Search

Attention is being paid to the use of different tillage regimes as a means of retaining soil organic carbon ( SOC) and sequestering more SOC. Alongside earlier measurements of total SOC stocks under different tillage regimes, we have examined the distribution of nitrogen ( N), microbial activity and the structure of the soil bacterial community from differently tilled plots under continuous barley. The plots were established 5 yr before sampling and have been maintained annually under conventional tillage ( CT; moldboard ploughing to 20 cm and disking), deep ploughing ( DP; ploughing to 40 cm and disking), minimum tillage ( MT; disking to 7 cm) or zero tillage ( ZT). Our earlier work showed there was no difference in SOC contents down to 60-cm depth between the treatments, but now we report that there were significant differences in the total N and active microbial biomass (substrate-induced respiration) contents of the same soils. The N contents of the CT, DP and MT treatments were not significantly different, but the ZT contained significantly more N, indicating either greater N retention under the ZT treatment or preferential loss from the more intensively tilled treatments, or a combination of both. The microbial biomass content was greater for the CT and DP treatments than for the MT and ZT treatments, indicating greater sensitivity to treatment effects of the microbial biomass pool than the total C pool, consistent with its more dynamic nature. Terminal restriction fragment length polymorphism ( T- RFLP) analyses of the soil bacteria DNA (a method of assessing the bacterial community structure) enabled the samples to be distinguished both according to SOC content, which is to be expected, and to tillage regime with the greatest differences in community structure occurring in the ZT treatment and the least in DP and CT treatments, reflecting the degree of homogenization or disturbance resulting from tillage. [ABSTRACT FROM AUTHOR]

An accepted view, that unless nitrate concentrations in the soil solution are very low (e.g. below 0.1-0.2 molm-3) the growth of high-yielding crops is not limited by the availability of nitrogen, is challenged. Conventional analyses of nutrient supply and demand, based on calculations of apparent inflow rates (uptake rates per unit total root length) are invalid. Apparent inflow rates are inversely proportional to root length. The convention of using total root length grossly over-estimates the fraction of the root system active in nutrient uptake. Consequently, inflow rates based on total root lengths underestimate the true values, indicating unrealistically low nutrient concentration differentials between bulk soil and root surfaces required to drive uptake. An alternative method of analysis is suggested. This is based on total nutrient uptake rather than on inflow rate. Measurements of the former do not depend on estimates of active root length and can be made directly and reliably. The method was applied to data obtained from a pot experiment using spring wheat (Triticum aestivum L., cv. Wembley) grown in soil without nitrogen fertilizer (N0) or with nitrogen fertilizer equivalent to 200 kg N ha-1 (N+). Soil nitrate concentrations calculated using the conventional method based on total root length, suggested that any increases in concentration above those measured in the N0 treatment should not have resulted in increased uptake and growth. However, the N+ plants were always bigger than those in the N0 treatment, refuting this suggestion. Theoretical uptakes of nitrogen (calculated initially on the basis of a fully active root system) were adjusted, by reducing the effective root length incrementally, until the theoretical uptake matched the measured net uptake of nitrogen. The mean fractions of the root systems likely to have been involved in nitrate uptake were 11% and 3.5% of the total lengths of root in the N0 and N+ treatments, respectively. [ABSTRACT FROM AUTHOR]

Competing Interests: JP-S is Partner at Lane Clark & Peacock LLP, Chair of the Royal Society for Public Health and reports personal fees from Novo Nordisk and Pfizer Ltd outside of this submitted work. SM is Partner at Lane Clark & Peacock LLP and deputy Chair of the Continuous Mortality Investigation. All other authors declare no competing interests.

Vuity (pilocarpine HCL ophthalmic 1.25%) was approved for the treatment of presbyopia in October 2021. Previous case series have reported the presence of vitreofoveal traction and retinal detachment following pilocarpine administration, but this was not reported in the recent randomized control trials assessing the efficacy of Vuity. The authors report a case of a woman of 65 years who developed vitreomacular traction immediately following the first administration of Vuity, review the literature, and present considerations regarding screening and management of patients starting Vuity. [ Ophthalmic Surg Lasers Imaging Retina 2022; 53:410-411.] .

Plant-associated microbiomes assist their host in a variety of activities, spanning from nutrition to defence against herbivores and diseases. Previous research showed that plant-associated microbiomes shift their composition when plants are exposed to stressors, including herbivory. However, existing studies explored only single herbivore-plant combinations, whereas plants are often attacked by several different herbivores, but the effects of multiple herbivore types on the plant microbiome remain to be determined. Here, we first tested whether feeding by different herbivores (aphids, nematodes and slugs) produces a shift in the rhizosphere bacterial microbiota associated with potato plants. Then, we expanded this question asking whether the identity of the herbivore produces different effects on the rhizosphere microbial community. While we found shifts in microbial diversity and structure due to herbivory, we observed that the herbivore identity does not influence the diversity or community structure of bacteria thriving in the rhizosphere. However, a deeper analysis revealed that the herbivores differentially affected the structure of the network of microbial co-occurrences. Our results have the potential to increase our ability to predict how plant microbiomes assemble and aid our understanding of the role of plant microbiome in plant responses to biotic stress., (© 2021 The Authors. Environmental Microbiology Reports published by Society for Applied Microbiology and John Wiley & Sons Ltd.)

Background: There are growing concerns about the mental health and risk of suicide amongst university students., Aim: To investigate trends in the incidence and characteristics of university student suicides in England & Wales for the academic years 2000/01 to 2016/17., Method: Record linkage between Office for National Statistics mortality data and Higher Education Statistics Agency data for England and Wales. Poisson regression and chi-squared tests were used to investigate secular trends and the characteristics of students dying by suicide., Results: There were 1330 student suicide deaths from 2000/01 to 2016/17; the annual incidence in 2015/16-2016/17 was 4.7 per 100,000 students. There was evidence of a rise in incidence since 2009/10 (incidence rate ratio per year 1.04 ((95%CI 1.00-1.07) p = 0.029). Incidence in 2012/13 to 2016/17 was less than half the rate in the general population of a similar age. Incidence was higher in males than females and amongst undergraduates vs. postgraduates. There was some evidence of a reduced risk amongst black compared to white students (RR 0.53 (95%CI 0.32-0.88). Incidence was highest in January and lowest during the summer holidays (July-September)., Limitations: There was no age/sex or sociodemographic breakdown of the overall student population for 2000/01 to 2011/12., Conclusion: Rates of suicide are considerably lower amongst students than the general population. In keeping with trends in young people in the wider population, the incidence of student suicide has increased since 2009/10. To inform prevention, research is needed to understand reasons for the rise in suicide in young people., (Copyright © 2019. Published by Elsevier B.V.)

In the light of concern about the harmful effects of media reporting of suicides and a lack of comparative research, this study compares the number and characteristics of reports on suicides and road traffic accidents (RTAs) in young people (aged 11-18) in newspapers and Twitter during a 6-month period. Tweets about young people's suicides were more numerous than newspaper reports. Twitter and newspaper reports were more strongly correlated for suicides than for RTAs. Recent suicides were less likely to be reported in newspapers than recent deaths by RTA. Bullying-related suicides were especially newsworthy. Suicide prevention organizations should consider routinely monitoring social media reporting.

Questions have been raised in various fields of research about the consequences of plants with modified lignin production. As a result of their roles in nutrient cycling and plant diversity, plant-soil interactions should be a major focus of ecological studies on lignin-modified plants. However, most studies have been decomposition studies conducted in a single soil or in sterile soil. Thus, we understand little about plant-soil interactions in living lignin-modified plants. In lignin mutants of three different barley (Hordeum vulgare) cultivars and their corresponding wild-types associated with three different soil microbial communities, we asked: do plant-soil microbiome interactions influence the lignin content of plants?; does a mutation in lignin production alter the outcome of plant-soil microbiome interactions?; does the outcome of plant-soil microbiome interactions depend on host genotype or the presence of a mutation altering lignin production? In roots, the soil community explained 6% of the variation in lignin content, but, in shoots, the soil community explained 21% of the variation in lignin content and was the only factor influencing lignin content. Neither genotype nor mutations in lignin production explained associations with fungi. Lignin content changes in response to a plant's soil microbial community, and may be a defensive response to particular components of the soil community., (© 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.)

Research into plant-mediated indirect interactions between arbuscular mycorrhizal (AM) fungi and insect herbivores has focussed on those between plant shoots and above-ground herbivores, despite the fact that only below-ground herbivores share the same part of the host plant as AM fungi. Using Plantago lanceolata L., we aimed to characterise how early root herbivory by the vine weevil (Otiorhynchus sulcatus F.) affected subsequent colonization by AM fungi (Glomus spp.) and determine how the two affected plant growth and defensive chemistry. We exposed four week old P. lanceolata to root herbivory and AM fungi using a 2×2 factorial design (and quantified subsequent effects on plant biomass and iridoid glycosides (IGs) concentrations. Otiorhynchus sulcatus reduced root growth by c. 64%, whereas plant growth was unaffected by AM fungi. Root herbivory reduced extent of AM fungal colonization (by c. 61%). O. sulcatus did not influence overall IG concentrations, but caused qualitative shifts in root and shoot IGs, specifically increasing the proportion of the more toxic catalpol. These changes may reflect defensive allocation in the plant against further attack. This study demonstrates that very early root herbivory during plant development can shape future patterns of AM fungal colonization and influence defensive allocation in the plant.

A glasshouse experiment was undertaken to provide baseline data on the variation between conventional maize (Zea mays L.) varieties and genetically modified maize plants expressing the insecticidal Bacillus thuringiensis protein (Bt, Cry1Ab). The objective was to determine whether the variation in soil parameters under a range of conventional maize cultivars exceeded the differences between Bt and non-Bt maize cultivars. Variations in plant growth parameters (shoot and root biomass, percentage carbon, percentage nitrogen), Bt protein concentration in shoots, roots and soil, soil nematode abundance and soil microbial community structure were determined. Eight paired varieties (i.e. varieties genetically modified to express Bt protein and their near-isogenic control varieties) were investigated, together with a Bt variety for which no near-isogenic control was available (NX3622, a combined transformant expressing both Bt and herbicide tolerance) and a conventional barley (Hordeum vulgare L.) variety which was included as a positive control. The only plant parameter which showed a difference between Bt varieties and near-isogenic counterparts was the shoot carbon to nitrogen ratio; this was observed for only two of the eight varieties, and so was not attributable to the Bt trait. There were no detectable differences in the concentration of Bt protein in plant or soil with any of the Bt-expressing varieties. There were significant differences in the abundance of soil nematodes, but this was not related to the Bt trait. Differences in previously published soil nematode studies under Bt maize were smaller than these varietal effects. Soil microbial community structure, as determined by phospholipid fatty acid (PLFA) analysis, was strongly affected by plant growth stage but not by the Bt trait. The experimental addition of purified Cry1Ab protein to soil confirmed that, at ecologically relevant concentrations, there were no measurable effects on microbial community structure.

Studies on the effect of genetically modified Bacillus thuringiensis (Bt) crops on true soil dwelling non-target arthropods are scarce. The objective of this study was to assess the influence of a 4-week exposure to two Bt maize varieties (Cry1Ab) Cascade and MEB307 on the collembolan Protaphorura armata. For comparison three non-Bt maize varieties, Rivaldo (isogenic to Cascade), Monumental (isogenic to MEB307) and DK242, and two control diets based on baker's yeast (uncontaminated and contaminated with Bt toxin Cry1Ab) were also tested. Due to a lower C:N ratio, individuals reared on yeast performed significantly better in all of the measured endpoints than those reared on maize. P. armata performed equally well when reared on two Bt and three non-Bt maize varieties. Although there were no negative effects of Bt maize in this experiment, we recommend future studies on Bt crops to focus on species interactions in long-term, multi-species experiments.

The effects of maize (Zea mays L.), genetically modified to express the Cry1Ab protein (Bt), and an insecticide on soil microbial and faunal communities were assessed in a glasshouse experiment. Soil for the experiment was taken from field sites where the same maize cultivars were grown to allow comparison between results under glasshouse conditions with those from field trials. Plants were grown in contrasting sandy loam and clay loam soils, half were sprayed with a pyrethroid insecticide (deltamethrin) and soil samples taken at the five-leaf stage, flowering, and maturity. The main effect on all measured parameters was that of soil type and there were no effects of Bt trait or insecticide on plant growth. The Bt trait resulted in more soil nematodes and protozoa (amoebae), whereas insecticide application increased plant Bt concentration and altered nematode community structure. The only significant effects on soil microbial community structure, microarthropods, and larvae of a nontarget root-feeding Dipteran, were due to soil type and plant growth stage. The results indicate that, although there were statistically significant effects of the Bt trait on soil populations, they were small. The relative magnitude of the effect could best be judged by comparison with the insecticide treatment, which was representative of current best practice. The Bt trait had no greater effect than the insecticide treatment. Results from this glasshouse experiment were in broad agreement with conclusions from field experiments using the same plant material grown in the same soils.