Photosynthetic acclimation of shade-grown red pine (Pinus resinosa Ait.) seedlings to a high light environment

Photosynthetic light acclimation in red pine (Pinus resinosa Ait.) seedlings was examined in a greenhouse study to better understand the physiological response of this species to increased light intensity following release from competition. Seedlings grown in a high (HL), medium (ML) or low (LL) light environment for 12 weeks were transferred to high light. Gas exchange and chlorophyll fluorescence of ML and LL seedlings were measured prior to and following transfer and compared with the HL control treatment. Photosynthetic characteristics were related to initial light treatment and time after transfer. Acclimation of gas exchange features to high light in shade formed ML and LL foliage was relatively rapid, with similar values among light treatments within 57 days of transfer. Acclimation of net photosynthetic rate was similar in ML and LL seedlings, and was associated primarily with increased mesophyll conductance to CO₂. The ratio of variable to maximal chlorophyll fluorescence (F_v/F_m) decreased initially after transfer, especially in LL seedlings, but recovered to normal values after 57 days. Red pine seedlings appear to be well adapted for photosynthetic acclimation to high light intensity, consistent with that reported for other early successional tree species.     

Structural Characterisation of the Interaction between Triticum aestivum and the Dothideomycete Pathogen Stagonospora nodorum

The interaction between Stagonospora nodorum and a susceptible wheat cultivar was investigated using a range of microscopic techniques. Germination of pycnidiospores occurred approximately 3 h after making contact with the leaf surface and was followed by attempted penetration 8–12 h later. Penetration was observed through stomata and also directly through periclinal and anticlinal epidermal cell walls. Penetration down the anticlinal cell walls appeared to occur without a differentiated penetrating structure whilst structures identified as either lateral appressoria or hyphopodia were typically present when penetrating over a periclinal cell wall. Once inside the leaf, the fungus continued to grow for the next 4–5 days colonising all parts of the leaf except the vascular bundles. Only in the later phase of the infection was total host cell collapse apparent. Evidence of polyphenolic compounds was observed. The infection cycle was completed within 7 days as indicated by sporulation on the leaf surface. These results have allowed us to understand how the fungus physically interacts with the leaf and will help the overall understanding of the infection process.     

Fijian adolescents’ understanding and evaluation of climate change: Implications for enabling effective future adaptation

Pacific Island countries are particularly vulnerable to future manifestations of climate change due to high coastline‐to‐land‐area ratios, and high dependence of inhabitants on natural ecosystems. While everyone in the Pacific Islands should participate in climate change adaptation activities, it is the young people, given they are the generation likely to not only bear the burden of climate change, but to lead and live effective climate change adaptation activities and strategies specific to their region, the involvement of youth is critical. Pacific Island youths are often marginalised within traditional decision‐making hierarchies, therefore they are typically excluded from participating in meaningful discussions at community and government levels. Discussions were held with 30 adolescents aged 14–18 years in Fiji to explore knowledge and experiences regarding climate change. Participants revealed their dismay at their inability to talk to family – who they consider are not doing enough – about what they consider as appropriate responses to climate change, recommending the help of an authoritative outsider who could speak to their community leaders and family. Discussions also revealed that Fijian youth could not distinguish between changes in the climate and normal weather events, attesting to the importance of climate‐change education and awareness‐raising efforts within the Pacific Islands more generally.     

Rhizosphere micro-organisms of seminal and nodal roots of wheat grown in pots

Wheat grown in Gabalong soil was examined for the microflora of its seminal and nodal root systems of similar age. At all stages of sampling, the seminal roots were found to support a significantly-larger population of bacteria, actinomycetes and fungi in their rhizosphere than the nodal roots. The seminal roots had higher numbers of bacteria and actinomycetes in their residues, but fungal numbers were not significantly different. The “rhizosphere effects” of the two root systems, in the combined analysis, were significantly different only for fungi. An interesting trend on both root systems was that while the numbers of bacteria, actinomycetes and fungi in the rhizosphere decreased with root age, their numbers in the residue increased with age.     

Cause and Consequence in Maize Planting Dates in Germany

An important part of agricultural adaptation is the timing of crop sowing dates, affecting yields and the level of risk incurred during a particular season. Cold stress is especially relevant in maize, Zea mays L., so that the timing of planting in the spring is a tactical response to short‐term weather, but is also subject to strategic planning with regard to longer‐term climate. Both factors compare the potential implications of cold stress to the additional yield obtainable through earlier planting. New cultivars suited to growing conditions in Europe and generally increasing spring temperatures have enabled earlier planting, but it is still dependent on short‐term weather during the planting period. In the context of field‐level decision‐making, a panel regression is used to estimate the relationship between weekly local temperature and precipitation and planting dates at specific sites throughout Germany. Next, localised weather data and planting behaviour are linked to yields at the district (Landkreis) level to show the effects of planting date on yield. Based on these relationships optimal planting dates are explored with some associated costs and benefits. Results show a trend towards earlier planting that follows observed increasing spring temperatures and the availability of more cold‐tolerant cultivars but this advance is buffered by the increasing severity of minimum temperatures during a critical period. Earlier planting potentially increases yield but this is offset by additional management costs and risk. A robust and simple depiction of farmer behaviour in climatic, technological and economic context can help to understand trends in crop management and productivity that effect agricultural landscapes.     

Nitrous oxide emissions from fertilised grassland: A 2-year study of the effects of N fertiliser form and environmental conditions

The aim was to investigate the effects of different N fertilisers on nitrous oxide (N₂O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N₂O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N₂O flux and soil and environmental variables. The loss of N₂O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2, 1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd year gave an average emission factor of 0.8% – lower than from application of either individual fertiliser. We suggest that similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed to minimise N₂O emissions from agricultural land. Received: 30 August 1996     

Muscular thin films for building actuators and powering devices

We demonstrate the assembly of biohybrid materials from engineered tissues and synthetic polymer thin films. The constructs were built by culturing neonatal rat ventricular cardiomyocytes on polydimethylsiloxane thin films micropatterned with extracellular matrix proteins to promote spatially ordered, two-dimensional myogenesis. The constructs, termed muscular thin films, adopted functional, three-dimensional conformations when released from a thermally sensitive polymer substrate and were designed to perform biomimetic tasks by varying tissue architecture, thin-film shape, and electrical-pacing protocol. These centimeter-scale constructs perform functions as diverse as gripping, pumping, walking, and swimming with fine spatial and temporal control and generating specific forces as high as 4 millinewtons per square millimeter.     

Folic acid supplementation and social deprivation

OBJECTIVE: To assess the use of folic acid supplementation in relation to small-area measures of social deprivation. DESIGN: Cohort study. SETTING: Antenatal clinic, Women's Outpatients Services, Cumberland Infirmary, Carlisle, UK. SUBJECTS: Four hundred and fifty women attending their 18-week antenatal clinic appointment. No selection criteria were applied. Townsend scores were allocated using postcodes to provide a small-area measure (enumeration district) of social deprivation. RESULTS: Eighty-nine per cent of women took folic acid prior to their 18-week antenatal clinic appointment; 48% of women took folic acid before 4 weeks of gestation. Younger women and more socially deprived women were less likely to use folic acid supplements before 4 weeks of gestation. Women with a family history of neural tube defects were no more likely to take folic acid than were women with no family history of neural tube defects. CONCLUSION: A high proportion of women reported taking folic acid supplements during pregnancy but less than half took them at the most important time in early pregnancy. Younger women and women who were more socio-economically deprived were much less likely to take folic acid during the critical periconceptional period. Future strategies should promote prenatal folic acid supplementation in women under the age of 24 and in women of low socio-economic status. Further attention should also be given to the use of folic acid supplements in women with a family history of neural tube defects.