Conservation and reservation of non-vascular plants in Tasmania,with special reference to lichens

Conservation management of the Tasmanian flora is now focusing on non-vascular plants. Major problems include the low level of information on the composition of the flora and the low number of competent specialists available to deal with the plants. Collation of information from literature and from collections in herbaria is required to establish exactly which data are available and their reliability. An environmental domain analysis covering all ecosystems would indicate which environments were under-represented or absent from current reserves and where needs for conservation lie. Within practical time-frames, this process is probably the best method of capturing unknown components of the flora whilst also catering for widespread species and those closely associated with particular environments. It also incorporates regional variability. Minor habitats, which are often floristically rich, and very rare species are best dealt with on an individual basis. Basic research into taxonomy and ecology is paramount. Reservation and conservation management must be based on well-established and maintained databases which are in turn based on a coherent taxonomy and sound biogoographical information. It is only by pursuing an active research programme that the necessary accurate information can be obtained and the success of the management procedures can be gauged.     

Differences in tissue-specific lipid composition between embryos of wild and captive breeding alligators (Alligator mississippiensis)

Fertile eggs obtained from alligators reared in captivity typically exhibit high rates of embryonic mortality. Also, the fatty acid composition of the yolk lipid of the captive eggs is markedly different from that observed in eggs from wild alligators, possibly as a result of differences in maternal diet in the two situations. The fatty acid compositions of tissue lipids during the embryonic development of wild and captive alligators were compared. The lipids of liver, adipose tissue and heart of the two types of embryo displayed fatty acid profiles which generally reflected the acyl compositions of the respective yolks. Thus the lipids from these tissues of the captive embryos contained markedly higher proportionate levels of linoleic and linolenic acids, lower levels of palmitoleic acid, and, in general, lower levels of docosahexaenoic acid and other C20 and C22 polyunsaturates, in comparison to the values for the wild embryos. In contrast, the fatty acid composition of the brain phosphoglycerides was very similar in the two types of embryo. Thus, at least in those embryos which had survived during the developmental period studied, the brain was able to maintain a relatively constant fatty acid composition, in spite of major differences between the wild and captive eggs in the proportions of the various fatty acids supplied from the yolk. It is suggested that a major cause of embryonic mortality in the captive embryos could be a failure to maintain an adequate level of docosahexaenoic acid in the developing brain.     

Structural changes in the innercortex cells of soybean root nodules are induced by short-term exposure to high salt or oxygen concentrations

After a 2 h exposure of intact soybean nodules to high concentrations of NaCl (100mol m_?3) or oxygen (8OkPa O₂), morphometric computations carried out using an image analysis technique on semi-thin sections showed that both treatments induced a decrease in the area of the inner-cortex cells, which were then characterized by a tangential elongation. In contrast, no significant change in area occurred in the middle-cortex cells although their elongation decreased. Electron microscopic observations showed that in the inner-cortex cells changes included the presence of wall infoldings, an enlarged periplasmic space and a lobate nucleus whose chromatin distribution differed from that of the control. Structural changes also occurred in the endoplasmic reticulum, microbodies, mitochondria and plastids. From several of these changes, which are similar to those noted in osmocontractil cells in response to external stimuli, it can be hypothesized that the inner cortex may provide a potential mechanism for the control of oxygen diffusion through the nodules.     

Intracellular flux analysis applied to the effect of dissolved oxygen on hybridomas

Quantitative estimates of intracellular fluxes and measurements of intracellular concentrations were used to evaluate the effect of dissolved oxygen (DO) concentration on CRL 1606 hybridoma cells in batch culture. The estimates of intracellular fluxes were generated by combining material balances with measurements of extracellular metabolite rates of change. Experiments were performed at DO levels of 60% and 1% air saturation, as well as under oxygen-limited conditions. Cell extracts were analyzed to evaluate the effect of DO on the intracellular concentrations of the glutamate dehydrogenase reactants, as well as the redox state of the pyridine nucleotides in the cytosol and mitochondria. The relationship between cell density and pyridine nucleotide redox state was also investigated. Dissolved oxygen concentration had a significant effect on nitrogen metabolism and the flux through glutamate dehydrogenase was found to reverse at low DO, favoring glutamate formation. The NAD in the cytosol and mitochondria was more reduced under low DO conditions while the cytosolic NAD was more oxidized at low DO. Cytosolic NAD was reduced at higher cell densities while the redox states of cytosolic NADP and mitochondrial NAD did not exhibit significant variation with cell density. These results point to the fundamental role of the intracellular oxidation/reduction state in cell physiology and the possibility of controlling physiological processes through modulation of the dissolved oxygen level or the oxidation/reduction potential of the culture.     

Degradation of aromatic amino acids by Rhodococcus erythropolis

A Gram-positive Rhodococcus erythropolis strain S1 was shown to assimilate aromatic amino acids such as L-phenylalanine, L-tyrosine, L-tryptophan, D-phenylalanine, D-tyrosine and D-tryptophan, which were utilized not only as the sole carbon source but also as a suitable nitrogen source. The highest growth on these aromatic amino acids occurred at a temperature of 30°C. L-Phenylalanine, L-tyrosine and L-tryptophan degradative pathways would appear to be independent, and to be induced alternatively. The strain S1 also showed the ability to assimilate peptides which consisted of only L-phenylalanine and L-tyrosine.     

Scheduling algorithms for a two-machine flexible manufacturing system

The flexible manufacturing system (FMS) considered in this paper is composed of two CNC machines working in series—a punching machine and a bending machine connected through rollers acting as a buffer system of finite capacity. The main difference between the present problem and the standard two-machine flow shop problem with finite intermediate capacity is precisely the buffer system, which in our problem consists of two stacks of parts supported by rollers: the first stack contains the output of the punching machine, while the second stack contains the input for the bending machine. When the second stack is empty, the first stack may be moved over. Furthermore, the capacity of each stack depends on the particular part type being processed. The FMS can manufacture a wide range of parts of different types. Processing times on the two machines are usually different so that an unbalance results in their total workload. Furthermore, whenever there is a change of the part type in production, the machines must be properly reset—that is, some tools need to be changed or repositioned. A second important difference between the present problem and the usual two-machine flow shop problem is the objective. Given a list ofp part types to be produced in known quantities, the problem considered here is how to sequence or alternate the production of the required part types so as to achieve various hierarchical targets: minimize the makespan (the total time needed to complete production) and, for instance, compress the idle periods of the machine with less workload into a few long enough intervals that could be utilized for maintenance or other reasons. Although Johnson's rule is optimal in some particular cases, the problem addressed in the paper isNP-hard in general: heuristic procedures are therefore provided.