Erzsébet Mihalik

Cadmium-induced oxidative stress and antioxidative mechanisms in germinating Indian mustard (Brassica juncea L.) seeds

Cadmium, known as a non-essential heavy metal, can cause oxidative stress in plants. In this study we tried to find out whether oxidative changes could be measured in the early stages of ontogenesis in Indian mustard (Brassica juncea L.) seeds exposed to Cd stress. Cadmium-caused oxidative stress and antioxidative responses were investigated with respect to both time- and concentration-dependence. Parameters that were measured were follows: total antioxidant capacity (ferric reducing ability of plasma (FRAP)), glutathione (GSH) content, level of lipid peroxidation (LP), total protein content, and glutathione-S-transferase (GST, EC 2.5.1.18) activity. Seeds were germinated in vitro at 0, 50, 100 and 200mg/LCd concentrations in dark for 12, 24, 48 and 96h. Oxidative stress occurred in the seeds due to Cd treatment, the level of LP was high at the beginning of the germination at all concentrations used, but it attenuated later on. FRAP showed concentration-dependent increase during 24h, but it decreased later on. GSH content was also elevated by increasing concentrations of Cd, which referred to the activity of non-enzymatic antioxidant system. The GST activity induced with germination only after 24h at the highest Cd concentration. The results show that FRAP is a suitable parameter with which to assess the antioxidant capacity of heavy metal-stressed germinating seeds.

Corrosive effects of fluoride on titanium: Investigation by X-ray photoelectron spectroscopy, atomic force microscopy, and human epithelial cell culturing

High fluoride (F(-)) concentrations and acidic pH impair the corrosion resistance of titanium (Ti). Effects of F(-)-containing caries-preventive prophylactic rinses, and gels on Ti were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Human epithelial cell attachment and proliferation were investigated by dimethylthiazol-diphenyl tetrazolium bromide (MTT) and protein content assays. Aqueous 1% NaF solution (3800 ppm F(-), pH 4.5) or high (12,500 ppm) F(-) content gel (pH 4.8) strongly corroded the surface and modified its composition. XPS revealed formation of a strongly bound F(-)-containing complex (Na(2)TiF(6)). AFM indicated an increase in roughness (R(a)) of the surfaces: 10-fold for the NaF solution and smaller for the gel or a mouthwash (250 ppm F(-), pH 4.4). MTT revealed that cell attachment was significantly increased by the gel, but was not disturbed by either the mouthwash or the NaF. Cell proliferation determined by MTT decreased significantly only for the NaF-treated samples; protein content assay experiments showed no such effect. This study indicates that epithelial cell culturing results can depend on the method used, and the adverse effects of a high F(-) concentration and low pH should be considered when prophylactic gels are applied by patients with Ti implants or other dental devices.

Regularities of the essential oil accumulation in developing fruits of fennel (Foeniculum vulgare Mill.) and its histological background

Abstract Production biological and anatomical background of essential oil accumulation in the developing fruits of Foeniculum vulgare Mill, subsp. vulgare var. vulgare (chemovar.; anethole, chemoform; low anethole - low methyl chavicol) were studied. Nine different stages of development of generative organs were distinguished for analysis. It was proved by histological investigations, that oil ducts (vittae) are present in the early stages of development of generative organs, even at the time of bud formation, however their relative area (calculated to the cross section) shows maximum at the time of seed setting (53.6%). The oil yield shows its maximum (11.6%) at that special time and in the early development stages of fruits, when the relative ratio of oil ducts is high and the accumulation of the assimilates (development of endosperm) have not started yet. In contrary the oil yield calculated to one schizocarp is increasing up to the final ripening stages (0.787 μL/fruit) and the process can be describe...

Morph-specific variation of floral traits associated with reciprocal herkogamy in natural populations of Primula vulgaris and Primula veris

Documenting the morph-specific variation of floral traits associated with reciprocal herkogamy is of special importance for revealing the functional significance of traits in the evolution and maintenance of the heterostylous syndrome. In order to describe the extent and specificity of variation, stigma height, anther height, stigma-anther separation and corolla tube length were measured on 800 flowers collected in two natural populations of Primula vulgaris and P. veris. Beside the almost complete separation of stigma heights between the two morphs, we found appreciable intermorph overlap in anther height and relatively broad range of stigma-anther separation so far reported for heterostylous species. The corolla tube length–stigma-anther separation relationship showed striking difference between the two floral morphs, which supports the hypothesis that length of the corolla tube plays a more important role in positioning the sex-organs in the appropriate distance in the short-styled than in the long-styled morph.

Pattern of the floral variation in the hybrid zone of two distylous Primula species

Summary Pattern of the floral variation was investigated in the hybrid zone of two distylous Primula species. The three taxa of the P. vulgaris × P. veris hybrid zone were identified on the basis of flower color and inflorescence structure. Hybrids were significantly different from the two parental species for all the floral characters examined: four out of the seven characters exhibited extreme values, and three characters were intermediate. The lack of great morphological variation and histograms of the characters exhibiting intermediate values in hybrids give the impression that there is no introgression in the studied hybrid zone. Stigma heights and, to a lesser degree, anther heights were in two discrete classes corresponding to short-styled and long-styled flowers in all the three taxa. Relative reciprocity ratios and examination of individual flowers revealed that there was strict reciprocity between anther and stigma heights in the two parental species, but reciprocity was strongly broken in the hybrids. Both stigma and anther heights showed considerable relationship with corolla tube length, and increasing corolla tube length resulted in deviation from the strict reciprocity in both floral morphs. Short-tubed long-styled and long-tubed short-styled flowers seem to be at a disadvantage in mating, and this might explain the extremely low variability of corolla tube length. Our results on the floral morphology indicate that there are no barriers against formation of the F 1 hybrids in the adjacent populations of the two parental species. A possible explanation for the lack of introgression is also discussed.

Floral traits affecting fire blight infection and management

Erwinia amylovora, the causative agent of fire blight, colonizes primarily the flowers of the sub-family Maloideae. Commercially important fruit tree species such as apple (Malus domestica) and pear (Pyrus communis) are also affected by the disease. Epiphytic bacterial populations develop on the stigma, from where the pathogen colonizes the hypanthium, aided by moisture. Under favorable conditions, nectar provides a rich medium for growth, which allows bacterial invasion of tissues through the stomata of the nectary. The paper reviews various floral traits that may play a role in the onset and progression of the infection. Flower age, stigma morphology and longevity, the size of epiphytic bacterial population, morphology of the hypanthium, anatomy of the nectary, dynamics of nectar secretion, as well as the volume, concentration and composition of the nectar are discussed in detail, comparing traits of susceptible versus tolerant apple and pear cultivars. Management programs, aiming at the suppression of E. amylovora on floral parts by antibiotics, chemical compounds, natural substances or biological control agents, are also discussed.

Degradation of native feathers by a novel keratinase-producing, thermophilic isolate, Brevibacillus thermoruber T1E.

Strain T1E, isolated and identifi ed as Brevibacillus thermoruber, and evolutionally distant from the known keratinolytic isolates, proved to have feather-degrading ability. During the 7-day fermentation period, T1E consumed 10 g/l native goose feathers as the sole source of carbon and energy at 50 oC under aerobic conditions. The isolate secreted a thermostable, keratinolytic protease, which exhibited activity optimally at pH 6.5, whilst it was inhibited at alkaline pH. The keratin cleavage and catabolism resulted in the accumulation of free aspartic acid and soluble peptides with maximum values of 31.6 and 720 mg/l, respectively. The majority of the fermentation end-products were found to be small oligopeptides with an average molecular mass of 2275 Da.

Effect of caries preventive products on the growth of bacterial biofilm on titanium surface.

Fluorides may affect the oxide layer on titanium surface. Caries preventive mouthwashes or gels contain fluorides and are applied at low pH. The aim of the present work was to study whether various concentrations of fluoride at acidic pH cause changes in the surface structure on the polished region of Ti implants, and alter the adherence and colonization of bacteria. Commercially pure Ti grade 4 discs with a polished surface were treated with a mouthwash containing 0.025% fluoride, a gel containing 1.25% fluoride or a 1% aqueous solution of NaF (pH 4.5). The change of surface roughness of the samples and the colonization of Porphyromonas gingivalis strains were studied by scanning electron microscopy after 5 days of anaerobic incubation. The quantity of the bacterial protein was determined by protein assay analysis. Agents with high fluoride concentration at acidic pH increased the roughness of the Ti surface. A slight increase in the amount of bacteria was found on the surfaces treated with 1% NaF and gel in comparison with the control surface. This study suggested that a high fluoride concentration at acidic pH may hinder the development of a healthy transgingival epithelial junction on Ti implants, due to bacterial colonization.