Interpretation of Stark broadening measurements on a spatially integrated plasma spectral line

In thermal plasma spectroscopy, Stark broadening measurement of hydrogen spectral lines is considered to be a good and reliable measurement for electron density. Unlike intensity based measurements, Stark broadening measurements can pose a problem of interpretation when the light collected is the result of a spatial integration. Indeed, when assuming no self-absorption of the emission lines, intensities simply add up but broadenings do not. In order to better understand the results of Stark broadening measurements on our thermal plasma which has an unneglectable thickness, a Python code has been developed based on local thermodynamic equilibrium (LTE) assumption and calculated plasma composition and properties. This code generates a simulated pseudo experimental (PE) H$\alpha$ spectral line resulting from an integration over the plasma thickness in a selected direction for a given temperature profile. The electron density was obtained using the Stark broadening of the PE spectral line for different temperature profiles. It resulted that this measurement is governed by the maximum electron density profile up until the temperature maximum exceeds that of the maximum electron density. The electron density obtained by broadening measurement is 70% to 80% of the maximum electron density.Comment: European Physical Journal: Applied Physics, EDP Sciences, 202

Retraction Notice: Interpretation of Stark broadening measurements on a spatially integrated plasma spectral line

At the request of the corresponding Author, this article has been retracted. Shortly after publication, the Editorial Board of EPJ Applied Physics received comments from the corresponding Author. He informs that he has found an error in the numerical determination of the PE spectral line. According to him, this error does not affect the construction of the paper or its conclusions. The Authors prefer to submit again the manuscript with the correct results, to the journal for evaluation and a republication could be considered. The errors can be found highlighted in yellow in the Supplementary material

Interpretation of Stark broadening measurements on a spatially integrated plasma spectral line.

In thermal plasma spectroscopy, Stark broadening measurement of hydrogen spectral lines is considered to be a good and reliable measurement for electron density. Unlike intensity based measurements, Stark broadening measurements can pose a problem of interpretation when the light collected is the result of a spatial integration. Indeed, when assuming no self-absorption of the emission lines, intensities simply add up but broadenings do not. In order to better understand the results of Stark broadening measurements on our thermal plasma which has an unneglectable thickness, a Python code has been developed based on local thermodynamic equilibrium (LTE) assumption and calculated plasma composition and properties. This code generates a simulated pseudo experimental (PE) Hα spectral line resulting from an integration over the plasma thickness in a selected direction for a given temperature profile. The electron density was obtained using the Stark broadening of the PE spectral line for different temperature profiles. It resulted that this measurement is governed by the maximum electron density profile up until the temperature maximum exceeds that of the maximum electron density. The electron density obtained by broadening measurement is 70% to 80% of the maximum electron density

The Medicago truncatula HKT family: Ion transport properties and regulation of expression upon abiotic stresses and symbiosis

Soil salinity is one of the most important abiotic stresses affecting plant growth. In legumes, symbiotic nitrogen fixation in nodules is affected by salt stress, and salinity tolerance is variable among species. Genes from the High affinity K+ Transporter (HKT) family are known to play crucial roles in salt stress tolerance in different plant species. In legumes these transporters are still very poorly characterized. . Here we study the HKT transporter family from the model legume Medicago trunacatula, which is moderately tolerant to salinity. The genome of this species comprises five HKT genes, hereafter named MtHKT1;1 to MtHKT1;5. Phylogenetic analysis indicated that the MtHKT polypeptides belong to HKT subfamily 1. Three members (MtHKT1;2, MtHKT1;4 and MtHKT1;5) of the Medicago truncatula family were cloned and expressed in Xenopus oocytes. Their electrophysiological properties revealed a permeability 10 times higher for Na+ than for K+ and varying rectification properties. Expression analyses of the three MtHKT genes under different biotic and abiotic conditions suggested that MtHKT1;5 is the main transporter from this family in the root, the three genes sharing a decrease of expression in drought and salt stress conditions in non inoculated plants as well as plants inoculated with rhizobia. In the shoot, the three MtHKT would be present at similar levels independently on the applied stresses. Based on biomass and ion content analysis, the nodule appeared as the most sensitive organ to the applied salt and drought stresses. The level of expression of the three MtHKT genes was strongly decreased by both stresses in the nodule

Medicago truncatula possesses a single Shaker outward K+ channel: functional characterization and roles in planta

The model legume Medicago truncatula possesses a single outward Shaker K+ channel, while Arabidopsis thaliana possesses two channels of this type, named SKOR and GORK, the former having been shown to play a major role in K+ secretion into the xylem sap in the root vasculature and the latter to mediate the efflux of K+ across the guard cell membrane upon stomatal closure. Here we show that the expression pattern of the single M. truncatulaoutward Shaker channel, which has been named MtGORK, includes the root vasculature, guard cells and root hairs. As shown by patch-clamp experiments on root hair protoplasts, besides the Shaker-type slowly-activating outwardly-rectifying K+ conductance encoded by MtGORK, a second K+-permeable conductance, displaying fast activation and weak rectification, can be expressed by M. truncatula. A KO mutation resulting in absence of MtGORK activity is shown to weakly reduce K+ translocation to shoots, and only in plants engaged in rhizobial symbiosis, but to strongly affect the control of stomatal aperture and transpitational water loss. In legumes, the early electrical signaling pathway triggered by Nod Factor perception is known to comprise a short transient depolarization of the root hair plasma membrane. In absence of MtGORK functional expression, while the rate of the membrane repolarization is shown to be decreased by about 3 times, this defect is without any consequence on infection thread development and nodule production, indicating that the plant capacity to engage rhizobial symbiosis does not require integrity of the early electrical signaling event

Functional characterization and physiological roles of the single Shaker outward K + channel in Medicago truncatula

Functional characterization and physiological roles of the single Shaker outward K + channel in Medicago truncatul

Nuclear-localized cyclic nucleotide-gated channels mediate symbiotic calcium oscillations

Nuclear-associated Ca2+ oscillationsmediate plant responses to beneficial microbial partners—namely, nitrogen-fixing rhizobial bacteria that colonize roots of legumes and arbuscular mycorrhizal fungi that colonize roots of the majority of plant species. A potassium-permeable channel is known to be required for symbiotic Ca2+ oscillations, but the calcium channels themselves have been unknown until now.We show that three cyclic nucleotide–gated channels in Medicago truncatula are required for nuclear Ca2+ oscillations and subsequent symbiotic responses.These cyclic nucleotide–gated channels are located at the nuclear envelope and are permeable to Ca2+.We demonstrate that the cyclic nucleotide–gated channels form a complex with the postassium-permeable channel, which modulates nuclear Ca2+ release. These channels, like their counterparts in animal cells, might regulate multiple nuclear Ca2+ responses to developmental and environmental conditions

Prêtres et pasteurs

La fracture confessionnelle qui touche l’Occident chrétien au xvie siècle révolutionne durablement la place des clergés dans les sociétés et leur emprise sur les fidèles. Le principe originel du luthéranisme, puis des réformes de type suisse, du sacerdoce universel a été largement relativisé par la mise en place progressive d’un clergé protestant, mais il a ouvert une brèche que l’on peut suivre à l’époque des controverses et qui continue de fixer une différence fondamentale entre les deux camps. Pourtant, des influences réciproques et des contacts sont observables dans des zones de coexistence confessionnelle : les espaces de frontières peuvent faire figure d’observatoires privilégiés pour comprendre les influences réciproques entre clergés, jusque dans leur façon d’interpréter et de considérer le ministère pastoral et de forger leurs identités professionnelles et sociales. La formation des clergés, leur organisation, leur action, les oppositions auxquelles ils doivent faire face, leurs interactions, les points communs, voire les sociabilités de leurs membres sont ici étudiés à travers des pratiques très diverses (prédication, conférences et controverses, sociabilités érudites, missions, encadrement institutionnel, pratiques liturgiques, répression des déviances, ou encore définition de mémoires concurrentes). Ces études de cas nous plongent dans le processus de définition d’identités cléricales qui se constituent certes souvent contre l’autre, mais aussi, plus subtilement, en fonction de l’autre et sur des fondements communs

Prêtres et pasteurs

La fracture confessionnelle qui touche l’Occident chrétien au xvie siècle révolutionne durablement la place des clergés dans les sociétés et leur emprise sur les fidèles. Le principe originel du luthéranisme, puis des réformes de type suisse, du sacerdoce universel a été largement relativisé par la mise en place progressive d’un clergé protestant, mais il a ouvert une brèche que l’on peut suivre à l’époque des controverses et qui continue de fixer une différence fondamentale entre les deux camps. Pourtant, des influences réciproques et des contacts sont observables dans des zones de coexistence confessionnelle : les espaces de frontières peuvent faire figure d’observatoires privilégiés pour comprendre les influences réciproques entre clergés, jusque dans leur façon d’interpréter et de considérer le ministère pastoral et de forger leurs identités professionnelles et sociales. La formation des clergés, leur organisation, leur action, les oppositions auxquelles ils doivent faire face, leurs interactions, les points communs, voire les sociabilités de leurs membres sont ici étudiés à travers des pratiques très diverses (prédication, conférences et controverses, sociabilités érudites, missions, encadrement institutionnel, pratiques liturgiques, répression des déviances, ou encore définition de mémoires concurrentes). Ces études de cas nous plongent dans le processus de définition d’identités cléricales qui se constituent certes souvent contre l’autre, mais aussi, plus subtilement, en fonction de l’autre et sur des fondements communs

Nod Factor Effects on Root Hair-Specific Transcriptome of Medicago truncatula: Focus on Plasma Membrane Transport Systems and Reactive Oxygen Species Networks.

International audienceRoot hairs are involved in water and nutrient uptake, and thereby in plant autotrophy. In legumes, they also play a crucial role in establishment of rhizobial symbiosis. To obtain a holistic view of Medicago truncatula genes expressed in root hairs and of their regulation during the first hours of the engagement in rhizobial symbiotic interaction, a high throughput RNA sequencing on isolated root hairs from roots challenged or not with lipochitooligosaccharides Nod factors (NF) for 4 or 20 h was carried out. This provided a repertoire of genes displaying expression in root hairs, responding or not to NF, and specific or not to legumes. In analyzing the transcriptome dataset, special attention was paid to pumps, transporters, or channels active at the plasma membrane, to other proteins likely to play a role in nutrient ion uptake, NF electrical and calcium signaling, control of the redox status or the dynamic reprogramming of root hair transcriptome induced by NF treatment, and to the identification of papilionoid legume-specific genes expressed in root hairs. About 10% of the root hair expressed genes were significantly up- or down-regulated by NF treatment, suggesting their involvement in remodeling plant functions to allow establishment of the symbiotic relationship. For instance, NF-induced changes in expression of genes encoding plasma membrane transport systems or disease response proteins indicate that root hairs reduce their involvement in nutrient ion absorption and adapt their immune system in order to engage in the symbiotic interaction. It also appears that the redox status of root hair cells is tuned in response to NF perception. In addition, 1176 genes that could be considered as "papilionoid legume-specific" were identified in the M. truncatula root hair transcriptome, from which 141 were found to possess an ortholog in every of the six legume genomes that we considered, suggesting their involvement in essential functions specific to legumes. This transcriptome provides a valuable resource to investigate root hair biology in legumes and the roles that these cells play in rhizobial symbiosis establishment. These results could also contribute to the long-term objective of transferring this symbiotic capacity to non-legume plants