Influence of macro- and micronutrient fertilization on fungal contamination and fumonisin production in corn grains

The aim of this study was to investigate the effects of nutrients (nitrogen, zinc and boron) on fungal growth and fumonisins production in corn samples obtained at the beginning of grain formation and at harvest. Three nitrogen doses were applied to the corn plants through soil in combination with three zinc doses and two boron doses during sowing. Mycological analysis of grains, using Dichloran Rose-Bengal Chloramphenicol Agar, collected at the beginning of formation demonstrated a fungal population predominantly of yeasts. Analysis of freshly harvested corn revealed a higher frequency of Penicillium spp. (72%) and F verticillioides (27%). High Performance Liquid Chromatography analysis revealed that 100% of grains were contaminated with fumonisins B, at levels ranging from 0.3 to 24.3 mg/kg and 93% contaminated with fumonisin B(2) at levels ranging from 0.05 to 5.42 mg/kg. Nitrogen (50 kg/ha) in combination with boron (0.5 kg/ha) resulted in an increased fumonisin B2 production. (c) 2007 Elsevier Ltd. All rights reserved.

Molecular characterization and fumonisin production by Fusarium verticillioides isolated from corn grains of different geographic origins in Brazil

Gibberella moniliformis is most commonly associated with maize worldwide and produces high levels of fumonisins, some of the most agriculturally important mycotoxins. Studies demonstrate that molecular methods can be helpful for a rapid identification of Fusarium species and their levels of toxin production. The purpose of this research was to apply molecular methods (AFLP, TEF-1 alpha partial gene sequencing and PCR based on MAT alleles) for the identification of Fusarium species isolated from Brazilian corn and to verify if real time RT-PCR technique based on FUM1 and FUM19 genes is appropriated to estimate fumonisins B(1) and B(2) production levels. Among the isolated strains, 96 were identified as Fusarium verricillioides, and four as other Fusarium species. Concordant phylogenies were obtained by AFLP and TEF-1 alpha sequencing, permitting the classification of the different species into distinct clades. Concerning MAT alleles, 70% of the F. verricillioides isolates carried the MAT-1 and 30% MAT-2. A significant correlation was observed between the expression of the genes and toxin production r=0.95 and r=0.79 (correlation of FUM1 with FB(1) and FB(2), respectively, P < 0.0001): r=0.93 and r =0.78 (correlation of FUM19 with FB(1) and FB(2). respectively, P < 0.0001). Molecular methods used in this study were found to be useful for the rapid identification of Fusarium species. The high and significant correlation between FUM1 and FUM19 expression and fumonisins production suggests that real time RT-PCR is suitable for studies considering the influence of abiotic and biotic factors on expression of these genes. This is the first report concerning the expression of fumonisin biosynthetic genes in Fusarium strains isolated from Brazilian agricultural commodity. (c) 2010 Elsevier B.V. All rights reserved.

Molecular Ordering in Layer-by-Layer Polyelectrolyte Films Studied by Sum-Frequency Vibrational Spectroscopy: The Effects of Drying Procedures

Sum-Frequency Vibrational Spectroscopy (SFVS) has been used to investigate the effect of nitrogen-flow drying on the molecular ordering of Layer-by-Layer (LbL) films of poly(allylamine hydrochloride) (PAH) alternated with poly(styrene sulfonate) (PSS). We find that films dried by spontaneous water evaporation are more ordered and homogeneous than films dried by nitrogen flow. The latter are quite inhomogeneous and may have regions with highly disordered polymer conformation. We propose that drying by spontaneous water evaporation reduces the effect of drag by the drying front, while during nitrogen-flow drying the fast evaporation of water ""freezes"" the disordered conformation of adsorbed polyelectrolyte molecules. These findings are important for many applications of LbL films, since device performance usually depends on film morphology and its molecular structure.

Thermal analysis of biodegradable microparticles containing ciprofloxacin hydrochloride obtained by spray drying technique

Thermal analysis has been extensively used to obtain information about drug-polymer interactions and to perform pre-formulation studies of pharmaceutical dosage forms. In this work, biodegradable microparticles of poly(D,L-lactide-co-glycolide) (PLGA) containing ciprofloxacin hydrochloride (CP) in various drug:polymer ratios were obtained by spray drying. The main purpose of this study was to investigate the effect of the spray drying process on the drug-polymer interactions and on the stability of microparticles using differential scanning calorimetry (DSC), thermogravimetry (TG) and derivative thermogravimetry (DTG) and infrared spectroscopy (IR). The results showed that the high levels of encapsulation efficiency were dependant on drug:polymer ratio. DSC and TG/DTG analyses showed that for physical mixtures of the microparticles components the thermal profiles were different from those signals obtained with the pure substances. Thermal analysis data disclosed that physical interaction between CP and PLGA in high temperatures had occurred. The DSC and TG profiles for drug-loaded microparticles were very similar to the physical mixtures of components and it was possible to characterize the thermal properties of microparticles according to drug content. These data indicated that the spray dryer technique does not affect the physicochemical properties of the microparticles. In addition, the results are in agreement with IR data analysis demonstrating that no significant chemical interaction occurs between CP and PLGA in both physical mixtures and microparticles. In conclusion, we have found that the spray drying procedure used in this work can be a secure methodology to produce CP-loaded microparticles. (C) 2007 Elsevier B.V. All rights reserved.

Investigation of the drying process of linseed oil using FTIR and ToF-SIMS

The drying process of linseed oil, oxidized at 80 oC, has been investigated with rheology measurements, Fourier transformation infrared spectroscopy (FTIR), and time of flight secondary ion mass spectrometry (ToF-SIMS). The drying process can be divided into three main steps: initiation, propagation and termination. ToF-SIMS spectra show that the oxidation is initiated at the linolenic (three double bonds) and linoleic fatty acids (two double bonds). ToF-SIMS spectra reveal peaks that can be assigned to ketones, alcohols and hydroperoxides. In this article it is shown that FTIR in combination with ToF-SIMS are well suited tools for investigations of various fatty acid components and reaction products of linseed oil.

Drying front in a sloping aquifier: nonlinear effects

The profiles for the water table height h(x, t) in a shallow sloping aquifer are reexamined with a solution of the nonlinear Boussinesq equation. We demonstrate that the previous anomaly first reported by Brutsaert [1994] that the point at which the water table h first becomes zero at x = L at time t = t c remains fixed at this point for all times t > t c is actually a result of the linearization of the Boussinesq equation and not, as previously suggested [ Brutsaert, 1994 ; Verhoest and Troch, 2000 ], a result of the Dupuit assumption. Rather, by examination of the nonlinear Boussinesq equation the drying front, i.e., the point x f at which h is zero for times t ≥ t c , actually recedes downslope as physically expected. This points out that the linear Boussinesq equation should be used carefully when a zero depth is obtained as the concept of an “average” depth loses meaning at that time.

Zooplankton dynamics from inundation to drying in a complex ephemeral floodplain-wetland

Ecological responses to wetting and drying in dryland river floodplain systems are often described in terms of “boom” and “bust”. We suggest that patterns in floodplain species abundances and assemblage structures will be closely linked to the changes in spatial habitat heterogeneity that accompany flooding and drying phases. This study examined the responses of zooplankton through a wetting and drying cycle in a complex floodplain-wetland system in semi-arid Australia, the Narran Lakes. We illustrate the complexity of the zooplankton “boom” and “bust” response. Total densities of zooplankton varied considerably over time and patterns were very dissimilar between sites with abundances varying from <30 animals/L to over 4000 animals/L. We detected different patterns in the proportion of variance in abundances of the broad taxonomic groups (rotifers, cladocerans, ostracods, calanoid copepods, cyclopoid copepods and nauplii) explained by time and space. Site explained the highest proportion of variation in cladoceran and ostracod abundances,whereas variance in calanoid abundances was explained predominantly by time since inundation. Variation in the abundances of the remaining groups was explained largely by the site by time interaction. Zooplankton assemblages were observed to diverge during drying with highest between-site dissimilarities in assemblage structure occurring during the later stages of drying. Such high spatial and temporal variability in zooplankton abundances and community composition could have important consequences for consumers such as fish and some wetland birds that utilize these ephemeral systems for feeding and breeding while they are inundated.

Commensalism used by freshwater crayfish species to survive drying in seasonal habitats

Gramastacus insolitus is a very small non-burrowing Australian freshwater crayfish with a restricted distribution, occurring almost exclusively in seasonal habitats throughout its range. It is listed as a threatened species but its strategy for surviving dry periods was unknown. Eight seasonal surveys of crayfish distribution showed that members of G. insolitus were never found at sites that were outside the distribution of two larger burrowing freshwater crayfish species, Geocharax falcata and Cherax destructor. Excavation of 80 burrows of members of G. falcata and C. destructor in three different seasonal habitats in the Grampians National Park, Victoria, Australia, revealed that individuals of G. insolitus found refuge from drying by estivating in cracks and shallow depressions at the side of the main burrow tunnels constructed by larger species. Members of G. insolitus were not found estivating at the surface, such as under fallen wood, nor was it usually found in crayfish burrows unoccupied by the host crayfish. This study indicates that members of G. insolitus are commensal upon larger crayfish species, using their burrows to survive the seasonal drying of their habitat. Conservation strategies for populations of G. insolitus will need to consider co-existing species of burrowing crayfish.

Responses to flooding and drying in seedlings of a common Australian desert floodplain shrub : Muehlenbeckia florulenta Meisn. (tangled lignum)

We investigated the effects of flooding and drying over 6 months on growth and biomass allocation in seedlings of Muehlenbeckia florulenta Meisn. (tangled lignum), a common and widely distributed shrub of Australia's desert floodplains. We sought to determine if lignum seedlings respond to flooding or drying by altering traits or allocation patterns or instead display fixed patterns of development. Since desert floodplains are highly unpredictable and heterogeneous environments, we hypothesised that adaptive phenotypic plasticity is unlikely to have developed or be advantageous in seedlings of this species as environmental state changes are highly variable in their timing and duration and plants risk being caught out of kilter with environmental conditions. To test this, we conducted a glasshouse experiment in which lignum seedlings, grown in both clay and sandy sediments, were subjected to a range of hydrological conditions over a period of 6 months. Lignum seedlings exhibited considerable tolerance of both flooding and drying in our experiment and no mortality was observed. Growth was significantly reduced by flooding, however, and seedlings displayed extremely delayed development rather than plasticity in overall biomass allocation or any of the specific morphological variables we measured. Lignum seedlings were considerably more tolerant of drying than flooding and responded plastically by reducing leaf area ratios through reductions in specific leaf areas and leaf production and expansion. Sediment type had little effect on seedling development. Our results indicate that surface water hydrology is likely to be a major determinant of recruitment patterns in this ecologically significant species.

Solar thermal drying of canarium indicum nuts

Many situations exist in rural areas of developing countries where the help of simple technology can make substantial positive impacts on living conditions, finance, and in this case; sustainability. In the Melanesia region, there are numerous areas identified as needing improvement, including indigenous food preservation which will be addressed with a proposed solar thermal solution utilizing locally available materials as much as possible for low cost local construction. The current knowledge of the drying requirements for the product chosen in this study is quite limited. However, it is believed that solar thermal drying might be feasible for the remote sunny regions as in Melanesia. This paper describes the processes involved in determining the drying parameters of the Canarium indicum nut, and the proposed solar dryer designs that have been considered for the particular environmental conditions and product specifications. Through the selection process, a mixed mode, low-tunnel solar dryer was chosen as the best match to satisfy the different parameters.