Long- and short-term induction of defences in seedlings of Shorea leprosula (Dipterocarpaceae): support for the carbon: nutrient balance hypothesis

The induction of carbon-based secondary metabolites in leaves following damage has been proposed to be a result of a shift in the carbon:nutrient balance, when growth is limited by nutrients in relation to carbon. Here we test this hypothesis using seedlings of a tropical tree, Shorea leprosula (Dipterocarpaceae). In the short term, we analysed the phenolic content of leaves 7 d after damage on seedlings grown under differing light and nutrient treatments. In the long term, we examined the effect of nutrients, over 12 mo, on leaf phenolic concentration and seedling growth. In both the long and short term, levels of phenolics increased in damaged leaves under low nutrient treatments. No changes in leaf phenolics were detected under high nutrient regimes, or in the short term under low light. In addition, it was found that defoliation of seedlings in high-nutrient environments led to greater rates of leaf production than in undamaged seedlings, suggesting compensation

Collaborative goal setting with adults attending physiotherapy at a specialist neuromuscular centre: is it always appropriate? A cross-sectional survey

Objectives Collaborative goal setting is an integral component of treatment planning for adults with neuromuscular disorders (NMD). However, due to the unique challenges for these individuals, identifying a process for goal setting that is advantageous for all can be problematic. This study aimed to evaluate collaborative goal setting at a specialist NMD centre, as reported by service users attending physiotherapy. It also aimed to generate discussion about collaborative goal setting and the practice of goal setting in adults with NMD in order to inform future practice. Setting Specialist NMD community-based centre in the UK. Participants One hundred and four adults with NMD who attended the centre. Design Cross-sectional survey. Thematic and content analyses of goals set were performed alongside demographic data collection. Results One hundred and four patients (34 females) with a range of neuromuscular conditions – including Becker, facioscapularhumeral, limb girdle, Duchenne and myotonic muscular dystrophies – completed the survey. Thirty-six respondents (37%) stated that they had set goals with the physiotherapist, whilst 62 (63%) stated that they had not set goals with the physiotherapist. Respondents’ goals were grouped into four themes: symptom management, maintenance, improving physical condition, and learning to live with the condition. Conclusions Readiness to take part in collaborative goal setting is unique to each individual. Physiotherapists need to be skilful in supporting adults with NMD through the goal-setting process until they are capable of sharing responsibility. Setting personal goals to improve emotional well-being may help to develop confidence to take more control of their situation, hence facilitating skills in self-management

Genetic differentiation between Atlantic salmon populations in the Windermere catchment

Genetic analysis, using single locus probes for genomic DNA, revealed that the juvenile Atlantic salmon populations in the Rivers Leven, Rothay and Troutbeck were related but genetically distinct. This genetic differentiation is greater than might be expected (by comparison with other salmon populations in the UK) and it is recommended that no action is taken which might promote genetic exchange between the three rivers. Thus, future fisheries management practices should treat the salmon from each site as separate genetic stocks. It is unlikely that any attempts to encourage fish currently spawning in the River Leven (downstream of Windermere) to utilize the upper catchment will be successful. The faster growth rate of juvenile salmon in the River Leven, compared with the River Rothay, probably results from a difference in temperature between the inflowing streams and the main outflow of Windermere. Precocious sexual maturation of some male parr was found in all three populations but the incidence (13-33%) is well within the range reported for other waters. Because of their enhanced growth rate, it is likely that some of the precocious males in the River Leven were 0+ fish. A very high incidence of hybridization (>18%) between Atlantic salmon and brown/sea trout was found in Troutbeck but not in the other rivers. Mitochondrial DNA analysis of these hybrids revealed them to be the product of several, independent cross-fertilizations involving both sexes of both species. The implications of this finding are discussed in relation to the availability of suitable spawning sites in Troutbeck

The ecology of herbivore-induced silicon defences in grasses

Silicon as a defence against herbivory in grasses has gained increasing recognition and has now been studied in a wide range of species, at scales from individual plants in pots to plant communities in the field. The impacts of these defences have been assessed on herbivores ranging from insects to rodents to ungulates. Here, we review current knowledge of silicon mediation of plant-herbivore interactions in an ecological context. The production of silicon defences by grasses is affected by both abiotic and biotic factors and by their interactions. Climate, soil type and water availability all influence levels of silicon uptake, as does plant phenology and previous herbivory. The type of defoliation matters and artificial clipping does not appear to have the same impact on silicon defence induction as herbivory which includes the presence of saliva. Induction of silicon defences has been demonstrated to require a threshold level of damage, both in the laboratory and in the field. In recent studies of vole-plant interactions, the patterns of induction were found to be quantitatively similar in glasshouse compared with field experiments, in terms of both the threshold required for induction and timing of the induction response. The impacts of silicon defences differ between different classes of herbivore, possibly reflecting differences in body size, feeding behaviour and digestive physiology. General patterns are hard to discern however, and a greater number of studies on wild mammalian herbivores are required to elucidate these, particularly with an inclusion of major groups for which there are currently no data, one such example being marsupials. We highlight new research areas to address what still remains unclear about the role of silicon as a plant defence, particularly in relation to plant-herbivore interactions in the field, where the effects of grazing on defence induction are harder to measure. We discuss the obstacles inherent in scaling up laboratory work to landscape-scale studies, the most ecologically relevant but most difficult to carry out, which is the next challenge in silicon ecology

Are silica defences in grasses driving vole population cycles?

Understanding the factors that drive species population dynamics is fundamental to biology. Cyclic populations of microtine rodents have been the most intensively studied to date, yet there remains great uncertainty over the mechanisms determining the dynamics of most of these populations. For one such population, we present preliminary evidence for a novel mechanism by which herbivore-induced reductions in plant quality alter herbivore life-history parameters and subsequent population growth. We tested the effect of high silica levels on the population growth and individual performance of voles (Microtus agrestis) reared on their winter food plant (Deschampsia caespitosa). In sites where the vole population density was high, silica levels in D. caespitosa leaves collected several months later were also high and vole populations subsequently declined; in sites where the vole densities were low, levels of silica were low and population density increased. High silica levels in their food reduced vole body mass by 0.5% a day. We argue that silica-based defences in grasses may play a key role in driving vole population cycles

Induction of silicon defences in wheat landraces is local not systemic and driven by mobilisation of soluble silicon to damaged leaves

In response to herbivory, many grasses, including crops such as wheat, accumulate significant levels of silicon (Si) as an antiherbivore defence. Damage-induced increases in Si can be localised in damaged leaves or more systemic, but the mechanisms leading to these differences in Si distribution remain untested. Ten genetically diverse wheat landraces (Triticum aestivum) were used to assess genotypic variation in Si induction in response to mechanical damage and how this was affected by exogenous Si supply. Total and soluble Si levels were measured in damaged and undamaged leaves, as were Si levels in the phloem, to test how Si was allocated to different parts of the plant after damage. Localised, but not systemic, induction of Si defences occurred, more pronounced when plants had supplemental Si. Damaged plants had significant increases in Si concentration in their damaged leaves, while the Si concentration in undamaged leaves decreased, such that there was no difference in the average Si concentration of damaged and undamaged plants. The increased Si in damaged leaves was due to the redirection of soluble Si, present in the phloem, from undamaged to damaged plant parts, potentially a more cost-effective defence mechanism for plants than increased Si uptake

The effect of silicon on osmotic and drought stress tolerance in wheat landraces

Drought stress reduces annual global wheat yields by 20%. Silicon (Si) fertilisation has been proposed to improve plant drought stress tolerance. However, it is currently unknown if and how Si affects different wheat landraces, especially with respect to their innate Si accumulation properties. In this study, significant and consistent differences in Si accumulation between landraces were identified, allowing for the classification of high Si accumulators and low Si accumulators. Landraces from the two accumulation groups were then used to investigate the effect of Si during osmotic and drought stress. Si was found to improve growth marginally in high Si accumulators during osmotic stress. However, no significant effect of Si on growth during drought stress was found. It was further found that osmotic stress decreased Si accumulation for all landraces whereas drought increased it. Overall, these results suggest that the beneficial effect of Si commonly reported in similar studies is not universal and that the application of Si fertiliser as a solution to agricultural drought stress requires detailed understanding of genotype-specific responses to Si

Uptake of silicon in barley under contrasting drought regimes

Purpose Silicon (Si) accumulation in plant tissues plays a vital role in alleviating biotic and abiotic stresses, including drought. Temperate regions are predicted to experience reductions in the quantity and frequency of rainfall events, potentially impacting plant Si uptake via the transpiration stream. Despite the importance for predicting plant responses to Si amendments, the effects of changes in rainfall patterns on Si uptake in cereals have not been characterised. Methods Five watering regimes were applied based on predicted precipitation scenarios, varying the quantity of water delivered (ambient, 40% or 60% reduction) and watering frequency (40% reduction in quantity, applied 50% or 25% of ambient frequency), and the effects on growth and leaf Si concentrations of a barley landrace and cultivar were determined. Results Reductions in the quantity of water reduced plant growth and yield, whereas reducing the watering frequency had little impact on growth, and in some cases partially ameliorated the negative effects of drought. Reductions in quantity of water lowered leaf Si concentrations in both the cultivar and landrace, although this effect was alleviated under the drought/deluge watering regime. The landrace had greater leaf Si concentration than the cultivar regardless of watering regime, and under ambient watering deposited Si in all cells between trichomes, whereas the cultivar exhibited gaps in Si deposition. Conclusion The impact of future reductions in rainfall on barley productivity will depend upon how the water is delivered, with drought/deluge events likely to have smaller effects on yield and on Si uptake than continuous drought

Targeted plant defense: silicon conserves hormonal defense signaling impacting chewing but not fluid‐feeding herbivores

Plants deploy an arsenal of chemical and physical defenses against arthropod herbivores, but it may be most cost efficient to produce these only when attacked. Herbivory activates complex signaling pathways involving several phytohormones, including jasmonic acid (JA), which regulate production of defensive compounds. The Poaceae also have the capacity to take up large amounts of silicon (Si), which accumulates in plant tissues. Si accumulation has antiherbivore properties, but it is poorly understood how Si defenses relate to defense hormone signaling. Here we show that Si enrichment causes the model grass Brachypodium distachyon to show lower levels of JA induction when attacked by chewing herbivores. Triggering this hormone even at lower concentrations, however, prompts Si uptake and physical defenses (e.g., leaf hairs), which negatively impact chewing herbivores. Removal of leaf hairs restored performance. Crucially, activation of such Si-based defense is herbivore-specific and occurred only in response to chewing and not fluid-feeding (aphid) herbivores. This aligned with our meta-analysis of 88 studies that showed Si defenses were more effective against chewing herbivores than fluid feeders. Our results suggest integration between herbivore defenses in a model Si-accumulating plant, which potentially allows it to avoid unnecessary activation of other costly defenses

Ideals and practicalities of policy co-design – developing England’s post-Brexit Environmental Land Management (ELM) schemes

There are few examples of where co-design has been applied to active policy development on the scale or level of complexity of England's post-Brexit Environmental Land Management (ELM) schemes. ELM offers a fascinating ‘laboratory’ to analyse how co-design at this scale works in practice. This paper offers the first in-depth empirical assessment of the process from the perspectives of both the policy makers and stakeholders who were involved in the initial phase of ELM co-design from 2018 to 2020. Using interview data, we provide critical insights for both academics and government on 'pragmatic' applications of co-design to active policy development and reflect on what this tells us about the wider processes of policy development that may need to change in order to accommodate this more ‘democratic’ approach. Our analysis, which identified key barriers to co-design as articulated by institutional stakeholders and civil servants, revealed a mismatch between the principles and practices of ‘co-design’ in the initial development of ELM. These early-stage challenges included: (i) a lack of shared decision-making and empowering stakeholders to contribute to problem-definitions; (ii) confidentiality requirements that introduced barriers to information-sharing; (iii) insufficient transparency and feedback on what happened to stakeholder's contributions in terms of policy development; (iv) an absence of detail on the schemes, including proposed approaches, payment rates, advice, baseline measures, the kinds of ‘outcomes’ expected, and monitoring mechanisms; and (v) a repetition of themes that participants had already discussed. Many of these mismatches may be common to other policy arenas. We argue that improved application of policy co-design in government will rely on wider changes to political processes and the institutional culture and practices within the civil service