Arbuscular Mycorrhiza Symbiosis Enhances Water Status and Soil-Plant Hydraulic Conductance Under Drought

Recent studies have identified soil drying as a dominant driver of transpiration reduction at the global scale. Although Arbuscular Mycorrhiza Fungi (AMF) are assumed to play a pivotal role in plant response to soil drying, studies investigating the impact of AMF on plant water status and soil-plant hydraulic conductance are lacking. Thus, the main objective of this study was to investigate the influence of AMF on soil-plant conductance and plant water status of tomato under drought. We hypothesized that AMF limit the drop in matric potential across the rhizosphere, especially in drying soil. The underlying mechanism is that AMF extend the effective root radius and hence reduce the water fluxes at the root-soil interface. The follow-up hypothesis is that AMF enhance soil-plant hydraulic conductance and plant water status during soil drying. To test these hypotheses, we measured the relation between transpiration rate, soil and leaf water potential of tomato with reduced mycorrhiza colonization (RMC) and the corresponding wild type (WT). We inoculated the soil of the WT with Rhizophagus irregularis spores to potentially upsurge symbiosis initiation. During soil drying, leaf water potential of the WT did not drop below −0.8MPa during the first 6days after withholding irrigation, while leaf water potential of RMC dropped below −1MPa already after 4days. Furthermore, AMF enhanced the soil-plant hydraulic conductance of the WT during soil drying. In contrast, soil-plant hydraulic conductance of the RMC declined more abruptly as soil dried. We conclude that AMF maintained the hydraulic continuity between root and soil in drying soils, hereby reducing the drop in matric potential at the root-soil interface and enhancing soil-plant hydraulic conductance of tomato under edaphic stress. Future studies will investigate the role of AMF on soil-plant hydraulic conductance and plant water status among diverse plant species growing in contrasting soil textures

Teorijsko ab initio proučavanje učinaka električnog polja na građu i stabilnost baznog para G:C

The effect of applied external electric field on DNA occurs mostly at high field intensity. The results of a theoretical ab initio study of effects of applied electric field on G:C base pair components are reported. The geometries of the local minima were optimized without the symmetry restrictions by the gradient procedure at density-functional level of the theory and were verified by calculations of the second derivative of energy. The standard CEP-31G basis set was used. The geometrical parameters, relative stability and interaction energies are reported. The electric field mutation could be classified as a multi-point mutation.Učinak vanjskog električnog polja na DNA javlja se najčešće za jaka polja. Izvješćujemo o ishodima proučavanja učinaka vanjskog električnog polja na sastavnice baznog para G:C polazeći od osnova teorije. Razmještaj lokalnih minimuma smo optimizirali bez ograničenja na uvjete simetrije rabeći gradijentan postupak na razini teorije funkcionala gustoće i provjerili računima drugih derivacija energije. Primijenili smo uobičajen osnovni skup CEP-31G. Izvješćujemo o promjenama razmaka, stabilnosti i energijama međudjelovanja. Mutacije električnim poljem mogle bi se razvrstati u višemjesne mutacije

Teorijsko ab initio proučavanje učinaka električnog polja na građu i stabilnost baznog para G:C

The effect of applied external electric field on DNA occurs mostly at high field intensity. The results of a theoretical ab initio study of effects of applied electric field on G:C base pair components are reported. The geometries of the local minima were optimized without the symmetry restrictions by the gradient procedure at density-functional level of the theory and were verified by calculations of the second derivative of energy. The standard CEP-31G basis set was used. The geometrical parameters, relative stability and interaction energies are reported. The electric field mutation could be classified as a multi-point mutation.Učinak vanjskog električnog polja na DNA javlja se najčešće za jaka polja. Izvješćujemo o ishodima proučavanja učinaka vanjskog električnog polja na sastavnice baznog para G:C polazeći od osnova teorije. Razmještaj lokalnih minimuma smo optimizirali bez ograničenja na uvjete simetrije rabeći gradijentan postupak na razini teorije funkcionala gustoće i provjerili računima drugih derivacija energije. Primijenili smo uobičajen osnovni skup CEP-31G. Izvješćujemo o promjenama razmaka, stabilnosti i energijama međudjelovanja. Mutacije električnim poljem mogle bi se razvrstati u višemjesne mutacije

Root hydraulic phenotypes impacting water uptake in drying soils

Soil drying is a limiting factor for crop production worldwide. Yet, it is not clear how soil drying impacts water uptake across different soils, species, and root phenotypes. Here we ask (1) what root phenotypes improve the water use from drying soils? and (2) what root hydraulic properties impact water flow across the soil-plant continuum? The main objective is to propose a hydraulic framework to investigate the interplay between soil and root hydraulic properties on water uptake. We collected highly resolved data on transpiration, leaf and soil water potential across 11 crops and 10 contrasting soil textures. In drying soils, the drop in water potential at the soil-root interface resulted in a rapid decrease in soil hydraulic conductance, especially at higher transpiration rates. The analysis reveals that water uptake was limited by soil within a wide range of soil water potential (-6 to -1000 kPa), depending on both soil textures and root hydraulic phenotypes. We propose that a root phenotype with low root hydraulic conductance, long roots and/or long and dense root hairs postpones soil limitation in drying soils. The consequence of these root phenotypes on crop water use is discussed.ISSN:0140-7791ISSN:1365-304

Stomatal closure of tomato under drought is driven by an increase in soil–root hydraulic resistance

The fundamental question as to what triggers stomatal closure during soil drying remains contentious. Thus, we urgently need to improve our understanding of stomatal response to water deficits in soil and atmosphere. Here, we investigated the role of soil–plant hydraulic conductance (Ksp) on transpiration (E) and stomatal regulation. We used a root pressure chamber to measure the relation between E, leaf xylem water potential (ψleaf-x) and soil water potential (ψsoil) in tomato. Additional measurements of ψleaf-x were performed with unpressurized plants. A soil–plant hydraulic model was used to simulate E(ψleaf-x) for decreasing ψsoil. In wet soils, E(ψleaf-x) had a constant slope, while in dry soils, the slope decreased, with ψleaf-x rapidly and nonlinearly decreasing for moderate increases in E. The ψleaf-x measured in pressurized and unpressurized plants matched well, which indicates that the shoot hydraulic conductance did not decrease during soil drying and that the decrease in Ksp is caused by a decrease in soil–root conductance. The decrease of E matched well the onset of hydraulic nonlinearity. Our findings demonstrate that stomatal closure prevents the drop in ψleaf-x caused by a decrease in Ksp and elucidate a strong correlation between stomatal regulation and belowground hydraulic limitation. KEYWORDS belowground hydraulic, hydraulic conductivity, leaf water potential, soil drying, Solanum lycopersicum L., transpiration, water stres

Declining soil-root hydraulic conductance drives stomatocal closure of tomato under drought

The fundamental question as to what triggers stomatal closure during soil drying remains contentious. Thus, we urgently need to improve our understanding of stomatal response to water deficits in soil and atmosphere. Here, we investigated the role of soil-plant hydraulic conductance (Ksp) on transpiration (E) and stomata regulation. We used a root pressure chamber to measure the relation between E, leaf xylem water potential (ψleaf-x) and soil water potential (ψsoil) in tomato. Additional measurements of ψleaf-x were performed with unpressurized plants. A soil-plant hydraulic model was used to simulate E(ψleaf-x) for decreasing ψsoil. In wet soils, E(ψleaf-x) had a constant slope while in dry soils the slope decreased, with ψleaf-x rapidly and nonlinearly decreasing for moderate increases in E. The ψleaf-x measured in pressurized and unpressurized plants matched well, which indicates that the shoot hydraulic conductance did not decrease during soil drying and that the decrease in Ksp is caused by a decrease in soil-root conductance. The decrease of E matched well the onset of hydraulic nonlinearity. Our findings demonstrate that stomatal closure prevents the drop in ψleaf-x caused by a decrease in Ksp and elucidate a strong correlation between stomatal regulation and belowground hydraulic limitation