No abstract

No abstract

The effect of phosphate starvation on growth and acid phosphatases (APases) localization and activity in oat tissues was investigated. Oat cultivars (Avena sativa L.-Arab, Polar, Szakal) were grown for 1-3 weeks in complete nutrient medium (?P) and without phosphate (-P). Pi concentration in plant tissues decreased strongly after culturing on -P medium. Pi deficit reduced shoot growth, stimulated root elongation and increased ratio of root/shoot in all oat cultivars. Pi deficit had a greater impact on growth of oat cv. Polar than other varieties. A decrease in the internal Pi status led to an increase of acid phosphatase activities in extracts from shoots and roots, and in root exudates. The highest activity of secreted APases was observed for oat cv. Arab, during the third week of growth under Pi-deficient conditions. The activity of extracellular APase was high in young, growing zones of roots of -P plants. Histochemical visualization indicated high activity of APases in the epidermis and vascular tissues of -P plants. Pi deficiency increased intracellular APase activity in shoot mainly in oat cv. Polar, whereas APase activity in roots was the highest in oat cv. Szakal. Protein extracts from roots and shoots were run on native discontinuous PAGE to determine which isoform(s) may be affected by Pi deficiency. Three major APase isoforms were detected in all oat plants; one was strongly induced by Pi deficit. The studied oat cultivars differed in terms of acclimation to deficiency of phosphate-used various pools of APases to acquire Pi from external or internal sources.

Coating materials based on siloxane-containing polymer matrices that had been modified with fluoropolymer or acrylic resins and applied as organic components of hybrid systems were examined. The optimal recipes of the dispersion systems, applied as polymer matrix precursors, were determined on the basis of factorial experiments, designed as 2 2 with additional 'star' experimental points to obtain greater accuracy in the resulting regression equations. The siloxane cage formation was based on the following crosslinking reactions of functional polysiloxanes: (1) hydrosilylation of vinyl groups; (2) condensation of silanol groups. Moreover, the molecular modeling, using P3 semi-empirical methods, was applied to build the model structure of a siloxane-containing polymer matrix. The surface properties of these coatings were studied using wettability assessments (dynamic contact angle and surface-free energy evaluation), atomic force microscopy (AFM), and X-ray electron microscopy (ESCA-XPS). The morphology, roughness, and structural regularity are discussed to illustrate the effects of the organic component on the surface properties. The most significant changes were observed in the surface morphology of the coatings. The application properties of such coating materials for the protection of buildings were tested, based on studies of their water vapor permeability, water absorption, and weathering resistance (freezing/thawing, salt-saturated aqueous sodium sulfate solution). The effect of the chemical structure of the siloxane-containing polymer matrix on the properties of the resulting coatings was focused on the protection of porous building materials. A very good correlation of the application properties of these coating materials and their surface properties, such as high dynamic contact angle (DCA), low surface-free energy (SFE) and surface morphology, was observed and is discussed.

Silicone-containing hybrid systems including functionalized and modified silica nanospheres as well as silica aerogels were synthesized using sol-gel process. The most important advantage of the developed silicon-containing hybrids lies in their high application potential, e.g. for the production of façade paints, polymer nanocomposites, highly efficient insulating materials and other high-tech products for construction industry. The possibility of precise steering of sol-gel process and synergism of very rich silicon compound chemistry allows to obtain materials with strategically designed architecture. Original methods of manufacturing following silicon-containing hybrids such as functionalized and non-functionalized silica nanospheres, silica nanospheres containing immobilized silver and/or copper nanoparticles and silica aerogels were developed. Homogeneous structural properties of synthesized materials were achieved due to carefully selected parameters of sol-gel process. The technology offers a possibility to control the grain size and uniformity of nanospheres by process parameters. The smallest nanosphere size is 10 nm and the largest 600 nm. The properties of aerogels obtained according to the original technology developed in the Industrial Chemistry Research Institute (ICRI) are extremely good and repetitive particularly taking into account their thermal conductivity. The main advantages of the developed aerogels are very good mechanical properties, very low dust formation and significantly decreased costs when compared to traditional silica aerogels.