Ion and Glycerol Concentrations in 12 Isolates of Dunaliella

Ginzburg, M., and Ginzburg, B. Z., 1985. Ion and glycerol concentrationsin 12 isolates of Dunaliella.—J. exp. Bot. 36: 1064–1074. Twelve isolates of Dunaliella with average cell volumes rangingfrom 50 to 1400x10^–18 m³ were grown in batch culture at0.5 M or 2.0 M NaCl. Glycerol and ions (Na⁺, K⁺, Mg²⁺, CI^–,phosphate) were measured in log-phase cultures. The contentsof Mg²⁺, K⁺ and phosphate per cell were found to be a functionof cell-volume. Cell glycerol, Na⁺ and Cl^– were functionsof cell-volume and of the NaCl concentration in the medium.Solute concentrations were calculated from the measured cell-volumesand from the ³H₂O content of pellets corrected for intercellularspace using Blue Dextran. Cell glycerol was found to accountfor about one-half of the expected osmolarity, the remainderbeing largely accounted for by Na⁺ and CI^–. Key words: —Dunaliella, isolates, glycerol, ion concentrations     

Buckman's Paradox: variability and constraints on ammonoid ornament and shell shape

Buckman's Law of Covariation states that ammonoid shell shape and ornamentation are typically correlated, such that compressed, involute forms have light ornament while more inflated, evolute forms have heavier ornament. Such covariation has been observed in many ammonoid groups, and implies a link between the morphogenesis of shell shape and ornamentation. However, other evidence suggests that while ornament growth is controlled by the genetic‐developmental program of the ammonoid, shell shape is strongly influenced by environmental factors. These differing viewpoints lead to Buckman's Paradox – are ornamentation and shell shape tightly linked, as implied by Buckman's covariation, or is the morphogenesis of ornament controlled genetically, while shell shape is controlled environmentally? To address this issue, the variability of shell shape and rib morphology has been compared for a group of endemic acanthoceratid ammonites from the Cretaceous Western Interior Seaway of North America. If Buckman's Law holds due to a morphogenetic connection between shell shape and ornamentation, we would expect taxa with more variable shell shapes to also show more variable rib features and growth. Morphometric analysis of seven shell shape and two rib characters for the Western Interior acanthoceratids finds no such correlation, suggesting that shell shape and rib growth are controlled by different processes. Indeed, rib growth appears to be more constrained than shell shape, consistent with the view that ornamentation is more tightly controlled by the developmental‐genetic growth program of the ammonoid. These results emphasize the complexity of ammonoid morphogenesis and highlight our limited understanding of the causes underlying Buckman's Law.     

Comparison of distance based density estimates for some arid rangeland vegetation

A method was required for determining the effect of management on extensive populations of trees and shrubs in central Australian rangelands. One useful indicator of change in these populations is the density of individuals, and there are several methods available based on distance measurement for density estimation. This study compared those procedures. Samples were drawn by computer from ground maps of actual plant distributions for Acacia aneura, Cassia nemophila and Atalaya hemiglauca and from a map generated at random. These samples were drawn to examine the properties of the nearest neighbour, point centred quarter, conditioned distance and compound T-square estimates of density. Samples were drawn by two methods: simple random sampling and semisystematic sampling. In general, there was a tendency for all estimators of density to underestimate the true density of naturally occurring populations with the compound T-square method (Byth 1982) being most robust. The compound T-square method was least biased but its variance increased for more aggregated spatial distributions. Estimates of density were not altered by the use of semisystematic sampling, when compared to simple random sampling. The spatial distributions examined in this study have not previously been studied as theoretical models. Acacia aneura and Cassia nemophila showed some aggregation of clusters, while the Atalaya hemiglauca showed a more extreme form of clustering due to its root suckering propagation.     

Assessing the age of field female wheat bulb flies (Leptohylemyia coarctata)

From 1967 to 1971, wheat bulb fly females caught by sweeping from a number of localities contained mature eggs from the third week of July to the end of August. In 1971 when female wheat bulb flies were caught by sweeping, by white water traps, by suction traps as well as by light traps, the first flies containing mature eggs were caught 29 days after the first detected emergence while the first batch was laid 29–58 days after first emergence. The peak period of egg laying occurred in the fourth week of July, 24–38 days after the peak emergence. The second batch of eggs was laid when the flies were 8 weeks old, 29 days after the first; the peak for this batch was 35 days after the first. A few females laid a third batch of eggs 28 days after the first record of the laying of the second batch. A female that lives sufficiently long to lay the third batch of eggs is at least 12 weeks old. In 1970, when emergence started earlier in June, ripening and laying of eggs of the three batches was also earlier. After the harvest of cereal crops more females were caught by white water traps placed on the fallow than by other methods. The most important pathogen affecting adult wheat bulb flies was a fungus, probably Entomophthora muscae. When infection occurred early in July, fewer eggs from the first batch were laid than when infection developed later. Fewer flies were infected in 1971 than in 1970. To be effective against wheat bulb fly in the early spring, control measures-should be applied against adults before their eggs mature in early July of the preceding year.     

A world-wide survey of the microflora of Dactylis glomerata seed*

The fungal microflora of orchard (cock's-foot) grass seed (Dactylis glomerata L.) was determined for 140 samples obtained from thirteen countries. The microflora was assessed by visual examination of dry seed (20–50 x), by microscopic examination of centrifuged seed washings and by incubating seed on 2 % malt extract agar (MA) under a 10-day regime of diurnal cycling of temperature (23-9^oC/i8-3^oC) and near-ultraviolet radiation (12 h NUV/ 12 h dark). More than twenty-five species of potentially pathogenic fungi and forty species of saprophytes were detected. The pathogens included an Ascochyta sp., Botrytis cinerea, nine species of Drechslera including D. dactylitis (infested 23% of seed lots) and D. Useptatum (10% of seed lots), five species oiFusarium including F. avenaceum (5 % of seed lots), Lep-tosphaeria sp., Phleospora sp., Phoma sp., Phomopsis sp., Pyrenochaeta sp., Rhizoctonia sp., Rhynchophoma sp., Septoria sp. and Stagonospora sp. Many more fungi were identified from seed plated on MA and exposed to NUV than by examination of seed washings or visual examination of dry seed. Several of the fungi that were detected are known to produce mycotoxins.     

Mutant tRNA<Superscript>His</Superscript> Ineffective in Repression and Lacking Two Pseudouridine Modifications

TRANSFER RNA has been implicated in the regulation of a number of amino-acid biosynthetic operons^1–4. Histidyl-tRNA^His has been shown to be involved in regulation of the histidine operon by analysis of six genes (hisO, hisR, hisS, hisT, hisU, hisW), mutation of which causes derepression of the enzymes of the histidine biosynthetic pathway in Salmonella typhimurium^5–7. A class of derepressed mutants (hisR) has only about 55% as much tRNA^His as the wild type⁴ and in the one example sequenced, contains tRNA^HIS with a structure identical to that of the wild type⁸. Studies of mutants of the gene for histidyl-tRNA synthetase (hisS) indicated that the derepressed phenotype was associated with defects in the charging of tRNA^HISin vitro². The amounts of charged and uncharged tRNA^His present in vivo during physiological derepression of the wild type and in the six classes of regulatory mutants, have been determined⁹. This work has shown that repression of the histidine operon is correlated directly with the concentration of charged histidyl-tRNA^Hisin vivo and not with the ratio of charged to uncharged or the absolute amount of uncharged tRNA^His. The derepression observed in mutants, of hisS (the gene for histidyl-tRNA synthetase), hisR (the presumed structural gene for the single species of tRNA^His) and hisU and hisW (genes presumably involved in tRNA modification) may be explained by the lower cellular concentration of charged tRNA^His which these mutants contain.     

Microbiological Synthesis of Fat: THE EFFECTS OF VARYING PH, TEMPERATURE, NITROGEN, INCUBATION PERIOD, AND SUGAR CONCENTRATION ON FAT-PRODUCING MOULDS

1. A more detailed study has been made of the influence of thesefactors on fat formation by Aspergillus nidulans, Penicilliumspinulosum, and Penicillium javanicum. 2. The effect of halving the glucose, while keeping the ammoniumnitrate concentration constant, lowered the yield of fat onsugar used in A. nidulans and P. spinulosum but not in P. javanicumcultures. 3. Keeping the same N: C ratio and raising the glucose concentrationfrom ro to 20 per cent. showed that to per cent. glucose wasmore efficiently converted to fat by A. nidulans and P. javanicum. 4. The iodine values of the extracted fats were higher, in general,with increased length of incubation. Low ammonium nitrate concentrations,however, tended to give low iodine values. 5. The results have been applied on a larger scale by growthin Roux bottles, Glaxo flasks, and a flat stainless-steel tank.