Magdalena Fernandez and the ethos of digital geometric abstraction

This paper deals with the work of the Venezuelan artist Magdalena Fernandez whose practice emerges in the 1990s to explore the potentiality of the language of geometric abstraction at the intersection of visual arts and design. Whilst revisiting the legacy of Modernism through a Minimalist aesthetics, Fernandez contributes to the formulation of a grammar of geometric abstraction which articulates by means of digital and multimedia practices. In this regard, emblematic is the mobile painting, 2iPM009, 2009, in which Fernandez extends the canons of formal composition through a multiplicity of registers that integrates spatial, structural, and graphic investigations, all supported by a system of computation that uses digital animation techniques in analogy with sound and light effects through the format of a video-installation. This paper examines the artist’s interest in rethinking the pictorial language of modernist geometric abstraction through a multimedia language, questioning about agency and legacy

Responses of hydroponically grown maize to various urea to ammonium ratios: physiological and molecular data

To date urea and ammonium are two nitrogen (N) forms widely used in agriculture. Due to a low production cost, urea is the N form most applied in agriculture. However, its stability in the soil depends on the activity of microbial ureases, that operate the hydrolysis of urea into ammonium. In the soil ammonium is subjected to fast volatilization in form of ammonia, an environmental N loss that contributes to the atmospheric pollution and impacts on farm economies. Based on these considerations, the optimization of N fertilization is useful in order to maximize N acquired by crops and at the same time limit N losses in the environment. The use of mixed nitrogen forms in cultivated soils allows to have urea and ammonium simultaneously available for the root acquisition after a fertilization event. A combination of different N-sources is known to lead to positive effects on the nutritional status of crops. It is plausible suppose that N acquisition mechanisms in plants might be responsive to N forms available in the root external solution, and therefore indicate a cross connection among different N forms, such as urea and ammonium

With or Without You: Altered Plant Response to Boron-Deficiency in Hydroponically Grown Grapevines Infected by Grapevine Pinot Gris Virus Suggests a Relation Between Grapevine Leaf Mottling and Deformation Symptom Occurrence and Boron Plant Availability

Despite the increasing spread of Grapevine Leaf Mottling and Deformation (GLMD) worldwide, little is known about its etiology. After identification of grapevine Pinot gris virus (GPGV) as the presumptive causal agent of the disease in 2015, various publications have evaluated GPGV involvement in GLMD. Nevertheless, there are only partial clues to explain the presence of GPGV in both symptomatic and asymptomatic grapevines and the mechanisms that trigger symptom development, and so a consideration of new factors is required. Given the similarities between GLMD and boron (B)-deficiency symptoms in grapevine plants, we posited that GPGV interferes in B homeostasis. By using a hydroponic system to control B availability, we investigated the effects of different B supplies on grapevine phenotype and those of GPGV infection on B acquisition and translocation machinery, by means of microscopy, ionomic and gene expression analyses in both roots and leaves. The transcription of the genes regulating B homeostasis was unaffected by the presence of GPGV alone, but was severely altered in plants exposed to both GPGV infection and B-deficiency, allowing us to speculate that the capricious and patchy occurrence of GLMD symptoms in the field may not be related solely to GPGV, but to GPGV interference in plant responses to different B availabilities. This hypothesis found preliminary positive confirmations in analyses on field-grown plants

Filamentous sieve element proteins are able to limit phloem mass flow, but not phytoplasma spread

In Fabaceae, dispersion of forisomes\u2014highly ordered aggregates of sieve element proteins\u2014in response to phytoplasma infection was proposed to limit phloem mass flow and, hence, prevent pathogen spread. In this study, the involvement of filamentous sieve element proteins in the containment of phytoplasmas was investigated in non-Fabaceae plants. Healthy and infected Arabidopsis plants lacking one or two genes related to sieve element filament formation\u2014AtSEOR1 (At3g01680), AtSEOR2 (At3g01670), and AtPP2-A1 (At4g19840)\u2014were analysed. TEM images revealed that phytoplasma infection induces phloem protein filament formation in both the wild-type and mutant lines. This result suggests that, in contrast to previous hypotheses, sieve element filaments can be produced independently of AtSEOR1 and AtSEOR2 genes. Filament presence was accompanied by a compensatory overexpression of sieve element protein genes in infected mutant lines in comparison with wild-type lines. No correlation was found between phloem mass flow limitation and phytoplasma titre, which suggests that sieve element proteins are involved in defence mechanisms other than mechanical limitation of the pathogen

Dissecting the role of iron in the interaction between the host plant tomato and \u2018Candidatus Phytoplasma solani\u2019

Phytoplasmas are prokaryotic plant pathogens that colonize the sieve elements of the host plant, causing alteration in phloem function and impairment of assimilate translocation. Despite the huge impact on agriculture and the lack of effective curative strategies, mechanisms underlying plant host-phytoplasma interaction are still largely unexplored. In particular, no knowledge is available on the role of iron (Fe) in this interaction. Iron is an essential element for most living organisms, and competition for it can lead, as already observed in different pathosystems, to the development of an Fe-withholding response by plants that changes Fe distribution and trafficking. In the current study, we investigated on the role of Fe in the interaction between tomato and \u2018Candidatus Phytoplasma solani\u2019 by analyzing healthy plants (H/+Fe), Fe-starved plants (H/-Fe), phytoplasma-infected plants (I/+Fe) and phytoplasma-infected/Fe-starved plants (I/-Fe). Firstly, an experimental system was set up so that phytoplasma infection and occurrence of Fe deficiency symptoms were concomitant. Then, high-throughput RNA-sequencing focused on midrib-enriched tissue was conducted to profile leaf transcriptome changes in both stresses. We found that most of differentially regulated genes in common to I/+Fe and H/-Fe plants encode proteins involved in photosynthetic light reactions, in porphyrin and chlorophyll metabolism, and in carotenoid biosynthesis. These similarities supported the hypothesis that phytoplasma might induce alteration in cellular Fe homeostasis. Even if no significant difference in total Fe concentration emerged when comparing H and I plants under both nutritional conditions, the phytoplasma presence caused local modifications of Fe distribution visible by Perls\u2019-DAB staining, with a shift from the leaf lamina to the site of infection (the phloem). Similar to healthy (H/+Fe), Fe dots were localized to the phloem in the infected leaves (I/+Fe), but lacked in xylem parenchyma cells similar to H/-Fe leaves. Moreover, in both stresses the mesophyll palisade cells of the leaf lamina had fewer Fe dots than in H/+Fe condition. We examined the activity of genes involved in the Fe uptake and Fe homeostasis in roots. Under Fe-sufficient conditions, the phytoplasma apparently did not alter the acquisition mechanism. Under Fe-deficient conditions, the phytoplasma reduced the expression of all the examined genes, except for FRO1. These findings suggest that, under Fe-deficient conditions, the presence of phytoplasmas may compromise the communication of the Fe status between leaves and roots, possibly by the interference with the synthesis or transport of a promotive signal.Phytoplasmas are prokaryotic plant pathogens that colonize the sieve elements of the host plant, causing alteration in phloem function and impairment of assimilate translocation. Despite the huge impact on agriculture and the lack of effective curative strategies, mechanisms underlying plant host-phytoplasma interaction are still largely unexplored. In particular, no knowledge is available on the role of iron (Fe) in this interaction. Iron is an essential element for most living organisms, and competition for it can lead, as already observed in different pathosystems, to the development of an Fe-withholding response by plants that changes Fe distribution and trafficking. In the current study, we investigated on the role of Fe in the interaction between tomato and \u2018Candidatus Phytoplasma solani\u2019 by analyzing healthy plants (H/+Fe), Fe-starved plants (H/-Fe), phytoplasma-infected plants (I/+Fe) and phytoplasma-infected/Fe-starved plants (I/-Fe). Firstly, an experimental system was set up so that phytoplasma infection and occurrence of Fe deficiency symptoms were concomitant. Then, high-throughput RNA-sequencing focused on midrib-enriched tissue was conducted to profile leaf transcriptome changes in both stresses. We found that most of differentially regulated genes in common to I/+Fe and H/-Fe plants encode proteins involved in photosynthetic light reactions, in porphyrin and chlorophyll metabolism, and in carotenoid biosynthesis. These similarities supported the hypothesis that phytoplasma might induce alteration in cellular Fe homeostasis. Even if no significant difference in total Fe concentration emerged when comparing H and I plants under both nutritional conditions, the phytoplasma presence caused local modifications of Fe distribution visible by Perls\u2019-DAB staining, with a shift from the leaf lamina to the site of infection (the phloem). Similar to healthy (H/+Fe), Fe dots were localized to the phloem in the infected leaves (I/+Fe), but lacked in xylem parenchyma cells similar to H/-Fe leaves. Moreover, in both stresses the mesophyll palisade cells of the leaf lamina had fewer Fe dots than in H/+Fe condition. We examined the activity of genes involved in the Fe uptake and Fe homeostasis in roots. Under Fe-sufficient conditions, the phytoplasma apparently did not alter the acquisition mechanism. Under Fe-deficient conditions, the phytoplasma reduced the expression of all the examined genes, except for FRO1. These findings suggest that, under Fe-deficient conditions, the presence of phytoplasmas may compromise the communication of the Fe status between leaves and roots, possibly by the interference with the synthesis or transport of a promotive signal

Rheological Response of Polylactic Acid Dispersions in Water with Xanthan Gum

In this work, the rheological behavior of stable poly(lactic acid) (PLA) dispersions in water, intended for coating applications, was investigated. The newly prepared dispersion consists of PLA particles with an average diameter of 222 ± 2 nm based on dynamic light scattering (DLS) and scanning electron microscopy (SEM) analyses, at concentrations varying in the 5−22 wt % range. Xanthan gum (XG), a bacterial polysaccharide, was used as a thickening agent to modulate the viscosity of the formulations. The rheological properties of the PLA dispersions with different XG and PLA contents were studied in steady shear, amplitude sweep, and frequency sweep experiments. Under steady shear conditions, the viscosity of all the formulations showed a shear-thinning behavior similar to XG solutions in the whole investigated 1− 1000 s−1 range, with values dependent on both PLA particles and XG concentrations. Amplitude and frequency sweep data revealed a weak-gel behavior except in the case of the most diluted sample, with moduli dependent on both PLA and XG contents. A unified scaling parameter was identified in the volume fraction (ϕ) of the PLA particles, calculated by considering the dependence of the continuous phase density on the XG concentration. Accordingly, a master curve at different volume fractions was built using the time−concentration−superposition approach. The master curve describes the rheological response of the system over a wider frequency window than the experimentally accessible one and reveals the presence of a superimposed β relaxation process in the high-frequency region

Gimme shelter: three-dimensional architecture of the endoplasmic reticulum, the replication site of grapevine Pinot gris virus

Grapevine leaf mottling and deformation is a novel grapevine disease that has been associated with grapevine Pinot gris virus (GPGV). The virus was observed exclusively inside membrane-bound structures in the bundle sheath cells of the infected grapevines. As reported widely in the literature, many positive-sense single-stranded RNA viruses modify host-cell membranes to form a variety of deformed organelles, which shelter viral genome replication from host antiviral compounds. Morphologically, the GPGV-associated membranous structures resemble the deformed endoplasmic reticulum described in other virus-host interactions. In this study we investigated the GPGV-induced membranous structures observed in the bundle sheath cells of infected plants. The upregulation of different ER stress-related genes was evidenced by RT-qPCR assays, further confirming the involvement of the ER in grapevine/GPGV interaction. Specific labelling of the membranous structures with an antibody against luminal-binding protein identified them as ER. Double-stranded RNA molecules, which are considered intermediates of viral replication, were localised exclusively in the ER-derived structures and indicated that GPGV exploited this organelle to replicate itself in a shelter niche. Novel analyses using focussed ion-beam scanning electron microscopy (FIB-SEM) were performed in grapevine leaf tissues to detail the three-dimensional organisation of the ER-derived structures and their remodelling due to virus replication

Preparations of Poly(lactic acid) Dispersions in Water for Coating Applications

A green, effective methodology for the preparation of water-based dispersions of poly(lactic acid) (PLA) for coating purposes is herein presented. The procedure consists of two steps: in the first one, an oil-in-water emulsion is obtained by mixing a solution of PLA in ethyl acetate with a water phase containing surfactant and stabilizer. Different homogenization methods as well as oil/water phase ratio, surfactant and stabilizer combinations were screened. In the second step, the quantitative evaporation of the organic provides water dispersions of PLA that are stable, at least, over several weeks at room temperature or at 4 °C. Particle size was in the 200–500 nm range, depending on the preparation conditions, as confirmed by scanning electron microscope (SEM) analysis. PLA was found not to suffer significant molecular weight degradation by gel permeation chromatography (GPC) analysis. Furthermore, two selected formulations with glass transition temperature (Tg) of 51 °C and 34 °C were tested for the preparation of PLA films by drying in PTFE capsules. In both cases, continuous films that are homogeneous by Fourier-transform infrared spectroscopy (FT-IR) and SEM observation were obtained only when drying was performed above 60 °C. The formulation with lower Tg results in films which are more flexible and transparent

Organocatalytic synthesis of poly(hydroxymethylfuroate) via ring-opening polymerization of 5-hydroxymethylfurfural-based cyclic oligoesters

The synthesis of hydroxymethylfuroate macrocyclic oligoesters c(HMF)(n) promoted by an N-heterocyclic carbene (NHC) organocatalyst is herein presented together with the subsequent organocatalytic, entropically-driven ring-opening polymerization (ED-ROP) leading to the fully furan-based poly(hydroxymethylfuroate) (PHMF). The target macrocycles (mostly trimer and tetramer species) have been obtained directly from the platform chemical HMF (77% isolated yield) under high dilution conditions using a quinone as the external oxidant and the green solvent Me-THF. The ED-ROP of c(HMF)(n) has been optimized at 160 degrees C (melt condensation technique) with the couple triazabicyclodecene (TBD)/n-octanol (1 : 1) as catalyst/initiator of the polymerization process in the presence of commercial antioxidants Irganox 1010 (0.1% w/w) and Irgafos 126 (0.3% w/w) to suppress degradation side reactions. Under these conditions, the bio-based PHMF (poly-HMF) was obtained as a color-free polymer with number-average molecular weight up to 48 600 g mol(-1) and dispersity between 1.5 and 1.9 as determined by NMR and GPC analyses. The thermal behavior of the novel furan-based polyester PHMF was investigated (TGA and DSC analyses) observing a good thermal stability (onset temperature of degradation similar to 310 degrees C) and a semicrystalline structure with melting temperature above 160 degrees C when processed from solvent, thus making PHMF a promising material for processing as other commercial polyesters