Plant uptake of non-ionic organic chemicals

Plant uptake of organic chemicals is an important process when considering the risks associated with land contamination, the role of vegetation in the global cycling of persistent organic pollutants, and the potential for industrial discharges to contaminate the food chain. There have been some significant advances in our understanding of the processes of plant uptake of organic chemicals in recent years; most notably there is now a better understanding of the air to plant transfer pathway, which may be significant for a number of industrial chemicals. This review identifies the key processes involved in the plant uptake of organic chemicals including those for which there is currently little information, e.g., plant lipid content and plant metabolism. One of the principal findings is that although a number of predictive models exist using established relationships, these require further validation if they are to be considered sufficiently robust for the purposes of contaminated land risk assessment or for prediction of the global cycling of persistent organic pollutants. Finally, a number of processes are identified which should be the focus of future research

Elevated atmospheric CO2 changes phosphorus fractions in soils under a short rotation poplar plantation (EuroFACE)

Future high levels of atmospheric carbon dioxide (CO2) may increase biomass production of terrestrial plants and hence plant requirements for soil mineral nutrients to sustain a greater biomass production. Phosphorus (P), an element essential for plant growth, is found in soils both in inorganic and in organic forms. In this work, three genotypes of Populus were grown under ambient and elevated atmospheric CO2 concentrations (FACE) for 5 years. An N fertilisation treatment was added in years 4 and 5 after planting. Using a fractionation scheme, total P was sequentially extracted using H2O, NaOH, HCl and HNO3, and P determined as both molybdate (Mo) reactive and total P. Molybdate-reactive P is defined as mainly inorganic but also some labile organic P which is determined by Vanado-molybdophosphoric acid colorimetric methods. Organic P was also measured to assess all plant available and weatherable P pools. We tested the hypotheses that higher P demand due to increased growth is met by a depletion of easily weatherable soil P pools, and that increased biomass inputs increases the amount of organic P in the soil. The concentration of organic P increased under FACE, but was associated with a decrease in total soil organic matter. The greatest increase in the soil P due to elevated CO2 was found in the HCl-extractable P fraction in the non-fertilised treatment. In the NaOH-extractable fraction the Mo-reactive P increased under FACE, but total P did not differ between ambient and FACE. The increase in both the NaOH- and HCl-extractable fractions was smaller after N addition. The results showed that elevated atmospheric CO2 has a positive effect on soil P availability rather than leading to depletion.We suggest that the increase in the NaOH- and HCl-extractable fractions is biologically driven by organic matter mineralization, weathering and mycorrhizal hyphal turnover.

Variation in root-associated phosphatase activities in wheat contributes to the utilization of organic P substrates in vitro, but does not explain differences in the P-nutrition of plants when grown in soils

To understand whether genotypic variation in root-associated phosphatase activities in wheat impacts on its ability to acquire phosphorus (P), various phosphatase activities of roots were measured in relation to the utilization of organic P substrates in agar, and the P-nutrition of plants was investigated in a range of soils. Root-associated phosphatase activities of plants grown in hydroponics were measured against different organic P substrates. Representative genotypes were then grown in both agar culture and in soils with differing organic P contents and plant biomass and P uptake were determined. Differences in the activities of both root-associated and exuded phosphodiesterase and phosphomonoesterase were observed, and were related to the P content of plants supplied with either ribonucleic acid or glucose 6-phosphate, respectively, as the sole form of P. When the cereal lines were grown in different soils, however, there was little relationship between any root-associated phosphatase activity and plant P uptake. This indicates that despite differences in phosphatase activities of cereal roots, such variability appears to play no significant role in the P-nutrition of the plant grown in soil, and that any benefit derived from the hydrolysis of soil organic P is common to all genotypes.

Does speciation impact on Cu uptake by, and toxicity to, the earthworm Eisenia fetida?

Eisenia fetida were exposed to different concentrations (0.009, 0.049 and 0. 125 mg L-1) of Cu in an aqueous medium. Cu speciation was manipulated through the addition of different concentrations (0. 15, 0.35 and 50 mg L-1) of EDTA. Cu speciation (as labile and non-labile pools) was determined using Differential Pulse Anodic Stripping Voltammetry. Labile Cu includes free Cu ions together with weak inorganic Cu complexes and a small fraction of easily dissociable organic complexes. Metal uptake and earthworm mortality increased with total Cu concentration in the EDTA free solutions. In the presence of EDTA both metal uptake and mortality decreased. These experiments demonstrate that Cu speciation governs uptake and consequent toxicity of Cu to E. fetida. (c) 2007 Elsevier Masson SAS. All rights reserved.

The fate and toxicity of the flavonoids naringenin and formononetin in soil

The flavonoid class of plant secondary metabolites play a multifunctional role in below-ground plant-microbe interactions with their best known function as signals in the nitrogen fixing legume-rhizobia symbiosis. Flavonoids enter rhizosphere soil as a result of root exudation and senescence but little is known about their subsequent fate or impacts on microbial activity. Therefore, the present study examined the sorptive behaviour, biodegradation and impact on dehydrogenase activity (as determined by iodonitrotetrazolium chloride reduction) of the flavonoids naringenin and formononetin in soil. Organic carbon normalised partition coefficients, log K-oc, of 3.12 (formononetin) and 3.19 (naringenin) were estimated from sorption isotherms and, after comparison with literature log K-oc values for compounds whose soil behaviour is better characterised, the test flavonoids were deemed to be moderately sorbed. Naringenin (spiked at 50 mu g g(-1)) was biodegraded without a detectable lag phase with concentrations reduced to 0.13 +/- 0.01 mu g g(-1) at the end of the 96 h time course. Biodegradation of formononetin proceeded after a lag phase of similar to 24 with concentrations reduced to 4.5 +/- 1% of the sterile control after 72 h. Most probable number (MPN) analysis revealed that prior to the addition of flavonoids, the soil contained 5.4 x 10(6) MPNg(-1) (naringenin) and 7.9 x 10(5) MPNg(-1) (formononetin) catabolic microbes. Formononetin concentration had no significant (p > 0.05) effect on soil dehydrogenase activity, whereas naringenin concentration had an overall but non-systematic impact (p = 0.045). These results are discussed with reference to likely total and bioavailable concentrations of flavonoids experienced by microbes in the rhizosphere. (c) 2007 Elsevier Ltd. All rights reserved.

The gas-phase ozonolysis of unsaturated volatile organic compounds in the troposphere

The gas-phase reactions of ozone with unsaturated hydrocarbons are significant sources of free radical species (including (OH)-O-center dot) and particulate material in the Earth's atmosphere. In this tutorial review, the kinetics, products and mechanisms of these reactions are examined, starting with a discussion of the original mechanism proposed by Criegee and following with a summary presentation of the complex, free radical-mediated reactions of carbonyl oxide (Criegee) intermediates. The contribution of ozone-terpene reactions to the atmospheric burden of secondary organic aerosol material is also discussed from the viewpoint of the formation of non-volatile organic acid products from the complex chemistry of ozone with alpha-pinene. Throughout the article, currently accepted understanding is supported through the presentation of key experimental results, and areas of persistent or new uncertainty are highlighted.

Considerations on the use of the p-nitrophenyl phosphomonoesterase assay in the study of the phosphorus nutrition of soil borne fungi

The p-nitrophenyl phosphomonoesterase assay (p NPPase) is commonly used to measure cell-wall-associated and extracellular phosphatase activity of soil fungi. p NPPases are usually assayed in the context of fungal nutrition, where inorganic P supply might be enhanced by the mineralisation of monoester organic P sources in the soil. The importance of the assay to the P nutrition of soil fungi is considered based on the evidence currently available including the consistency of methodological approach. The nature of organic P in the soil and the relevance of the assay to some specific soil substrates is discussed, particularly the chemistry and bioavailability of myo-inositol hexakisphosphate and the lower inositol phosphates. The evidence for the long-term stability of p NPPases in the soil is examined in the light of the persistence of p NPPase in soils. The role of persistent extracellular fungal p NPPases in the soil P cycle is discussed. Conclusions from p NPPase based studies must be based upon an appreciation of the constraints of the assay and the complex chemistry of organic P and p NPPase in the soil.

Some potential inaccuracies of the p -nitrophenyl phosphomonoesterase assay in the study of the phosphorus nutrition of soil borne fungi

The p-nitrophenol phosphomonoesterase assay (pNPPase) is commonly used to measure cell-wall-associated and extracellular phosphatase activity of soil fungi. pNPPases are usually assayed in the context of fungal nutrition, where inorganic P supply might be enhanced by the mineralisation of organic P sources in the soil. We report here on a series of experiments with the ectomycorrhizal basidiomycete Hebeloma cylindrosporum that highlight components of accepted methodology that might impinge on the reliability of the assay. These include the loss of pNPPase after filtration, inaccuracies in measuring wall-associated enzyme and the ample pool of intracellular pNPPase can be mistakenly measured as external pNPPase if cells are accidentally damaged.

Microbial and biochemical soil quality indicators and their potential for differentiating areas under contrasting agricultural management regimes

The aim of this study was to examine interrelationships between functional biochemical and microbial indicators of soil quality, and their suitability to differentiate areas under contrasting agricultural management regimes. The study included five 0.8 ha areas on a sandy-loam soil which had received contrasting fertility and cropping regimes over a 5 year period. These were organically managed vegetable, vegetable -cereal and arable rotations, an organically managed grass clover ley, and a conventional cereal rotation. The organic areas had been converted from conventional cereal production 5 years prior to the start of the study. All of the biochemical analyses, including light fraction organic matter (LFOM) C and N, labile organic N (LON), dissolved organic N and water-soluble carbohydrates showed significant differences between the areas, although the nature of the relationships between the areas varied between the different parameters, and were not related to differences in total soil organic matter content. The clearest differences were seen in LFOM C and N and LON, which were higher in the organic arable area relative to the other areas. In the case of the biological parameters, there were differences between the areas for biomass-N, ATP, chitin content, and the ratios of ATP: biomass and basal respiration: biomass. For these parameters, the precise relationships between the areas varied. However, relative to the conventionally managed area, areas under organic management generally had lower biomass-N and higher ATP contents. Arbuscular mycorrhizal fungus colonization potential was extremely low in the conventional area relative to the organic areas. Further, metabolic diversity and microbial community level physiological profiles, determined by analysis of microbial community metabolism using Biolog GN plates and the activities of eight key nutrient cycling enzymes, grouped the organic areas together, but separated them from the conventional area. We conclude that microbial parameters are more effective and consistent indicators of management induced changes to soil quality than biochemical parameters, and that a variety of biochemical and microbial analyses should be used when considering the impact of management on soil quality. (C) 2004 Elsevier Ltd. All rights reserved.

Effects of manure and fertilizer on grain yield, soil carbon and phosphorus in a 13-year field trial in semi-arid Kenya

Long-term indicators of soil fertility were assessed by measuring grain yield, soil organic carbon (SOC) and soil Olsen phosphorous for a P-deficient soil. In one set of treatments, goat manure was applied annually for 13 years at 0, 5 and 10 t ha(-1), and intercrops of sorghum/cowpea, millet/green gram and maize/pigeonpea were grown. Yield depended on rainfall and trends with time were not identifiable. Manure caused an upward trend in SOC, but 10 t ha(-1) manure did not give significantly more SOC than 5 t ha(-1). Only 10 t ha(-1) manure increased Olsen P. Measurements of both SOC and Olsen P are recommended. In another set of treatments, manure was applied for four years; the residual effect lasted another seven to eight years when assessed by yield, SOC and Olsen P Treatment with mineral fertilizers provided the same rates of N and P as 5 t hat manure and yields from manure and fertilizer were similar. Fertilizer increased Olsen P but not SOC. Management systems with occasional manure application and intermediate fertilizer applications should be assessed. Inputs and offtakes of C, N and P were measured for three years. Approximately 16, 25 and 11% of C, N and P respectively were stabilized into soil organic matter from 5 t ha(-1) a(-1) manure. The majority of organic P was fixed as soil inorganic P.

Juvenile-mature wood transition in pine: correlation between wood properties and candidate gene expression profiles

There is a strong desire to exploit transcriptomics data from model species for the genetic improvement of non-model crops. Here, we use gene expression profiles from the commercial model Pinus taeda to identify candidate genes implicated in juvenile-mature wood transition in the non-model relative, P. sylvestris. Re-analysis of 'public domain' SAGE data from xylem tissues of P. taeda revealed 283 mature-abundant and 396 juvenile-abundant tags (P < 0.01), of which 70 and 137, respectively matched to genes with known function. Based on sequence similarity, we then isolated 16 putative homologues of genes that in P. taeda exhibited widest divergence in expression between juvenile and mature samples. Candidate expression levels in P. sylvestris were almost invariably differential between juvenile and mature woody tissue samples among two cohorts of five trees collected from the same seed source and selected for genetic uniformity by genetic distance analysis. However, the direction of differential expression was not always consistent with that described in the original P. taeda SAGE data. Correlation was observed between gene expression and juvenile-mature wood anatomical characteristics by OPLS analysis. Four candidates (alpha-tubulin, porin MIP1, lipid transfer protein and aquaporin like protein) apparently had greatest influence on the wood traits measured. Speculative function of these genes in relation to juvenile-mature wood transition is briefly explored. Thus, we demonstrate the feasibility of exploiting SAGE data from a model species to identify consistently differentially expressed candidates in a related non-model species.

Interaction of PPARG Pro12Ala with dietary fat influences plasma lipids in subjects at cardiometabolic risk

The PPARγ2 gene SNP Pro12Ala has shown variable association with metabolic syndrome traits in healthy subjects. We investigated the effect of interaction between genotype and the ratio of polyunsaturated:saturated (P:S) fatty acid intake on plasma lipids in 367 White subjects aged 30-70 y at increased cardiometabolic risk, in the RISCK study. Interaction was determined after habitual diet at recruitment, at baseline after a 4-week high-SFA (HS) diet and after 24-week reference (HS), high-MUFA (HM) and low-fat (LF) diets. At recruitment, there were no significant associations between genotype and plasma lipids, however, P:S x genotype interaction influenced plasma total cholesterol (TC) (P=0.02), LDL-cholesterol (LDL-C) (P=0.002) and triglyceride (TG) (P=0.02) concentrations. At P:S ratio ≤0.33, mean TC and LDL-C concentrations in Ala12 allele carriers were significantly higher than in non-carriers (respectively P=0.003; P=0.0001). Significant trends in reduction of plasma TC (P=0.02) and TG (P=0.002) concentrations occurred with increasing P:S (respectively ≤0.33 to >0.65 and 0.34 to >0.65) in Ala12 allele carriers. There were no significant differences between carriers and non-carriers after the 4-week HS diet or 24-week interventions. Plasma TC and TG concentrations in PPARG Ala12 allele carriers decrease as P:S increases, but are not dependent on a reduction in SFA intake.

Eight-plex iTRAQ analysis of variant metastatic human prostate cancer cells identifies candidate biomarkers of progression: an exploratory study.

BACKGROUND: Due to the heterogeneity in the biological behavior of prostate cancer, biomarkers that can reliably distinguish indolent from aggressive disease are urgently needed to inform treatment choices. METHODS: We employed 8-plex isobaric Tags for Relative and Absolute Quantitation (iTRAQ), to profile the proteomes of two distinct panels of isogenic prostate cancer cells with varying growth and metastatic potentials, in order to identify novel biomarkers associated with progression. The LNCaP, LNCaP-Pro5, and LNCaP-LN3 panel of cells represent a model of androgen-responsive prostate cancer, while the PC-3, PC-3M, and PC-3M-LN4 panel represent a model of androgen-insensitive disease. RESULTS: Of the 245 unique proteins identified and quantified (>or=95% confidence; >or=2 peptides/protein), 17 showed significant differential expression (>or=+/-1.5), in at least one of the variant LNCaP cells relative to parental cells. Similarly, comparisons within the PC-3 panel identified 45 proteins to show significant differential expression in at least one of the variant PC-3 cells compared with parental cells. Differential expression of selected candidates was verified by Western blotting or immunocytochemistry, and corresponding mRNA expression was determined by quantitative real-time PCR (qRT-PCR). Immunostaining of prostate tissue microarrays for ERp5, one of the candidates identified, showed a significant higher immunoexpression in pre-malignant lesions compared with non-malignant epithelium (P < 0.0001, Mann-Whitney U-test), and in high Gleason grade (4-5) versus low grade (2-3) cancers (P < 0.05). CONCLUSIONS: Our study provides proof of principle for the application of an 8-plex iTRAQ approach to uncover clinically relevant candidate biomarkers for prostate cancer progression.

Impact of the quantity and flavonoid content of fruits and vegetables on markers of intake in adults with an increased risk of cardiovascular disease: the FLAVURS Trial

Purpose Limited robust randomised controlled trials investigating fruit and vegetable (F&V) intake in people at risk of cardiovascular disease (CVD) exist. We aimed to design and validate a dietary strategy of increasing flavonoid-rich versus flavonoid-poor F&V consumption on nutrient biomarker profile. Methods A parallel, randomised, controlled, dose–response dietary intervention study. Participants with a CVD relative risk of 1.5 assessed by risk scores were randomly assigned to one of the 3 groups: habitual (control, CT), high-flavonoid (HF) or low-flavonoid (LF) diets. While the CT group (n = 57) consumed their habitual diet throughout, the HF (n = 58) and LF (n = 59) groups sequentially increased their daily F&V intake by an additional 2, 4 and 6 portions for 6-week periods during the 18-week study. Results Compliance to target numbers and types of F&V was broadly met and verified by dietary records, and plasma and urinary biomarkers. Mean (±SEM) number of F&V portions/day consumed by the HF and LF groups at baseline (3.8 ± 0.3 and 3.4 ± 0.3), 6 weeks (6.3 ± 0.4 and 5.8 ± 0.3), 12 weeks (7.0 ± 0.3 and 6.8 ± 0.3) and 18 weeks (7.6 ± 0.4 and 8.1 ± 0.4), respectively, was similar at baseline yet higher than the CT group (3.9 ± 0.3, 4.3 ± 0.3, 4.6 ± 0.4, 4.5 ± 0.3) (P = 0.015). There was a dose-dependent increase in dietary and urinary flavonoids in the HF group, with no change in other groups (P = 0.0001). Significantly higher dietary intakes of folate (P = 0.035), non-starch polysaccharides (P = 0.001), vitamin C (P = 0.0001) and carotenoids (P = 0.0001) were observed in both intervention groups compared with CT, which were broadly supported by nutrient biomarker analysis. Conclusions The success of improving nutrient profile by active encouragement of F&V intake in an intervention study implies the need for a more hands-on public health approach.

Genetic responses to phosphorus deficiency

Background: Phosphorus (P) is an essential macronutrient for plants. Plants take up P as phosphate (Pi) from the soil solution. Since little Pi is available in most soils, P fertilizers are applied to crops. However, the use of P fertilizers is unsustainable and may cause pollution. Consequently, there is a need to develop more P-use-efficient (PUE) crops and precise methods to monitor crop P-status. Scope: Manipulating the expression of genes to improve the PUE of crops could reduce their P fertilizer requirement. This has stimulated research towards the identification of genes and signalling cascades involved in plant responses to P deficiency. Genes that respond to P deficiency can be grouped into 'early' genes that respond rapidly and often non-specifically to P deficiency, or 'late' genes that impact on the morphology, physiology or metabolism of plants upon Prolonged P deficiency. Summary: The use of micro-array technology has allowed researchers to catalogue the genetic responses of plants to P deficiency. Genes whose expression is altered by P deficiency include various transcription factors, which are thought to coordinate plant responses to P deficiency, and other genes involved in P acquisition and tissue P economy. Several common cis-regulatory elements have been identified in the promoters of these genes, suggesting that their expression might be coordinated. It is suggested that knowledge of the genes whose expression changes in response to P deficiency might allow the development of crops with improved PUE, and could be used in diagnostic techniques to monitor P deficiency in crops either directly using 'smart' indicator plants or indirectly through transcript profiling. The development of crops with improved PUE and the adoption of diagnostic technology could reduce production costs, minimize the use of a non-renewable resource, reduce pollution and enhance biodiversity.