The response of sorghum and sunflower to short-term waterlogging

Summary Sorghum and sunflower were waterlogged for nine days during the vegetative, floral initiation/buds-visible or anthesis stage of growth under glasshouse conditions to observe the effects on root growth and development. In addition, some plants were waterlogged at all three stages to observe any adaptations induced by waterlogging. The most marked effects occurred at the initiation/buds-visible stage where a 30% reduction in root length and a 40% reduction in root dry weight of sorghum occurred with comparable figures for sunflower being 50 and 60% respectively. Generally, sorghum roots had a higher porosity than sunflower which may contribute to its greater tolerance to waterlogging. The observed changes in root growth are discussed in relation to previously documented effects of waterlogging on growth of the two species and changes which occur in the soil environment.     

Invasive cane toads might initiate cascades of direct and indirect effects in a terrestrial ecosystem

Understanding the impacts that invasive vertebrates have on terrestrial ecosystems extends primarily to invaders’ impacts on species with which they interact directly through mechanisms such as predation, competition and habitat modification. In addition to direct effects, invaders can also initiate ecological cascades via indirect population level effects on species with which they do not directly interact. However, evidence that invasive vertebrates initiate ecological cascades in terrestrial ecosystems remains scarce. Here, we ask whether the invasion of the cane toad, a vertebrate invader that is toxic to many of Australia’s vertebrate predators, has induced ecological cascades in a semi-arid rangeland. We compared activity of a large predatory lizard, the sand-goanna, and abundances of smaller lizards preyed upon by goannas in areas of high toad activity near toads’ dry season refuges and areas of low toad activity distant from toads’ dry season refuges. Consistent with the hypothesis that toad invasion has led to declines of native predators susceptible to poisoning, goanna activity was lower in areas of high toad activity. Consistent with the hypothesis that toad-induced goanna decline lead to increases in abundance the prey of goannas, smaller lizards were more abundant in areas of high toad activity. Structural equation modelling showed a positive correlation between goanna activity and distance from dry season refuge habitats used by toads. The abundances of small lizards was correlated negatively with goanna activity and distance from dry season refuges of toads. Our findings provide support for the notion that invasions by terrestrial vertebrates can trigger ecological cascades.     

Substitution reaction mechanisms of dihydrido-ruthenium(II) phosphine complexes: hydribe basicity and molecular hydrogen intermediates

Kinetic and activation parameter data for the reactions of cct-Ru(H)₂(CO)₂(PPh₃)₂ (1) (cct = cis, cis, trans) in THF with thiols, CO and PPh₃ to give cct-RuH(SR)(CO)₂(PPh₃)₂, Ru(CO)₃(PPh₃)₂ and Ru(CO)₂(PPh₃)₂, respectively, reveal a common, rate-determining step, the initial dissociation of H₂ from 1; the activated complex probably resembles the corresponding Ru(η²-H₂) species. Reaction of Ru(H)₂(dppm)₂ (2) (as a cis/trans mixture, DPPM = bis(diphenylphosphino)methane) with thiols initially generated cis- and trans- RuH(SR) (dppm)₂ with a rate that depends on both the type and concentration of thiol. The higher basicity of the hydride ligands in 2 (versus 1), which is demonstrated by deuterium exchange with CD₃OD, gives rise in the thiol reaction to an initial protonation step prior to loss of H₂. A species detected in the thiol reaction is possibly [RuH(η²-H₂ (dppm)₂]², the anticipated intermediate for this reaction and for the hydrogen exchange with alcohol. A longer reaction of 2 with PhCH₂SH gives solely cis-Ru(SCH₂Ph)₂(dppm)₂.     

Ac/Ds transposon mutagenesis in Arabidopsis thaliana: mutant spectrum and frequency of Ds insertion mutants

Using a two-component Ac/Ds system consisting of a stabilized Ac element (Ac_c1) and a non-autonomous element (Ds_A), 650 families of plants carrying independent germinal Ds_A excisions/transpositions were isolated. Progenies of 559 of these Ac_c1/Ds_A families, together with 43 families of plants selected for excision/transposition of wild-type (wt)Ac, were subjected to a broad screening program for mutants exhibiting visible alterations. This resulted in the identification of 48 mutants showing a wide variety of mutant phenotypes, including embryo lethality (24 mutants), chlorophyll defects (5 mutants), defective seedlings (2 mutants), reduced fertility (5 mutants), reduced size (3 mutants), altered leaf morphology (2 mutants), dark green, unexpanded rosette leaves (3 mutants), and aberrant flower or shoot morphology (4 mutants). To test whether these mutants were due to transposon insertions, a series of Southern blot experiments was performed on 28 families, comparing in each case several mutant plants with others showing the wild-type phenotype. A preliminary analysis revealed in 4 of the 28 families analyzed a common, novel Ds_A fragment in all mutant plants, which was present only in heterozygous plants with wt phenotype, as expected for Ds_A insertion mutations. These four mutants included two showing embryo lethality, one with dark green, unexpanded rosette leaves and stunted inflorescences, and one with curly growth of stems, leaves and siliques. Further evidence for Ds_A insertion mutations was obtained for one embryo lethal mutant and for the stunted mutant, while in case of the second embryo lethal mutant, the Ds_A insertion could be separated from the mutant locus by genetic recombination.     

A note on the use of a scanning laser densitometer to analyse silver-stained lipopolysaccharide patterns on polyacrylamide gels and antigenic profiles on nitrocellulose sheets produced by immunoblotting

Silver-stained patterns of lipopolysaccharide on sodium dodecyl sulphate polyacrylamide gels and microbial antigenic profiles on nitrocellulose sheets produced by electroblotting and immunodetection were analysed with a laser scanning densitometer. Because the patterns fade rapidly it is usual to photograph them immediately to obtain optimum resolution. It has been shown that because of its high resolution the laser densitometer can be used to scan 35 mm photographic negatives without appreciable loss of detail. The method might be of value with whole cell immunoblot antigen profiles as characteristic fingerprints, for example, in taxonomic studies.     

Nucleolar number variation in Hordeum species,their haploids and interspecific hybrids

Nucleolar number variation has been investigated in root tip cells by cytologically determining the number of nucleoli per cell in autoploids and alloploids of Hordeum species, their haploids and interspecific hybrids. The nucleolus organisers in autoploid types of H. vulgare or H. bulbosum did not show any alterations irrespective of the ploidy level. The nucleolar number variation in these species results from a definite pattern of fusion and the maximum number of nucleoli per nucleus corresponds to the number of secondary constrictions. Nucleolus formation in alloploids and interspecific hybrids is impaired on some of the NORs, suggesting differential amphiplasty or nucleolar dominance. A comparison of nucleolar formation in the alloploid species (brachyantherum, arizonicum, procerum and parodii), their haploids, and the interspecific hybrids revealed different degrees of variation from the expected mean and maximum numbers of nucleoli. While the deviations in hybrids between alloploids (H. arizonicum and H. brachyantherum or H. procerum and H. brachyantherum) are marginal, nucleolar dominance is more pronounced in hybrids involving H. vulgare or H. bulbosum as one of the parents and is invariably associated with the disappearance of the secondary constriction(s) from the NOR(s) contributed by one of the parents, and the number of nucleoli is appropriately reduced.     

Distribution, seasonal use, and predation of incubation mounds of Orange-footed Scrubfowl on Komodo Island, Indonesia

ABSTRACT.   Megapodes are unique in using only heat from the environment, rather than body heat, to incubate their eggs as well as the precocious independence of their chicks on hatching. Of 22 recognized species of megapodes, 9 are listed as threatened due to factors including habitat loss and fragmentation, and predation on eggs and chicks. Orange-footed Scrubfowl ( Megapodius reinwardt ) are conspicuous components of the Oriental/Austral avifauna that inhabit the monsoon forests of the Lesser Sunda chain of islands in Indonesia. We examined the abundance, patterns of distribution, physical characteristics, seasonal activity, and predation risk of incubation mounds of Orange-footed Scrubfowl on Komodo Island in eastern Indonesia. We surveyed 13 valleys on Komodo Island from April 2002 to January 2005 and located 113 tended and 107 untended incubation mounds. Densities of scrubfowl mounds in our study were similar to that reported by investigators during the 1970s, suggesting little change in the scrubfowl population since then. Most scrubfowl mounds were on sandy or loamy soils in open monsoon forest with little overhead shade, and placement of mounds in such areas may ensure adequate temperatures for egg incubation. Although some mounds were tended during all months, mound use peaked during the late wet season in March. During the dry season (April–November), only a few mounds were tended. Komodo dragons ( Varanus komodoensis ) and wild pigs ( Sus scrofa ) were the primary predators of scrubfowl eggs, with no indication of egg predation by humans. The valley with the largest number of untended mounds in our study also had the largest number of active Komodo dragon nests. This suggests an effect of Komodo dragons on scrubfowl numbers, but additional study is needed.     

5-Fluorocytosine derivatives as inhibitors of deoxycytidine kinase

A series of potent piperidine-linked cytosine derivatives were prepared as inhibitors of deoxycytidine kinase (dCK). Compound 9h was discovered to be a potent inhibitor of dCK and shows a good combination of cellular potency and pharmacokinetic parameters. Compound 9h blocks the incorporation of radiolabeled cytosine into mouse T-cells in vitro, as well as in vivo in mice following a T-cell challenge.