Effects of three different nano-silver formulations on cut Acacia holosericea vase life

The relative efficacies of three chemically different nano-silver (NS) formulations were evaluated for their potential to extend the vase life of short-lived cut Acacia holosericea foliage. The novel proprietary formulations were neutral NS, acidic NS and ionic NS. They were characterised in terms of particle size, pH value, colour and odour. The NS treatments were applied as vase (lower concentrations) or pulse (higher concentrations) solutions. Among the treatments compared, neutral NS as a 4 mg L-1 vase solution or as a 40 mg L-1 24 h pulse treatment and acidic NS as a 0.5 mg L-1 vase solution or as a 5 mg L-1 24 h pulse treatment significantly (P <= 0.05) extended the vase life of A. holosericea. Vase life extensions over the deionised water (DI) controls were associated with better maintenance of relative fresh weight and vase water uptake, suppression of bacterial growth in the vase water and stem-end, and delaying stem blockage. In contrast, ionic-NS applied as a 0.5 or 1 mg L-1 vase solution treatment or as a 5 or 10 mg L-1 pulse treatment caused severe phytotoxicity to cut A. holosericea stems. The results suggest that NS treatments, especially neutral NS and acidic NS pulse treatments, could be a potential postharvest technology for commercial application to cut A. holosericea. (C) 2011 Elsevier B.V. All rights reserved.

A convenient sample preparation protocol for scanning electron microscope examination of xylem-occluding bacterial biofilm on cut flowers and foliage

Microbes and their exopolysaccharides (EPS) can block xylem vessels, thereby increasing the hydraulic resistance and decreasing the vase life of cut flowers and foliage. Scanning electron microscopy (SEM) provides a powerful tool for investigation of bacteria-induced xylem occlusion. However, conventional preparation protocols for SEM involving chemicals can cause loss of hydrated EPS material, and thereby damage the bacterial biofilms during dehydration. A modified chemical fixation protocol involving pre-fixation with 75 mM lysine plus 2.5% glutaraldehyde followed by the normal fixation in 3% glutaraldehyde was, therefore, tested for improved preservation of bacterial biofilm at the stem-ends of cut Acacia holosericea foliage stems. Stem-end segments with different stages of bacterial growth were obtained from stems stood into water. The lysine-based protocol was compared with four other processing protocols of critical point drying (CPD) without fixation (control), freeze-drying (FD), conventional chemical fixation followed by drying with hexamethyldisilazane (HMDS), and conventional chemical fixation with CPD. The non-fixed control. FD and the glutaraldehyde fixation with HMDS drying gave poor preservation of hydrated material, including bacterial EPS. Conventional glutaraldehyde fixation followed by CPD was superior to these three methods in terms of better preserving the EPS. However, this fourth method gave condensation of biofilms during dehydration. In contrast, the modified lysine-based protocol resulted in superior preservation of EPS and biofilm structure. Thus, this fifth method was the most appropriate for examination of bacterial stem-end blockage in cut ornamentals. (C) 2012 Elsevier B.V. All rights reserved.

Effectiveness of commercial harvesting in controlling feral-pig populations

Context. The feral pig (Sus scrofa) is a widespread pest species in Australia and its populations are commonly controlled to reduce damage to agriculture and the environment. Feral pigs are also a resource and harvested for commercial export as game meat. Although many other control techniques are used, commercial harvesting of feral pigs is often encouraged by land managers, because it carries little or no cost and is widely perceived to control populations. Aims. To use feral-pig harvesting records, density data and simple harvest models to examine the effectiveness of commercial harvesting to reduce feral-pig populations. Methods. The present study examined commercial harvest off-take on six sites (246-657 km2) in southern Queensland, and 20 large blocks (~2-6000 km2) throughout Queensland. The harvest off-take for each site was divided by monthly or average annual population size, determined by aerial survey, to calculate monthly and annual harvest rates.Asimple harvest model assuming logistic population growth was used to determine the likely effectiveness of harvesting. Key results. Commercial harvest rates were generally low (<~20%) and are likely to provide only modest reductions in population size. Additionally, harvest rates capable of substantial reductions (>50%) in long-term population size were isolated occurrences and not maintained across sites and years. High harvest rates were observed only at low densities. Although these harvest rates may be sufficiently high to hold populations at low densities, the population is likely to escape this entrapment following a flush in food supply or a reduction in harvest effort. Implications. Our results demonstrated that, at current harvest rates, commercial harvesting is ineffective for the landscape-scale control of feral-pig populations. Unless harvest rates can be significantly increased, commercial harvesting should be used as a supplement to, rather than as a substitute for, other damage-control techniques.

Localization of feeding of Anomalococcus indicus (Hemiptera: Lecanodiaspididae) and supplementary biological notes: Towards the biological management of the invasive tree Vachellia nilotica indica (Fabales: Mimosoideae) in North-Eastern Australia

. Management of the invasive Vachellia nilotica indica infesting tropical grasslands of Northern Australia has remained unsuccessful to date. Presently Anomalococcus indicus is considered a potential agent in the biological management of V. n. indica. Whereas generic biological details of A. indicus have been known, their feeding activity and details of their mouthparts and the sensory structures that are associated with their feeding action are not known. This paper provides details of those gaps. Nymphal instars I and II feed on cortical-parenchyma cells of young stems of V. n. indica, whereas nymphal instars III and adult females feed on phloem elements of older shoots. Nymphal instars and adults (females) trigger stress symptoms in the feeding tissue with cells bearing enlarged and disfigured nuclei, cytoplasmic shrinkage, cytoplasmic trabeculae, abnormal protuberances and uneven cell wall thickening, unusual cell membrane proliferation, and exhausted and necrosed cells. Continuous nutrient extraction by A. indicus can cause stem death. We provide evidence that A. indicus, by virtue of its continuous feeding activity and intense population build up, can be an effective biological-management agent to regulate populations of V. n. indica in infested areas. © 2014 © 2014 Société entomologique de France.

Boronia heterophylla vase life is influenced more by ethylene than by bacterial numbers or vase solution pH

Bacterial proliferation in both vase solutions and in cut flower stems has been implicated in reducing the vase life of numerous genera. Boronia heterophylla F. Muell. (Red Boronia) vase life was assessed at two stages of floral maturity for nine vase solution treatments covering a pH range of 2.5-5.7. Vase life for advanced harvest maturity stems ranged from 4.2 d in 10 mM citric acid + 50 mg L-1 chlorine (pH 2.5) to 12.9 d after STS pulsing (pH 5.7). For normal harvest maturity stems, the corresponding range was 5.8-19.0 d, respectively. Vase solutions containing 50 mg L-1 chlorine biocide resulted in decreased longevity. In contrast, pulsing with the ethylene-binding inhibitor, STS, significantly increased vase life. The number of bacteria in the vase solutions after 11 d was determined in stems of advanced maturity. The solution with the greatest number of bacteria, 4.0 x 10(10) cfu mL(-1), was water used after STS pulsing and in which the flowers lasted longest. Vase solution bacteria were enumerated on days 0,3, 6, 9 and 12 of the vase period with stems of normal harvest maturity. There was no relationship between vase life and vase solution bacterial numbers ((R) over bar (2) = 0.000). Moreover, there was a negative relationship between numbers of bacteria in basal 0-5 cm stem segments and vase life. As no correlations were evident between longevity and either the pH or vase solution bacterial numbers, B. heterophylla vase life was evidently limited principally by ethylene action. (C) 2013 Elsevier B.V. All rights reserved.

Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake

Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by: (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves; and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice.

Structural Veneer Based Composite Products from Hardwood Thinning - Part I: Background and Manufacturing

In Australia, plantation forests have increased in area by around 50% in the last 10 years. While this expansion has seen a modest 8% increase for softwoods, hardwood plantations have dramatically increased by over 150%. Hardwood plantations grown for high quality sawn timber are slow to mature, with a crop rotation time potentially reaching 35 years. With this long lead-time, each year the risk from fire, pests and adverse weather events dramatically increases, while not translating into substantially higher financial returns to the grower. To justify continued expansion of Australia's current hardwood plantation estate, it is becoming necessary to develop higher value end-uses for both pulpwood and smaller 'sawlog' resources. The use of the low commercial value stems currently culled during thinning appears to be a necessary option to improve the industry profitability and win new markets. This paper provides background information on Australian forests and plantations and gives an overview of potential uses of Australian hardwood plantation thinning logs, as their mechanical properties. More specifically, this paper reports on the development of structural Veneer Based Composite (VBC) products from hardwood plantation thinning logs, taking advantage of a recent technology developed to optimise the processing of this resource. The process used to manufacture a range of hollow-form veneer laminated structural products is presented and the mechanical characteristics of these products are investigated in the companion paper. The market applications and future opportunities for the proposed products are also discussed, as potential benefits to the timber industry. © RILEM 2014.

Infection of mungbean seed by Macrophomina phaseolina is more likely to result from localized pod infection than from systemic plant infection

The ubiquitous fungal pathogen Macrophomina phaseolina is best known as causing charcoal rot and premature death when host plants are subject to post-flowering stress. Overseas reports of M.phaseolina causing a rapid rot during the sprouting of Australian mungbean seed resulted in an investigation of the possible modes of infection of seed. Isolations from serial portions of 10 mungbean plants naturally infected with the pathogen revealed that on most plants there were discrete portions of infected tissue separated by apparently healthy tissue. The results from these studies, together with molecular analysis of isolates collected from infected tissue on two of the plants, suggested that aerial infection of aboveground parts by different isolates is common. Inoculations of roots and aboveground parts of mungbean plants at nine temperaturexsoil moisture incubation combinations and of detached green pods strongly supported the concept that seed infection results from infection of pods by microsclerotia, rather than from hyphae growing systemically through the plant after root or stem infection. This proposal is reinforced by anecdotal evidence that high levels of seed infection are common when rainfall occurs during pod fill, and by the isolation of M.phaseolina from soil peds collected on pods of mungbean plants in the field. However, other experiments showed that when inoculum was placed within 130mm of a green developing pod and a herbicide containing paraquat and diquat was sprayed on the inoculated plants, M.phaseolina was capable of some systemic growth from vegetative tissue into the pods and seeds.

Biological management of the invasive Vachellia nilotica ssp. indica (Benth.) Kyal. & Boatwr. (Fabales: Mimosoideae) in tropical Australia: stress-inducing potential of Anomalococcus indicus Ramakrishna (Insecta: Hemiptera: Coccoidea: Lecanodiaspididae), an agent of promise

Vachellia nilotica ssp. indica (hereafter, V. n. indica) is an important tree weed in Australia. Its dense populations induce undesirable changes in the vast areas of northern Australia. Because chemical and mechanical management options appear unviable for various reasons, biological management of this tree is considered a better option. Among the many trialled arthropods in Australian context, Anomalococcus indicus, a lecanodiaspid native to India, has been identified as a potent-candidate, since in India, its native terrain, it is the most widespread and occurs throughout the year. Severe infestations of A. indicus cause defoliation, wilting and death of branches, and occasionally the tree. Populations of A. indicus have been brought into Australia and are being tested for its host specificity under quarantine conditions. This article reports the physiological damage and stress it inflicts in the shoots of V. n. indica. Younger-nymphal instars of A. indicus feed on cortical-parenchyma cells of young stems, whereas the older instars and adults feed from the phloem of old stems. Two conspicuous responses of V. n. indica arising in response to the feeding action of A. indicus are changes in the cell-wall dynamics and irregular cell divisions. The feeding action of A. indicus elicits a sequence of reactions in the stem tissues of V. n. indica such as differentiation of thick-walled elements in the outer cortical parenchyma, differential thickening of cells with supernumerary layers of either suberin or lignin, proliferations of parenchyma and phloem, wall thickening and obliteration of inner lumen of phloem cells, and the sieve plates plugged with callosic deposits. The responses are the culminations of interaction between the virulence factor (one or more of the salivary proteins?) from A. indicus and the resistance factor in V. n. indica. We have analysed structural changes in the context of their functions, by comparing the feeding action of A. indicus with that of other hemipteroids. From the level of stress it induces, this study confirms that A. indicus has the potential to be an effective biological management of V. n. indica in Australia. © 2014 © 2014 Taylor & Francis and Aboricultural Association.

A retrospective study of vase life determinants for cut Acacia holosericea foliage

Short and variable vase life of cut Acacia holosericea foliage stems limits its commercial potential. Retrospective evaluation of factors affecting the vase life of this cut foliage line was assessed using primary data collected from 30 individual experiments. These data had been collected by four different researchers over 17 months, from late Summer to mid Winter across two consecutive years. Vase life data of cut A. holosericea stems held in deionised water (DIW) was analysed for general vase life variation and to define the most influential factor affecting vase life of the cut stems. Meanwhile, vase life of cut stems exposed to various chemical and physical postharvest treatments was analysed using meta-analysis to evaluate their efficacy in prolonging vase life of the stems. The overall mean vase life (±standard deviation) of cut A. holosericea stems was 6.4 ± 1.2 days (n = 30 trials). Longer vase life of ≥7 days was obtained from cut stems harvested at vegetative and flowering stage, which was between Summer and Autumn. Cut stems harvested at fruiting stage, between Winter and Spring displayed shorter vase life of ≤5.5 days. Mixed model analysis indicated that vase life variation of the cut stems was mostly determined by season (P < 0.001). In averaged, postharvest treatments increased vase life 1.4-fold compared to stems in DIW, with 68.32% had a large positive treatment effect size (d). Among the treatments, nano silver (NS) and copper (Cu2+) were the most beneficial to vase life. Retrospective analysis was found to be beneficial for identifying conditions and targeting practices to maximise the vase life of cut A. holosericea and, potentially for other species.

Effects of age, length, and pattern of burial on survival of Mikania micrantha stem sections

For many landholders in the South Pacific, weed control of Mikania micrantha Kunth is conducted by manual or mechanical means, leaving fragments on or below the ground to reshoot and grow. Effects of age, length (number of nodes), and pattern of burial on the survival of stem sections of M. micrantha were examined in the field in Viti Levu, Fiji. The experiment was arranged in a randomized factorial design, with number of nodes, age of stem sections, and pattern (depth and orientation) of stem burial as factors. Stem sections with two or three nodes had significantly greater survival (30% and 25%, respectively) than those with one node (12%). Mature stem sections had a significantly greater survival rate (31%) than young stem sections (13%) when buried in either the horizontal or the vertical position. Vertical plantings had significantly greater survival (43%) than horizontal plantings (10%), and for both orientations survival decreased with depth of burial. Only 8% of stem sections survived when cut into smaller (3 to 5 cm) sections and buried at a depth of 10 cm. This study revealed that cutting the M. micrantha stems into smaller sections (<3 cm) and burying them at depths of 10 cm or greater would improve the overall management of M. micrantha in crop and noncrop systems.

Stem anatomy and adventitious root formation in cuttings of Angophora, Corymbia and Eucalyptus

Many plantation eucalypts are difficult to propagate from cuttings, and their rooted cuttings often possess very few adventitious roots. We microscopically examined the stem anatomy of cuttings from 12 species of eucalypts and we determined whether adventitious root formation in auxin-treated cuttings of four species was limited to particular positions around the vascular tissue. Most species contained a central pith that was arranged in a four-pointed stellate pattern. The surrounding vascular tissue was also arranged in a stellate pattern near the shoot apex but it developed a more rectangular shape at the outer phloem as the stems enlarged radially. Adventitious roots formed at, or slightly peripheral to, the vascular cambium, and they formed at both the corners and the sides of the rectangular-shaped vascular tissue. The study highlighted that auxin-treated eucalypt cuttings can produce roots at multiple positions around the vascular tissue and so propagation methods can aim to produce more than four adventitious roots per rooted cutting. Higher numbers of adventitious roots could improve the root system symmetry, stability, survival and growth rate of clonal eucalypt trees. © 2015 by the authors; licensee MDPI, Basel, Switzerland.