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1.
Introduction
In a recent paper, Warren et al. (2013) illustrated the potential of neutron radiography to visualize water dynamics in soil and plants.Methods
After injection of deuterated water (D2O) in soil, the authors could monitor the changes of D2O concentration in roots.Results
Based on the radiographs, the authors concluded that D2O was transported from roots growing in a wet soil region to roots in a dry region, proving hydraulic redistribution between roots. However, this interpretation depends on the correct estimation of D2O concentration in soil.Conclusions
The experiments of Warren et al. (2013) could also be explained by diffusion of D2O from soil to roots, without hydraulic redistribution within the root system. 相似文献2.
Changes in soil hyphal abundance and viability can alter the patterns of hydraulic redistribution by plant roots 总被引:1,自引:0,他引:1
José Ignacio Querejeta Louise M. Egerton-Warburton Iván Prieto Rodrigo Vargas Michael F. Allen 《Plant and Soil》2012,355(1-2):63-73
Background and aims
We conducted a mesocosm study to investigate the extent to which the process of hydraulic redistribution of soil water by plant roots is affected by mycorrhizosphere disturbance.Methods
We used deuterium-labeled water to track the transfer of hydraulically lifted water (HLW) from well-hydrated donor oaks (Quercus agrifolia Nee.) to drought-stressed receiver seedlings growing together in mycorrhizal or fungicide-treated mesocosms. We hypothesized that the transfer of HLW from donor to receiver plants would be enhanced in undisturbed (non-fungicide-treated) mesocosms where an intact mycorrhizal hyphal network was present.Results
Contrary to expectations, both upper soil and receiver seedlings contained significantly greater proportions of HLW in mesocosms where the abundance of mycorrhizal hyphal links between donor and receiver roots had been sharply reduced by fungicide application. Reduced soil hyphal density and viability likely hampered soil moisture retention properties in fungicide-treated mesocosms, thus leading to faster soil water depletion in upper compartments. The resulting steeper soil water potential gradient between taproot and upper compartments enhanced hydraulic redistribution in fungicide-treated mesocosms.Conclusions
Belowground disturbances that reduce soil hyphal density and viability in the mycorrhizosphere can alter the patterns of hydraulic redistribution by roots through effects on soil hydraulic properties. 相似文献3.
Katrin Huber Jan Vanderborght Mathieu Javaux Natalie Schröder Ian C. Dodd Harry Vereecken 《Plant and Soil》2014,384(1-2):93-112
Aims
A simulation model to demonstrate that soil water potential can regulate transpiration, by influencing leaf water potential and/or inducing root production of chemical signals that are transported to the leaves.Methods
Signalling impacts on the relationship between soil water potential and transpiration were simulated by coupling a 3D model for water flow in soil, into and through roots (Javaux et al. 2008) with a model for xylem transport of chemicals (produced as a function of local root water potential). Stomatal conductance was regulated by simulated leaf water potential (H) and/or foliar chemical signal concentrations (C; H?+?C). Split-root experiments were simulated by varying transpiration demands and irrigation placement.Results
While regulation of stomatal conductance by chemical transport was unstable and oscillatory, simulated transpiration over time and root water uptake from the two soil compartments were similar for both H and H?+?C regulation. Increased stomatal sensitivity more strongly decreased transpiration, and decreased threshold root water potential (below which a chemical signal is produced) delayed transpiration reduction.Conclusions
Although simulations with H?+?C regulation qualitatively reproduced transpiration of plants exposed to partial rootzone drying (PRD), long-term effects seemed negligible. Moreover, most transpiration responses to PRD could be explained by hydraulic signalling alone. 相似文献4.
Aims
Root-specific responses to stress are not well-known, and have been largely based on indirect measurements of bulk soil water extraction, which limits mechanistic modeling of root function.Methods
Here, we used neutron radiography to examine in situ root-soil water dynamics of a previously droughted black cottonwood (Populus trichocarpa) seedling, contrasting water uptake by the two major components of the root system that differed in initial recovery rate as apparent by ‘new’ (whiter, thinner), or ‘old’ (darker, thicker) parts of the fine root system.Results
The smaller diameter ‘new’ roots had greater water uptake per unit surface area than the larger diameter ‘old’ roots, but they had less total surface area leading to less total water extraction; rates ranged from 0.0027–0.0116 g cm?2 h?1. The finest most-active roots were not visible in the radiographs, indicating the need to include destructive sampling. Analysis based on root-free bulk soil hydraulic properties indicated substantial redistribution of water via saturated/unsaturated flow and capillary wicking across the layers - suggesting water uptake dynamics following an infiltration event may be more complex than approximated by common soil hydraulic or root surface area modeling approaches.Conclusions
Our results highlight the need for continued exploration of root-trait specific water uptake rates in situ, and impacts of roots on soil hydraulic properties – both critical components for mechanistic modeling of root function.5.
Background and aims
Soil compaction strongly affects water uptake by roots. The aim of the work was to examine soil—plant interactions with focus on the impact of distribution of compacted soil layers on growth and water uptake by wheat roots.Methods
The growth-chamber experiment was conducted on wheat growth in soil with compacted soil layers. The system for maintaining constant soil water potential and measurement of daily water uptake from variously compacted soil layers was used.Results
Layered soil compaction differentiated vertical root distribution to higher extent for root length than root mass. The propagation rate of a water extraction front was the highest through layers of moderately compacted soil. The root water uptake rate was on average 67 % higher from moderately than heavily compacted soil layers. Correlations between water uptake and the length of thick roots were increasing with increasing level of soil compaction.Conclusions
The study shows that root amount, water uptake, propagation of water extraction and shoot growth strongly depend on the existence of compacted layers within soil profile. The negative effects of heavily compacted subsoil layer on water uptake were partly compensated by increased uptake from looser top soil layers and significant contribution of thicker roots in water uptake. 相似文献6.
David M. Deery John B. Passioura Jason R. Condon Asitha Katupitiya 《Plant and Soil》2013,368(1-2):649-667
Aim
To test for the presence of an impediment to water flow at the soil-root interface.Methods
Wheat plants were grown in repacked and undisturbed field soil. Their transpiration rate, E, was varied in several steps from low to high and then back to low again, while the hydrostatic pressure in the leaf xylem, ψ xylem, was measured non-destructively and continuously. These measurements were compared to a mathematical model that calculated ψ xylem by assuming that the hydraulic resistance across the plant was constant and that the radial flow of water to unit length of a typical plant root generated gradients in pressure in the soil water.Results
For the repacked soil, the radial flow model could not match the experiment during the falling phase of E, unless it was assumed that either an additional, constant, interfacial resistance between the soil and the roots had developed when E was large and ψ xylem was rapidly falling, or that the resistance within the plant had changed. For the undisturbed field soil, the radial flow model did not agree with the experiment. Plausible agreement was achieved when plant water uptake was accounted for using a distributed sink model in HYDRUS-1D, with E integrated across the rootzone. This approach was based on the measured large variation in the vertical distribution of roots.Conclusions
There was no strong evidence of large drawdowns of soil water in the rhizosphere, even when ψ xylem was falling rapidly when E was large and the soil was moderately dry. Thus, there seems to have been an additional impediment to water flow from soil to plant, either within the plant, or at the interface between the two. 相似文献7.
Bárbara Elias Reis Hodecker Nairam Félix De Barros Ivo Ribeiro Da Silva Valdir Diola Jorge Eduardo Souza Sarkis Marcelo Ehlers Loureiro 《Plant and Soil》2014,384(1-2):185-199
Background
Water and nutritional restrictions are limiting factors for the growth of Eucalyptus trees in tropical climates. In the dry season, boron (B) uptake is severely affected.Aims
The objectives of this study were to evaluate the phloem mobility of B and whether its deficiency can increase plant sensitivity to osmotic stress. It was also tested to what extent foliar application of B could mitigate the negative effects of drought under low B supply.Methods
Seedlings of a drought tolerant Eucalyptus urophylla (Blake, S. T.) clone were grown in nutrient solution, subjected to low availability of B for 25 days, and then submitted to a progressive osmotic stress. After imposition of osmotic stress, B was applied to young or mature leaves.Results
B applications, mainly to mature leaf, stimulated root growth and delayed dehydration under osmotic stress and led to an increased B translocation and carbon isotopic composition. The expression of B transporters and pectin metabolism genes were also increased in water-stressed plants supplied with B by foliar application.Conclusions
B deficiency led to increased plant dehydration and decreased root growth under osmotic stress. The application of B to mature leaf of water-stressed plants proved effective in mitigating the negative effects of water deficit in root growth. 相似文献8.
9.
Pou Alícia Medrano Hipólito Tomàs Magdalena Martorell Sebastià Ribas-Carbó Miquel Flexas Jaume 《Plant and Soil》2012,354(1-2):335-345
Aims
Arbuscular mycorrhizal fungi (AMF) can control root-knot nematode infection, but the mode of action is still unknown. We investigated the effects of AMF and mycorrhizal root exudates on the initial steps of Meloidogyne incognita infection, namely movement towards and penetration of tomato roots.Methods
M. incognita soil migration and root penetration were evaluated in a twin-chamber set-up consisting of a control and mycorrhizal (Glomus mosseae) plant compartment (Solanum lycopersicum cv. Marmande) connected by a bridge. Penetration into control and mycorrhizal roots was also assessed when non-mycorrhizal or mycorrhizal root exudates were applied and nematode motility in the presence of the root exudates was tested in vitro.Results
M. incognita penetration was significantly reduced in mycorrhizal roots compared to control roots. In the twin-chamber set-up, equal numbers of nematodes moved to both compartments, but the majority accumulated in the soil of the mycorrhizal plant compartment, while for the control plants the majority penetrated the roots. Application of mycorrhizal root exudates further reduced nematode penetration in mycorrhizal plants and temporarily paralyzed nematodes, compared with application of water or non-mycorrhizal root exudates.Conclusions
Nematode penetration was reduced in mycorrhizal tomato roots and mycorrhizal root exudates probably contributed at least partially by affecting nematode motility. 相似文献10.
Sara Tramontini Cornelis van Leeuwen Jean-Christophe Domec Agnès Destrac-Irvine Cyril Basteau Marco Vitali Olaf Mosbach-Schulz Claudio Lovisolo 《Plant and Soil》2013,368(1-2):215-230
Aims
All components of the soil-plant-atmosphere (s-p-a) continuum are known to control berry quality in grapevine (Vitis vinifera L.) via ecophysiological interactions between water uptake by roots and water loss by leaves. The scope of the present work was to explore how the main hydraulic components of grapevine influence fruit quality through changes in liquid- and gas-phase hydraulic conductance.Methods
To reach our objectives, determinations of shoot growth, berry size and sugar content, leaf gas exchange, predawn leaf water potential (as a proxy of soil water potential), midday stem water potential and leaf water potential were performed in conjunction with anatomical measurements of shoot xylem. All measurements were conducted in two different cultivars (Cabernet franc and Merlot) and on three different soil types (clayey, gravelly, and sandy).Results
Shoot xylem morphometric characteristics and whole-plant hydraulic conductance were influenced by cultivar and soil type. Differences in leaf gas exchange parameters and water potentials were determined by soil type significantly more than by cultivar. Between the two extremes (gravelly soil imposing drought conditions and sandy soil with easily accessible water) the clayey soil expressed an intermediate plant water consumption and highest sugar accumulation in berry.Conclusions
Hydraulic and non hydraulic limitations to vine/berry interactions supported the conclusion that water availability in the soil overrides differences due to cultivar in determining the productive potential of the vineyard. Non hydraulic stomatal control was expected to be an important component on plants grown on the clayey soil, which experienced a moderate water stress. Possible links between hydraulic traits and berry development and quality are discussed. 相似文献11.
Yingchun Liao M. Luke McCormack Houbao Fan Huimin Wang Jianping Wu Jie Tu Wenfei Liu Dali Guo 《Plant and Soil》2014,381(1-2):225-234
Background and aims
Growth and distribution of fine roots closely depend on soil resource availability and affect soil C distribution in return. Understanding of relationships between fine root distribution and soil C can help to predict the contribution of fine root turnover to soil C accumulation.Methods
A study was conducted in a subtropical Cunninghamia lanceolata plantation to assess the fine root mass density (FRMD), fine root C density (FRCD) of different fine root groups as well as their relations with soil C.Results
The FRMD and FRCD of short-lived roots, dead roots and herb roots peaked in the 0–10 cm soil layer and decreased with soil depth, while FRMD, FRCD of long-lived roots peaked in the 10–20 cm soil layer. Soil C was positively related to FRMD and FRCD of total fine roots (across all three soil layers), dead roots (0–10 cm) and herb roots (10–20 cm) as well as FRCD of short-lived roots (20–40 cm) (P <0.05).Conclusions
Soil C was mainly affected by herb roots in upper soil layers and by woody plant roots in deeper soil layers. 相似文献12.
Background and Aims
We developed a method for processing roots from soil cores and monoliths in the laboratory to reduce the time and cost devoted to separating roots from debris and improve the accuracy of root variable estimates. The method was tested on soil cores from a California oak savanna, with roots from trees, Quercus douglasii, and annual grasses.Methods
In the randomized sampling method, one isolates the sample fraction consisting of roots and organic debris?<?= 1 cm in length, and randomizes it through immersion in water and vigorous mixing. Sub-samples from the mixture are then used to estimate the percentage of roots in this fraction, thereby enabling an estimate of total sample biomass.Results
We found that root biomass estimates, determined through the randomization method, differed from total root biomass established by meticulously picking every root from a sample with an error of 3.0 % +/? 0.6 %?s.e.Conclusions
This method greatly reduces the time and resources required for root processing from soil cores and monoliths, and improves the accuracy of root variable estimates compared to standard methods. This gives researchers the ability to increase sample frequency and reduce the error associated with studying roots at the landscape and plant scales. 相似文献13.
Sandra Spielvogel Jörg Prietzel Jana Leide Michael Riedel Julian Zemke Ingrid Kögel-Knabner 《Plant and Soil》2014,376(1-2):95-110
Background and aims
The rhizosphere, the soil immediately surrounding roots, provides a critical bridge for water and nutrient uptake. The rhizosphere is influenced by various forms of root–soil interactions of which mechanical deformation due to root growth and its effects on the hydraulics of the rhizosphere are the least studied. In this work, we focus on developing new experimental and numerical tools to assess these changes.Methods
This study combines X-ray micro-tomography (XMT) with coupled numerical simulation of fluid and soil deformation in the rhizosphere. The study provides a new set of tools to mechanistically investigate root-induced rhizosphere compaction and its effect on root water uptake. The numerical simulator was tested on highly deformable soil to document its ability to handle a large degree of strain.Results
Our experimental results indicate that measured rhizosphere compaction by roots via localized soil compaction increased the simulated water flow to the roots by 27 % as compared to an uncompacted fine-textured soil of low bulk density characteristic of seed beds or forest topsoils. This increased water flow primarily occurred due to local deformation of the soil aggregates as seen in the XMT images, which increased hydraulic conductivity of the soil. Further simulated root growth and deformation beyond that observed in the XMT images led to water uptake enhancement of ~50 % beyond that due to root diameter increase alone and demonstrated the positive benefits of root compaction in low density soils.Conclusions
The development of numerical models to quantify the coupling of root driven compaction and fluid flow provides new tools to improve the understanding of plant water uptake, nutrient availability and agricultural efficiency. This study demonstrated that plants, particularly during early growth in highly deformable low density soils, are involved in active mechanical management of their surroundings. These modeling approaches may now be used to quantify compaction and root growth impacts in a wide range of soils. 相似文献14.
15.
Background and aims
Nitrogen (N) availability affects water uptake from the roots, which decreases upon N deprivation and increases upon resupply. The aim of this study was to reveal possible mechanisms of regulation of water transport in roots through physiological and morphological adaptations to N availability.Methods
The effects of continuous N deprivation and following resupply on root morphology, osmotic hydraulic conductivity, and expression of genes for aquaporins (water channels) were examined in rice (Oryza sativa L.) plants. The effect of local N availability was examined by using a split-root system.Results
N deprivation decreased the expression of root-specific aquaporin genes, whereas N resupply increased their expression. Changes in aquaporin gene expression were correlated with changes in hydraulic conductivity. N deprivation increased dry matter allocation to the roots. In a split-root experiment, the expression of root-specific aquaporin genes was down-regulated in the N-deprived half, whereas it was up-regulated in the N-supplied half.Conclusion
Our results suggest that expression of genes for root-specific aquaporins underlies the changes in conductivity during continuous N deprivation and resupply. Rice plants seem to adapt to N availability through coordinated adjustment of root proliferation and abundance of aquaporins. 相似文献16.
Spatio-temporal mapping of local soil pH changes induced by roots of lupin and soft-rush 总被引:1,自引:0,他引:1
Nicole Rudolph Sebastian Voss Ahmad B. Moradi Stefan Nagl Sascha E. Oswald 《Plant and Soil》2013,369(1-2):669-680
Aims
The rhizosphere is a dynamic system strongly influenced by root activity. Roots modify the pH of their surrounding soil causing the soil pH to vary as a function of distance from root surface, location along root axes, and root maturity. Non-invasive imaging techniques provide the possibility to capture pH patterns around the roots as they develop.Methods
We developed a novel fluorescence imaging set up and applied to the root system of two lupin (Lupinus albus L., Lupinus angustifolius L.) and one soft-rush (Juncus effusus L.) species. We grew plants in glass containers filled with soil and equipped with fluorescence sensor foils on the container side walls. We gained highly-resolved data on the spatial distribution of H+ around the roots by taking time-lapse images of the samples over the course of several days.Results
We showed how the soil pH in the vicinity of roots developed over time to different values from that of the original bulk soil. The soil pH in the immediate vicinity of the root surface varied greatly along the root length, with the most acidic point being at 0.56–3.36 mm behind the root tip. Indications were also found for temporal soil pH changes due to root maturity.Conclusion
In conclusion, this study shows that this novel optical fluorescence imaging set up is a powerful tool for studying pH developments around roots in situ. 相似文献17.
Saoirse R. Tracy Colin R. Black Jeremy A. Roberts Ann McNeill Rob Davidson Mark Tester Marko Samec Dean Koro?ak Craig Sturrock Sacha J. Mooney 《Plant and Soil》2012,353(1-2):195-208
Aims
X-ray Micro Computed Tomography (CT) enables interactions between roots and soil to be visualised without disturbance. This study examined responses of root growth in three Triticum aestivum L. (wheat) cultivars to different levels of soil compaction (1.1 and 1.5?g?cm?3).Methods
Seedlings were scanned 2, 5 and 12?days after germination (DAG) and the images were analysed using novel root tracking software, RootViz3D?, to provide accurate visualisation of root architecture. RootViz3D? proved more successful in segmenting roots from the greyscale images than semi-automated segmentation, especially for finer roots, by combining measurements of pixel greyscale values with a probability approach to identify roots.Results
Root density was greater in soil compacted at 1.5?g?cm?3 than at 1.1?g?cm?3 (P?=?0.04). This effect may have resulted from improved contact between roots and surrounding soil. Root diameter was greater in soil at a high bulk density (P?=?0.006) but overall root length was reduced (P?=?0.20). Soil porosity increased with time (P?<?0.001) in the uncompacted treatment.Conclusions
RootViz3D? root tracking software in X-ray CT studies provided accurate, non-destructive and automated three dimensional quantification of root systems that has many applications for improving understanding on root-soil interactions. 相似文献18.
Daniel M. Johnson Mark E. Sherrard Jean-Christophe Domec Robert B. Jackson 《Trees - Structure and Function》2014,28(5):1323-1331
Key message
Deep root hydraulic conductance is upregulated during severe drought and is associated with upregulation in aquaporin activity.Abstract
In 2011, Texas experienced the worst single-year drought in its recorded history and, based on tree-ring data, likely its worst in the past millennium. In the Edwards Plateau of Texas, rainfall was 58 % lower and the mean daily maximum temperatures were >5 °C higher than long-term means in June through September, resulting in extensive tree mortality. To better understand the balance of deep and shallow root functioning for water supply, we measured root hydraulic conductance (K R) in deep (~20 m) and shallow (5–10 cm) roots of Quercus fusiformis at four time points in the field in 2011. Deep roots of Q. fusiformis obtained water from a perennial underground (18–20 m) stream that was present even during the drought. As the drought progressed, deep root K R increased 2.6-fold from early season values and shallow root K R decreased by 50 % between April and September. Inhibitor studies revealed that aquaporin contribution to K R increased in deep roots and decreased in shallow roots as the drought progressed. Deep root aquaporin activity was upregulated during peak drought, likely driven by increased summer evaporative demand and the need to compensate for declining shallow root K R. A whole-tree hydraulic transport model predicted that trees with greater proportions of deep roots would have as much as five times greater transpiration during drought periods and could sustain transpiration during droughts without experiencing total hydraulic failure. Our results suggest that trees shift their dependence on deep roots versus shallow roots during drought periods, and that upregulation of aquaporin activity accounts for at least part of this increase. 相似文献19.
S. P. Sah C. L. Bryant J. Leppälammi-Kujansuu K. Lõhmus I. Ostonen H.-S. Helmisaari 《Plant and Soil》2013,363(1-2):77-86
Background and aims
The main objectives of this study were to determine how the carbon age of fine root cellulose varies between stands, tree species, root diameter and soil depth. In addition, we also compared the carbon age of fine roots from soil cores of this study with reported values from the roots of the same diameter classes of ingrowth cores on the same sites.Methods
We used natural abundance of 14C to estimate root carbon age in four boreal Norway spruce and Scots pine stands in Finland and Estonia.Results
Age of fine root carbon was older in 1.5–2 mm diameter fine roots than in fine roots with <0.5 mm diameter, and tended to be older in mineral soil than in organic soil. Fine root carbon was older in the less fertile Finnish spruce stands (11–12 years) than in the more fertile Estonian stand (3 and 8 years), implying that roots may live longer in less fertile soil. We further observed that on one of our sites carbon in live fine roots with the 1.5–2 mm diameter was of similar C age (7–12 years) than in the ingrowth core roots despite the reported root age in the ingrowth cores – being not older than 2 years.Conclusions
From this result, we conclude that new live roots may in some cases use old carbon reserves for their cellulose formation. Future research should be oriented towards improving our understanding of possible internal redistribution and uptake of C in trees. 相似文献20.
Susan Zappala Stefan Mairhofer Saoirse Tracy Craig J. Sturrock Malcolm Bennett Tony Pridmore Sacha J. Mooney 《Plant and Soil》2013,370(1-2):35-45