Root‐to‐shoot signalling when soil moisture is heterogeneous: increasing the proportion of root biomass in drying soil inhibits leaf growth and increases leaf abscisic acid concentration

Martin-Vertedor, Ana Isabel; Dodd, Ian C.

doi:10.1111/j.1365-3040.2011.02315.x

Cited by 83 publications

(34 citation statements)

References 44 publications

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“…Wheat plants regulated stomata in response to drying signals from the roots in the top drying layer of the soil profile even though leaf water status was maintained by unlimited water supply from deeper soil layers (Blum and Johnson, 1993; Saradadevi et al, 2015). These findings were substantiated with increased ABA concentration in barley leaves when more seminal roots were distributed in the dry half of the pots (Martin-Vertedor and Dodd, 2011). This proves that root distribution plays an important role in signal generation and subsequent stomatal regulation.…”

Section: Root Distribution In Stomatal Regulationmentioning

confidence: 77%

ABA-Mediated Stomatal Response in Regulating Water Use during the Development of Terminal Drought in Wheat

2017

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End-of-season drought or “terminal drought,” which occurs after flowering, is considered the most significant abiotic stress affecting crop yields. Wheat crop production in Mediterranean-type environments is often exposed to terminal drought due to decreasing rainfall and rapid increases in temperature and evapotranspiration during spring when wheat crops enter the reproductive stage. Under such conditions, every millimeter of extra soil water extracted by the roots benefits grain filling and yield and improves water use efficiency (WUE). When terminal drought develops, soil dries from the top, exposing the top part of the root system to dry soil while the bottom part is in contact with available soil water. Plant roots sense the drying soil and produce signals, which on transmission to shoots trigger stomatal closure to regulate crop water use through transpiration. However, transpiration is linked to crop growth and productivity and limiting transpiration may reduce potential yield. While an early and high degree of stomatal closure affects photosynthesis and hence biomass production, a late and low degree of stomatal closure exhausts available soil water rapidly which results in yield losses through a reduction in post-anthesis water use. The plant hormone abscisic acid (ABA) is considered the major chemical signal involved in stomatal regulation. Wheat genotypes differ in their ability to produce ABA under drought and also in their stomatal sensitivity to ABA. In this viewpoint article we discuss the possibilities of exploiting genotypic differences in ABA response to soil drying in regulating the use of water under terminal drought. Root density distribution in the upper drying layers of the soil profile is identified as a candidate trait that can affect ABA accumulation and subsequent stomatal closure. We also examine whether leaf ABA can be designated as a surrogate characteristic for improved WUE in wheat to sustain grain yield under terminal drought. Ease of collecting leaf samples to quantify ABA compared to extracting xylem sap will facilitate rapid screening of a large number of germplasm for drought tolerance.

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Section: Root Distribution In Stomatal Regulationmentioning

confidence: 77%

ABA-Mediated Stomatal Response in Regulating Water Use during the Development of Terminal Drought in Wheat

2017

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“…Whole plant transpiration rate was monitored gravimetrically, and corrected for soil evaporation using pots without plants for both watering regimes. Leaf water and osmotic potentials were measured as previously described (Martin-Vertedor & Dodd, 2011). Leaf water potential was measured in 8 mm discs punched from young fully expanded leaves at the top of the canopy just prior to irrigation (thus at the period of maximum soil water deficit).…”

Section: Pot Experimentsmentioning

confidence: 99%

Rhizobacteria that produce auxins and contain 1‐amino‐cyclopropane‐1‐carboxylic acid deaminase decrease amino acid concentrations in the rhizosphere and improve growth and yield of well‐watered and water‐limited potato (Solanum tuberosum)

Белимов

Dodd

Safronova

et al. 2015

Annals of Applied Biology

134

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Plant-growth-promoting rhizobacteria (PGPR) utilise amino acids exuded from plant root systems, but hitherto there have been no direct measurements of rhizosphere concentrations of the amino acid 1-amino-cyclopropane-1-carboxylic acid (ACC) following inoculation with PGPR containing the enzyme ACC deaminase. When introduced to the rhizosphere of two potato (Solanum tuberosum) cultivars (cv. Swift and cv. Nevsky), various ACC deaminase containing rhizobacteria (Achromobacter xylosoxidans Cm4, Pseudomonas oryzihabitans Ep4 and Variovorax paradoxus 5C-2) not only decreased rhizosphere ACC concentrations but also decreased concentrations of several proteinogenic amino acids (glutamic acid, histidine, isoleucine, leucine, phenylalanine, serine, threonine, tryptophan, tyrosine, valine). These effects were not always correlated with the ability of the bacteria to metabolise these compounds in vitro, suggesting bacterial mediation of root amino acid exudation. All rhizobacteria showed similar root colonisation following inoculation of sand cultures, thus species differences in amino acid utilisation profiles apparently did not confer any selective advantage in the potato rhizosphere. Rhizobacterial inoculation increased root biomass (by up to 50%) and tuber yield (by up to 40%) in pot trials, and tuber yield (by up to 27%) in field experiments, especially when plants were grown under water-limited conditions. Nevertheless, inoculated and control plants showed similar leaf water relations, indicating that alternative mechanisms (regulation of phytohormone balance) were responsible for growth promotion. Rhizobacteria generally increased tuber number more than individual tuber weight, suggesting that accelerated vegetative development was responsible for increased yield.

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“…Thus, we addressed the effects of exogenous ABA on AQPs and hydraulic conductance of barley plants differing in ABA concentration. We compared the abundance of ABA and AQP isoforms in root tissues and Lp Root in the ABA-deficient (but not insensitive) barley mutant Az34 (Walker-Simmons et al, 1989, Martin-Vertedor andDodd, 2011) and its parent 'Steptoe'. Previous studies indicated that Az34 retained normal stomatal (Mulholland et al, 1996) and leaf growth (Martin-Vertedor and Dodd, 2011) sensitivity to addition of exogenous ABA.…”

Section: Introductionmentioning

confidence: 99%

Exogenous application of abscisic acid (ABA) increases root and cell hydraulic conductivity and abundance of some aquaporin isoforms in the ABA-deficient barley mutant Az34

Sharipova

Веселов

Kudoyarova

et al. 2016

Ann Bot

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Background and Aims Regulation of water channel aquaporins (AQPs) provides another mechanism by which abscisic acid (ABA) may influence water flow through plants. To the best of our knowledge, no studies have addressed the changes in ABA levels, the abundance of AQPs and root cell hydraulic conductivity (Lp Cell ) in the same tissues. Thus, we followed the mechanisms by which ABA affects root hydraulics in an ABA-deficient barley mutant Az34 and its parental line 'Steptoe'. We compared the abundance of AQPs and ABA in cells to determine spatial correlations between AQP abundance and local ABA concentrations in different root tissues. In addition, abundance of AQPs and ABA in cortex cells was related to Lp Cell.Methods Root hydraulic conductivity (Lp Root ) was measured by means of root exudation analyses and Lp Cell using a cell pressure probe. The abundance of ABA and AQPs in root tissues was assessed through immunohistochemical analyses. Isoform-specific antibodies raised against HvPIP2;1, HvPIP2;2 and HvPIP2;5 were used.Key Results Immunolocalization revealed lower ABA levels in root tissues of Az34 compared with 'Steptoe'. Root hydraulic conductivity (Lp Root ) was lower in Az34, yet the abundance of HvPIPs in root tissues was similar in the two genotypes. Root hair formation occurred closer to the tip, while the length of the root hair zone was shorter in Az34 than in 'Steptoe'. Application of external ABA to the root medium of Az34 and 'Steptoe' increased the immunostaining of root cells for ABA and for HvPIP2;1 and HvPIP2;2 especially in root epidermal cells and the cortical cell layer located beneath, parallel to an increase in Lp Root and Lp Cell . Treatment of roots with Fenton reagent, which inhibits AQP activity, prevented the ABA-induced increase in root hydraulic conductivity.Conclusion Shortly after (<2 h) ABA application to the roots of ABA-deficient barley, increased tissue ABA concentrations and AQP abundance (especially the plasma-membrane localized isoforms HvPIP2;1 and HvPIP2;2) were spatially correlated in root epidermal cells and the cortical cell layer located beneath, in conjunction with increased Lp Cell of the cortical cells. In contrast, long-term ABA deficiency throughout seedling development affects root hydraulics through other mechanisms, in particular the developmental timing of the formation of root hairs closer to the root tip and the length of the root hair zone.

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Root‐to‐shoot signalling when soil moisture is heterogeneous: increasing the proportion of root biomass in drying soil inhibits leaf growth and increases leaf abscisic acid concentration

Abstract: To determine whether root-to-shoot signalling of soil moisture heterogeneity depended on root distribution, wild-type (WT) and abscisic acid (

Cited by 83 publications

References 44 publications

ABA-Mediated Stomatal Response in Regulating Water Use during the Development of Terminal Drought in Wheat

ABA-Mediated Stomatal Response in Regulating Water Use during the Development of Terminal Drought in Wheat

Rhizobacteria that produce auxins and contain 1‐amino‐cyclopropane‐1‐carboxylic acid deaminase decrease amino acid concentrations in the rhizosphere and improve growth and yield of well‐watered and water‐limited potato (Solanum tuberosum)

Exogenous application of abscisic acid (ABA) increases root and cell hydraulic conductivity and abundance of some aquaporin isoforms in the ABA-deficient barley mutant Az34

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