STUDY OF THE CHARACTERISTICS OF INORGANIC LAYERS OBTAINED BY PLASMA-CHEMICAL PRECIPITATION ON POLYMERS

Les méthodes de l'XPS, la spectroscopie IR de la réflexion de surface et la spectroscopie électronique ont été utilisées pour l'étude des couches inorganiques obtenues sur le polymère pendant la synthèse plasmochimique. Les couches de Si3N4, ALN, SiO2 ont été synthétisées sur la surface des polymides par des méthodes plasmochimiques diverses. Les investigations par la méthode XPS ont démontrées que le substrat polymérique participe activement au processus de la synthèse. L'étude par la microscopie électronique des étapes initiales a démontrée que la croissance commence par la formation de noyaux ayant le structure de dendrites typiques pour les couches polymériques déposées. Les résultats expérimentaux permettent de tirer la conclusion qu'il est possible d'obtenir les diverses structures polymére-inorganiques à l'exception entièrement de l'interface.Inorganic films obtained on the polymer support during plasma-chemical synthesis have investigated by XPS, IR-reflectance spectroscopy and SEM. The layers of Si3 N4, ALN, SiO2 were obtained of plasma chimical precipitation on the surface of polyimide films. The results of XPS investigations showed that the polymer support takes an active part in the formation of the inorganic film. The data of electron microscopy in the initial stages of film growth indicate that in the first stage nuclei are formed. They are uniformly distributed on the surface of the polymer support and exhibit a pronounced dendrite structure. The experimental results suggest that under experimental conditions makes it possible to obtain various polymer-inorganic structure devoid of the interface

Glutathione peroxidase regulation of reactive oxygen species level is crucial for in vitro plant differentiation.

Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is overexpressed in plants under abiotic and biotic stress conditions that mediate oxidative stress. To study its biological role and its ability to confer stress resistance in plants, we tried to obtain transgenic plants overexpressing citrus (Citrus sinensis) PHGPx (cit-PHGPx). All attempts to obtain regenerated plants expressing this enzyme constitutively failed. However, when the enzyme's catalytic activity was abolished by active site-directed mutagenesis, transgenic plants constitutively expressing inactive cit-PHGPx were successfully regenerated. Constitutive expression of enzymatically active cit-PHGPx could only be obtained when transformation was based on non-regenerative processes. These results indicate that overexpression of the antioxidant enzyme PHGPx interferes with shoot organogenesis and suggests the involvement of reactive oxygen species (ROS) in this process. Using transgenic tobacco (Nicotiana tabacum) leaves obtained from plants transformed with a beta-estradiol-inducible promoter, time-dependent induction of cit-PHGPx expression was employed. A pronounced inhibitory effect of cit-PHGPx on shoot formation was found to be limited to the early stage of the regeneration process. Monitoring the ROS level during regeneration revealed that upon cit-PHGPx induction, the lowest level of ROS correlated with the maximal level of shoot inhibition. Our results clearly demonstrate the essential role of ROS in the early stages of in vitro shoot organogenesis and the possible involvement of PHGPx in maintaining ROS homeostasis at this point