Influence of soil and host plant crop on the genetic diversity of Azospirillum amazonense isolates

The genetic structure of Azospirillum amazonense populations isolated from the rhizosphere soil and washed and surface-sterilised roots of rice, maize and sorghum plants, cropped simultaneously in two different soils (clay loam and sandy loam) was characterised. Genetic diversity was measured by restriction fragment length polymorphism of the amplified 16S–23S rDNA intergenic spacer region (RISA-RFLP) and cluster analysis. Four genetically distinct clusters of isolates were observed with 78% similarity, suggesting that the A. amazonense population was heterogeneous at the strain level regardless of the soil type or host plant. Analysis of molecular variance (AMOVA) demonstrated that the host plant had a highly significant selective effect on the genetic structure of this species, especially on those isolates intimately associated with them, but also to a lesser extent on isolates from the rhizosphere and washed roots. The soil type also had a highly significant selective effect on A. amazonense genetic diversity, especially for those isolates from the rhizosphere soil. The selective effect of the soil type combined with that of the host plant suggests that environmental factors, such as soil texture and composition of exudates provided by C₃ or C₄ plants, play major roles in the overall genetic structure of A. amazonense populations associated with these cereals.     

Multielemental Determinations in Chocolate Drink Powder Using Multivariate Optimization and ICP OES

In this work multivariate experiments were conducted to optimize the operating conditions for inductively coupled plasma optical emission spectrometry (ICP OES) for multielemental determinations in chocolate drink powder. The operating conditions were investigated using a 2(3) central composite design, where the variables studied were radio frequency power, nebulization flow rate, and auxiliary argon flow rate. The effects of these parameters on plasma robustness and on signal to background ratio (SBR) were considered in parallel, allowing the evaluation of robustness and detectability using few and fast experiments to select the best conditions for the determination of the analytes. In this case, the proposed experiments were applied to the optimization of a method aimed at the determination of Al, Ba, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, P, Pb, V, and Zn in chocolate drink powder. The compromise conditions that allowed obtaining a robust and sensitive analytical method were radio frequency power of 1200 W, nebulization flow rate of 0.6 L/min, and auxiliary argon flow rate of 0.3 L/min. Using these conditions, recoveries between 95 and 105% and relative standard deviations lower than 5% were obtained for the majority of the analytes. The proposed method was successfully applied to the analysis of 15 samples of chocolate drink powder. The highest concentrations of metallic species were found in diet and light products.     

The fate of Amazonian forest fragments: A 32-year investigation

We synthesize findings to date from the world’s largest and longest-running experimental study of habitat fragmentation, located in central Amazonia. Over the past 32 years, Amazonian forest fragments ranging from 1 to 100 ha have experienced a wide array of ecological changes. Edge effects have been a dominant driver of fragment dynamics, strongly affecting forest microclimate, tree mortality, carbon storage, fauna, and other aspects of fragment ecology. However, edge-effect intensity varies markedly in space and time, and is influenced by factors such as edge age, the number of nearby edges, and the adjoining matrix of modified vegetation surrounding fragments. In our study area, the matrix has changed markedly over the course of the study (evolving from large cattle pastures to mosaics of abandoned pasture and regrowth forest) and this in turn has strongly influenced fragment dynamics and faunal persistence. Rare weather events, especially windstorms and droughts, have further altered fragment ecology. In general, populations and communities of species in fragments are hyperdynamic relative to nearby intact forest. Some edge and fragment-isolation effects have declined with a partial recovery of secondary forests around fragments, but other changes, such as altered patterns of tree recruitment, are ongoing. Fragments are highly sensitive to external vicissitudes, and even small changes in local land-management practices may drive fragmented ecosystems in markedly different directions. The effects of fragmentation are likely to interact synergistically with other anthropogenic threats such as logging, hunting, and especially fire, creating an even greater peril for the Amazonian biota.     

Evaluation of Magnetic Coagulant (α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-MO) and its Reuse in Textile Wastewater Treatment

The textile industries are characterized as one of the biggest consumers of potable water and chemical products throughout its process, being responsible for the elevated wastewater generation with intense coloration and wide polluting potential. In this context, the present study proposes the development and application of a new coagulant material for textile wastewater treatment. The proposed coagulant (α-Fe₂O₃-MO) was composed by hematite nanoparticles (α-Fe₂O₃) obtained by a simple non-pollutant methodology, associated with Moringa oleifera (MO) seeds saline extract compounds. Coagulation/flocculation (CF) efficiency was evaluated by removal of physicochemical parameters such as apparent color, turbidity, and compounds with absorption at UV_254nm (UV_254nm) through CF tests carried out on Jar test equipment and sedimentation carried out in the presence and absence of external magnetic field (600 k Am^?1). Kinetics sedimentation was from 0 to 90 min. The use of this new coagulant allowed the removal of 92.37% for apparent color, 91.43% for turbidity, and 46.09% for UV_254nm, indicating that the proposed coagulant association was efficient in the treatment of this type of wastewater under external magnetic field with only 10 min of sedimentation. In addition, the resulting sludge from CF process was tested as base material for a new coagulant synthesis, demonstrating great reuse potential. Therefore, the new proposed coagulant, composed of α-Fe₂O₃ and the compounds present in the seed extract of MO, has applicability for textile wastewater treatment demonstrating high removal rate for all evaluated parameters with cost reduction in the proposed treatment for this wastewater.     

Evaluation of the Effective Inactivation of Enteric Bacteria and Viruses From Swine Effluent and Sludge at Tropical Temperatures

The safe recycling of organic wastes such as the nutrients obtained from agriculture activities is a relevant aspect of the “One Health” strategy, a worldwide initiative including all aspects of health care for humans and animals, as well as aspects related to the conservation and development of the environment. It represents an important opportunity to mitigate the potential impact of microbial pathogens likely present in nutrient natural sources, as digestate, when applied to land as fertilizers. The objectives of the current study were to determine the inactivation of enteric microorganisms in swine digestate (effluent and sludge) during storage in anaerobic conditions and at different ambient temperatures of tropical zones (16, 22, and 37 °C). Human adenovirus 2 (HAdV-2), bacteriophage PhiX-174, and Salmonella enterica serovar typhimurium (S. typhimurium) were used as enteric microbial models to determine the minimum storage time required to reduce at least 3log of enteric microorganisms load in both matrices at the mentioned temperatures. The minimum storage time required for S. typhimurium was shorter than those observed for viruses at 37 °C, while reduction of at least 3log for S. typhimurium was observed after just 1 day; 20 and 90 days were needed for similar reductions for HAdV-2 and PhiX-174, respectively. Similar results were also observed at lower temperatures: 30 and 45 days were needed for S. typhimurium at 22 and 16 °C, respectively, but 30 and 90 days were needed at 22 °C for HAdV-2 PhiX-174, respectively, or 90 and 120 days at 16 °C for HAdV-2 PhiX-174, respectively. This is a pioneering study on the evaluation of inactivation of enteric viruses in swine digestate in usual tropical ambient temperatures; it demonstrates that the time for a considerable inactivation is longer than that observed for a enteric microorganisms (S. typhimurium), and shows that the storage of swine digestate at the referred temperatures can be used as a low-cost post-treatment to inactivate enteric microorganisms, allowing a further use as safer fertilizer.     

Optimum N and P rates for greenhouse production of vegetative coleus using constant liquid feed

Many new coleus (C. hybridus cv.) cultivars are vegetatively propagated and require different fertilization practices from seed propagated cultivars. Two experiments were conducted to evaluate growth responses of Henna, Indian Summer, Mint Mocha, New Orleans Red, Red Head, and Trusty Rusty to 0, 70, 140, 280 and 420 mg·L^?1 nitrogen (N), and Henna, Mint Mocha, Red Head, and Trusty Rusty to 0, 6.2, 12.4, 24.8, or 49.6 mg·L^?1 phosphorus (P) to determine optimum constant liquid feed rates to produce marketable size plants from rooted cuttings. Positive growth responses in terms of biomass were found with increasing N rates but not P rates. For medium-sized cultivars such as Henna, Indian Summer, and New Orleans Red, quadratic responses were found in aboveground biomass, and N at 280 mg·L^?1 resulted in similar plant size and dry weight as those fertilized at 140 and 420 mg·L^?1 N. For large-sized cultivars such as Mint Mocha, Red Head and Trusty Rusty, plant dry weight responded linearly within the N range tested and were greatest at 420 mg·L^?1. However, plant visual quality was negatively affected by N rates at 280 and 420 mg·L^?1 in that, leaf color became less intense at these high N rates. Plants fertilized at 70 mg·L^?1 were smaller than those fertilized at 140 mg·L^?1, however, they received similar visual quality ratings because of more intense leaf color. Therefore, N at 70 to 140 mg·L^?1 can be used to grow most vegetative coleus for similar marketable quality. Mint Mocha and Henna were the only cultivars responded to P treatments that, 12.4 mg·L^?1 P rate resulted in greater biomass than the no-P control. All other cultivars had no response to supplemental P except a linear response in tissue P%. Therefore, supplemental P is not required during the 8 week production period when there is an initial P charge in the substrate. We found that substrate pH decreases with higher P rates, therefore supplemental P fertilizer can be used for adjusting pH. Both N and P rates found optimum in this study are lower than current industry practices (N at 150 to 250 mg·L^?1 and P at 24 mg·L^?1) and can significantly lower production cost and potential leaching of excessive nutrient into waterway. Nutrient treatments in further study on postharvest performance of vegetative coleus will be selected based on this study.     

Differential exudation of two benzoxazinoids--one of the determining factors for seedling allelopathy of Triticeae species

Benzoxazinoids (Bx) are natural phytotoxins that function as chemical defense compounds in several species. The release of Bx by intact plant roots associated these compounds with root allelopathy in Triticeae species; however, the significance of exudate concentrations of Bx for plant-plant interactions is still a controversial question. A biological screening of 146 cultivars of four Triticeae species (Triticum aestivum L., Triticum durum Desf., Triticum spelta L., and Secale cereale L.) demonstrated a high cultivar dependence to suppress the root growth of Sinapis alba L. by root allelopathy in a dose-response bioassay. Only a few cultivars possessed a marked high or low allelopathic activity, whereby high-performance liquid chromatography-diode array detection analysis of root exudates revealed that these cultivars differed considerably in their ability to exude the two Bx aglucones, DIBOA [2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one] and DIMBOA [2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one]. The total amount of DIBOA and DIMBOA exuded showed a significant correlation to the growth inhibition in bioassay with a statistically estimated contribution to the overall allelopathic effect of 48-72%. In a bioassay with pure phytotoxins, Bx concentrations consistent with the amounts quantified in the screening bioassay caused detrimental effects on S. alba and almost reproduced the statistically estimated contribution. The observed causal association between the allelopathic activity under laboratory conditions and the exudate concentrations of Bx suggests that this association might have implications for the interference of Triticeae species in natural plant communities.