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The viability of a programme for delivering aerosolized pentamidine within the patient's home setting for the secondary prophylaxis of Pneumocystis carinii pneumonia (PCP) has been explored with seven homosexual AIDS patients, the major objectives being the assessment of the safety and acceptability of the treatment and the discovery of the most suitable care setting (home, ward, outpatient clinic) for the administration of therapy. It is concluded that a domiciliary prophylaxis programme is a viable alternative.

Uniform populations of spores of Drechslera rostrata (Drechsler), produced simultaneously, were subsequently aged for different periods and tested for sensitivity to soil fungistasis by measuring the effect on three parameters of germination. Sensitivity was found to change with age of the spore according to a definite pattern which was similar for all three parameters of germination. Sensitivity was high in newly harvested spores, declined to a minimum level over a period of about 3 weeks, and then gradually increased over a further 7-week period to a high level in 10-week-old spores. Evidence was obtained that the permeability of the spore to electrolytes changes with age in a way that parallels the changes in sensitivity to fungistasis over the initial 3-week period of ageing. A decrease in nutrient status of spores, resulting from outflow of materials due to high permeability, is suggested as one possible mechanism leading to increased sensitivity of spores to soil fungistasis.

Winter wheat and barley shoots sampled at the tillering stage from 12 farms in two intensive cereal production areas of Northern Ireland were analysed for trace elements B, Co, Cu, Fe, Mn, Mo and Zn plus Ca and Mg. Soil pH values were also determined for each field. Shoot concentrations of all elements were normal except for five fields of winter wheat which initially showed low Mn concentrations but exhibited normal levels when re-sampled 5 weeks later. None of the plants showed deficiency symptoms for any element. Significant correlations were found between shoot concentrations of some nutrients and soil pH and their significance is discussed.

In three glasshouse experiments the grassland plants Anthoxanthum odorattum. Lolium perenne , Plantayo lanceolata and Trifolium repens were grown in pots of grassland soil, in monocultures and various two-species mixtures. Mixed-species and single-species swards were also sown in a garden bed; and in a permanent pasture P. lanceolata individuals whose surrounding vegetation had been removed were compared with control plants. Abundance of root-surface bacteria and fungi, and of internal mycorrhizal infection were measured by direct observation of randomly-selected root segments. The abundance of all three microbial groups on a given “host” species was often significantly altered by the presence of other plant species. Bacteria usually changed in the same direction as fungi, but proportionately less. Mycorrhizas usually changed less than the other two groups and not always in the same direction. In the pot experiments, when growth in a mixture resulted in a plant being larger and having higher nutrient concentration than in monoculture, the abundance of fungi on its roots also increased; bacteria and mycorrhizas showed this correlation less clearly. Superimposed on this relationship was a general tendency for fungi, and to a lesser extent bacteria, to be more abundant in mixture than monoculture even when the plants did not change in size. Possible mechanisms involved in these responses are discussed.

Grassland herbage samples with a range of copper (3–11 mg kg−1)) and zinc (10–53 mg kg−1) contents were analysed for Cu and Zn following sample solution preparation by four methods. An acid digestion procedure incorporating chloroform extraction and a second digestion step was compared with micro and macro digestion methods (both without solvent extraction) and a dry ashing method. The residues were dissolved in HCl and the metals determined by atomic absorption spectrophotometry. Results for Cu were much less variable than those for Zn. The dry ashing procedure gave higher analytical precision than did the acid digestion methods. However, when between-plot field variation was included, the four methods gave similar coefficients of variation. Thus acid digestion, including the rapid micro method, appears to be suitable for routine analysis of herbage from field experiments. The double digestion procedure often gave low mean values for samples with high Cu and Zn contents, but it may be suitable for small numbers of samples with low Cu and Zn concentrations, while the higher precision of the dry ashing method may be useful for glasshouse or controlled environment studies with lower between-plot variation.

Samples of two contrasting grassland soils were fumigated with chloroform, incubated at 25°C for 10 days and their CO 2 -C evolution measured. When different sample weights and incubation jar sizes were used it was found that jar size was not a significant factor but sample weight was highly significantly related to CO 2 evolution. When various sample weights were incubated in different sizes of cylindrical vessels within the incubation jars in order to produce a range of soil depths during incubation, sample weight per se no longer affected the results but soil depth during incubation was highly significant. Curves were fitted for both soils relating CO 2 -C evolution to sample depth during incubation. The critical depths above which consistent rates of CO 2 (below 90% of the theoretical minimum) were evolved were 3.2 cm (sandy day loam) and 3.7cm (clay). As soil depth decreased below these values, rate of CO 2 -C evolution increased exponentially. There was also evidence that small soil samples dried out during weighing, resulting in a flush of soil respiration. It is important therefore to ensure adequate soil sample depth during incubation and protection of small soil samples against desiccation before fumigation when using the fumigation-incubation method.

Field plots of perennial ryegrass, both pure and mixed with white clover, were killed and directly re-seeded with perennial ryegrass. Herbage dry matter (DM) and nitrogen (N) yields and soil mineral N concentrations were determined before and after re-seeding. The amounts of C and N in the soil microbial biomass were determined by the chloroform fumigation-incubation method. Biomass C and N contents were similar in pure and mixed plots of the original sward shortly before the sward was killed. Shortly after the sward was killed there was a significant increase in biomass C and N. Biomass C had started to decline again by the second cut of re-seeded grass but biomass N remained high. Biomass C-to-N ratio did not change on the death of the sward when the size of the biomass increased, but soil mineral N in the mixed swards (but not in the pure grass) did increase at this stage. By the first grass cut, the biomass C-to-N ratio increased in both plot types and soil mineral N decreased. By the second cut both plot types had biomass C-to-N ratios similar to those of the original grass plots. Clover had thus a residual effect on soil mineral N that was transient and associated with changes in biomass C-to-N ratio. The occurrence of this residual effect of clover was further supported by significant correlations between the clover content of the original sward at the end of the previous growing season and herbage N content at the first cut of re-seeded grass, herbage DM and N yields at both cuts, soil mineral N at all sampling occasions except after the second cut, biomass C after the sward was killed, and biomass C-to-N ratio at the first cut of re-seeded grass.

Rhizoctonia colonized the root surfaces of different species of grassland plants to different extents, being more common on grasses than dicotyledons. No other fungi that were isolated by plating out root segments showed a statistically significant difference between host species. The Rhizoctonia isolate used had little, if any, effect on the growth of Lolium perenne and was not pathogenic, either in normal soil with increased levels of Rhizoctonia or under gnotobiotic conditions.

SummaryA field experiment is described in which three rates of pig and cow slurry were applied to a ryegrass sward over a period of 16 years. The experiment included control plots and plots receiving fertilizer supplying 200 kg N, 32 kg P and 160 kg K/ha per year.The slurry nutrient concentrations were similar to published values. Pig slurry was more variable than cow slurry and both varied significantly from year to year. Slurry was applied at 50, 100 or 200 m3/ha per year, with each rate divided into three equal applications.Even the highest slurry application rate did not depress herbage yield, which showed a typical response curve to the amount of soluble nitrogen applied. The ammoniumnitrogen content of slurry (61% on average) gave an adequate measure of its effect on herbage yield when it was applied three times per year in spring and summer.Recovery of phosphorus in the herbage averaged 30% from pig slurry, 40% from cow slurry and 66% from-fertilizer. Pig slurry supplied more phosphorus than did cow slurry, and herbage phosphorus content was significantly correlated with the amount applied. Much of the slurry phosphorus may have been organically bound and not available to plants in the short term.Recovery of potassium from pig slurry and fertilizer was nearly 90% and from cow slurry about 70%. Cow slurry supplied potassium in excess of crop requirements so that it accumulated in the soil under the largest dressing. Soil phosphorus reserves declined under the smallest dressing of cow slurry but were maintained at higher application rates. The pig slurry produced a marked accumulation of phosphorus under the largest dressing. The substantial accumulations of phosphorus and potassium from pig and cow slurry respectively gave marked penetration of the soil below 10 cm depth only at the highest application rate. The data suggest that at rates typical of farm practice significant losses of phosphorus and potassium from the rooting zone would be unlikely to occur.The main invading plant species were Agrostis stolonifera L. and Poa spp. Small slurry dressings produced a similar botanical composition to that of plots given fertilizer. Increasing slurry application rates decreased the proportion of L. perenne and increased that of A. stolonifera but only under the largest dressing did L. perenne fall to a small proportion of the sward and A. stolonifera become very dominant. L. perenne made maximum contribution to herbage dry-matter yield early in the season while the proportion of A. stolonifera increased as the season progressed.Under these conditions even extremely large slurry dressings did not depress herbage yield and may not necessarily have reduced herbage quality despite marked changes in sward botanical composition.

Background A climate-controlled pot experiment was conducted to investigate the effects of planting alfalfa and applying organic fertilizer on the dissipation of benzo[a]pyrene from an aged contaminated agricultural soil. Results Short-term planting of alfalfa inhibited the dissipation of benzo[a]pyrene from the soil by 8.9%, and organic fertilizer enhanced benzo[a]pyrene removal from the soil by 11.6% compared with the unplanted and unfertilized treatments, respectively. No significant interaction was observed between alfalfa and organic fertilizer on benzo[a]pyrene dissipation. Sterilization completely inhibited the removal of benzo[a]pyrene from the soil indicating that its degradation by indigenous microorganisms may have been the main mechanism of dissipation. Furthermore, significant positive relationships were observed between benzo[a]pyrene removal and the contents of soil ammonium nitrogen, nitrate nitrogen, and total mineral nitrogen at the end of the experiment, suggesting that competition between plants and microorganisms for nitrogen may have inhibited benzo[a]pyrene dissipation in the rhizosphere of alfalfa and the addition of organic fertilizer may facilitate microbial degradation of benzo[a]pyrene in the soil.

Apercu des methodes utilisees pour l'indexation de deux journaux du 19eme siecle: Le «North Devon Journal» et le «Bideford Gazette»

A modified glass bead compartment cultivation system is described in which glass beads continue to be used in the hyphal compartment but are replaced by coarse river sand in the compartments for host plant roots and mycorrhizal hyphae. Arbuscular mycorrhizal (AM) associations were established using two host plant species, maize (Zea mays L.) and red clover (Trifolium pratense L.) and two AM fungi, Glomus mosseae and G. versiforme. When the standard and modified cultivation systems were compared, the new method yielded much more fungal tissue in the hyphal compartment. Using G. versiforme as the fungal symbiont, up to 30 mg of fungal dry matter (DM) was recovered from the hyphal compartment of mycorrhizal maize and about 6 mg from red clover. Multi-element analysis was conducted on samples of host plant roots and shoots and on harvested fungal biomass. Concentrations of P, Cu and Zn were much higher in the fungal biomass than in the roots or shoots of the host plants but fungal concentrations of K, Ca, Mg, Fe and Mn were similar to or lower than those in the plants. There were also significant differences in nutrient concentrations between the two AM fungi and these may be related to differences in their proportions of extraradical mycelium to spores. The high affinity of the fungal mycelium for Zn was very striking and is discussed in relation to the potential use of arbuscular mycorrhiza in the phytoremediation of Zn-polluted soils.

Seasonal outbreaks of influenza exert a considerable burden on health services, and are notorious for their variability from year to year. Making use of historical data from the Scottish sentinelle surveillance since 1972, a potential candidate model has been derived based on simple linear regression. It was applied with a measure of success in the 1999–2000 winter season.

NEIGHBOURING plants usually influence each other's growth. These interactions are very important in determining the composition and structure of plant communities, but much remains to be discovered about the mechanisms by which plants influence each other. Often plants compete for requirements such as light and mineral nutrients. Some plants exude substances which are toxic to others1–3. Another possibility, as yet unexplored, is that interactions occur through changes in the microbial populations on the root surface or in the rhizosphere (the soil near the root surface). It is known that rhizosphere and root surface microorganisms can affect the plant's nutrient uptake and growth4,5, but up to now there has been no evidence on whether plant species which naturally grow together can influence each other's microbial populations. We present here such evidence for two species common in British lowland grassland, Lolium perenne L. (perennial ryegrass) and Plantago lanceolata L. (ribwort plantain, a dicotyledonous species).

(1) A randomized-block field experiment compared three application rates (50, 100 and 200 m3 haI year1) of pig and cow slurries with fertilized and control plots of perennial ryegrass for 17 years. Soil samples were analysed for pH, biomass carbon and nitrogen, soil organic carbon, total nitrogen and EDTA-extractable copper and zinc concentrations at different depths within the profile. Herbage copper and zinc contents were determined at the first cut of 1986. (2) Treatment effects on all variables studied were less pronounced with increasing soil depth. (3) The amounts of carbon and nitrogen in the soil biomass were strongly correlated with soil pH. These relationships varied with soil depth within the top 15 cm of the profile. No lime was applied and the soil was acidified under all treatments except the highest application rate of cow slurry, which maintained the pH in the top 15 cm at 6 3. The soil became more acidic with increasing application rate of pig slurry but the opposite trend was shown under cow slurry. (4) The highest application rate of pig slurry lowered the soil biomass carbon content and increased soil organic carbon content in the top 5 cm of the profile after 16 years. Biomass nitrogen and soil total nitrogen showed similar but less pronounced trends, indicating a reduction in both the size of the microbial biomass and the turnover of soil carbon and nitrogen in this treatment. These effects cannot be attributed solely to differences in soil pH. (5) The highest application rate of pig slurry also led to marked accumulations of EDTA-extractable copper (> 80 mg kg') and zinc (50 mg kg-') in the top 5 cm of the soil after 17 years. Pig slurry also increased the proportions of soil copper and zinc present in extractable form, particularly at the highest application rate. Herbage concentrations of copper and zinc reached 10 and 44 mg kg-', respectively, after 16 years. Herbage copper could be toxic to sheep at concentrations > 10 mg kg. (6) Slurry application rates typical of farm practice did not reduce the size of the soil biomass, lead to phytotoxic concentrations of copper or zinc in the soil, or increase herbage copper or zinc to concentrations likely to be toxic to grazing animals. (7) The nitrifying microbial population in the soil did not appear to be inhibited by high application rates of pig slurry. Increasing application rate of both types of slurry increased potential nitrification rates in the soil as shown by the proportion of nitrogen mineralized, which was in the form of nitrate in incubated soil samples.