A tillering inhibition gene influences root-shoot carbon partitioning and pattern of water use to improve wheat productivity in rainfed environments.

Genetic modification of shoot and root morphology has potential to improve water and nutrient uptake of wheat crops in rainfed environments. Near-isogenic lines (NILs) varying for a tillering inhibition (tin) gene and representing multiple genetic backgrounds were phenotyped in contrasting, controlled environments for shoot and root growth. Leaf area, shoot and root biomass were similar until tillering, whereupon reduced tillering in tin-containing NILs produced reductions of up to 60% in total leaf area and biomass, and increases in total root length of up to 120% and root biomass to 145%. Together, the root-to-shoot ratio increased two-fold with the tin gene. The influence of tin on shoot and root growth was greatest in the cv. Banks genetic background, particularly in the biculm-selected NIL, and was typically strongest in cooler environments. A separate de-tillering study confirmed greater root-to-shoot ratios with regular tiller removal in non-tin-containing genotypes. In validating these observations in a rainfed field study, the tin allele had a negligible effect on seedling growth but was associated with significantly (P<0.05) reduced tiller number (-37%), leaf area index (-26%), and spike number (-35%) to reduce plant biomass (-19%) at anthesis. Root biomass, root-to-shoot ratio at early stem elongation, and root depth at maturity were all increased in tin-containing NILs. Soil water use was slowed in tin-containing NILs, resulting in greater water availability, greater stomatal conductance, cooler canopy temperatures, and maintenance of green leaf area during grain-filling. Together these effects contributed to increases in harvest index and grain yield. In both the controlled and field environments, the tin gene was commonly associated with increased root length and biomass, but the significant influence of genetic background and environment suggests careful assessment of tin-containing progeny in selection for genotypic increases in root growth.

The Coordinators of Psychiatric Education (COPE) Residency In-Training Exam: a preliminary psychometric assessment.

OBJECTIVE: The Coordinators of Psychiatric Education (COPE) Residency In-Training Exam is a formative exam for Canadian psychiatric residents that was reconstructed using assessment best practices. An assessment of psychometric properties was subsequently performed on the exam to ensure preliminary validity and reliability. METHODS: An exam blueprint was developed based on the 2007 Royal College objectives for psychiatric training. A minimum pass level was established using a modified Angoff method. The exam was administered to all Canadian psychiatric residents in postgraduate years 2 to 5 with test reliability (Cronbach alpha) and item analysis performed. Exam validity was assessed through blueprint adherence and cross-year resident performance analysis. RESULTS: Four hundred two exams were suitable for analysis. The overall mean score for all residents was 69.6% (SD=8.5) with significant differences in total scores between each of the postgraduate year groups, with consistently better performance with increasing time in residency. Cronbach alpha was 0.79. CONCLUSION: The present study provides preliminary support that the reconstructed COPE Residency In-Training Exam demonstrates adequate reliability and validity, including showing the capacity to discriminate between levels of training.

Movement of newly assimilated 13C carbon in the grass Lolium perenne and its incorporation into rhizosphere microbial DNA.

One of the key processes that drives rhizosphere microbial activity is the exudation of soluble organic carbon (C) by plant roots. We describe an experiment designed to determine the impact of defoliation on the partitioning and movement of C in grass (Lolium perenne L.), soil and grass-sterile sand microcosms, using a (13)CO(2) pulse-labelling method. The pulse-derived (13)C in the shoots declined over time, but that of the roots remained stable throughout the experiment. There were peaks in the atom% (13)C of rhizosphere CO(2) in the first few hours after labelling probably due to root respiration, and again at around 100 h. The second peak was only seen in the soil microcosms and not in those with sterilised sand as the growth medium, indicating possible microbial activity. Incorporation of the (13)C label into the microbial biomass increased at 100 h when incorporation into replicating cells, as indicated by the amounts of the label in the microbial DNA, started to increase. These results indicate that the rhizosphere environment is conducive to bacterial growth and replication. The results also show that defoliation had no impact on the pattern of movement of (13)C from plant roots into the microbial population in the rhizosphere.

The effects of dwarfing genes on seedling root growth of wheat.

Most modern wheat cultivars contain major dwarfing genes, but their effects on root growth are unclear. Near-isogenic lines (NILs) containing Rht-B1b, Rht-D1b, Rht-B1c, Rht8c, Rht-D1c, and Rht12 were used to characterize the effects of semi-dwarfing and dwarfing alleles on root growth of 'Mercia' and 'Maris Widgeon' wheat cultivars. Wheat seedlings were grown in gel chambers, soil-filled columns, and in the field. Roots were extracted and length and dry mass measured. No significant differences in root length were found between semi-dwarfing lines and the control lines in any experiment, nor was there a significant difference between the root lengths of the two cultivars grown in the field. Total root length of the dwarf lines (Rht-B1c, Rht-D1c, and Rht12) was significantly different from that of the control although the effect was dependent on the experimental methodology; in gel chambers root length of dwarfing lines was increased by approximately 40% while in both soil media it was decreased (by 24-33%). Root dry mass was 22-30% of the total dry mass in the soil-filled column and field experiments. Root length increased proportionally with grain mass, which varied between NILs, so grain mass was a covariate for the analysis of variance. Although total root length was altered by dwarf lines, root architecture (average root diameter, lateral root:total root ratio) was not affected by reduced height alleles. A direct effect of dwarfing alleles on root growth during seedling establishment, rather than a secondary partitioning effect, was suggested by the present experiments.

Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil Sitona lepidus (Coleoptera: Curculionidae).

The respiratory emission of CO2 from roots is frequently proposed as an attractant that allows soil-dwelling insects to locate host plant roots, but this role has recently become less certain. CO2 is emitted from many sources other than roots, so does not necessarily indicate the presence of host plants, and because of the high density of roots in the upper soil layers, spatial gradients may not always be perceptible by soil-dwelling insects. The role of CO2 in host location was investigated using the clover root weevil Sitona lepidus Gyllenhall and its host plant white clover (Trifolium repens L.) as a model system. Rhizochamber experiments showed that CO2 concentrations were approximately 1000 ppm around the roots of white clover, but significantly decreased with increasing distance from roots. In behavioural experiments, no evidence was found for any attraction by S. lepidus larvae to point emissions of CO2, regardless of emission rates. Fewer than 15% of larvae were attracted to point emissions of CO2, compared with a control response of 17%. However, fractal analysis of movement paths in constant CO2 concentrations demonstrated that searching by S. lepidus larvae significantly intensified when they experienced CO2 concentrations similar to those found around the roots of white clover (i.e. 1000 ppm). It is suggested that respiratory emissions of CO2 may act as a 'search trigger' for S. lepidus, whereby it induces larvae to search a smaller area more intensively, in order to detect location cues that are more specific to their host plant.

Climate change and food security.

Dynamic interactions between and within the biogeophysical and human environments lead to the production, processing, distribution, preparation and consumption of food, resulting in food systems that underpin food security. Food systems encompass food availability (production, distribution and exchange), food access (affordability, allocation and preference) and food utilization (nutritional and societal values and safety), so that food security is, therefore, diminished when food systems are stressed. Such stresses may be induced by a range of factors in addition to climate change and/or other agents of environmental change (e.g. conflict, HIV/AIDS) and may be particularly severe when these factors act in combination. Urbanization and globalization are causing rapid changes to food systems. Climate change may affect food systems in several ways ranging from direct effects on crop production (e.g. changes in rainfall leading to drought or flooding, or warmer or cooler temperatures leading to changes in the length of growing season), to changes in markets, food prices and supply chain infrastructure. The relative importance of climate change for food security differs between regions. For example, in southern Africa, climate is among the most frequently cited drivers of food insecurity because it acts both as an underlying, ongoing issue and as a short-lived shock. The low ability to cope with shocks and to mitigate long-term stresses means that coping strategies that might be available in other regions are unavailable or inappropriate. In other regions, though, such as parts of the Indo-Gangetic Plain of India, other drivers, such as labour issues and the availability and quality of ground water for irrigation, rank higher than the direct effects of climate change as factors influencing food security. Because of the multiple socio-economic and bio-physical factors affecting food systems and hence food security, the capacity to adapt food systems to reduce their vulnerability to climate change is not uniform. Improved systems of food production, food distribution and economic access may all contribute to food systems adapted to cope with climate change, but in adopting such changes it will be important to ensure that they contribute to sustainability. Agriculture is a major contributor of the greenhouse gases methane (CH4) and nitrous oxide (N2O), so that regionally derived policies promoting adapted food systems need to mitigate further climate change.

Host plant recognition by the root feeding clover weevil, Sitona lepidus (Coleoptera: Curculionidae).

This study investigated the ability of neonatal larvae of the root-feeding weevil, Sitona lepidus Gyllenhal, to locate white clover Trifolium repens L. (Fabaceae) roots growing in soil and to distinguish them from the roots of other species of clover and a co-occurring grass species. Choice experiments used a combination of invasive techniques and the novel technique of high resolution X-ray microtomography to non-invasively track larval movement in the soil towards plant roots. Burrowing distances towards roots of different plant species were also examined. Newly hatched S. lepidus recognized T. repens roots and moved preferentially towards them when given a choice of roots of subterranean clover, Trifolium subterraneum L. (Fabaceae), strawberry clover Trifolium fragiferum L. (Fabaceae), or perennial ryegrass Lolium perenneL. (Poaceae). Larvae recognized T. repens roots, whether released in groups of five or singly, when released 25 mm (meso-scale recognition) or 60 mm (macro-scale recognition) away from plant roots. There was no statistically significant difference in movement rates of larvae.

An X-ray micro-tomography system optimised for the low-dose study of living organisms.

An X-ray micro-tomography system has been designed that is dedicated to the low-dose imaging of radiation sensitive living organisms and has been used to image the early development of the first few days of plant development immediately after germination. The system is based on third-generation X-ray micro-tomography system and consists of an X-ray tube, two-dimensional X-ray detector and a mechanical sample manipulation stage. The X-ray source is a 50kVp X-ray tube with a silver target with a filter to centre the X-ray spectrum on 22keV.A 100mm diameter X-ray image intensifier (XRII) is used to collect the two-dimensional projection images. The rotation tomography table incorporates a linear translation mechanism to eliminate ring artefact that is commonly associated with third-generation tomography systems. Developing maize seeds (Triticum aestivum) have been imaged using the system with a cubic voxel linear dimension of 100 microm, over a diameter of 25mm and the root lengths and volumes measured. The X-ray dose to the plants was also assessed and found to have no effect on the plant root development.

Plant roots release phospholipid surfactants that modify the physical and chemical properties of soil.

• Plant root mucilages contain powerful surfactants that will alter the interaction of soil solids with water and ions, and the rates of microbial processes. • The lipid composition of maize, lupin and wheat root mucilages was analysed by thin layer chromatography and gas chromatography-mass spectrometry. A commercially available phosphatidylcholine (lecithin), chemically similar to the phospholipid surfactants identified in the mucilages, was then used to evaluate its effects on selected soil properties. • The lipids found in the mucilages were principally phosphatidylcholines, composed mainly of saturated fatty acids, in contrast to the lipids extracted from root tissues. In soil at low tension, lecithin reduced the water content at any particular tension by as much as 10 and 50% in soil and acid-washed sand, respectively. Lecithin decreased the amount of phosphate adsorption in soil and increased the phosphate concentration in solution by 10%. The surfactant also reduced net rates of ammonium consumption and nitrate production in soil. • These experiments provide the first evidence we are aware of that plant-released surfactants will significantly modify the biophysical environment of the rhizosphere.

Complicated crown fracture of an unerupted permanent tooth--a case report.

Trauma to primary teeth may result in direct damage to underlying developing permanent teeth because of the close relationship that exists between the apices of the primary teeth and their permanent successors. Injuries to developing teeth have been classified into ten different categories, using a classification that is largely based on developmental alterations to the permanent teeth. However, this classification does not include other types of trauma that may occur to developing teeth, such as crown fractures. Although apparently rare, such injuries can occur by direct contact of the impacting object with a developing tooth, as illustrated by the following case report.

Parental awareness of the emergency management of avulsed teeth in children.

Although public awareness campaigns on avulsed teeth have been mounted in the past, no study has investigated the knowledge parents possess of the protocol for the management of this dental emergency. The purpose of this investigation was to evaluate, by means of a questionnaire, the parental awareness of the emergency management of avulsed teeth in children. Over 2000 parents were surveyed during a four-week period at 20 suburban vacation swimming centres. The results indicated that almost two-thirds of respondents would attempt replantation of an avulsed tooth but further questioning showed they did not know the correct procedures. Thirty-three per cent of respondents were unaware of any after-hours emergency dental services. Ninety-two per cent felt they should seek professional help urgently following an avulsion injury, but their knowledge of transport media for the tooth was poor. Only 5 per cent knew that milk was the medium of choice for both washing and transporting an avulsed tooth. Ninety per cent of parents surveyed had never received advice on what to do in the event of an accident where a permanent tooth was avulsed. This study revealed the need for educational campaigns aimed at parents to increase their knowledge of the emergency procedures required when the tooth is avulsed.

Sources of sulphur in rain collected below a wheat canopy.

Vegetation plays an important role in the cycle of sulphur between the atmosphere and the soil. We have measured the quantity of sulphur in rain collected below a maturing wheat canopy. This sulphur has three sources: first, the atmosphere, from which falling rain gains SO2 and sulphate; second, leaf surfaces, from which rain washes sulphur which was previously deposited by turbulent transfer ('dry deposition'), and third, leaf tissue, from which rain leaches sulphur. We have now deduced from field and laboratory measurements that leaching supplied nearly 90% of the sulphur gained by rain as it fell through the wheat canopy. Only a small fraction of sulphur which had been dry-deposited on the surface of leaves could be washed off.