Evaluation of fly ash as a component of potting substrates

A series of laboratory and glasshouse experiments were undertaken to assess the potential for incorporation of fly ash in soilless potting substrates. The physical and chemical properties of a commercially available bark based substrate, the University of California (UC) 1:1 peat:sand mix and a range uf test substrates containing fly ash were characterised. In test mixtures, fly ash was substituted for a portion of either the peat or sand component of the UC mix, at rates of 10, 20, 30 and 50% of the mix volume, Incorporation of fly ash greatly increased the plant available water capacity (10-1500 kPa) of the substrate. However, high pH, increased substrate strength and reduced air-filled porosity were considered adverse effects, particularly at ash rates > 20%. The growth of tomato (Lycopersicon esculentum), petunia (Petunia x hybrida grandiflora) and Boston fern (Nephrolepis exaltata) in the substrates was assessed. Two watering regimes, capillary watering and irregular hosing, were used to identify effects of available water capacity on plant growth, but no effect was identified. Test mixtures containing fly ash as 20% of the substrate volume produced growth equal to that in the UC mix, with substrates containing 10% ash producing significantly greater growth of tomato and petunia. At rates of incorporation > 20% reduced plant growth was attributed to both adverse physical and chemical characteristics of the substrate. As fly ash is available at low cost and can be successfully substituted for a considerable portion of the expensive peat component, its use at low application rates in potting substrates may be desirable from an economic viewpoint.

The role of physiological understanding in plant breeding; From a breeding perspective

The role of physiological understanding in improving the efficiency of breeding programs is examined largely from the perspective of conventional breeding programs. Impact of physiological research to date on breeding programs, and the nature of that research, was assessed from (i) responses to a questionnaire distributed to plant breeders and physiologists, and (ii) a survey of literature abstracts. Ways to better utilise physiological understanding for improving breeding programs are suggested, together with possible constraints to delivering beneficial outcomes. Responses from the questionnaire indicated a general view that the contribution by crop physiology to date has been modest. However, most of those surveyed expected the contribution to be larger in the next 20 years. Some constraints to progress perceived by breeders and physiologists were highlighted. The survey of literature abstracts indicated that from a plant breeding perspective, much physiological research is not progressing further than making suggestions about possible approaches to selection. There was limited evidence in the literature of objective comparison of such suggestions with existing methodology, or of development and application of these within active breeding programs. It is argued in this paper that the development of outputs from physiological research for breeding requires a good understanding of the breeding program(s) being serviced and factors affecting its performance. Simple quantitative genetic models, or at least the ideas they represent, should be considered in conducting physiological research and in envisaging and evaluating outputs. The key steps of a generalised breeding program are outlined, and the potential pathways for physiological understanding to impact on these steps are discussed. Impact on breeding programs may arise through (i) better choice of environments in which to conduct selection trials, (ii) identification of selection criteria and traits for focused introgression programs, and (iii) identifying traits for indirect selection criteria as an adjunct to criteria already used. While many breeders and physiologists apparently recognise that physiological understanding may have a major role in the first area, there appears to be relatively Little research activity targeting this issue, and a corresponding bias, arguably unjustified, toward examining traits for indirect selection. Furthermore, research on traits aimed at crop improvement is often deficient because key genetic parameters, such as genetic variation in relevant breeding populations and genetic (as opposed to phenotypic) correlations with yield or other characters of economic importance, are not properly considered in the research. Some areas requiring special attention for successfully interfacing physiology research with breeding are discussed. These include (i) the need to work with relevant genetic populations, (ii) close integration of the physiological research with an active breeding program, and (iii) the dangers of a pre-defined or narrow focus in the physiological research.

New gene technologies and their potential value for sugarcane

An efficient system is now in place for improving diverse sugarcane cultivars by genetic transformation, that is, the insertion of useful new genes into single cells followed by the regeneration of genetically modified (transgenic) plants. The method has already been used to introduce genes for resistance to several major diseases, insect pests and a herbicide, Field testing has begun, and research is underway to identify other genes for increased environmental stress resistance, agronomic efficiency and yield of sucrose or other valuable products. Experience in other crops has shown that genetically improved varieties which provide genuine environmental and consumer benefits are welcomed by producers and consumers. Substantial research is still needed, but these new gene technologies will reshape the sugar industry and determine the international competitive efficiency of producers.

Environmental control of potential yield of sunflower in the subtropics

A simple framework was used to analyse the determinants of potential yield of sunflower (Helianthus annuus L.) in a subtropical environment. The aim was to investigate the stability of the determinants crop duration, canopy light interception, radiation use efficiency (RUE), and harvest index (HI) at 2 sowing times and with 3 genotypes differing in crop maturity and stature. Crop growth, phenology, light interception, yield, prevailing temperature, and radiation were recorded and measured throughout the crop cycle. Significant differences in grain yield were found between the 2 sowings, but not among genotypes within each sowing. Mean yields (0% moisture) were 6 . 02 and 2 . 17 t/ha for the first sowing, on 13 September (S1), and the second sowing, on 5 March (S2), respectively. Exceptionally high yields in S1 were due to high biomass assimilation associated with the high radiation environment, high light interception owing to a greater leaf area index, and high RUE (1 . 47-1 . 62 g/MJ) across genotypes. It is proposed that the high RUE was caused by high levels of available nitrogen maintained during crop growth by frequent applications of fertiliser and sewage effluent as irrigation. In addition to differences in the radiation environment, the assimilate partitioned to grain was reduced in S2 associated with a reduction in the duration of grain-filling. Harvest index was 0 . 40 in S1 and 0 . 25 in S2. It is hypothesised that low minimum temperatures experienced in S2 reduced assimilate production and partitioning, causing premature maturation.

Quantum dynamics of an atomic Bose-Einstein condensate in a double-well potential

We consider the quantum dynamics of a neutral atom Bose-Einstein condensate in a double-well potential, including many-body hard-sphere interactions. Using a mean-field factorization we show that the coherent oscillations due to tunneling are suppressed when the number of atoms exceeds a critical value. An exact quantum solution, in a two-mode approximation, shows that the mean-field solution is modulated by a quantum collapse and revival sequence.

The distribution of naloxone to heroin users

Overdose deaths are a manor contributor to excess mortality among heroin users. It has been proposed that opioid overdose morbidity and mortality could be reduced substantially by distributing the opioid antagonist naloxone to heroin users. The ethical issues raised by this proposal are evaluated from a utilitarian perspective. The potential advantages of naloxone distribution include the increased chance of comatose opioid users being quickly resuscitated by others present at the time of an overdose, naloxone's safety and its lack of abuse potential. The main problems raised by the proposal are: the medico-legal complications of medical practitioners prescribing a drug that is most likely to be administered to and by people other than the one for whom it is prescribed; the economic costs of distributing naloxone sufficiently widely to have an impact on overdose morbidity and mortality; and the potentially greater cost-effectiveness of simpler educational interventions. Given the possible benefits of naloxone distribution, it may be worthwhile considering a controlled trial of naloxone distribution to high-risk heroin users.

Potential GABAB receptor antagonists .9. The synthesis of 3-amino-3-(4-chlorophenyl)propanoic acid, 2-amino-2-(4-chlorophenyl)ethylphosphonic acid and 2-amino-2-(4-chlorophenyl)ethanesulfonic acid

This paper describes the synthesis of 3-amino-3-(4-chlorophenyl)propanoic acid and the corresponding phosphonic and sulfonic acids, lower homologues of baclofen, phaclofen and saclofen respectively. The chlorinated acids were all weak specific antagonists of GABA at the GABAB receptor, with the sulfonic acid (pA(2) 4.0) being stronger than the phosphonic acid (pA(2) 3.8) and carboxylic acid (pA(2) 3.5).

Potential demand for hedging by Australian wheat producers

The potential for hedging Australian wheat with the new Sydney Futures Exchange wheat contract is examined using a theoretical hedging model parametised from previous studies. The optimal hedging ratio for an 'average' wheat farmer was found to be zero under reasonable assumptions about transaction costs and based on previously published measures of risk aversion. The estimated optimal hedging ratios were found by simulation to be quite sensitive to assumptions about the degree of risk aversion. If farmers are significantly more risk averse than is currently believed, then there is likely to be an active interest in the new futures market.