scholarly journals A Negative Hydraulic Message from Oxygen-Deficient Roots of Tomato Plants? (Influence of Soil Flooding on Leaf Water Potential, Leaf Expansion, and Synchrony between Stomatal Conductance and Root Hydraulic Conductivity)

1995 ◽  
Vol 109 (3) ◽  
pp. 1017-1024 ◽  
Author(s):  
M. A. Else ◽  
W. J. Davies ◽  
M. Malone ◽  
M. B. Jackson
Keyword(s):  
Hydraulic Conductivity ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Leaf Expansion ◽  
Leaf Water ◽  
Root Hydraulic Conductivity ◽  
Tomato Plants ◽  
Soil Flooding

A model of stomatal closure driven by nonlinearities in soil-plant hydraulics

2021 ◽  
Author(s):  
Fabian Wankmüller ◽  
Mohsen Zarebanadkouki ◽  
Andrea Carminati
Keyword(s):  
Hydraulic Conductivity ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Environmental Conditions ◽  
Plant Traits ◽  
Stomatal Closure ◽  
Leaf Water ◽  
Optimization Models ◽  
Soil Conditions

<p>Predicting plant responses to drought is a long-standing research goal. Since stomata regulate gas-exchange between plants and the atmosphere, understanding their response to drought is fundamental. Current predictions of stomatal behavior during drought mainly rely on empirical models. These models may suit well to a specific set of plant traits and environmental growth conditions, but their predictive value is doubtful when atmospheric and soil conditions change. Stomatal optimization offers an alternative framework to predict stomatal regulation in response to drought for varying environmental conditions and plant traits. Models which apply this optimization principle posit that stomata maximize the carbon gain in relation to a penalty caused by water loss, such as xylem cavitation. Optimization models have the advantage of requiring a limited number of parameters and have been successfully used to predict stomatal response to drought for varying environmental conditions and species. However, a mechanism that enables stomata to optimally close in response to water limitations, and more precisely to a drop in the ability of the soil-plant continuum to sustain the transpiration demand, is not known. Here, we propose a model of stomatal regulation that is linked to abscisic acid (ABA) dynamics (production, degradation and transport) and that allows plants to avoid excessive drops in leaf water potential during soil drying and increasing vapor pressure deficit (VPD). The model assumes that: 1) stomatal conductance (g<sub>s</sub>) decreases when ABA concentration close to the guard cells (C<sub>ABA</sub>) increases; 2) C<sub>ABA</sub> increases with decreasing leaf water potential (due to higher production); and 3) C<sub>ABA</sub> decreases with increasing photosynthesis (e.g. due to faster degradation or transport to the phloem). Our model includes simulations of leaf water potential based on transpiration rate, soil water potential and variable hydraulic conductances of key elements (rhizosphere, root and xylem), and a function linking stomatal conductance to assimilation. It was tested for different soil properties and VPD. The model predicts that stomata close when the relation between assimilation and leaf water potential becomes nonlinear. In wet soil conditions and low VPD, when there is no water limitation, this nonlinearity is controlled by the relation between stomatal conductance and assimilation. In dry soil conditions, when the soil hydraulic conductivity limits the water supply, nonlinearity is controlled by the excessive drop of leaf water potential for increasing transpiration rates. The model predicts different relations between stomatal conductance and leaf water potential for varying soil properties and VPD. For instance, the closure of stomata is more abrupt in sandy soil, reflecting the steep decrease in hydraulic conductivity of sandy soils. In summary, our model results in an optimal behavior, in which stomatal closure avoids excessive (nonlinear) decrease in leaf water potential, similar to other stomatal optimization models. As based on ABA concentration which increases with decreasing leaf water potential but declines with assimilation, this model is a preliminary attempt to link optimization models to a physiological mechanism.</p>

scholarly journals Rapid changes in root HvPIP2;2 aquaporins abundance and ABA concentration are required to enhance root hydraulic conductivity and maintain leaf water potential in response to increased evaporative demand

2018 ◽  
Vol 45 (2) ◽  
pp. 143 ◽  
Author(s):  
Dmitry S. Veselov ◽  
Guzel V. Sharipova ◽  
Stanislav Yu. Veselov ◽  
Ian C. Dodd ◽  
Igor Ivanov ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Water Potential ◽  
Air Temperature ◽  
Leaf Water Potential ◽  
Vapour Pressure Deficit ◽  
Leaf Water ◽  
Evaporative Demand ◽  
Root Hydraulic Conductivity ◽  
Rapid Changes ◽  
Aba Content

To address the involvement of abscisic acid (ABA) in regulating transpiration and root hydraulic conductivity (LpRoot) and their relative importance for maintaining leaf hydration, the ABA-deficient barley mutant Az34 and its parental wild-type (WT) genotype (cv. Steptoe) were grown in hydroponics and exposed to changes in atmospheric vapour pressure deficit (VPD) imposed by air warming. WT plants were capable of maintaining leaf water potential (ψL) that was likely due to increased LpRoot enabling higher water flow from the roots, which increased in response to air warming. The increased LpRoot and immunostaining for HvPIP2;2 aquaporins (AQPs) correlated with increased root ABA content of WT plants when exposed to increased air temperature. The failure of Az34 to maintain ψL during air warming may be due to lower LpRoot than WT plants, and an inability to respond to changes in air temperature. The correlation between root ABA content and LpRoot was further supported by increased root hydraulic conductivity in both genotypes when treated with exogenous ABA (10−5 M). Thus the ability of the root system to rapidly regulate ABA levels (and thence aquaporin abundance and hydraulic conductivity) seems important to maintain leaf hydration.

scholarly journals 082 OFFSETTING EFFECTS OF REDUCED ROOT HYDRAULIC CONDUCTIVITY AND OSMOTIC ADJUSTMENTIN DROUGHT-STRESSED PEACH, OLIVE, CITRUS, AND PISTACHIO

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 439g-440
Author(s):  
M. Rieger
Keyword(s):  
Hydraulic Conductivity ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Prunus Persica ◽  
Stomatal Closure ◽  
Leaf Water ◽  
Poncirus Trifoliata ◽  
Potential Range ◽  
Root Hydraulic Conductivity ◽  
Turgor Maintenance

Root hydraulic conductivity (Lp) and osmotic potential (π) were measured in young, drought-stressed and non-stressed peach (Prunus persica), Olive (Olea europea), Citrumelo (Citrus paradisi x Poncirus trifoliata) and Pistachio (Pistachia integerrima) plants. Drought stress reduced Lp 2.5 to 4.2-fold, depending on species, but π was reduced only in expanded citrumelo leaves and unexpanded olive leaves by 0.34 and 1.4 MPa, respectively. A simulation model of plant water uptake and leaf water relations was constructed to quantify the offsetting effects of reduced Lp and osmotic adjustment (OA) on turgor maintenance. For olive data, a 2.5-fold reduction of Lp caused a linear decrease in turgor pressure difference between stressed and non-stressed plants, such that the effect of OA was totally offset at a leaf water potential (stressed) of ≈ -3.0 MPa. For citrumelo, because the degree of OA was lower, the water potential at which the effects of OA and reduced Lp were offsetting with respect to turgor maintenance was ≈ -0.6 MPa. The analysis suggests that some level of stomatal closure would be necessary to extend the water potential range over which stressed plants maintain higher turgor than non-stressed plants for citrumelo. Conversely, no degree of stomatal closure would be required of stressed olive plants to maintain higher turgor than non-stressed counterparts over a physiologically meaningful range of leaf water potential.

scholarly journals Interactions between leaf water potential, stomatal conductance and abscisic acid content of orange trees submitted to drought stress

2004 ◽  
Vol 16 (3) ◽  
pp. 155-161 ◽  
Author(s):  
Mara de Menezes de Assis Gomes ◽  
Ana Maria Magalhães Andrade Lagôa ◽  
Camilo Lázaro Medina ◽  
Eduardo Caruso Machado ◽  
Marcos Antônio Machado
Keyword(s):  
Abscisic Acid ◽  
Water Stress ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Acid Content ◽  
Stomatal Closure ◽  
Leaf Water ◽  
Orange Trees ◽  
Abscisic Acid Content

Thirty-month-old 'Pêra' orange trees grafted on 'Rangpur' lemon trees grown in 100 L pots were submitted to water stress by the suspension of irrigation. CO2 assimilation (A), transpiration (E) and stomatal conductance (g s) values declined from the seventh day of stress, although the leaf water potential at 6:00 a.m. (psipd) and at 2:00 p.m. (psi2) began to decline from the fifth day of water deficiency. The CO2 intercellular concentration (Ci) of water-stressed plants increased from the seventh day, reaching a maximum concentration on the day of most severe stress. The carboxylation efficiency, as revealed by the ratio A/Ci was low on this day and did not show the same values of non-stressed plants even after ten days of rewatering. After five days of rewatering only psi pd and psi2 were similar to control plants while A, E and g s were still different. When psi2 decreases, there was a trend for increasing abscisic acid (ABA) concentration in the leaves. Similarly, stomatal conductance was found to decrease as a function of decreasing psi2. ABA accumulation and stomatal closure occurred when psi2 was lower than -1.0 MPa. Water stress in 'Pera´ orange trees increased abscisic acid content with consequent stomatal closure and decreased psi2 values.

Drought tolerance of clonal Malus determined from measurements of stomatal conductance and leaf water potential

2000 ◽  
Vol 20 (8) ◽  
pp. 557-563 ◽  
Author(s):  
C. J. Atkinson ◽  
M. Policarpo ◽  
A. D. Webster ◽  
G. Kingswell
Keyword(s):  
Stomatal Conductance ◽  
Drought Tolerance ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Leaf Water

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.

Water Relations and Leaf Structure of the Evergreen Shrubs Eurya emarginata (Theaceae) and E. japonica in Coastal and Inland Habitats

1998 ◽  
Vol 46 (1) ◽  
pp. 135 ◽  
Author(s):  
Masako Mishio ◽  
Naoki Kachi
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Water Content ◽  
Leaf Water Potential ◽  
Unit Area ◽  
Leaf Water ◽  
Photon Flux ◽  
Leaf Water Content ◽  
Shrub Species ◽  
Eurya Emarginata

Stomatal conductance and leaf water potential at around noon, pre-dawn leaf water potential, pressure–volume parameters, and leaf structural characteristics including leaf thickness, leaf dry mass per unit area and turgid leaf water content per unit area were compared between a coastal shrub species, Eurya emarginata (Thunb.) Makino and an inland shrub species, E. japonica Thunb. The pre-dawn leaf water potential was only slightly lower in E. emarginata than in E. japonica, and the environmental conditions such as the photosynthetic photon flux density and the vapour pressure deficit did not differ obviously between the two habitats. No apparent differences were observed in the pressure–volume parameters between the two species. On the other hand, E. emarginata had much higher stomatal conductance and significantly thicker leaves with higher turgid leaf water content per unit area than E. japonica. The thicker leaf with higher water content on an area basis in E. emarginata maintains adequate leaf turgor pressure against a higher rate of transpiration.

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