Ageing delays the cellular stages of adventitious root formation in pine.

Vegetative propagation programs internationally are affected by the significant decline of rooting success as trees mature. This study compared the cellular stages of root formation in stem cuttings from 15-week-old (juvenile) and 9-y-old (mature) stock plants of the slash x Caribbean pine hybrid (Pinus elliottii var. elliottii x P. caribaea van hondurensis). The cellular stages of root formation were the same in both juvenile and mature cuttings, beginning with cell divisions of the vascular cambium forming callus tissue. Within the callus, tracheids differentiated and elongated to form root primordia. Roots in juvenile cuttings developed faster than those in mature cuttings and the juvenile cuttings had a much higher rooting percent at the end of the study (92% and 26% respectively). Cuttings of the two juvenile genotypes had more primary roots (5.5 and 3.3) than the three mature genotypes (0.96, 0.18 and 0.07). The roots of juvenile cuttings were more evenly distributed around the basal circumference when compared with those on cuttings from the mature genotypes. Further work is needed to improve understanding of physiological changes with maturation so that the rooting success and the speed of development in cuttings from mature stock plants can be optimised, hence improving genetic gain.

Structural Changes Accompanying the Formation of Isopentane Glass

On the basis of a detailed Monte Carlo study, it is found that considerable molecular reorientation occurs on the formation of the glassy state of isopentane. The reorientational contribution to the increase in the intermolecular energy on vitrification is at least 50% and reorientational freezing plays a major role near the glass transition. Annealing affects the structure of the glass by a rearrangement involving molecular reorientation.

The formation of carbon nanostructures by in situ TEM mechanical nanoscale fatigue and fracture of carbon thin films

A technique to quantify in real time the microstructural changes occurring during mechanical nanoscale fatigue of ultrathin surface coatings has been developed. Cyclic nanoscale loading, with amplitudes less than 100 nm, is achieved with a mechanical probe miniaturized to fit inside a transmission electron microscope (TEM). The TEM tribological probe can be used for nanofriction and nanofatigue testing, with 3D control of the loading direction and simultaneous TEM imaging of the nano-objects. It is demonstrated that fracture of 10-20 nm thick amorphous carbon films on sharp gold asperities, by a single nanoscale shear impact, results in the formation of < 10 nm diameter amorphous carbon filaments. Failure of the same carbon films after cyclic nanofatigue, however, results in the formation of carbon nanostructures with a significant degree of graphitic ordering, including a carbon onion.

High temperature stability of oxysulfides containing Ce3+ and Y3+ ions

Standard Gibbs energies of formation of oxysulfides of cerium and yttrium from their respective oxedes were determined using solid oxide galvanic cells incorporating calcia-stabilized zirconia as the electrolyte in the temperature range 870–1120 K. The sulfur potential over the electrode containing the oxide and oxysulfide was fixed by a buffer mixture of Ag + Ag2S. A small amount of CaH2 was added to the buffer to generate an equilibrium ratio of H2S and H2 species in a closed system containing the buffer and the electrode. The sulfur potential is transmitted to the electrode via the gas phase. The results can be summarized by the equations 2left angle bracketCeO2right-pointing angle bracket+1/2(S2)→left angle bracketCe2O2Sright-pointing angle bracket+(O2) ΔG°=430600−109·7T(±400)J mol−1 left angle bracketY2O3right-pointing angle bracket+1/2(S2)→left angle bracketY2O2Sright-pointing angle bracket+1/2(O2) ΔG°=114780−1·45T(±200)J mol−1 The values are compared with data reported in the literature. The stability field diagram for the Ce---O---S system has been developed using the results of this study for Ce2O2S and data for other phases from the literature.

Negotiating and Renegotiating Conversational Ground Rules : Formation of an Artifact Designed to Mediate Exploratory Collaboration

This study highlights the formation of an artifact designed to mediate exploratory collaboration. The data for this study was collected during a Finnish adaptation of the thinking together approach. The aim of the approach is to teach pulps how to engage in educationally beneficial form of joint discussion, namely exploratory talk. At the heart of the approach lies a set of conversational ground rules aimed to promote the use of exploratory talk. The theoretical framework of the study is based on a sociocultural perspective on learning. A central argument in the framework is that physical and psychological tools play a crucial role in human action and learning. With the help of tools humans can escape the direct stimulus of the outside world and learn to control ourselves by using tools. During the implementation of the approach, the classroom community negotiates a set of six rules, which this study conceptualizes as an artifact that mediates exploratory collaboration. Prior research done about the thinking together approach has not extensively researched the formation of the rules, which give ample reason to conduct this study. The specific research questions asked were: What kind of negotiation trajectories did the ground rules form during the intervention? What meanings were negotiated for the ground rules during the intervention The methodological framework of the study is based on discourse analysis, which has been specified by adapting the social construction of intertextuality to analyze the meanings negotiated for the created rules. The study has town units of analysis: thematic episode and negotiation trajectory. A thematic episode is a stretch of talk-in-interaction where the participants talk about a certain ground rule or a theme relating to it. A negotiation trajectory is a chronological representation of the negotiation process of a certain ground rule during the intervention and is constructed of thematic episodes. Thematic episodes were analyzed with the adapted intertextuality analysis. A contrastive analysis was done on the trajectories. Lastly, the meanings negotiated for the created rules were compared to the guidelines provided by the approach. The main result of the study is the observation, that the meanings of the created rules were more aligned with the ground rules of cumulative talk, rather than exploratory talk. Although meanings relating also to exploratory talk were negotiated, they clearly were not the dominant form. In addition, the study observed that the trajectories of the rules were non identical. Despite connecting dimensions (symmetry, composition, continuity and explicitness) none of the trajectories shared exactly the same features as the others.

Key Role of Fe2+ in Epithiospecifier Protein Activity.

The chemical nature of the hydrolysis products from the glucosinolate-myrosinase system depends on the presence or absence of supplementary proteins such as epithiospecifier proteins (ESPs). ESPs promote the formation of epithionitriles from terminal alkenyl glucosinolates and, as recent evidence suggests, simple nitriles at the expense of isothiocyanates. From a human health perspective isothiocyanates are the most important because they are major inducers of carcinogen-detoxifying enzymes. Fe2+ is an essential factor in ESP activity, although several recent studies have highlighted discrepancies in the understanding of the ESP-iron interaction. To investigate further the role iron species play in regulating ESP activity, four ESP-containing seedpowders were analyzed for ESP and myrosinase activities, endogenous iron content, and glucosinolate degradation products after the addition of iron species, specific chelators, and reducing agents. For the first time this paper shows the effect of these additions on the hydrolysis of individual glucosinolates that constitute the total pool. Aged seeds and 3-day seedlings were also tested to investigate the effects of seed storage and early plant development on iron levels and ESP activity. The four ESP-containing plant systems tested gave two distinctive responses, thus providing strong evidence that ESPs vary markedly in their Fe2+ requirement for activity. The results also indicated that reduction of ferric to ferrous iron drives variations in ESP activity during early plant development. The reverse oxidation reaction provided a convincing explanation for the loss of ESP activity during seed storage. Aged seeds produced seedlings with substantially lower ESP activity, and there was a concomitant loss in germination rate. It was concluded that manipulation of endogenous iron levels of ESP-containing plants could increase the conversion of glucosinolates to isothiocyanates and enhance potential health benefits.

Pyrrolizidine Alkaloids in Crotalaria Taxa from Northern Australia: Risk to Grazing Livestock.

Crotalaria species containing hepatotoxic pyrrolizidine alkaloids grow widely in pastures in northern Australia and have sporadically poisoned grazing livestock. The diverse Crotalaria taxa present in these pastures include varieties, subspecies, and chemotypes not previously chemically examined. This paper reports the pyrrolizidine alkaloid composition and content of 24 Crotalaria taxa from this region and assesses the risk of poisoning in livestock consuming them. Alkaloids present in C. goreensis, C. aridicola subsp. densifolia, and C. medicaginea var. neglecta lack the esterified 1,2-unsaturated functionality required for pyrrole adduct formation, and these taxa are not hepatotoxic. Taxa with high levels of hepatotoxic alkaloids, abundance, and biomass pose the greatest risk to livestock health, particularly C. novae-hollandiae subsp. novae-hollandiae, C. ramosissima, C. retusa var. retusa, and C. crispata. Other species containing moderate alkaloid levels, C. spectabilis and C. mitchellii, also pose significant risk when locally abundant.

Taxonomy, distribution and ecology of Zoysia macrantha desv., an Australian native species with turf breeding potential

Only three of the 11 species in the genus Zoysia Willd. have thus far contributed to commercially available turfgrass varieties. One of the neglected taxa is Z. macrantha Desv., an Australian native species further divided into two subspecies. The coarser Z. macrantha subsp. macrantha occurs on sand dunes, headlands and tidal areas along eastern and southeastern coasts from about 23 to 38°S latitude. The shorter, denser-growing Z. macrantha subsp. walshii M.E. Nightingale is found on the southern mainland (South Australia and Victoria from longitude 137° to 148°E and at latitudes higher than 36°S), adjacent offshore islands, and northern, eastern and central Tasmania to 43°S growing on the edges of coastal, sub-coastal and even inland salt lakes, in riverine environments, and from moist grassy depressions (both coastal and inland) to rocky headlands. The latter subspecies has the more discontinuous and specialised distribution, largely determined by the need for an appropriate level of peat, clay or silt in the soil to maintain adequate moisture during the dry summers in southern Australia while at the same time avoiding anything more than temporary waterlogging. It grows on low fertility soils ranging from strongly acid to neutral or mildly alkaline, and is often very closely grazed by marsupials. Both subspecies are salt and drought tolerant, but not notably shade tolerant. Their potential to add greater drought tolerance in particular to the Asian Zoysia material in current use through future breeding programs is discussed.

The use of temperate species in the Australian subtropics.

Temperate species and tropical crop silage are the basis for forage production for the dairy industry in the Australian subtropics. Irrigation is the key resource needed for production, with little survival of temperate species under rain-grown conditions except for lucerne. Annual ryegrass (Lolium multiflorum), fertilised with either inorganic nitrogen or grown with clovers, is the main cool season forage for the dairy industry. It is sown into fully prepared seedbeds, oversown into tropical grasses, especially kikuyu (Pennisetum clandestinum) or sown after mulching. There has been a continual improvement in the performance of annual and hybrid ryegrass cultivars over the last 25 years. In small plot, cutting experiments, yields of annual ryegrass typically range from 15 to 21 t DM/ha, with equivalent on-farm yields of 7 to 14 t DM/ha of utilised material. Rust (Puccinia coronata) remains the major concern although resistance is more stable than in oats. There have also been major improvements in the performance of perennial ryegrass (L. perenne) cultivars although their persistence under grazing is insufficient to make them a reliable forage source for the subtropics. On the other hand, tall fescue (Festuca arundinacea) and prairie grass (Bromus willdenowii) cultivars perform well under cutting and grazing, although farmer resistance to the use of tall fescue is strong. White clover (Trifolium repens) is a reliable and persistent performer although disease usually reduces its performance in the third year after sowing. Persian (Shaftal) annual clover (T. resupinatum) gives good winter production but the performance of berseem clover (T. alexandrinum) is less reliable and the sub clovers (T. subterraneum) are generally not suited to clay soils of neutral to alkaline pH. Lucerne (Medicago sativa), either as a pure stand or in mixtures, is a high producing legume under both irrigation and natural rainfall. Understanding the importance of leaf and crown diseases, and the development of resistant cultivars, have been the reasons for its reliability. Insects on temperate species are not as serious a problem in the subtropics as in New Zealand (NZ). Fungal and viral diseases, on the other hand, cause many problems and forage performance would benefit from more research into resistance.

A novel species of mastrevirus (family Geminiviridae) isolated from Digitaria didactyla grass from Australia.

Mastreviruses (family Geminiviridae) that infect monocotyledonous plants occur throughout the temperate and tropical regions of Asia, Africa, Europe and Australia. Despite the identification of a very diverse array of mastrevirus species whose members infect African monocots, few such species have been discovered in other parts of the world. For example, the sequence of only a single monocot-infecting mastrevirus, Chloris striate mosaic virus (CSMV), has been reported so far from Australia, even though earlier biological and serological studies suggested that other distinct mastreviruses were present. Here, we have obtained the complete nucleotide sequence of a virus from the grass Digitaria didactyla originating from Australia. Analysis of the sequence shows the virus to be a typical mastrevirus, with four open reading frames, two in each orientation, separated by two non-coding intergenic regions. Although it showed the highest levels of sequence identity to CSMV (68.7%), their sequences are sufficiently diverse for the virus to be considered a member of a new species in the genus Mastrevirus, based on the present species demarcation criteria. We propose that the name first used during the 1980s be used for this species, Digitaria didactyla striate mosaic virus (DDSMV).

New Modified Dipping Method Using 4-hexylresorcinol for Preventing Blackspot Formation in Prawns.

Industry acceptance of alternative sulphite treatments for preventing blackspot in prawns is limited. This study demonstrated that dipping prawns (Penaeus monodon and Fenneropenaeus merguiensis) in a less concentrated solution for longer times provides better control of blackspot formation than the recommended 2 minute dip in 50 mg/L 4-hexylresorcinol. Protection improved as modified dipping times and solution concentrations increased. Blackspot protection provided by most of the modified dip methods was more effective than a 1 minute dip in 1% sodium metabisulphite. The recommended 2 minute dip method should be limited to 125 kg when used on consecutive 25-kg batches of prawns. Yields increased by less than 10% even after 72-hour exposure in the modified dip. The new dipping method meets most international residue standards when applying the modified treatments evaluated.

Biophysical Characterization of Oxidized Phospholipids : Implications for Altered Membrane Structure and Function

The present study aims to elucidate the modifications in the structure and functionality of the phospholipid matrix of biological membranes brought about by free radical-mediated oxidative damage of its molecular constituents. To this end, the surface properties of two oxidatively modified phospholipids bearing an aldehyde or carboxyl function at the end of truncated sn-2 acyl chain were studied using a Langmuir balance. The results obtained reveal both oxidized species to have a significant impact on the structural dynamics of phospholipid monolayers, as illustrated by the progressive changes in force-area isotherms with increasing mole fraction of the oxidized lipid component. Moreover, surface potential measurements revealed considerable modifications in the electric properties of oxidized phospholipid containing monolayers during film compression, suggesting a packing state-controlled reorientation of the intramolecular electric dipoles of the lipid headgroups and acyl chains. Based on the above findings, a model describing the conformational state of oxidized phospholipid molecules in biological membranes is proposed, involving the protrusion of the acyl chains bearing the polar functional groups out from the hydrocarbon phase to the surrounding aqueous medium. Oxidative modifications alter profoundly the physicochemical properties of unsaturated phospholipids and are therefore readily anticipated to have important implications for their interactions with membrane-associating molecules. Along these lines, the carboxyl group bearing lipid was observed to bind avidly the peripheral membrane protein cytochrome c. The binding was reversed following increase in ionic strength or addition of polyanionic ATP, thus suggesting it to be driven by electrostatic interactions between cationic residues of the protein and the deprotonated lipid carboxyl exposed to the aqueous phase. The presence of aldehyde function bearing oxidized phospholipid was observed to enhance the intercalation of four antimicrobial peptides into phospholipid monolayers and liposomal bilayers. Partitioning of the peptides to monolayers was markedly attenuated by the aldehyde scavenger methoxyamine, revealing it to be mediated by the carbonyl moiety possibly through efficient hydrogen bonding or, alternatively, formation of covalent adduct in form of a Schiff base between the lipid aldehydes and primary amine groups of the peptide molecules. Lastly, both oxidized phospholipid species were observed to bind with high affinity three small membrane-partitioning therapeutic agents, viz. chlorpromazine, haloperidol, and doxorubicin. In conclusion, the results of studies conducted using biomimetic model systems support the notion that oxidative damage influences the molecular architecture as well as the bulk physicochemical properties of phospholipid membranes. Further, common polar functional groups carried by phospholipids subjected to oxidation were observed to act as molecular binding sites at the lipid-water interface. It is thus plausible that oxidized phospholipid species may elicit cellular level effects by modulating integration of various membrane-embedded and surface-associated proteins and peptides, whose conformational state, oligomerization, and functionality is known to be controlled by highly specific lipid-protein interactions and proper physical state of the membrane environment.

Relationships between Indole-3-butyric Acid, Photoinhibition and Adventitious rooting of Corymbia torelliana, C. citriodora and F1 Hybrid Cuttings

Rooted cutting propagation is widely used for maximising tree yield, quality and uniformity in conjunction with clonal selection. Some eucalypt species are deployed as rooted cuttings but many are considered to difficult to root. This study examined IBA effects on photoinhibition, root formation, mortality and root and shoot development in cuttings of Corymbia torelliana, C. citriodora and their hybrids. IBA had little or no effect on photoinhibition but it had strong, dose-dependent effects on root formation and mortality. IBA frequently increases primary root number of rooted cutting but it did not increase total root weight, length, surface area or volume, possibly because the highest doe (8g IBA/kg IBA/kg powder) caused leaf abscission and sometimes reduced leaf area (by 55-79%)or shoot dry weight (by 40-58%). An intermediate dose (3g IBA/kg powder) most consistnely improved root formation with little or no effect on mortality or shoot development. Across the F1 hybrid families this treatment increased the number of rooted cuttings by 72-121% and more than ddoubled the number of primary roots per rooted cutting (from 1.1-1.7 roots to 3.5-4.1 roots). This simple treatment will facilitate commercial multiplication of superior individuals or selected families of C. torelliana x C. citriodora through a vegetative propagation system.

Infection and disease development of Quambalaria spp. on Corymbia and Eucalyptus spp.

Quambalaria spp. are eucalypt leaf and shoot pathogens of growing global importance, yet virtually nothing is known regarding the manner in which they infect and colonize their hosts. A study of the infection process of Q. pitereka and Q.eucalypti on Corymbia and Eucalyptus species was thus undertaken using light, scanning and transmission electron microscopy after artificial inoculation. Conidial germination was triggered when relative humidity levels exceeded 90% and commenced within 2 h in the presence of free water. Light reduced germination but did not prevent germination from occurring. Conidial germination and hyphal growth occurred on the upper and lower leaf surfaces with penetration occurring via the stomata or wounds on the leaf surface or juvenile stems. There was no evidence of direct penetration of the host. Following penetration through the stomata, Q. pitereka and Q. eucalypti hyphae grew only intercellularly without the formation of haustoria or interaction apparatus, which is characteristic of the order Microstromatales. Instead, the presence of an interaction zone is demonstrated in this paper. Conidiophores arose through stomatal openings producing conidia 7 days after infection.