pH Of Exudate Research Articles

Wound Infection Detection Using a Rapid Biomarker.

To evaluate the performance of a rapid, point-of-care diagnostic biomarker that is sensitive to overexpression of gelatinases, the major expressed biomolecules during wound infection. Wound exudate composition and pH are key determinants of infection, and rapid infection detection has an important role in wound healing. The biomarker was first investigated for cytotoxic effects, and irritation and sensitization tests were carried out. The biomarker was then tested on 198 patients suffering from different types of wounds. Data including age, sex, wound type, depth, site, etiology, and exudate pH were collected. Wound pH was measured to determine if it could be a possible early indicator of infection, and bacterial wound cultures were performed as a control. Analysis revealed that the biomarker had no cytotoxicity and caused no erythema, edema, or other adverse response. The rapid diagnostic biomarker demonstrated overall clinical sensitivity, specificity, accuracy, positive predictive value, and negative predictive value: 96.84%, 97.5%, 96.96%, 99.35%, and 88.63%, respectively. Moreover, infected wounds had higher pH values according to culture results and nearly 80% of chronic, nonhealing wounds were infected. This biomarker enables caregivers to detect wound infection in a timely manner and treat it efficiently. Wound pH monitoring may potentially be a useful method for indicating the presence or absence of infection.

Comparison Between Numeric Parameters From Acute and Chronic Venous Leg Ulcers: Identification of Potential Objective Nonhealing Parameters

BACKGROUND: Some authors claim that the clinical methods often employed to assess chronic venous leg ulcers (CVLU) are based on subjective interpretation. The treatments based on a subjective characterization could become a trial-and-error therapy, resulting in longer evolutions and high recurrence rates. PURPOSE: The aim of this work was to compare numeric parameters from acute and chronic venous leg ulcers to identify potential objective nonhealing parameters. METHODS: The study was performed with hospital outpatients from 2016 to 2019. Cohorts were established according to the ulcer evolution time. Data collected related to ulcer characteristics included exudate pH, lactate and glucose concentrations, temperatures, microbiology findings, and imaging study results. RESULTS: Approximately 83% of the examined ulcers were chronic. Seventy-one percent of CVLUs and 59% of the acute ulcers had a pH ≥8. A high variability was found for the concentration of glucose and lactate in exudates of both acute and chronic ulcers. Variations of temperatures of normal skin (ΔT1) and periulcer zone (ΔT2) in reference to the wound bed temperature with values above 1 could indicate the presence of an inflammatory process and be used as a new potential marker of inflammation. All the acute ulcers and 88% of CVLUs showed <80% of granulation tissue in the imaging study. Finally, more than 105 organisms per gram of tissuewere found in 100% of the analyzed samples. CONCLUSIONS: Whereas there were not significant differences among the clinical measured parameters between acute and chronic ulcers, further research on the use of objective measurable parameters is needed to establish cutoff points to differentiate the “chronic state” of an ulcer as a “nonhealing state” regardless of the evolution time. Also, the use of these easily obtainable and low-cost nonhealing parameters would be a new approach to accurately monitor this pathology.

Оценка эффективности эндоскопической биканаликулярной интубации слезоотводящих путей силиконовым дренажем при врожденном дакриоцистите

Purpose. To evaluate effectiveness of nasolacrimal duct intubation with silicone tube in congenital dacryocystitis (CD) and substantiate optimal timing of its removal. Material and Methods. 25 patients with CD were operated in the Khabarovsk branch of the S. Fyodorov Eye Microsurgery Federal State Institution in order to restoring conductivity of nasolacrimal duct of using the intubation set FCI (France). In addition to ophthalmic examination methods, all children underwent scleral examination which includes determination of acid base state (pH) of the wound exudate (secretion) from the nasal cavity. Inflammatory index was also scored which characterized the severity of standard signs of inflammation in the nasal mucosa after surgery. Results. There were no complications during the surgery. Normalization of nasal exudate pH values in children with uncomplicated СD was registered by the 4th week after the surgery. Normalization of nasal exudate pH values in children with recurrent СD was registered by the 6th week, coinciding with full disappearance clinical signs of inflammation. At the indicated periods, the silastic tubes were removed. One child had relapse of disease after suffering acute rhinitis 6 months after the surgery. This patient underwent dacryocystorhinostomy with positive effect. Conclusion. Bicanalicular temporary intubation of nasolacrimal duct using silicone tube in children with CD is considered as an effective treatment. In accordance with obtained results, in children with uncomplicated CD the removal of silicone implant is advisable 4 weeks after its installation, in children with recurrent CD the removal of silicone implant is advisable no earlier than 6 weeks. Key words: congenital dacryostenosis, intubation set, endoscopic rhinoscopy.

Physiological and Root Exudation Response of Maize Seedlings to TiO2 and SiO2 Nanoparticles Exposure

How the NPs effect the growth and physiological response like the release of organic acids along the root exudates is largely unknown yet. In this study, the effects of titanium dioxide (TiO2) and silicon dioxide (SiO2) nanoparticles (NPs) treatments (1000 mg/L) on maize seedlings for 6 days were examined. Plant biomass, pigment, malondialdehyde (MDA), reactive oxygen species (ROS) production, and contents of organic acids in root exudates were analyzed. SiO2 NPs significantly reduced (p 0.05) in chlorophyll a content compared to the CK, while chlorophyll b increased by 28.9% (p < 0.05), and chlorophyll a/b ratio and content of carotenoid decreased by 16.8% and 54.7% (p < 0.05), respectively. MDA content significantly diminished in roots and leaves under SiO2 NPs. However, O2·ˉ production increased in roots by 17.2% and 23.8% (p < 0.05), respectively, under TiO2 and SiO2 NPs treatment. The pH of root exudates was declined by 17.4% and 14.2% (p < 0.05) respectively under both NPs treatment. Organic acid contents under TiO2 NPs significantly heightened (p < 0.05) by 60.7%, 31.2%, and 50.5% for citric, lactic, and fumaric acid, respectively, while formic and oxalic acid decreased by 27.8% and 26.4% respectively compared to the CK. In SiO2 NPs case, oxalic acid increased by 41.1% (p < 0.05), while malic and citric acid decreased by 62.6% and 45.7% respectively compared to the CK. In conclusion, both NPs treatments showed alternative impacts on maize seedlings.

A near-infrared fluorescent pH sensing film for wound milieu pH monitoring.

Studies have shown that wound pH is a potentially influential factor in the healing process. Due to the flaws of traditional pH measurement approaches, wound pH measurement has not become part of current standard of care. A near-infrared pH-sensitive ratiometric film was created and characterized for measuring wound pH. This film was fabricated by physically absorbing poly (N-isopropyl Acrylamide) nanoparticles conjugated with pH-sensitive (CypHer5E) and pH-insensitive (Cy7) fluorescent dyes into 2-hydroxyethyl methacrylate hydrogel film. The pH pattern on wounds can be indirectly measured by pressing freshly discarded wound dressing on top of the pH-sensitive film and imaging it. In vitro tests show that the film can accurately and rapidly detect a wide range of pH (from pH 4 to 8) in wound milieu. Further, patient studies showed that, by measuring pH on wound contact side of discarded wound gauze, the pH and its non-homogeneous distribution on wounds can be indirectly determined. By comparing patients with different wound conditions, we find that near-infrared pH sensing film can be used to measure wound exudate pH with high accuracy and efficiency. In addition, wound pH determination can provide an accurate assessment of wound healing activity in real time.

PH-responsive materials for optical monitoring of wound status

The monitoring of infection status of wounds is an emerging field and the pH of wound exudate is considered one potential indicator of infection. pH indicators intended for use in medical devices, such as swabs or dressings, need to be fixed in place, however, visual pH indicators are usually soluble molecules so are not inherently suitable for use in devices. To address this, we developed a rapid and simple immobilisation method for coupling pH-responsive dyes onto solid phases. The use of a silane based coupling agent for immobilisation of bromocresol purple led to a shift in the pH dependent spectral properties of the resulting material. The pH responsive material changes from yellow to green to blue with rising pH providing an ideal contrast to the reddish colour of most wound exudates. This is a key advantage over currently available alternatives when considering the suitability of this material for incorporation into various medical devices. In addition, we analysed clinical study samples to verify the association between wound infection and elevated pH-values. A device with an embedded indicator that changes to a contrast colour could represent a simple and easy-to-use system for detecting wounds at risk of infection.

Foliar application of 5-aminolevulinic acid to promote bioactive potential and nutritional value of purslane, a vegetable for future

Decent taste and the salt and drought tolerance of purslane (Portulaca oleracea L.) make it a potential vegetable crop for the future. This study investigates the effects of foliar application of 5-aminolevulinic acid (5-ALA), a new plant growth regulator, on the growth, mineral composition, and bioactive compounds of purslane. Three different levels of 5-ALA (0, 25 and 50 mg L-1) were sprayed at 1) two leaved stage and 2) upon the onset of inflorescence appearance on purslane seedlings. Results showed that 5-ALA application enhanced biomass accumulation in the plant shoot and increased shoot length. Concentration of nitrogen, potassium, magnesium, zinc and iron increased in the shoots of 5-ALA treated plants, while the calcium concentration remained unaffected. Phenolic compounds of the plant were catechin, chlorogenic acid, and ellagic acid, with catechin being the main compound. Further on, Trans-ferulic acid, hesperedin and eugenol were detected in the extract of 5-ALA-treated plants. Application of 5-ALA also increased fatty acids in the plant leaves. Total phenolics, ascorbic acid contents and antioxidative activity of shoot were increased in the 5-ALA-treated plants. Moreover, pH of root exudates of the plants was decreased in 5-ALA treated plants. The results revealed that exogenous 5-ALA has growth regulatory effects and can enhance the growth, and improve nutritional quality and pharmaceutical properties of P. oleracea. In this regard, the best results were obtained by application of 50 mg 5-ALA L-1.

Factors influencing the release of the biological nitrification inhibitor 1,9-decanediol from rice (Oryza sativa L.) roots

Root exudates of rice (Oryza sativa L.) can inhibit nitrification in Nitrosomonas bioassays, and 1,9-decanediol was recently identified as an important new biological nitrification inhibitor (BNI) from rice. However, the release characteristics of 1,9-decanediol have not been studied. The present study was designed to identify the major factors influencing the release of 1,9-decanediol from rice roots. Rice plants were hydroponically grown in controlled environment chambers for 6 weeks, and root exudates were collected. Responses of exudate release to nitrogen form and concentration, pH, aeration, and bacterial inoculation were explored. The pH of root exudates, collected under different nitrogen-provision regimes, was determined, and 1,9-decanediol levels in exudates were monitored. Ammonium (NH4+) and low pH in the root environment stimulated the release of 1,9-decanediol from rice roots. When only a part of the root system was exposed to NH4+, the secretion of 1,9-decanediol was triggered in the whole root system. Aeration of the root environment significantly enhanced 1,9-decanediol release. The presence of two major nitrifiers (Nitrosomonas europaea and Nitrosomonas stercoris) in the root medium stimulated release of 1,9-decanediol, whereas denitrifiers had no effect. Our results demonstrate that the release of 1,9-decanediol is enhanced by low to moderate concentrations of NH4+ (≤1.0 mM), low pH, and aeration of the rhizosphere. Our study provides the first evidence of significant 1,9-decanediol secretion induced by nitrifying bacteria.

Physiological Potential Evaluation of Myracrodruon urundeuva Stored Diaspores

The conservation of seeds in an appropriate location combined with the utilization of rapid tests for monitoring the physiological aspects is essential for quality seedlings. Thus, the study aimed to evaluate the behavior of Myracrodruon urundeuva diaspore under different periods and storage environments, and verify the testing of individual exudate pH in the physiological monitoring. The experimental design was completely randomized, factorial 2 × 8 (8 periods of storage and 2 storage environments) with four replications of 25 diaspores, using the Tukey test at 5% probability for average comparisons. After analysis of variance, it was performed regression analysis for the quantitative factor and simple Pearson correlation test. The variables analyzed were moisture content, seedling emergence (E) emergence velocity index (IVE), mean emergence time (TME) and the pH of the individual exudate. The results of E, IVE, TME tests indicated that the Myracrodruon urundeuva diaspores could be stored for ten months in room fridge, with low vigor loss. The pH test individual exudate showed lower estimates of simple Pearson correlation with the emergence test, not monitoring the physiological potential of Myracrodruon urundeuva diaspores.

EXUDATE pH AND FLOODING TESTS TO EVALUATE THE PHYSIOLOGICAL QUALITY OF SOYBEAN SEEDS

ABSTRACT The present study aimed to assess the variations in the parameters of the exudate pH and flooding tests to evaluate the physiological quality of soybean seeds. We subjected the lots of soybean seeds to germination, emergence, exudate pH, and flooding tests. Further, water content of the seeds, first count of germination, and emergence speed index were also determined. The exudate pH test studied the variations in the soaking period and temperature, while the flooding test assessed the variations in the amount of water and temperature at different periods of immersion. The experiment design was completely randomized. The results were presented as means and were compared using the Scott-Knott test at 5% probability. The Pearson’s correlation coefficient between the exudate pH and emergence of seedlings, and also between the flooding test result and emergence of seedlings were calculated. The results of the study indicated that the exudate pH test can be used to evaluate the physiological quality of soybean seeds after 30 min of imbibition at 20 °C. Further, the flooding test was efficient in evaluating the vigor of soybean seeds after 4 h of immersion either in 50 mL of distilled water at 25 °C or in 75 mL of distilled water at 30 °C.

AVALIAÇÃO DO POTENCIAL FISIOLÓGICO DE SEMENTES DE &lt;i&gt;Encholirium spectabile &lt;/i&gt;Mart. ex Schult. &amp; Schult. f.

A bromeliácea Encholirium spectabile Mart. ex Schult. &amp; Schult. f. para que seja explorada comercialmente, pela indústria farmacêutica, necessita de estudos quanto a sua propagação via sementes com o intuito de estabelecer plantios comerciais. Os testes rápidos de vigor destacam-se por fornecer resultados rápidos e precisos que complementam os de germinação para melhor aferir o potencial fisiológico da semente. Objetivou-se avaliar o potencial fisiológico das sementes de Encholirium spectabile procedentes de Graça-CE e Serra Talhada-PE, através dos testes de lixiviação de potássio e pH do exsudato-fenolftaleína. Os experimentos foram conduzidos em delineamento inteiramente casualizado em arranjo fatorial (duas regiões geográficas e períodos de embebição). Para avaliação do teste do pH do exsudato-fenolftaleína as sementes foram embebidas por 15, 30, 45 e 60 minutos e as análises com base na lixiviação de potássio por 30, 60, 90, 120, 150 e 180 minutos de embebição imersas em 25, 50 e 75 mL de água destilada. Paralelamente, realizou-se a caracterização fisiológica das sementes por meio do teor de água, teste de germinação, índice de velocidade e tempo médio de germinação, comprimento da parte aérea e do sistema radicular e massa seca de plântulas. As sementes de Encholirium spectabile com poder germinativo semelhante foram classificadas em níveis distintos de vigor pelos testes de lixiviação de potássio e do pH do exsudato-fenolftaleína. Pelo teste de lixiviação de potássio, o período de embebição de 30 minutos foi eficiente para classificar as sementes de Encholirium spectabile quanto ao vigor, de acordo com a região geográfica de coleta, independentemente do volume de água utilizado.

Peritonitis aggressiveness assessment

Peritonitis due to perforated duodenal ulcer was taken as a model. Patients were conditionally divided into three groups depending on the time after perforation: 6-12, 13-24 and over 24 hours. Analysis of microflora and pH of abdominal exudate was performed immediately after laparotomy. AIM: simple and reproducible method for determining the aggressiveness of peritonitis was developed. The authors believe that the diagnostic test is useful to individualize surgical approach in patient with advanced. peritonitis regardless time after perforation.

&lt;i&gt;In Situ&lt;/i&gt; Bioremediation of Tailings by Sulfate Reducing Bacteria and Iron Reducing Bacteria: Lab- and Field-Scale Remediation of Sulfidic Mine Tailings

To research the remediation efficiency of sulfate reducing bacteria and iron reducing bacteria on heavy metals, the remediation experiments of laboratory-scale and field-scale were conducted respectively with chalcopyrite tailings and 3 hectares lead-zinc sulfides mine tailings. The ion concentration of exudate was determined using inductively coupled plasma atomic emission spectroscopy, and key bacterial strains were investigated by real-time PCR. The laboratory-scale experiment of chalcopyrite tailings indicated pH of exudate rose to neutral, penetration time of exudate significantly increased, redox potential and dissolved iron notably decreased, and black metal sulfides were formed during remediation by sulfate reducing bacteria and iron reducing bacteria. The field-scale lead-zinc sulfides mine tailings remediation results indicated that the concentration of dissolved heavy metals in exudate decreased, and the growth of both moss and plants were promoted.

PH of exudate test in the physiological quality of crambe seeds

ABSTRACT: Crambe is a rapeseed with high oil content and can be used as a winter cover or as a source of raw material for the production of biodiesel, however espite the growing interest in the culture, research on the subject is still incipient, especially concerning the seed production and analysis technology. The purpose of this study is to evaluate the physiological quality of crambe seeds, 'FMS Brilhante' cultivar, by testing the pH of exudate. Five seed lots were submitted to the determination of water content and the tests of germination and vigor (first count, emergence and tetrazolium). In the conduction of pH exudate test, temperatures (25 and 30oC), and periods of seed imbibition in water (15, 30 and 45 minutes) were tested. The experiment was conducted in a completely randomized manner, with four replicates, and the mean values were compared by the Tukey test at 5% probability; Pearson correlation between the pH of the exudate and initial tests was also made. Testing the pH of exudate is promising for separating lots of crambe seeds and the following combinations of 25°C/30 minutes or 30°C/45 minutes can be used.

The effect of Ringer's solution within a dressing to elicit pain relief.

Clinical studies suggest that dressings containing Ringer's solution, such as the TenderWet and HydroClean families, provide relief from wound pain. This report reviews the available evidence and possible mechanisms for the relief of wound pain by these dressings. The ability of dressings containing Ringer's solution to provide pain relief is likely to be through providing a moist environment that is favourable for wound healing; furthermore, the dressing augments the protective barrier function by having additional fluid under the dressing, which covers exposed nerve endings and protects against friction damage. Ringer's solution will have a dilution effect and an influence on the pH of exudate. Diluting cytokines within the exudate would be expected to decrease inflammation in chronic wounds and reduce the influence of caustic components such as matrix metalloproteases (MMPs). Altering the pH of the wound bed could inactivate proteins and glycoproteins implicated in the pain response such as MMPs and sodium and calcium channels. The moist environment may also be better at recruiting leukocytes that release natural painkillers at areas of injury. These mechanisms are likely to act in combination to explain why dressings containing Ringer's solution can have analgesic effects.

Root acidification, a rapid method of screening soybean genotypes for low-phosphorus stress

Carboxylate efflux in response to low-phosphorus (P) is one of the plant's adaptive strategies. Genotypic variation between the type and amount of root-exuded carboxylates determines the differential P acquisition efficiency (PAE) in soybean (Glycine max (L.) Merrill.). We compared direct (using HPLC) and indirect methods (total carbon exudation, and use of bromocresol purple dye) for quantifying root acidification. Total carbon exudation did not correlate to carboxylate efflux, whereas a significant linear relationship between exudate pH and carboxylate concentration suggested that measure of root acidification might predict the genotypic potential for low-P induced carboxylate efflux.

Recombinant Lucilia Sericata chymotrypsin in a topical hydrogel formulation degrades human wound eschar ex vivo

Larval biotherapy is a debridement tool used in wound management. The mechanism of action involves degradation of eschar by serine proteases including chymotrypsin within the alimentary fluids of first instar Lucilia sericata. With the rationale of obviating some limitations of biotherapy, including cost, complexity of use, and patient reticence, the present study describes a mobile hydrogel formulation containing freeze-dried recombinant L. sericata chymotrypsin designed for topical application. Neither freeze-drying nor formulation into the hydrogel significantly attenuated the measured activity of released enzyme compared to fresh-frozen enzyme in aqueous solution. Gel electrophoresis confirmed qualitatively that the chymotrypsin/hydrogel formulation both with and without supplementary urea at 10% (w) /(v) degraded human chronic wound eschar ex vivo. Mindful that the hallmark of intractability of chronic wounds is aberrant biochemistry, the pH activity profile for the enzyme/hydrogel formulation was compared with exudate pH in chronic wounds of mixed aetiology in a cohort of 48 hospital in-patients. Five patients' wounds were acidic, however, the remainder were predominantly alkaline and coincided with the pH optimum for the insect enzyme. Thus, a recombinant L. sericata chymotrypsin and hydrogel formulation could represent a pragmatic alternative to larval therapy for the management of chronic wounds.

NO TITLE AVAILABLE

A utilização das popularmente chamadas, sementes crioulas de soja ou sementes salvas pelos produtores é uma constante no Centro-Oeste Brasileiro. Este trabalho teve o objetivo de avaliar a qualidade das sementes de soja produzidas, colhidas e armazenadas por uma empresa produtora de sementes, e das sementes utilizadas pelos produtores de grãos, produzidas sem seguir os procedimentos técnicos de produção de sementes. As parcelas conduzidas para produção de sementes comerciais, foram retiradas do campo logo que atingiram a maturação de campo com umidade de 16,3%, receberam quatro aplicações de inseticidas durante o seu ciclo, para o controle de percevejos e, foram colhidas com colhedora de fluxo axial com rotação de cilindro de 500 rpm, enquanto as outras parcelas foram retiradas do campo com umidades de 14,7 e 12,3%, receberam apenas três aplicações de inseticida e, foram colhidas com colhedora de cilindro côncavo com velocidade de rotação do cilindro de 700 rpm. Após a colheita foram utilizados diferentes processos de secagem, beneficiamento e armazenamento para as sementes comerciais e para as sementes salvas. No início e no final do armazenamento, todas as unidades experimentais foram analisadas com os seguintes testes: de germinação, de tetrazólio 1-8 , do pH do exsudato, de envelhecimento acelerado, de desenvolvimento de plântula, de tetrazólio 1-3 e de 1º contagem do teste de germinação. Os resultados permitem concluir que: sementes comerciais, produzidas de acordo com as recomendações técnicas de produção de sementes, apresentam qualidade fisiológica superior; a qualidade fisiológica de materiais conduzidos como grãos é reduzida com o armazenamento, impedindo sua utilização como sementes para formação de lavouras de grãos comerciais.

NH 4 + triggers the synthesis and release of biological nitrification inhibition compounds in Brachiaria humidicola roots

The release of chemical compounds from plant roots that suppress soil nitrification is termed biological nitrification inhibition (BNI). Determining the environmental factors that control the synthesis and release of BNI-compounds from Brachiaria humidicola (Rendle) Schweick, a tropical pasture grass that thrives on acid soils, is the focus of this investigation. Because the BNI trait is related to the N status of the plant, we investigated the possibility that the expression of this trait would be related to the forms of N found in the root environment. Plants were grown with two sources of N, NH4+ or NO3− for 60 days and the release of BNI-compounds monitored. Only plants grown with NH4+ released BNI-compounds from roots. The presence of NH4+ and possibly the secondary effect of its uptake (i.e., acidic pH) in the root environment significantly enhanced the release of BNI-compounds. Both the NH4+ and NO3− grown plants responded to the stimulus from NH4+ in the root environment. BNI-compounds found in root tissue and their release were nearly three times greater in NH4+ grown than from NO3− grown plants. The BNI-compounds released from roots composed of at least three active components—Type-I (stable to pH changes from 3.0 to 10), Type-II (temporarily loses its inhibitory effect at a pH higher than a threshold pH of 4.5 and the inhibitory effect is reestablished when the root exudate pH is adjusted to <4.5) and Type-III (inhibitory effect is irreversibly lost if the pH of the root exudate reaches 10.0 or above). A major portion of BNI-compounds released in the presence of NH4+ is of Type-I. In the absence of NH4+, mostly Type-II and Type-III BNI-compounds were released. The BNI-compounds inhibited the function of Nitrosomonas europaea through the blocking of both ammonia monooxygenase and hydroxylamino oxidoreductase pathways. These results indicate that the release of BNI-compounds from B. humidicola roots is a regulated function and that presence of NH4+ in the root environment is necessary for the sustained synthesis and release of BNI.

Carboxylate release of wheat, canola and 11 grain legume species as affected by phosphorus status

The capacity of plant roots to increase their carboxylate exudation at a low plant phosphorus (P) status is an adaptation to acquire sufficient P at low soil P availability. Our objective was to compare crop species in their adaptive response to a low-P availability, in order to gain knowledge to be used for improving crop P-acquisition efficiency from soils that are low in P or that have a high capacity to retain P. In the present screening study we compared 13 crop species, grown in sand at either 3 or 300 μM of P, and measured root mass ratio, cluster-root development, rhizosphere pH and carboxylate composition of root exudates. Root mass ratio decreased with increasing P supply for Triticum aestivum L., Brassica napus L., Cicer arietinum L. and Lens culinaris Medik., and increased only for Pisum sativum L., while the Lupinus species and Vicia faba L. were not responsive. Lupinus species that had the potential to produce root clusters either increased or decreased biomass allocation to clusters at 300 μM of P compared with allocation at 3 μM of P. All Lupinus species acidified their rhizosphere more than other species did, with average pH decreasing from 6.7 (control) to 4.3 for Lupinus pilosus L. and 5.9 for Lupinus atlanticus L.; B. napus maintained the most alkaline rhizosphere, averaging 7.4 at 300 μM of P. Rhizosphere carboxylate concentrations were lowest for T. aestivum, B. napus, V. faba, and L. culinaris than for the other species. Exuded carboxylates were mainly citrate and malate for all species, with the exception of L. culinaris and C. arietinum, which produced mainly citrate and malonate. Considerable variation in the concentration of exuded carboxylates and protons was found, even with a genus. Cluster-root forming species did not invariably have the highest concentrations of rhizosphere carboxylates. Lupinus species varied both in P-uptake and in the sensitivity of their cluster-root development to external P supply. Given the carbon cost of cluster roots, a greater plasticity in their formation and exudation (i.e. reduced investment in cluster roots and exudation at higher soil P, a negative feedback response) is a desirable trait for agricultural species that may have variable access to readily available P.