{"type": "FeatureCollection", "features": [{"id": "10.1111/j.1461-0248.2010.01570.x", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:17:46Z", "type": "Journal Article", "created": "2010-12-22", "title": "Enhanced Root Exudation Induces Microbial Feedbacks To N Cycling In A Pine Forest Under Long-Term Co2 Fumigation", "description": "

Ecology Letters (2011) 14: 187\uffe2\uff80\uff93194

Abstract

The degree to which rising atmospheric CO2 will be offset by carbon (C) sequestration in forests depends in part on the capacity of trees and soil microbes to make physiological adjustments that can alleviate resource limitation. Here, we show for the first time that mature trees exposed to CO2 enrichment increase the release of soluble C from roots to soil, and that such increases are coupled to the accelerated turnover of nitrogen (N) pools in the rhizosphere. Over the course of 3\uffe2\uff80\uff83years, we measured in situ rates of root exudation from 420 intact loblolly pine (Pinus taeda L.) roots. Trees fumigated with elevated CO2 (200 p.p.m.v. over background) increased exudation rates (\uffce\uffbcg\uffe2\uff80\uff83C\uffe2\uff80\uff83cm\uffe2\uff88\uff921\uffe2\uff80\uff83root\uffe2\uff80\uff83h\uffe2\uff88\uff921) by 55% during the primary growing season, leading to a 50% annual increase in dissolved organic inputs to fumigated forest soils. These increases in root\uffe2\uff80\uff90derived C were positively correlated with microbial release of extracellular enzymes involved in breakdown of organic N (R2\uffe2\uff80\uff83=\uffe2\uff80\uff830.66; P\uffe2\uff80\uff83=\uffe2\uff80\uff830.006) in the rhizosphere, indicating that exudation stimulated microbial activity and accelerated the rate of soil organic matter (SOM) turnover. In support of this conclusion, trees exposed to both elevated CO2 and N fertilization did not increase exudation rates and had reduced enzyme activities in the rhizosphere. Collectively, our results provide field\uffe2\uff80\uff90based empirical support suggesting that sustained growth responses of forests to elevated CO2 in low fertility soils are maintained by enhanced rates of microbial activity and N cycling fuelled by inputs of root\uffe2\uff80\uff90derived C. To the extent that increases in exudation also stimulate SOM decomposition, such changes may prevent soil C accumulation in forest ecosystems.

", "keywords": ["0106 biological sciences", "Nitrogen", "Plant Exudates", "Pinus taeda", "04 agricultural and veterinary sciences", "15. Life on land", "Carbon Dioxide", "01 natural sciences", "Plant Roots", "Carbon", "Trees", "Soil", "13. Climate action", "Rhizosphere", "North Carolina", "0401 agriculture", " forestry", " and fisheries", "Soil Microbiology"]}, "links": [{"href": "https://doi.org/10.1111/j.1461-0248.2010.01570.x"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Ecology%20Letters", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1111/j.1461-0248.2010.01570.x", "name": "item", "description": "10.1111/j.1461-0248.2010.01570.x", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1111/j.1461-0248.2010.01570.x"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2010-12-22T00:00:00Z"}}, {"id": "10.1007/s00374-014-0975-y", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:14:31Z", "type": "Journal Article", "created": "2014-10-23", "title": "Liming Of Anthropogenically Acidified Soil Promotes Phosphorus Acquisition In The Rhizosphere Of Wheat", "description": "We studied the effect of liming and P fertilization of extremely acid soil (accidently acidified by sulfidic mining waste) on P availability and the subsequent adaptive responses of wheat roots. The wheat plants were grown in rhizoboxes allowing precise sampling of rhizosphere and bulk soil for sequential extraction of P fractions and determination of exchangeable Al. Root exudates were collected by pieces of paper for electrophoresis and subjected to HPLC analysis. Expression of organic anions and Pi transporter genes was analyzed by a real-time quantitative PCR. The concomitant application of lime with P fertilization increased the concentrations of plant-available P fractions in both rhizosphere and bulk compartments. The applied soil amendments strongly affected plant growth, biomass partitioning and shoot P accumulation. Liming enhanced root exudation of citrate in P unfertilized plants, while the high malate efflux was maintained until both P deficiency and Al toxicity were eliminated by the amendments. We showed the importance of liming for recovering of P acquisition potential of wheat roots, which can be strongly impaired in acid soils. Our results clearly demonstrated that P-deficient roots not subjected to Al stress in the limed soil can maintain high efflux of malate and even increase efflux of citrate along with the enhanced expression of related anion transporters (TaMATE1 and TaALMT1).", "keywords": ["0301 basic medicine", "2. Zero hunger", "0303 health sciences", "03 medical and health sciences", "Wheat", "Rhizosphere", "Liming", "15. Life on land", "Root exudates", "Phosphorus deficiency", "Polluted acid soil"]}, "links": [{"href": "https://doi.org/10.1007/s00374-014-0975-y"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Biology%20and%20Fertility%20of%20Soils", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1007/s00374-014-0975-y", "name": "item", "description": "10.1007/s00374-014-0975-y", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1007/s00374-014-0975-y"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2014-10-24T00:00:00Z"}}, {"id": "10.1007/s00425-024-04556-2", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:14:33Z", "type": "Journal Article", "created": "2024-10-23", "title": "Root exudation patterns of contrasting rice (Oryza sativa L.) lines in response to P limitation", "description": "Abstract Main conclusion

Rice exudation patterns changed in response to P deficiency. Higher exudation rates were associated with lower biomass production. Total carboxylate exudation rates mostly decreased under P-limiting conditions.

Abstract

Within the rhizosphere, root exudates are believed to play an important role in plant phosphorus (P) acquisition. This could be particularly beneficial in upland rice production where P is often limited. However, knowledge gaps remain on how P deficiency shapes quality and quantity of root exudation in upland rice genotypes. We therefore investigated growth, plant P uptake, and root exudation patterns of two rice genotypes differing in P efficiency in semi-hydroponics at two P levels (low P\uffe2\uff80\uff89=\uffe2\uff80\uff891\uffc2\uffa0\uffc2\uffb5M, adequate P\uffe2\uff80\uff89=\uffe2\uff80\uff89100\uffc2\uffa0\uffc2\uffb5M). Root exudates were collected hydroponically 28 and 40\uffc2\uffa0days after germination to analyze total carbon (C), carbohydrates, amino acids, phenolic compounds spectrophotometrically and carboxylates using a targeted LC\uffe2\uff80\uff93MS approach. Despite their reported role in P solubilization, we observed that carboxylate exudation rates per unit root surface area were not increased under P deficiency. In contrast, exudation rates of total C, carbohydrates, amino acids and phenolics were mostly enhanced in response to low P supply. Overall, higher exudation rates were associated with lower biomass production in the P-inefficient genotype Nerica4, whereas the larger root system with lower C investment (per unit root surface area) in root exudates of the P-efficient DJ123 allowed for better plant growth under P deficiency. Our results reveal new insights into genotype-specific resource allocation in rice under P-limiting conditions that warrant follow-up research including more genotypes.

", "keywords": ["Genotype", "Hydroponics", "carbohydrates ; phenolics ; amino acids ; carboxylates ; phosphorus", "Plant Exudates", "Rhizosphere", "Original Article", "Oryza", "Phosphorus", "Biomass", "Amino Acids", "Plant Roots", "Carbon"], "contacts": [{"organization": "Henning Schwalm, Christiana Staudinger, Mohammad-Reza Hajirezaei, Eva Mundschenk, Alireza Golestanifard, Maire Holz, Matthias Wissuwa, Eva Oburger,", "roles": ["creator"]}]}, "links": [{"href": "https://doi.org/10.1007/s00425-024-04556-2"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Planta", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1007/s00425-024-04556-2", "name": "item", "description": "10.1007/s00425-024-04556-2", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1007/s00425-024-04556-2"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2024-10-23T00:00:00Z"}}, {"id": "10.1007/s11104-019-03939-9", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:14:55Z", "type": "Journal Article", "created": "2019-02-01", "title": "Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis", "description": "Rhizodeposits collected from hydroponic solutions with roots of maize and barley, and seed mucilage washed from chia, were added to soil to measure their impact on water retention and hysteresis in a sandy loam soil at a range of concentrations. We test the hypothesis that the effect of plant exudates and mucilages on hydraulic properties of soils depends on their physicochemical characteristics and origin.Surface tension and viscosity of the exudate solutions were measured using the Du No\u00fcy ring method and a cone-plate rheometer, respectively. The contact angle of water on exudate treated soil was measured with the sessile drop method. Water retention and hysteresis were measured by equilibrating soil samples, treated with exudates and mucilages at 0.46 and 4.6\u00a0mg\u00a0g-1 concentration, on dialysis tubing filled with polyethylene glycol (PEG) solution of known osmotic potential.Surface tension decreased and viscosity increased with increasing concentration of the exudates and mucilage in solutions. Change in surface tension and viscosity was greatest for chia seed exudate and least for barley root exudate. Contact angle increased with increasing maize root and chia seed exudate concentration in soil, but not barley root. Chia seed mucilage and maize root rhizodeposits enhanced soil water retention and increased hysteresis index, whereas barley root rhizodeposits decreased soil water retention and the hysteresis effect. The impact of exudates and mucilages on soil water retention almost ceased when approaching wilting point at -1500\u00a0kPa matric potential.Barley rhizodeposits behaved as surfactants, drying the rhizosphere at smaller suctions. Chia seed mucilage and maize root rhizodeposits behaved as hydrogels that hold more water in the rhizosphere, but with slower rewetting and greater hysteresis.", "keywords": ["DYNAMICS", "/dk/atira/pure/subjectarea/asjc/1100/1111", "seed exudate", "FLOW", "QH301 Biology", "/dk/atira/pure/subjectarea/asjc/1100/1110", "root exudate", "630", "QH301", "soil water retention", "ROOT", "surface tension", "DIMR 646809", "Contact angle", "contact angle", "PHOSPHOLIPID SURFACTANTS", "2. Zero hunger", "STABILITY", "BB/J000868/1", "Surface tension", "Civil_env_eng", "Viscosity", "Hysteresis", "name=Soil Science", "Root exudate", "RHIZOSPHERE HYDRAULIC-PROPERTIES", "EXUDATION", "Regular Article", "04 agricultural and veterinary sciences", "15. Life on land", "540", "Soil water retention", "6. Clean water", "Seed exudate", "BB/J011460/1", "hysteresis", "BB/L026058/1", "viscosity", "Biotechnology and Biological Sciences Research Council (BBSRC)", "0401 agriculture", " forestry", " and fisheries", "name=Plant Science", "MAIZE", "BB/P004180/1", "European Research Council"]}, "links": [{"href": "https://repository.uwl.ac.uk/id/eprint/5787/1/Naveed2019_Article_SurfaceTensionRheologyAndHydro.pdf"}, {"href": "https://eprints.soton.ac.uk/428238/1/Naveed2019_Article_SurfaceTensionRheologyAndHydro.pdf"}, {"href": "http://link.springer.com/content/pdf/10.1007/s11104-019-03939-9.pdf"}, {"href": "https://doi.org/10.1007/s11104-019-03939-9"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Plant%20and%20Soil", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1007/s11104-019-03939-9", "name": "item", "description": "10.1007/s11104-019-03939-9", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1007/s11104-019-03939-9"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2019-02-02T00:00:00Z"}}, {"id": "10.1021/acs.jafc.1c02821", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:16:33Z", "type": "Journal Article", "created": "2021-08-04", "title": "Determination of the Effect of Co-cultivation on the Production and Root Exudation of Flavonoids in Four Legume Species Using LC\u2013MS/MS Analysis", "description": "Flavonoids play a key role in the regulation of plant-plant and plant-microbe interactions, and factors determining their release have been investigated in most of the common forage legumes. However, little is known about the response of flavonoid production and release to co-cultivation with other crop species. This study investigated alterations in the concentration of flavonoids in plant tissues and root exudates in four legumes [alfalfa (Medicago sativa L.), black medic (Medicago polymorpha L.), crimson clover (Trifolium incarnatum L.), and subterranean clover (Trifolium subterraneum L.)] co-cultivated with durum wheat [Triticum turgidum subsp. durum (Desf.) Husn.]. For this purpose, we carried out two experiments in a greenhouse, one with glass beads as growth media for root exudate extraction and one with soil as growth media for flavonoid detection in shoot and root biomass, using LC-MS/MS analysis. This study revealed that interspecific competition with wheat negatively affected legume growth and led to a significant reduction in shoot and root biomass compared with the same legume species grown in monoculture. In contrast, the concentration of flavonoids significantly increased both in legume biomass and in root exudates. Changes in flavonoid concentration involved daidzein, genistein, medicarpin, and formononetin, which have been found to be involved in legume nodulation and regulation of plant-plant interaction. We hypothesize that legumes responded to the co-cultivation with wheat by promoting nodulation and increasing exudation of allelopathic compounds, respectively, to compensate for the lack of nutrients caused by the presence of wheat in the cultivation system and to reduce the competitiveness of neighboring plants. Future studies should elucidate the bioactivity of flavonoid compounds in cereal-legume co-cultivation systems and their specific role in the nodulation process and inter-specific plant interactions such as potential effects on weeds.", "keywords": ["Flavonoids", "2. Zero hunger", "0301 basic medicine", "0303 health sciences", "medicarpin", "living mulch", "root exudate", "Fabaceae", "15. Life on land", "plant interactions", "Plant Roots", "03 medical and health sciences", "Tandem Mass Spectrometry", "wheat", "allelopathy", "intercropping", "wheat", " intercropping", " living mulch", " root exudate", " plant interactions", " medicarpin", " allelopathy", "Chromatography", " Liquid"]}, "links": [{"href": "https://www.iris.sssup.it/bitstream/11382/540035/1/Leoni%20et%20al_2021_jafc_1c02821.pdf"}, {"href": "https://pubs.acs.org/doi/pdf/10.1021/acs.jafc.1c02821"}, {"href": "https://doi.org/10.1021/acs.jafc.1c02821"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Journal%20of%20Agricultural%20and%20Food%20Chemistry", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1021/acs.jafc.1c02821", "name": "item", "description": "10.1021/acs.jafc.1c02821", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1021/acs.jafc.1c02821"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2021-08-04T00:00:00Z"}}, {"id": "10.1186/s40793-021-00381-2", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:18:09Z", "type": "Journal Article", "created": "2021-02-10", "title": "Soil, senescence and exudate utilisation: characterisation of the\u00a0Paragon var. spring bread wheat root microbiome", "description": "Abstract

Conventional methods of agricultural pest control and crop fertilisation are contributing to a crisis of biodiversity loss, biogeochemical cycle dysregulation, and ecosystem collapse. Thus, we must find ecologically responsible means to control disease and promote crop yields. The root-associated microbiome may contribute to this goal as microbes can aid plants with disease suppression, abiotic stress relief, and nutrient bioavailability. We applied 16S rRNA gene & fungal 18S rRNA gene (ITS2 region) amplicon sequencing to profile the diversity of the bacterial, archaeal & fungal communities associated with the roots of UK elite spring bread wheat varietyTriticum aestivum var.Paragon in different soils and developmental stages. This revealed that community composition shifted significantly for all three groups across compartments. This shift was most pronounced for bacteria and fungi, while we observed weaker selection on the ammonia oxidising archaea-dominated archaeal community. Across multiple soil types we found that soil inoculum was a significant driver of endosphere community composition, however several bacterial families were identified as core enriched taxa in all soil conditions. The most abundant of these wereStreptomycetaceaeandBurkholderiaceae.Moreover, as the plants senesce, both families were reduced in abundance, indicating that input from the living plant was required to maintain their abundance in the endosphere. To understand which microbes are using wheat root exudates in the rhizosphere, root exudates were labelled in a13CO2DNA stable isotope probing experiment. This shows that bacterial taxa within theBurkholderiaceaefamily among other core enriched taxa, such asPseudomonadaceae,were able to use root exudates butStreptomycetaceaewere not. Overall, this work provides a better understanding of the wheat microbiome, including the endosphere community. Understanding crop microbiome formation will contribute to ecologically responsible methods for yield improvement and biocontrol in the future.

", "keywords": ["2. Zero hunger", "0301 basic medicine", "570", "0303 health sciences", "Exudate", "15. Life on land", "Senescence", "Microbiology", "630", "QR1-502", "Environmental sciences", "03 medical and health sciences", "Root", "Wheat", "GE1-350", "Microbiome", "Endosphere", "Research Article"]}, "links": [{"href": "http://oro.open.ac.uk/77831/1/40793_2021_Article_381.pdf"}, {"href": "https://ueaeprints.uea.ac.uk/id/eprint/80327/1/Published_Version.pdf"}, {"href": "https://link.springer.com/content/pdf/10.1186/s40793-021-00381-2.pdf"}, {"href": "https://doi.org/10.1186/s40793-021-00381-2"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Environmental%20Microbiome", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1186/s40793-021-00381-2", "name": "item", "description": "10.1186/s40793-021-00381-2", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1186/s40793-021-00381-2"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2021-02-09T00:00:00Z"}}, {"id": "10.1111/gcb.12161", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:17:32Z", "type": "Journal Article", "created": "2013-02-06", "title": "Enhanced Root Exudation Stimulates Soil Nitrogen Transformations In A Subalpine Coniferous Forest Under Experimental Warming", "description": "Abstract

Despite the perceived importance of exudation to forest ecosystem function, few studies have attempted to examine the effects of elevated temperature and nutrition availability on the rates of root exudation and associated microbial processes. In this study, we performed an experiment in whichin situexudates were collected fromPicea asperataseedlings that were transplanted in disturbed soils exposed to two levels of temperature (ambient temperature and infrared heater warming) and two nitrogen levels (unfertilized and 25\uffc2\uffa0g N\uffc2\uffa0m\uffe2\uff88\uff922\uffc2\uffa0a\uffe2\uff88\uff921). Here, we show that the trees exposed to an elevated temperature increased their exudation rates I (\uffce\uffbcg\uffc2\uffa0C\uffc2\uffa0g\uffe2\uff88\uff921root biomass\uffc2\uffa0h\uffe2\uff88\uff921), II (\uffce\uffbcg\uffc2\uffa0C\uffc2\uffa0cm\uffe2\uff88\uff921\uffc2\uffa0root length\uffc2\uffa0h\uffe2\uff88\uff921) and III (\uffce\uffbcg\uffc2\uffa0C\uffc2\uffa0cm\uffe2\uff88\uff922\uffc2\uffa0root area\uffc2\uffa0h\uffe2\uff88\uff921) in the unfertilized plots. The altered morphological and physiological traits of the roots exposed to experimental warming could be responsible for this variation in root exudation. Moreover, these increases in root\uffe2\uff80\uff90derived C were positively correlated with the microbial release of extracellular enzymes involved in the breakdown of organic N (R2\uffc2\uffa0=\uffc2\uffa00.790;P\uffc2\uffa0=\uffc2\uffa00.038), which was coupled with stimulated microbial activity and accelerated N transformations in the unfertilized soils. In contrast, the trees exposed to both experimental warming and N fertilization did not show increased exudation rates or soil enzyme activity, indicating that the stimulatory effects of experimental warming on root exudation depend on soil fertility. Collectively, our results provide preliminary evidence that an increase in the release of root exudates into the soil may be an important physiological adjustment by which the sustained growth responses of plants to experimental warming may be maintained via enhanced soil microbial activity and soil N transformation. Accordingly, the underlying mechanisms by which plant root\uffe2\uff80\uff90microbe interactions influence soil organic matter decomposition and N cycling should be incorporated into climate\uffe2\uff80\uff90carbon cycle models to determine reliable estimates of long\uffe2\uff80\uff90term C storage in forests.

", "keywords": ["2. Zero hunger", "China", "Soil", "Plant Exudates", "0401 agriculture", " forestry", " and fisheries", "Biomass", "04 agricultural and veterinary sciences", "Models", " Theoretical", "Nitrogen Cycle", "Picea", "15. Life on land", "Global Warming", "Plant Roots"], "contacts": [{"organization": "Juan Xiao, Huajun Yin, Zhenfeng Xu, Xinyin Cheng, Yufei Li, Qing Liu,", "roles": ["creator"]}]}, "links": [{"href": "https://doi.org/10.1111/gcb.12161"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Global%20Change%20Biology", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1111/gcb.12161", "name": "item", "description": "10.1111/gcb.12161", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1111/gcb.12161"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2013-04-18T00:00:00Z"}}, {"id": "10.1093/treephys/tpu116", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:17:19Z", "type": "Journal Article", "created": "2015-01-24", "title": "Dinitrogen Fixation By Legume Shade Trees And Direct Transfer Of Fixed N To Associated Cacao In A Tropical Agroforestry System", "description": "Natural abundance of (15)N (\u03b4\u2009(15)N) was determined in bulk soil, rhizospheric soil and vegetation in an organically managed cacao (Theobroma cacao L.) plantation with Inga edulis Mart. legume trees (inga) as the principal shade for studying the nitrogen (N) cycle in the system. Cacao without contact with legumes in an adjacent plantation was used as the reference for N2 fixation and direct N transfer calculations. Bulk and rhizospheric soils contained 72 and 20%, respectively, of whole- system N. No vegetation effect on \u03b4\u2009(15)N in rhizospheric soil was detected, probably due to the high native soil N pool. Fine roots of the cacaos associated with inga contained \u223c35% of N fixed from the atmosphere (Nf) out of the total N. Leaves of all species had significantly higher \u03b4\u2009(15)N than fine roots. Twenty percent of system Nf was found in cacao suggesting direct N transfer from inga via a common mycelial network of mycorrhizal fungi or recycling of N-rich root exudates of inga. Inga had accumulated 98\u2005kg [Nf] ha(-1) during the 14-year history of the plantation. The conservative estimate of current N2 fixation rate was 41\u2005kg [Nf] ha(-1)\u2005year(-1) based on inga biomass only and 50\u2005kg [Nf] ha(-1)\u2005year(-1) based on inga and associated trees.", "keywords": ["2. Zero hunger", "Cacao", "Tropical Climate", "Nitrogen Isotopes", "Nitrogen", "Plant Exudates", "Fabaceae", "04 agricultural and veterinary sciences", "Forests", "15. Life on land", "Plant Roots", "Trees", "Plant Leaves", "Soil", "Mycorrhizae", "Nitrogen Fixation", "0401 agriculture", " forestry", " and fisheries", "Biomass", "Soil Microbiology"]}, "links": [{"href": "https://doi.org/10.1093/treephys/tpu116"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Tree%20Physiology", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1093/treephys/tpu116", "name": "item", "description": "10.1093/treephys/tpu116", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1093/treephys/tpu116"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2015-01-24T00:00:00Z"}}, {"id": "10.1101/2021.02.09.430461", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:17:22Z", "type": "Journal Article", "created": "2021-02-10", "title": "Soil, senescence and exudate utilisation: Characterisation of the Paragon var. spring bread wheat root microbiome", "description": "Abstract

Conventional methods of agricultural pest control and crop fertilisation are contributing to a crisis of biodiversity loss, biogeochemical cycle dysregulation, and ecosystem collapse. Thus, we must find ecologically responsible means to control disease and promote crop yields. The root-associated microbiome may contribute to this goal as microbes can aid plants with disease suppression, abiotic stress relief, and nutrient bioavailability. We applied 16S rRNA gene & fungal 18S rRNA gene (ITS2 region) amplicon sequencing to profile the diversity of the bacterial, archaeal & fungal communities associated with the roots of UK elite spring bread wheat varietyTriticum aestivum var.Paragon in different soils and developmental stages. This revealed that community composition shifted significantly for all three groups across compartments. This shift was most pronounced for bacteria and fungi, while we observed weaker selection on the ammonia oxidising archaea-dominated archaeal community. Across multiple soil types we found that soil inoculum was a significant driver of endosphere community composition, however several bacterial families were identified as core enriched taxa in all soil conditions. The most abundant of these wereStreptomycetaceaeandBurkholderiaceae.Moreover, as the plants senesce, both families were reduced in abundance, indicating that input from the living plant was required to maintain their abundance in the endosphere. To understand which microbes are using wheat root exudates in the rhizosphere, root exudates were labelled in a13CO2DNA stable isotope probing experiment. This shows that bacterial taxa within theBurkholderiaceaefamily among other core enriched taxa, such asPseudomonadaceae,were able to use root exudates butStreptomycetaceaewere not. Overall, this work provides a better understanding of the wheat microbiome, including the endosphere community. Understanding crop microbiome formation will contribute to ecologically responsible methods for yield improvement and biocontrol in the future.We hypothesized that plant exudates could either gel or disperse soil depending on their chemical characteristics. Barley (Hordeum vulgare L. cv. Optic) and maize (Zea mays L. cv. Freya) root exudates were collected using an aerated hydroponic method and compared with chia (Salvia hispanica L.) seed exudate, a commonly used root exudate analogue. Sandy loam soil was passed through a 500\uffe2\uff80\uff90\uffce\uffbcm mesh and treated with each exudate at a concentration of 4.6 mg exudate g\uffe2\uff88\uff921 dry soil. Two sets of soil samples were prepared. One set of treated soil samples was maintained at 4\uffc2\uffb0C to suppress microbial processes. To characterize the effect of decomposition, the second set of samples was incubated at 16\uffc2\uffb0C for 2 weeks at \uffe2\uff88\uff9230 kPa matric potential. Gas chromatography\uffe2\uff80\uff93mass spectrometry (GC\uffe2\uff80\uff93MS) analysis of the exudates showed that barley had the largest organic acid content and chia the largest content of sugars (polysaccharide\uffe2\uff80\uff90derived or free), and maize was in between barley and chia. Yield stress of amended soil samples was measured by an oscillatory strain sweep test with a cone plate rheometer. When microbial decomposition was suppressed at 4\uffc2\uffb0C, yield stress increased 20\uffe2\uff80\uff90fold for chia seed exudate and twofold for maize root exudate compared with the control, whereas for barley root exudate decreased to half. The yield stress after 2 weeks of incubation compared with soil with suppressed microbial decomposition increased by 85% for barley root exudate, but for chia and maize it decreased by 87 and 54%, respectively. Barley root exudation might therefore disperse soil and this could facilitate nutrient release. The maize root and chia seed exudates gelled soil, which could create a more stable soil structure around roots or seeds.

Highlights

Rheological measurements quantified physical behaviour of plant exudates and effect on soil stabilization.

Barley root exudates dispersed soil, which could release nutrients and carbon.

Maize root and chia seed exudates had a stabilizing effect on soil.

Physical engineering of soil in contact with plant roots depends on the nature and origin of exudates.

Feedback between plants and soil microbial communities can be a powerful driver of vegetation dynamics. Plants elicit changes in the soil microbiome that either promote or suppress conspecifics at the same location, thereby regulating population density\uffe2\uff80\uff90dependence and species co\uffe2\uff80\uff90existence. Such effects are often attributed to the accumulation of host\uffe2\uff80\uff90specific antagonistic or beneficial microbiota in the rhizosphere. However, the identity and host\uffe2\uff80\uff90specificity of the microbial taxa involved are rarely empirically assessed. Here we review the evidence for host\uffe2\uff80\uff90specificity in plant\uffe2\uff80\uff90associated microbes and propose that specific plant\uffe2\uff80\uff93soil feedbacks can also be driven by generalists. We outline the potential mechanisms by which generalist microbial pathogens, mutualists and decomposers can generate differential effects on plant hosts and synthesize existing evidence to predict these effects as a function of plant investments into defence, microbial mutualists and dispersal. Importantly, the capacity of generalist microbiota to drive plant\uffe2\uff80\uff93soil feedbacks depends not only on the traits of individual plants but also on the phylogenetic and functional diversity of plant communities. Identifying factors that promote specialization or generalism in plant\uffe2\uff80\uff93microbial interactions and thereby modulate the impact of microbiota on plant performance will advance our understanding of the mechanisms underlying plant\uffe2\uff80\uff93soil feedback and the ways it contributes to plant co\uffe2\uff80\uff90existence.

Flavonoids are a broad class of secondary metabolites with multifaceted functionalities for plant homeostasis and are involved in facing both biotic and abiotic stresses to sustain plant growth and health. Furthermore, they were discovered as mediators of plant networking with the surrounding environment, showing a surprising ability to perform as signaling compounds for a multitrophic inter-kingdom level of communication that influences the plant host at the phytobiome scale. Flavonoids orchestrate plant-neighboring plant allelopathic interactions, recruit beneficial bacteria and mycorrhizal fungi, counteract pathogen outbreak, influence soil microbiome and affect plant physiology to improve its resilience to fluctuating environmental conditions. This review focuses on the diversified spectrum of flavonoid functions in plants under a variety of stresses in the modulation of plant morphogenesis in response to environmental clues, as well as their role as inter-kingdom signaling molecules with micro- and macroorganisms. Regarding the latter, the review addresses flavonoids as key phytochemicals in the human diet, considering their abundance in fruits and edible plants. Recent evidence highlights their role as nutraceuticals, probiotics and as promising new drugs for the treatment of several pathologies.

", "keywords": ["0301 basic medicine", "phytochemicals; root exudates; phytobiome; plant-microbe interactions; beneficial microbes; plant secondary metabolites; abiotic stress; biotic stress; rhizosphere; microbiome", "0303 health sciences", "03 medical and health sciences", "beneficial microbes", "QH301-705.5", "phytobiome", "plant-microbe interactions", "Review", "Biology (General)", "phytochemicals", "root exudates", "plant secondary metabolites"]}, "links": [{"href": "https://air.unimi.it/bitstream/2434/949072/2/Ghitti%20et%20al%202022%20flavonoids%20are%20intra%20and%20inter%20kingdom%20modulator%20signals.pdf"}, {"href": "https://doi.org/2434/949072"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Microorganisms", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "2434/949072", "name": "item", "description": "2434/949072", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/2434/949072"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2022-12-15T00:00:00Z"}}, {"id": "10.3389/fenvs.2018.00032", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:19:14Z", "type": "Journal Article", "created": "2018-05-25", "title": "Correlative Visualization of Root Mucilage Degradation Using X-ray CT and MRI", "description": "Root exudates are a crucial component of the rhizosphere. Often, they take a form of a gel exuded by the plant roots and are thought to influence the soil aggregation, root penetration into soil, soil nutrient availability, immobilization of toxic cations, and microbial activity amongst other things. In addition, the capacity of exudates to store water makes the plants potentially less susceptive to drought. Major components of root exudates are high molecular weight organic compounds consisting of predominantly polysaccharides and proteins, which makes it challenging to visualize using current rhizosphere visualization techniques, such as X-ray computed tomography (CT). In this contribution, we use correlative X-ray CT (resolution ~20 \u03bcm) in combination with Magnetic Resonance Imaging (MRI, resolution ~120 \u03bcm) to set up groundwork to enable in situ visualization of mucilage in soil. This multimodal approach is necessary because mucilage density closely matches that of water. We use chia seeds as mucilage analog, because it has been found to have a similar consistency to root mucilage. Moreover, to understand mucilage development in time, a series of samples made by chia seeds placed in different porous media were prepared. Structurally and chemically, mucilage breaks down toward a water-like substance over a course of 2 weeks. Depending on its relative concentration, these changes were found to be less dominant when seeds were mixed in porous media. Having set up the groundwork for correlative imaging of chia seeds in water and an artificial soil (Nafion and sand/beads) this enables us to expand this imaging to deal with plant root exudates under natural conditions.", "keywords": ["2. Zero hunger", "570", "X-ray CT", "chia", "polysaccharides", "04 agricultural and veterinary sciences", "15. Life on land", "630", "6. Clean water", "root-exudate", "Environmental sciences", "1H-MRI", "0401 agriculture", " forestry", " and fisheries", "GE1-350", "mucilage"]}, "links": [{"href": "https://eprints.soton.ac.uk/421014/1/NMRI_imaging_chia_review_final_2_TR_01_05_2018.pdf"}, {"href": "https://eprints.soton.ac.uk/421014/2/fenvs_06_00032.pdf"}, {"href": "https://doi.org/10.3389/fenvs.2018.00032"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Frontiers%20in%20Environmental%20Science", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.3389/fenvs.2018.00032", "name": "item", "description": "10.3389/fenvs.2018.00032", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.3389/fenvs.2018.00032"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2018-05-25T00:00:00Z"}}, {"id": "10.2136/vzj2017.04.0083", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:19:02Z", "type": "Journal Article", "created": "2018-02-15", "title": "Rhizosphere\u2010Scale Quantification of Hydraulic and Mechanical Properties of Soil Impacted by Root and Seed Exudates", "description": "Core Ideas

We hypothesized that plant exudates gel soil particles and on drying enhance water repellency.

This has been carried out using rhizosphere\uffe2\uff80\uff90scale mechanical and hydraulic measurements.

Plant exudates enhanced soil hardness and modulus of elasticity as chia seed > maize root > barley root.

Plant exudates caused measureable decreases in soil wetting rates through water repellency.

Using rhizosphere\uffe2\uff80\uff90scale physical measurements, we tested the hypothesis that plant exudates gel together soil particles and, on drying, enhance soil water repellency. Barley (Hordeum vulgare L. cv. Optic) and maize (Zea mays L. cv. Freya) root exudates were compared with chia (Salvia hispanica L.) seed exudate, a commonly used root exudate analog. Sandy loam and clay loam soils were treated with root exudates at 0.46 and 4.6 mg exudate g\uffe2\uff88\uff921 dry soil and chia seed exudate at 0.046, 0.46, 0.92, 2.3 and 4.6 mg exudate g\uffe2\uff88\uff921 dry soil. Soil hardness and modulus of elasticity were measured at \uffe2\uff88\uff9210 kPa matric potential using a 3\uffe2\uff80\uff90mm\uffe2\uff80\uff90diameter spherical indenter. The water sorptivity and repellency index of air\uffe2\uff80\uff90dry soil were measured using a miniaturized infiltrometer device with a 1\uffe2\uff80\uff90mm tip radius. Soil hardness increased by 28% for barley root exudate, 62% for maize root exudate, and 86% for chia seed exudate at 4.6 mg g\uffe2\uff88\uff921 concentration in the sandy loam soil. For the clay loam soil, root exudates did not affect soil hardness, whereas chia seed exudate increased soil hardness by 48% at 4.6 mg g\uffe2\uff88\uff921 concentration. Soil water repellency increased by 48% for chia seed exudate and 23% for maize root exudate but not for barley root exudate at 4.6 mg g\uffe2\uff88\uff921 concentration in the sandy loam soil. For the clay loam soil, chia seed exudate increased water repellency by 45%, whereas root exudates did not affect water repellency at 4.6 mg g\uffe2\uff88\uff921 concentration. Water sorptivity and repellency were both correlated with hardness, presumably due to the combined influence of exudates on the hydrological and mechanical properties of the soils.The importance of plant rhizodeposition to sustain microbial growth and induce xenobiotic degradation in polluted environments is increasingly recognized.

Methods

Here the \uffe2\uff80\uff9ccry-for-help\uffe2\uff80\uff9d hypothesis, consisting in root chemistry remodeling upon stress, was investigated in the presence of polychlorinated biphenyls (PCBs), highly recalcitrant and phytotoxic compounds, highlighting its role in reshaping the nutritional and signaling features of the root niche to accommodate PCB-degrading microorganisms.

Results

Arabidopsis exposure to 70 \uffc2\uffb5M PCB-18 triggered plant-detrimental effects, stress-related traits, and PCB-responsive gene expression, reproducing PCB phytotoxicity. The root exudates of plantlets exposed for 2 days to the pollutant were collected and characterized through untargeted metabolomics analysis by liquid chromatography\uffe2\uff80\uff93mass spectrometry. Principal component analysis disclosed a different root exudation fingerprint in PCB-18-exposed plants, potentially contributing to the \uffe2\uff80\uff9ccry-for-help\uffe2\uff80\uff9d event. To investigate this aspect, the five compounds identified in the exudate metabolomic analysis (i.e., scopoletin, N-hydroxyethyl-\uffce\uffb2-alanine, hypoxanthine, L-arginyl-L-valine, and L-seryl-L-phenylalanine) were assayed for their influence on the physiology and functionality of the PCB-degrading strains Pseudomonas alcaliphila JAB1, Paraburkholderia xenovorans LB400, and Acinetobacter calcoaceticus P320. Scopoletin, whose relative abundance decreased in PCB-18-stressed plant exudates, hampered the growth and proliferation of strains JAB1 and P320, presumably due to its antimicrobial activity, and reduced the beneficial effect of Acinetobacter P320, which showed a higher degree of growth promotion in the scopoletin-depleted mutant f6\uffe2\uff80\uff99h1 compared to Arabidopsis WT plants exposed to PCB. Nevertheless, scopoletin induced the expression of the bph catabolic operon in strains JAB1 and LB400. The primary metabolites hypoxanthine, L-arginyl-L-valine, and L-seryl-L-phenylalanine, which increased in relative abundance upon PCB-18 stress, were preferentially used as nutrients and growth-stimulating factors by the three degrading strains and showed a variable ability to affect rhizocompetence traits like motility and biofilm formation.

Discussion

These findings expand the knowledge on PCB-triggered \uffe2\uff80\uff9ccry-for-help\uffe2\uff80\uff9d and its role in steering the PCB-degrading microbiome to boost the holobiont fitness in polluted environments.

Flavonoids are a broad class of secondary metabolites with multifaceted functionalities for plant homeostasis and are involved in facing both biotic and abiotic stresses to sustain plant growth and health. Furthermore, they were discovered as mediators of plant networking with the surrounding environment, showing a surprising ability to perform as signaling compounds for a multitrophic inter-kingdom level of communication that influences the plant host at the phytobiome scale. Flavonoids orchestrate plant-neighboring plant allelopathic interactions, recruit beneficial bacteria and mycorrhizal fungi, counteract pathogen outbreak, influence soil microbiome and affect plant physiology to improve its resilience to fluctuating environmental conditions. This review focuses on the diversified spectrum of flavonoid functions in plants under a variety of stresses in the modulation of plant morphogenesis in response to environmental clues, as well as their role as inter-kingdom signaling molecules with micro- and macroorganisms. Regarding the latter, the review addresses flavonoids as key phytochemicals in the human diet, considering their abundance in fruits and edible plants. Recent evidence highlights their role as nutraceuticals, probiotics and as promising new drugs for the treatment of several pathologies.

", "keywords": ["0301 basic medicine", "phytochemicals; root exudates; phytobiome; plant-microbe interactions; beneficial microbes; plant secondary metabolites; abiotic stress; biotic stress; rhizosphere; microbiome", "0303 health sciences", "03 medical and health sciences", "beneficial microbes", "QH301-705.5", "phytobiome", "plant-microbe interactions", "Review", "Biology (General)", "phytochemicals", "root exudates", "plant secondary metabolites"]}, "links": [{"href": "https://air.unimi.it/bitstream/2434/949072/2/Ghitti%20et%20al%202022%20flavonoids%20are%20intra%20and%20inter%20kingdom%20modulator%20signals.pdf"}, {"href": "https://doi.org/10.3390/microorganisms10122479"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Microorganisms", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.3390/microorganisms10122479", "name": "item", "description": "10.3390/microorganisms10122479", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.3390/microorganisms10122479"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2022-12-15T00:00:00Z"}}, {"id": "3177278914", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:23:12Z", "type": "Journal Article", "created": "2021-02-10", "title": "Soil, senescence and exudate utilisation: Characterisation of the Paragon var. spring bread wheat root microbiome", "description": "Abstract

Conventional methods of agricultural pest control and crop fertilisation are contributing to a crisis of biodiversity loss, biogeochemical cycle dysregulation, and ecosystem collapse. Thus, we must find ecologically responsible means to control disease and promote crop yields. The root-associated microbiome may contribute to this goal as microbes can aid plants with disease suppression, abiotic stress relief, and nutrient bioavailability. We applied 16S rRNA gene & fungal 18S rRNA gene (ITS2 region) amplicon sequencing to profile the diversity of the bacterial, archaeal & fungal communities associated with the roots of UK elite spring bread wheat varietyTriticum aestivum var.Paragon in different soils and developmental stages. This revealed that community composition shifted significantly for all three groups across compartments. This shift was most pronounced for bacteria and fungi, while we observed weaker selection on the ammonia oxidising archaea-dominated archaeal community. Across multiple soil types we found that soil inoculum was a significant driver of endosphere community composition, however several bacterial families were identified as core enriched taxa in all soil conditions. The most abundant of these wereStreptomycetaceaeandBurkholderiaceae.Moreover, as the plants senesce, both families were reduced in abundance, indicating that input from the living plant was required to maintain their abundance in the endosphere. To understand which microbes are using wheat root exudates in the rhizosphere, root exudates were labelled in a13CO2DNA stable isotope probing experiment. This shows that bacterial taxa within theBurkholderiaceaefamily among other core enriched taxa, such asPseudomonadaceae,were able to use root exudates butStreptomycetaceaewere not. Overall, this work provides a better understanding of the wheat microbiome, including the endosphere community. Understanding crop microbiome formation will contribute to ecologically responsible methods for yield improvement and biocontrol in the future.Feedback between plants and soil microbial communities can be a powerful driver of vegetation dynamics. Plants elicit changes in the soil microbiome that either promote or suppress conspecifics at the same location, thereby regulating population density\uffe2\uff80\uff90dependence and species co\uffe2\uff80\uff90existence. Such effects are often attributed to the accumulation of host\uffe2\uff80\uff90specific antagonistic or beneficial microbiota in the rhizosphere. However, the identity and host\uffe2\uff80\uff90specificity of the microbial taxa involved are rarely empirically assessed. Here we review the evidence for host\uffe2\uff80\uff90specificity in plant\uffe2\uff80\uff90associated microbes and propose that specific plant\uffe2\uff80\uff93soil feedbacks can also be driven by generalists. We outline the potential mechanisms by which generalist microbial pathogens, mutualists and decomposers can generate differential effects on plant hosts and synthesize existing evidence to predict these effects as a function of plant investments into defence, microbial mutualists and dispersal. Importantly, the capacity of generalist microbiota to drive plant\uffe2\uff80\uff93soil feedbacks depends not only on the traits of individual plants but also on the phylogenetic and functional diversity of plant communities. Identifying factors that promote specialization or generalism in plant\uffe2\uff80\uff93microbial interactions and thereby modulate the impact of microbiota on plant performance will advance our understanding of the mechanisms underlying plant\uffe2\uff80\uff93soil feedback and the ways it contributes to plant co\uffe2\uff80\uff90existence.Plant root exudation is an inherent metabolic process that enhances various functions of the root system like the mobilization of nutrients and interactions with surrounding microbial communities. The role and extent of root exudation in soilless crop production is poorly investigated. Here, we analyzed soilless lettuce and show that the root exudation rate declines with plant age. Furthermore, the impact of light quality and substrate was assessed by growing soilless lettuce in 100% red light (660 nm), 100% blue light (450 nm), and white light (full-light spectrum) and in 100% perlite, 100% potting soil, or mixtures of both materials. Root exudates were collected at 10, 17 and 24 days after transplanting. The total carbon root exudation rate was influenced by light conditions and substrate composition at the earliest timepoint of the culture but not at later growth stages. The total carbohydrate exudation rate was significantly higher under pure blue and red light compared to white light. The impact of light depended on the presence of perlite in the substrate. The total phenolic compound exudation rate was most strongly influenced by the substrate composition and reached the highest level in either pure potting soil or pure perlite. These findings underscore the importance of root exudation during the initial stages of development. Light and growing media influence the exudation rate at this early stage, suggesting that exudation is an adaptive process of the soilless lettuce culture.

HIGHLIGHT

At an initial stage of development, soilless lettuce exudation rates are high and modulated by light and substrate composition, whereas older plants show lower rates that are not influenced by these environmental conditions.

We hypothesized that plant exudates gel soil particles and on drying enhance water repellency.

This has been carried out using rhizosphere\uffe2\uff80\uff90scale mechanical and hydraulic measurements.

Plant exudates enhanced soil hardness and modulus of elasticity as chia seed > maize root > barley root.

Plant exudates caused measureable decreases in soil wetting rates through water repellency.

Using rhizosphere\uffe2\uff80\uff90scale physical measurements, we tested the hypothesis that plant exudates gel together soil particles and, on drying, enhance soil water repellency. Barley ( Hordeum vulgare L. cv. Optic) and maize ( Zea mays L. cv. Freya) root exudates were compared with chia ( Salvia hispanica L.) seed exudate, a commonly used root exudate analog. Sandy loam and clay loam soils were treated with root exudates at 0.46 and 4.6 mg exudate g \uffe2\uff88\uff921 dry soil and chia seed exudate at 0.046, 0.46, 0.92, 2.3 and 4.6 mg exudate g \uffe2\uff88\uff921 dry soil. Soil hardness and modulus of elasticity were measured at \uffe2\uff88\uff9210 kPa matric potential using a 3\uffe2\uff80\uff90mm\uffe2\uff80\uff90diameter spherical indenter. The water sorptivity and repellency index of air\uffe2\uff80\uff90dry soil were measured using a miniaturized infiltrometer device with a 1\uffe2\uff80\uff90mm tip radius. Soil hardness increased by 28% for barley root exudate, 62% for maize root exudate, and 86% for chia seed exudate at 4.6 mg g \uffe2\uff88\uff921 concentration in the sandy loam soil. For the clay loam soil, root exudates did not affect soil hardness, whereas chia seed exudate increased soil hardness by 48% at 4.6 mg g \uffe2\uff88\uff921 concentration. Soil water repellency increased by 48% for chia seed exudate and 23% for maize root exudate but not for barley root exudate at 4.6 mg g \uffe2\uff88\uff921 concentration in the sandy loam soil. For the clay loam soil, chia seed exudate increased water repellency by 45%, whereas root exudates did not affect water repellency at 4.6 mg g \uffe2\uff88\uff921 concentration. Water sorptivity and repellency were both correlated with hardness, presumably due to the combined influence of exudates on the hydrological and mechanical properties of the soils.

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We test the hypothesis that the effect of plant exudates and mucilages on hydraulic properties of soils depends on their physicochemical characteristics and origin.Surface tension and viscosity of the exudate solutions were measured using the Du No\u00fcy ring method and a cone-plate rheometer, respectively. The contact angle of water on exudate treated soil was measured with the sessile drop method. Water retention and hysteresis were measured by equilibrating soil samples, treated with exudates and mucilages at 0.46 and 4.6\u00a0mg\u00a0g-1 concentration, on dialysis tubing filled with polyethylene glycol (PEG) solution of known osmotic potential.Surface tension decreased and viscosity increased with increasing concentration of the exudates and mucilage in solutions. Change in surface tension and viscosity was greatest for chia seed exudate and least for barley root exudate. Contact angle increased with increasing maize root and chia seed exudate concentration in soil, but not barley root. Chia seed mucilage and maize root rhizodeposits enhanced soil water retention and increased hysteresis index, whereas barley root rhizodeposits decreased soil water retention and the hysteresis effect. The impact of exudates and mucilages on soil water retention almost ceased when approaching wilting point at -1500\u00a0kPa matric potential.Barley rhizodeposits behaved as surfactants, drying the rhizosphere at smaller suctions. Chia seed mucilage and maize root rhizodeposits behaved as hydrogels that hold more water in the rhizosphere, but with slower rewetting and greater hysteresis.", "keywords": ["DYNAMICS", "/dk/atira/pure/subjectarea/asjc/1100/1111", "seed exudate", "FLOW", "QH301 Biology", "/dk/atira/pure/subjectarea/asjc/1100/1110", "root exudate", "630", "QH301", "soil water retention", "ROOT", "surface tension", "DIMR 646809", "Contact angle", "contact angle", "PHOSPHOLIPID SURFACTANTS", "2. Zero hunger", "STABILITY", "BB/J000868/1", "Surface tension", "Civil_env_eng", "Viscosity", "Hysteresis", "name=Soil Science", "Root exudate", "RHIZOSPHERE HYDRAULIC-PROPERTIES", "EXUDATION", "Regular Article", "04 agricultural and veterinary sciences", "15. Life on land", "540", "Soil water retention", "6. Clean water", "Seed exudate", "BB/J011460/1", "hysteresis", "BB/L026058/1", "viscosity", "Biotechnology and Biological Sciences Research Council (BBSRC)", "0401 agriculture", " forestry", " and fisheries", "name=Plant Science", "MAIZE", "BB/P004180/1", "European Research Council"]}, "links": [{"href": "https://repository.uwl.ac.uk/id/eprint/5787/1/Naveed2019_Article_SurfaceTensionRheologyAndHydro.pdf"}, {"href": "https://eprints.soton.ac.uk/428238/1/Naveed2019_Article_SurfaceTensionRheologyAndHydro.pdf"}, {"href": "http://link.springer.com/content/pdf/10.1007/s11104-019-03939-9.pdf"}, {"href": "https://doi.org/2164/11863"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Plant%20and%20Soil", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "2164/11863", "name": "item", "description": "2164/11863", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/2164/11863"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2019-02-02T00:00:00Z"}}, {"id": "2164/9551", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:22:45Z", "type": "Journal Article", "created": "2017-10-27", "title": "Plant exudates may stabilize or weaken soil depending on species, origin and time", "description": "Summary

We hypothesized that plant exudates could either gel or disperse soil depending on their chemical characteristics. Barley ( Hordeum vulgare L. cv. Optic) and maize ( Zea mays L. cv. Freya) root exudates were collected using an aerated hydroponic method and compared with chia ( Salvia hispanica L.) seed exudate, a commonly used root exudate analogue. Sandy loam soil was passed through a 500 \uffe2\uff80\uff90 \uffce\uffbcm mesh and treated with each exudate at a concentration of 4.6 mg exudate g \uffe2\uff88\uff921 dry soil. Two sets of soil samples were prepared. One set of treated soil samples was maintained at 4\uffc2\uffb0C to suppress microbial processes. To characterize the effect of decomposition, the second set of samples was incubated at 16\uffc2\uffb0C for 2 weeks at \uffe2\uff88\uff9230 kPa matric potential. Gas chromatography\uffe2\uff80\uff93mass spectrometry ( GC \uffe2\uff80\uff93 MS ) analysis of the exudates showed that barley had the largest organic acid content and chia the largest content of sugars (polysaccharide\uffe2\uff80\uff90derived or free), and maize was in between barley and chia. Yield stress of amended soil samples was measured by an oscillatory strain sweep test with a cone plate rheometer. When microbial decomposition was suppressed at 4\uffc2\uffb0C, yield stress increased 20\uffe2\uff80\uff90fold for chia seed exudate and twofold for maize root exudate compared with the control, whereas for barley root exudate decreased to half. The yield stress after 2 weeks of incubation compared with soil with suppressed microbial decomposition increased by 85% for barley root exudate, but for chia and maize it decreased by 87 and 54%, respectively. Barley root exudation might therefore disperse soil and this could facilitate nutrient release. The maize root and chia seed exudates gelled soil, which could create a more stable soil structure around roots or seeds.

Highlights

Rheological measurements quantified physical behaviour of plant exudates and effect on soil stabilization.

Barley root exudates dispersed soil, which could release nutrients and carbon.

Maize root and chia seed exudates had a stabilizing effect on soil.

Physical engineering of soil in contact with plant roots depends on the nature and origin of exudates.

", "keywords": ["construction", "0301 basic medicine", "EP/M020355/1", "seed exudate", "QH301 Biology", "610", "root exudate", "630", "QH301", "03 medical and health sciences", "DIMR 646809", "microbial decompisition", "Physical Processes and Function", "NE/L00237/1", "2. Zero hunger", "soil gelling", "BB/J000868/1", "Civil_env_eng", "Natural Environment Research Council (NERC)", "04 agricultural and veterinary sciences", "15. Life on land", "6. Clean water", "yield stress", "BB/J011460/1", "BB/L026058/1", "Engineering and Physical Sciences Research Council (EPSRC)", "soil dispersion", "viscosity", "Biotechnology and Biological Sciences Research Council (BBSRC)", "0401 agriculture", " forestry", " and fisheries", "microbial decomposition", "yeild stress", "European Research Council"]}, "links": [{"href": "https://repository.uwl.ac.uk/id/eprint/4980/1/Naveed_et_al-2017-European_Journal_of_Soil_Science.pdf"}, {"href": "https://eprints.soton.ac.uk/414238/1/EJSS_submitted_Manuscript.pdf"}, {"href": "http://onlinelibrary.wiley.com/wol1/doi/10.1111/ejss.12487/fullpdf"}, {"href": "https://doi.org/2164/9551"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/European%20Journal%20of%20Soil%20Science", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "2164/9551", "name": "item", "description": "2164/9551", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/2164/9551"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2017-10-27T00:00:00Z"}}, {"id": "2434/1081417", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-21T16:22:49Z", "type": "Journal Article", "created": "2024-07-05", "title": "Polychlorinated biphenyls modify Arabidopsis root exudation pattern to accommodate degrading bacteria, showing strain and functional trait specificity", "description": "Introduction

The importance of plant rhizodeposition to sustain microbial growth and induce xenobiotic degradation in polluted environments is increasingly recognized.

Methods

Here the \uffe2\uff80\uff9ccry-for-help\uffe2\uff80\uff9d hypothesis, consisting in root chemistry remodeling upon stress, was investigated in the presence of polychlorinated biphenyls (PCBs), highly recalcitrant and phytotoxic compounds, highlighting its role in reshaping the nutritional and signaling features of the root niche to accommodate PCB-degrading microorganisms.

Results

Arabidopsis exposure to 70 \uffc2\uffb5M PCB-18 triggered plant-detrimental effects, stress-related traits, and PCB-responsive gene expression, reproducing PCB phytotoxicity. The root exudates of plantlets exposed for 2 days to the pollutant were collected and characterized through untargeted metabolomics analysis by liquid chromatography\uffe2\uff80\uff93mass spectrometry. Principal component analysis disclosed a different root exudation fingerprint in PCB-18-exposed plants, potentially contributing to the \uffe2\uff80\uff9ccry-for-help\uffe2\uff80\uff9d event. To investigate this aspect, the five compounds identified in the exudate metabolomic analysis (i.e., scopoletin, N-hydroxyethyl-\uffce\uffb2-alanine, hypoxanthine, L-arginyl-L-valine, and L-seryl-L-phenylalanine) were assayed for their influence on the physiology and functionality of the PCB-degrading strains Pseudomonas alcaliphila JAB1, Paraburkholderia xenovorans LB400, and Acinetobacter calcoaceticus P320. Scopoletin, whose relative abundance decreased in PCB-18-stressed plant exudates, hampered the growth and proliferation of strains JAB1 and P320, presumably due to its antimicrobial activity, and reduced the beneficial effect of Acinetobacter P320, which showed a higher degree of growth promotion in the scopoletin-depleted mutant f6\uffe2\uff80\uff99h1 compared to Arabidopsis WT plants exposed to PCB. Nevertheless, scopoletin induced the expression of the bph catabolic operon in strains JAB1 and LB400. The primary metabolites hypoxanthine, L-arginyl-L-valine, and L-seryl-L-phenylalanine, which increased in relative abundance upon PCB-18 stress, were preferentially used as nutrients and growth-stimulating factors by the three degrading strains and showed a variable ability to affect rhizocompetence traits like motility and biofilm formation.

Discussion

These findings expand the knowledge on PCB-triggered \uffe2\uff80\uff9ccry-for-help\uffe2\uff80\uff9d and its role in steering the PCB-degrading microbiome to boost the holobiont fitness in polluted environments.Conventional methods of agricultural pest control and crop fertilisation are contributing to a crisis of biodiversity loss, biogeochemical cycle dysregulation, and ecosystem collapse. Thus, we must find ecologically responsible means to control disease and promote crop yields. The root-associated microbiome may contribute to this goal as microbes can aid plants with disease suppression, abiotic stress relief, and nutrient bioavailability. We applied 16S rRNA gene & fungal 18S rRNA gene (ITS2 region) amplicon sequencing to profile the diversity of the bacterial, archaeal & fungal communities associated with the roots of UK elite spring bread wheat varietyTriticum aestivum var.Paragon in different soils and developmental stages. This revealed that community composition shifted significantly for all three groups across compartments. This shift was most pronounced for bacteria and fungi, while we observed weaker selection on the ammonia oxidising archaea-dominated archaeal community. Across multiple soil types we found that soil inoculum was a significant driver of endosphere community composition, however several bacterial families were identified as core enriched taxa in all soil conditions. The most abundant of these wereStreptomycetaceaeandBurkholderiaceae.Moreover, as the plants senesce, both families were reduced in abundance, indicating that input from the living plant was required to maintain their abundance in the endosphere. To understand which microbes are using wheat root exudates in the rhizosphere, root exudates were labelled in a13CO2DNA stable isotope probing experiment. This shows that bacterial taxa within theBurkholderiaceaefamily among other core enriched taxa, such asPseudomonadaceae,were able to use root exudates butStreptomycetaceaewere not. Overall, this work provides a better understanding of the wheat microbiome, including the endosphere community. Understanding crop microbiome formation will contribute to ecologically responsible methods for yield improvement and biocontrol in the future.Rice exudation patterns changed in response to P deficiency. Higher exudation rates were associated with lower biomass production. Total carboxylate exudation rates mostly decreased under P-limiting conditions.

Abstract

Within the rhizosphere, root exudates are believed to play an important role in plant phosphorus (P) acquisition. This could be particularly beneficial in upland rice production where P is often limited. However, knowledge gaps remain on how P deficiency shapes quality and quantity of root exudation in upland rice genotypes. We therefore investigated growth, plant P uptake, and root exudation patterns of two rice genotypes differing in P efficiency in semi-hydroponics at two P levels (low P\uffe2\uff80\uff89=\uffe2\uff80\uff891\uffc2\uffa0\uffc2\uffb5M, adequate P\uffe2\uff80\uff89=\uffe2\uff80\uff89100\uffc2\uffa0\uffc2\uffb5M). Root exudates were collected hydroponically 28 and 40\uffc2\uffa0days after germination to analyze total carbon (C), carbohydrates, amino acids, phenolic compounds spectrophotometrically and carboxylates using a targeted LC\uffe2\uff80\uff93MS approach. Despite their reported role in P solubilization, we observed that carboxylate exudation rates per unit root surface area were not increased under P deficiency. In contrast, exudation rates of total C, carbohydrates, amino acids and phenolics were mostly enhanced in response to low P supply. Overall, higher exudation rates were associated with lower biomass production in the P-inefficient genotype Nerica4, whereas the larger root system with lower C investment (per unit root surface area) in root exudates of the P-efficient DJ123 allowed for better plant growth under P deficiency. Our results reveal new insights into genotype-specific resource allocation in rice under P-limiting conditions that warrant follow-up research including more genotypes.

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Reports, articles, papers, scientific and non - scientific works of any form, including tables, maps, or any other kind of output, in printed or electronic form, based in whole or in part on the data supplied, must contain an acknowledgement of the form: \"Data reused from the BonaRes Data Centre www.bonares.de. This data were created as part of the ZALF Datenerfassung's research activities.\" Although every care has been taken in preparing and testing the data, the ZALF Datenerfassung and the BonaRes Data Centre cannot guarantee that the data are correct; neither does the ZALF Datenerfassung and the BonaRes Data Centre accept any liability whatsoever for any error, missing data or omission in the data, or for any loss or damage arising from its use. The ZALF Datenerfassung and BonaRes Data Centre will not be responsible for any direct or indirect use which might be made of the data.", "updated": "2026-01-13", "type": "Dataset", "created": "2025-10-01", "language": "eng", "title": "Rhizotrait DOC photometer method", "description": "The dataset includes measurements of absorbance, Dissolved Organic Carbon (DOC), and Total Organic Carbon (TOC) concentrations in root exudate samples. 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