Nutricioni i hormonalni faktori rastenja kalusnog tkiva graška

A callus tissue was obtained from an immature embryo of Meteor pea (Pisum sativum cv. Meteor) and its requirements for optimal growth were investigated. The tissue showed rather peculiar responses in respect to the concentration of mineral salts, to the carbohydrate used and to the kind of auxin supplied to the medium. Of the five mineral solutions tested, only two could support growth, in which the concentration of mineral salts was relatively high. It was not possible to show the specific role for any particular element. However, the stimulating effect of any ion was not evident, unless the content of potassium was increased at the same time. Sucrose was the best carbon source, while the tissue could not grow on media containing glucose or fructose. The addition of thiamine was necessary, while nicotinic acid had a beneficial effect. An absolute requirement for auxin was shown. Only the synthetic auxins could stimulate growth of the tissue, while IAA was almost ineffective. Cytokinins and gibberellic acid were not needed, but they considerably increased the weight of the tissue.Kalusna kultura tkiva graška (Pisum sativum L. cv. Meteor) dobijena je od nezrelog embriona i ispitivani su faktori neophodni za njeno optimalno rastenje. Od pet mineralnih rastvora samo dva, koji imaju relativno visoku koncentraciju mineralnih soli, mogu da stimuliraju rastenje. Nijedan elemenat posebno nema u tome specifičnu ulogu. Međutim, stimulativni efekat bilo kog jona opaža se samo ako je u isto vreme i koncentracija kalij uma povećana. Najbolji izvor ugljenika je saharoza, dok na rastvorima sa glukozom ili fruktozom tkiva ne mogu da rastu. Vitamin Bt je neophodan za rastenje, dok nikotinska kiselina ima povoljan efekat. Takođe je pokazano da je neophodno dodavati auksin. Međutim, samo sintetički auksini mogu da indukuju rastenje, a IAA je skoro sasvim neaktivna. Citokinini i giberelini nisu neophodni, ali znatno povećavaju težinu tkiva

Horse chestnut pollen quality

Pollen quality of horse chestnut, expressed as pollen productivity, viability and germination was studied. Anthers of horse chestnut genotypes had pollen production from 3.66 to 5.06 x 10 3 pollen grains per anther, depending of genotype. Also, pollen of horse chestnut Ah1-Ah4 genotypes showed different viability (from 56 to 68%), after staining with fluorescein diacetate. Pollen germination of Ah1-Ah4 genotypes varied from 50-66% on basic medium. Inclusion of polyethylene glycol-PEG from 10%, 15% and 20% v/w increased pollen germination. The best results were achieved on medium with the largest PEG concentration. On these medium 76-91% pollen grains were germinated, depending of genotype. The best pollen quality, for all tested parameters, had genotype Ah2. Knowledge about morphology, production, viability, in vitro germination, tube growth as well as pollen: ovule ratio can be of great importance for future pollen biology studies.Genetika (2017), 49(1): 105-11

Abstract metric spaces and Hardy-Rogers-type theorems

The purpose of the present paper is to establish coincidence point theorem for two mappings and fixed point theorem for one mapping in abstract metric space which satisfy contractive conditions of Hardy-Rogers type. Our results generalize fixed point theorems of Nemytzki [V.V. Nemytzki, Fixed point method in analysis, Uspekhi Mat. Nauk 1 (1936) 141-174], Edelstein I M. Edelstein, On fixed and periodic point under contractive mappings, J. Lond. Math. Soc. 37 (1962) 74-79] and Huang, Zhang [LG. Huang, X. Zhang, Cone metric spaces and fixed point theorems of contractive mappings, J. Math. Anal. Appl. 332 (2)(2007) 1468-1476] from abstract metric spaces to symmetric spaces (Theorem 2.1) and to metric spaces (Theorem 2.4, Corollaries 2.6-2.8). Two examples are given to illustrate the usability of our results

Stem segment in vitro culture of chrysanthemum as a method for micropropagation

The effect of several nutritional media on in vitro shoot multiplication of 13 chrysanthemum cultivars grown in our country was investigated. Medium supplemented with a-naphtalenacetic acid and 6-benzylaminopurine was the most efficient for shoot multiplication. The highest shoot multiplication index was achieved for cultivar 'Tigerrag'. Successful rooting of shoots, depending on cultivars, was obtained on a hormone free medium. Acclimatization of 'in vitro' plants was 55-84%. After growing in the field under suitable photoperiod regime, all cultivars flowered.Proučavan je uticaj nekoliko hranljivih podloga na in vitro umnožavanje izdanaka 13 sorti hrizantema koje se gaje u našoj zemlji. Hranljive podloge obogaćene a-naftil sirćetnom i benzil-aminopurinom su bile najefikasnije za mikropropagaciju izdanaka. Najveći indeks umnožavanja izdanaka je postignut kod sorte 'Tigerrag'. Uspešno ožiljavanje (81-100%), u zavisnosti od sorte, je postignuto na hranljivoj podlozi bez hormona. Aklimatizacija 'in vitro' biljčica hrizantema se kretala u opsegu od 55-84%. Posle gajenja u uslovima polja pri odovarajućem fotoperiodu sve sorte su cvetale

Performances of Vermiculite and Perlite Based Thermal Insulation Lightweight Concretes

This experimental study was conducted with an aim to investigate the effect of the elevated temperature on the mineral phase composition, microstructure and mechanical properties of the thermal insulation lightweight concretes. The first group of experimental concretes was based on the expanded vermiculite and expanded perlite used as lightweight aggregates (in 65 wt%) in combination with either ordinary Portland cement or refractory calcium aluminate cement. The mix-design of the second group of concretes comprised standard quartz aggregate, vermiculite or perlite as aggregate replacement (25 wt%) and binder (PC or CAC). A total of 10 concrete mix-designs were fabricated in form of 40x40x160 mm samples which were submitted to heat-treatment at 400 degrees, 600 degrees, 800 degrees and 1000 degrees C upon standard 28-days period of curing and hardening. The changes in crystallinity and mineral phase composition induced by temperature were monitored by X-ray diffraction technique. Microstructural visualizations of the non-fired and fired concrete samples were conducted by scanning electron microscopy accompanied with EDX analysis. The results indicated that despite the decrease in compressive strengths upon firing, investigated lightweight concretes can be categorized both as thermal insulators and structural materials

Corundum and Bauxite Refractory Shotcretes based on Activated Waste Coal Ash: Investigation of Thermally Induced Properties Change

The necessity for application of activated secondary raw materials in refractory industry is caused by a growing demand for refractory castables with advanced properties and continuous technological evolution of high-temperature materials. In this investigation, refractory shotcretes with the same matrix composition were prepared from 15 wt.% of high aluminate cement and 45 wt.% of bauxite aggregate + 30 wt.% of chamotte filler, i.e. 75% of corundum aggregate. The request for obtaining a low-cement castable is fulfilled by application of 10 wt.% of mechanically activated coal ash as the cement substitution in the shotcretes. The ash was activated by means of various high energy mechano-activators. Results were compared in order to choose the most efficient activation procedure. The properties have been studied at temperatures ranging from room temperature to adopted maximal temperature 1400°C. Mechanisms of hydration and sintering were investigated by means of differential thermal analysis at three different heating rates. The measurements showed different activation energies for ordinary shotcretes and shotcretes with activated ash. The evolution of the refractory shotcretes properties was investigated and correlated to microstructural changes induced by temperature and microfiller addition. The combination of advantages in investigated refractory shotcretes makes them suitable for use in severe conditions at high temperature applications especially in refractory industries

Leaching of the potentially toxic pollutants from composites based on waste raw material

Odlaganje letećeg pepela dobijenog u procesu sagorevanja uglja u termo-elektranama predstavlja veliki rizik za prirodnu sredinu zbog mogućnosti luženja opasnih čestica kao što su toksični metali. Takođe, opasnost od izluživanja je prisutna čak i kada je leteći pepeo ugrađen u konstukcioni kompozit. Leteći pepeli sa različitih deponija su upotrebljeni za spravljanje uzoraka različitih kompozita (malter, beton ili opeka) pri čemu na pepelu nije sproveden nikakav fizički ili termički pred-tretman. Ispitivano je luženje potencijalno toksičnih elemenata prisutnih u proizvodima na bazi letećeg pepela. Praćeno je izluživanje i mogući uticaj na prirodnu sredinu 11 potencijalno opasnih elemenata: Pb, Cd, Zn, Cu, Ni, Cr, Hg, As, Ba, Sb i Se. Sprovedeno je detaljno istraživanje fizičko-hemijskih svojstava letećeg pepela, sa posebnim naglaskom na ispitivanju hemijskog sastava i prisutnosti elemenata u tragovima. Fizičko-hemijska svojstva pepela su ispitivana sledećim metodama: X-ray fluorescenicija, difrakciona termička analiza i X-ray difrakciona metoda. Skenirajući elektronski mikroskop je primenjen u mikrostukturnoj analizi. Rezultati su pokazali da se većina elemenata lakše izlužuje iz pepela nego kompozita spravljenih na bazi pepela. Izluživanje svih ispitivanih toksičnih elemenata je bilo u dozvoljenim granicama što znači da se ispitivani leteći pepeo može upotrebiti u proizvodnji konstrukcionih materijala.The disposal of fly ash generated in coal based power-plants may pose a significant risk to the environment due to the possible leaching of hazardous pollutants, such as toxic metals. Also, there is a risk of leaching even when fly ash is built in the construction composites. Fly ashes from various landfills were applied in several composite samples (mortar, concrete and brick) without any physical or thermal pre-treatment. The leachability of the potentially toxic pollutants from the fly ash based products was investigated. The leaching behaviour and potential environmental impact of 11 potentially hazardous elements was tracked: Pb, Cd, Zn, Cu, Ni, Cr, Hg, As, Ba, Sb and Se. A detailed study of physico-chemical characteristics of the fly ash, with an accent on trace elements and the chemical composition investigation is included. Physicochemical properties of fly ash were investigated by means of X-ray fluorescence, differential thermal analysis and X-ray diffraction methods. Scanning electron microscopy was used in microstructure analysis. The results show that most of the elements are more easily leachable from the fly ash in comparison to the fly ash based composites. The leaching of investigated pollutants is within allowed range thus investigated fly ashes can be reused in construction materials production

Stem segment in vitro culture of chrysanthemum as a method for micropropagation

The effect of several nutritional media on in vitro shoot multiplication of 13 chrysanthemum cultivars grown in our country was investigated. Medium supplemented with a-naphtalenacetic acid and 6-benzylaminopurine was the most efficient for shoot multiplication. The highest shoot multiplication index was achieved for cultivar 'Tigerrag'. Successful rooting of shoots, depending on cultivars, was obtained on a hormone free medium. Acclimatization of 'in vitro' plants was 55-84%. After growing in the field under suitable photoperiod regime, all cultivars flowered.Proučavan je uticaj nekoliko hranljivih podloga na in vitro umnožavanje izdanaka 13 sorti hrizantema koje se gaje u našoj zemlji. Hranljive podloge obogaćene a-naftil sirćetnom i benzil-aminopurinom su bile najefikasnije za mikropropagaciju izdanaka. Najveći indeks umnožavanja izdanaka je postignut kod sorte 'Tigerrag'. Uspešno ožiljavanje (81-100%), u zavisnosti od sorte, je postignuto na hranljivoj podlozi bez hormona. Aklimatizacija 'in vitro' biljčica hrizantema se kretala u opsegu od 55-84%. Posle gajenja u uslovima polja pri odovarajućem fotoperiodu sve sorte su cvetale

Clonal fidelity of chrysanthemum regenerated from long term cultures

Morphological characteristics of flowers of long term regenerated chrysanthemum, cv. "White Spider", after ten years of micropropagation are investigated. Shoot cultures are established and maintained more than ten years by stem segment culture on MS medium supplemented with BAP and NAA (1.0, 0.1 mgL-1, respectively). Rooting of shoots (100 %) has done on MS medium without hormones and it was very successful after ten years, as well as, after two or eight years of micropropagation. Acclimation of rooted chrysanthemum plantlets at greenhouse conditions was excellent and after appropriate photoperiod "in vitro" plants flowered 90.3 % and have the same flower color, shape and size as mother plants. Flower color changes of "in vitro" plants are observed during another flowering cycle one year after acclimatization. Observed variations of chrysanthemum flowers could be attributed to epigenetic factors.Praćene su morfološke karakteristike cvetova regeneranata cv. "White Spider" posle deset godina gajenja u kulturi in vitro. Izdanci su umnožavani u kulturi segmenata stabla preko aksilarnih pupoljaka na MS podlozi sa α-naftilsirćetnom kiselinom i benzilaminopurinom (0,5 odnosno 1,0 mgL-1), . Praćeno je umnožavanje izdanaka u periodu od devetnaest pasaža (tri godine) kada je došlo do sukcesivnog smanjenja indeksa umnožavanja. Oživljavanje izdanaka je praćeno na MS podlozi bez hormona i bilo je podjednako uspešno posle dve, kao i posle osam i deset godina mikropropagacije. Oživljene biljke hrizantema su uspešno aklimatizovane na uslove staklenika (97 %). Nakon odgovarajućeg fotoperioda, 90,3 % biljaka je cvetalo i imale su identičnu boju cveta matičnim biljkama hrizantema. Promene u boji cveta su uočene kod "in vitro" biljaka u sledećem ciklusu cvetanja, tj. godinu dana posle aklimatizacije. Ove promene bi se mogle pripisati epigenetskim faktorima.nul