied to the root systems in either one or both compartments. At the end of the experiment plant sap extracts were collected and their effects on stomatal conductance were determined by leaf bioassay. Inoculation or drought imposed in both compartments resulted in decreases in stomatal conductance (gs), transpiration rate, soil-to-leaf specific hydraulic conductance, leaf water potential, xylem [ABA] and root biomass, but not in the ratio of root-to-leaf mass in inoculated plants. Conversely, only gs and xylem [ABA] were affected in plants inoculated or droughted in one compartment, and no changes were detectable in leaf water potential and soil-to-leaf specific hydraulic conductance. The leaf bioassay showed that gs in chestnut was sensitive to ABA but not to Phytophthora elicitins. Stomatal conductance was reduced by some sap extracts, both from control and inoculated plants. Our results suggest the involvement of different signals, chemical and hydraulic, in regulating stomatal conductance of chestnut at different stages of stress.

Leaf Gas Exchange and Water Relations of Lupins and Wheat. II. Root and Shoot Water Relations of Lupin During Drought-Induced Stomatal Closure

1989 ◽  
Vol 16 (5) ◽  
pp. 415 ◽  
Author(s):  
CR Jensen ◽  
IE Henson ◽  
NC Turner
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Transport ◽  
Water Uptake ◽  
Water Relations ◽  
Leaf Gas Exchange ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Root Water Uptake ◽  
Leaf Conductance

Plants of Lupinus cosentinii Guss. cv. Eregulla were grown in a sandy soil in large containers in a glasshouse and exposed to drought by withholding water. Under these conditions stomatal closure had previously been shown to be initiated before a significant reduction in leaf water potential was detected. In the experiments reported here, no significant changes were found in water potential or turgor pressure of roots or leaves when a small reduction in soil water potential was induced which led to a 60% reduction in leaf conductance. The decrease in leaf conductance and root water uptake closely paralleled the fraction of roots in wet soil. By applying observed data of soil water and root characteristics, and root water uptake for whole pots in a single-root model, the average water potential at the root surface was calculated. Potential differences for water transport in the soil-plant system, and the resistances to water flow were estimated using the 'Ohm's Law' analogy for water transport. Soil resistance was negligible or minor, whereas the root resistance accounted for 61-72% and the shoot resistance accounted for about 30% of the total resistance. The validity of the measurements and calculations is discussed and the possible role of root- to-shoot communication raised.

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