Preferences for different nitrogen forms by co-existing plant species and soil microbes: reply

The growing awareness that plants might use a variety of nitrogen (N) forms, both organic and inorganic, has raised questions about the role of resource partitioning in plant communities. It has been proposed that coexisting plant species might be able to partition a limited N pool, thereby avoiding competition for resources, through the uptake of different chemical forms of N. In this study, we used in situ stable isotope labeling techniques to assess whether coexisting plant species of a temperate grassland (England, UK) display preferences for different chemical forms of N, including inorganic N and a range of amino acids of varying complexity. We also tested whether plants and soil microbes differ in their preference for different N forms, thereby relaxing competition for this limiting resource. We examined preferential uptake of a range of 13C15N-labeled amino acids (glycine, serine, and phenylalanine) and 15N-labeled inorganic N by coexisting grass species and soil microbes in the field. Our data show that while coexisting plant species simultaneously take up a variety of N forms, including inorganic N and amino acids, they all showed a preference for inorganic N over organic N and for simple over the more complex amino acids. Soil microbes outcompeted plants for added N after 50 hours, but in the long term (33 days) the proportion of added 15N contained in the plant pool increased for all N forms except for phenylalanine, while the proportion in the microbial biomass declined relative to the first harvest. These findings suggest that in the longer term plants become more effective competitors for added 15N. This might be due to microbial turnover releasing 15N back into the plant–soil system or to the mineralization and subsequent plant uptake of 15N transferred initially to the organic matter pool. We found no evidence that soil microbes preferentially utilize any of the N forms added, despite previous studies showing that microbial preferences for N forms vary over time. Our data suggest that coexisting plants can outcompete microbes for a variety of N forms, but that such plant species show similar preferences for inorganic over organic N

Quantification of priming and CO2 emission sources following the application of different slurry particle size fractions to a grassland soil

The highest emissions of CO2 from soils and most pronounced priming effect (PE) from soils generally occur immediately after slurry application. However, the influence of different particle size slurry fractions on net soil C respiration dynamics and PE has not been studied. Therefore, a slurry separation technique based on particle sizes was used in the present study. Six distinct fractions (>2000, 425–2000, 250–425, 150–250, 45–150, 250 μm fractions. The overall contribution of slurry C to total CO2 emissions was higher in smaller slurry particle size treatments in the first days after application. The addition of the various slurry fractions to soil caused both significant positive and negative PEs on the soil organic matter mineralization. The timing and type (positive or negative) of PE depended on the slurry particle size. Clearly, farm based separation pre-treatment leading to two or more fractions with different particle sizes has also the potential to reduce or modify short-term CO2 emissions immediately after slurry application to soil

The Effects of Self-Regulation Strategies on Middle School Students\u27 Calibration Accuracy and Achievement

This study investigated the impact that self-regulation strategies have on metacognitive judgements (calibration) and mathematics achievement of typical and advanced achieving 7th grade mathematics students over a period of seven weeks. Self-regulation strategies, four square graphic organizers and vocabulary games were implemented with the treatment condition while online games were implemented with the control condition. The results revealed that participants in the treatment condition were more accurate in their calibrations than participants in the control condition, more specifically for postdiction accuracy. Although the participants in the treatment condition scored higher on their achievement tests than the participants in the control condition, there were no significant differences between the conditions

Assessing the potential of co-composting rose waste as a sustainable waste management strategy:Nutrient availability and disease control

The current limited usage of rose waste makes rose cultivation far from a sustainable circular industry. Unfavorable properties of horticultural waste such as the high lignin content of stems and high polyphenol levels in both flowers and leaves makes it difficult to re-use. These traits hamper an effective composting process and so far little studies have focused on optimizing this process. The aim of this study was to investigate the potential of (co-)composting rose waste with other on-farm available green wastes (tomato and kalanchoe) or mature rose compost to obtain an improved compost with high fertilizing capacity. In a small-scale composting system the evolution of five mixtures was closely monitored in terms of their physico-chemical parameters. The in-vitro disease suppressive capacity of mature rose compost was assessed. All mixtures resulted in stable and mature compost after six months showing industry standard suitable macro- and micro-nutrient concentrations. The matured compost showed a C/N below 10, a strong decrease in polyphenols of ≥70% and a good fertilizing capacity with an increase in cation exchange capacity since the start of ≥100%. These results demonstrate that the ligneous character of rose waste is not preventing an effective composting process. However, an increased duration of the maturation phase might be favored for optimal results. The addition of mature compost accelerated the composting process as shown by significantly increases in OM degradation rates. For the first time a high disease suppressive capacity against several common rose pathogens was shown for mature rose compost. Overall, this study showed the potential of (co-)composting rose waste as sustainable waste management strategy to further improve the circular economy waste-based objectives of the horticultural sector.</p

Spatial distribution of organic carbon in the Atacama Desert, Chile

The Atacama Desert in northern Chile is known as the driest region on earth; however traces of life, can still be found. Soils are the habitat and reservoir for plants and microorganisms, which leave their fingerprints as organic residues. Here we identify and quantify organic carbon in soil profiles and along potential plant dispersal corridors in the Atacama Desert. We hypothesize that preferential pathways or barriers of the dispersal of life exist, which can be related to soil properties such as bulk density. We further assume that due to dust and salt accumulation at the surface, in particular the subsoils will reveal an unique though little explored archive of organic matter. The analytical assessment of Corg at very low levels is challenging. It was found that SOC in hyperarid soils ranged from 1.8 – 125 µg C per g soil for 0-1 m (1). We here present an improved Corg analysis, which is based on a temperature gradient method (DIN19539; Soli TOC cube, Elementar, Hanau). This allows combustion of samples with up to 5 g sample weight without the need to remove carbonate. This avoids loss and increases precision of Corg quantification at lowest concentrations. We can show that Corg contents decrease from 1.47 % to 0.1 % in the first 14 km of the gradient. However, first results suggest that within the hyper-arid core of the Atacama Corg contents increase. This gives first hints to the vegetation history of the desert and the dispersal of life

Lorentz angle measurements in irradiated silicon detectors between 77 K and 300 K

Future experiments are using silicon detectors in a high radiation environment and in high magnetic fields. The radiation tolerance of silicon improves by cooling it to temperatures below 180 K. At low temperatures the mobility increases, which leads to larger deflections of the charge carriers by the Lorentz force. A good knowledge of the Lorentz angle is needed for design and operation of silicon detectors. We present measurements of the Lorentz angle between 77 K and 300 K before and after irradiation with a primary beam of 21 MeV protons.Comment: 13 pages, 9 figures, submitted to ICHEP2000, Osaka, Japa

Molecular cloning of the double-stranded RNA of beet cryptic viruses.

Three of the four dsRNA components of purified beet cryptic virus (BCV) were copied into cDNA and cloned into pUC9. Clones corresponding to RNAs 1, 3 and 4 did not hybridize to each other or to RNA 2, suggesting that there is no significant sequence homology between the four dsRNA components. RNA extracted from 15 BCV-infected beet plants was analysed by Northern blotting using the cDNA clones as probes. Nine plants were found to contain RNAs 1, 3 and 4 whereas in six plants only RNAs 3 and 4 were detectable. The results are compatible with the occurrence of two different viruses. The sensitivity and specificity of the cDNA hybridization assay was greater than that of immunosorbent electron microscopy in the detection of BCVs. Beet cryptic virus (BCV) has isometric particles about 30 nm in diameter and is widespread in different cultivars of Beta vulgaris but induces no apparent symptoms (Kassanis et al., 1977). Furthermore, it is transmitted only through seed and pollen, and cannot be transmitted by mechanical inoculation (Kassanis et al., 1977, 1978). BCV purified from seedlings of beet cv. Sharpes Klein E contains two proteins (mol. wt. 52 500 and 54 500) and four dsRNA components (mol. wt. 1.36 × 10 6, 1.15 x 10 6, 0-94 x 106 and 0.87 x 10 6) (Accotto &amp; Boccardo, 1986). Bee

On Rank Problems for Planar Webs and Projective Structures

We present old and recent results on rank problems and linearizability of geodesic planar webs.Comment: 31 pages; LaTeX; corrected the abstract and Introduction; added reference

Nuclear DDX3 expression predicts poor outcome in colorectal and breast cancer

Purpose: DEAD box protein 3 (DDX3) is an RNA helicase with oncogenic properties that shuttles between the cytoplasm and nucleus. The majority of DDX3 is found in the cytoplasm, but a subset of tumors has distinct nuclear DDX3 localization of yet unknown biological significance. This study aimed to evaluate the significance of and mechanisms behind nuclear DDX3 expression in colorectal and breast cancer. Methods: Expression of nuclear DDX3 and the nuclear exporter chromosome region maintenance 1 (CRM1) was evaluated by immunohistochemistry in 304 colorectal and 292 breast cancer patient samples. Correlations between the subcellular localization of DDX3 and CRM1 and the difference in overall survival between patients with and without nuclear DDX3 were studied. In addition, DDX3 mutants were created for in vitro evaluation of the mechanism behind nuclear retention of DDX3. Results: DDX3 was present in the nucleus of 35% of colorectal and 48% of breast cancer patient samples and was particularly strong in the nucleolus. Nuclear DDX3 correlated with worse overall survival in both colorectal (hazard ratio [HR] 2.34, P&#60;0.001) and breast cancer (HR 2.39, P=0.004) patients. Colorectal cancers with nuclear DDX3 expression more often had cytoplasmic expression of the nuclear exporter CRM1 (relative risk 1.67, P=0.04). In vitro analysis of DDX3 deletion mutants demonstrated that CRM1-mediated export was most dependent on the N-terminal nuclear export signal. Conclusion: Overall, we conclude that nuclear DDX3 is partially CRM1-mediated and predicts worse survival in colorectal and breast cancer patients, putting it forward as a target for therapeutic intervention with DDX3 inhibitors under development in these cancer types