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Authors provide a 6-year study about aspects of development of Cameraria ohridella and its parasitoids in different leaf types of horse-chestnut trees. Investigations were carried out near Hédervár, North-West Hungary between 1999 and 2004.It was ascertained that in large leaves at low foliage levels as well as in large leaves exposed to direct sunlight developed more moths than in other leaf types of equal quantity (i.e. equal number of leaflets). On the other hand, there were not considerable differences between shaded and sun-exposed leaves in this regard if their quantity is measured in grams. Moreover, comparing the numbers of hatched moths per unit leaf weight, the values for minute leaves were the highest. The differences were explained on the basis of diverse microclimatic conditions in the mines, height preference of the moth or variations in dry weights per unit leaf area.Parasitism of Cameraria ohridella showed significant yearly differences between canopy levels and a tendency of changes during the years. Parasitism was higher in shaded than in sun-exposed leaves. Lowest values were found in minute leaves among all leaf types investigated what was explained with a presumed foraging behaviour of the parasitoids.Structure and species constitution of the parasitoid community and its changes in time are discussed in different leaf types. Temporal changes of several characteristics found in different leaf types refer to an adaptation process of the horse-chestnut leafminer.

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The horse-chestnut leafminer is a new pest which was established in North-West Hungary ca. 10 years prior to these investigations. Due to the very limited time, there are relatively few studies on the parasitoid community of the moth and its connection with the leafminer host. Authors used twig-isolators to find out which larval/pupal instars are mostly parasitized and by which chalcidoid species. They also made an attempt to calculate density curves of different developmental stages of the moth and to compare them with flight curves of the parasitoids. Experiences indicated that 4-week-old larval (pupal) instars were parasitized to the highest degree. The most frequent parasitoids were Pediobius saulius and Pnigalio agraules . Statements about a poor synchronization between moth and parasitoids were confirmed but possibility of a shift in swarming times on location was suggested. Different methods to calculate rate of parasitism were compared and evaluated.

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This paper presents the so far only partially published research material of the late Bálint Zólyomi on one of his major fields of interest, the forest steppe vegetation. The phytosociological tables presented here were found in his bequest indicating that he was going to publish a grand synthesis on this topic, which, however, has not come true. Since no written text accompanied the original tables, a historical overview and a short explanation to the tables are also provided.

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Medium chain fatty acids are candidates of partial sulphur dioxide replacement in wine, as a solution to the growing consumer concerns about chemical additives. In botrytised sweet wine specialties, large amount of sulphur dioxide addition is one of the effective practices to stop alcoholic fermentation. Increasing medium chain fatty acid levels up to 80 mg l-1 was tested as a sole inhibitor on solid agar surface. S. bacillaris seemed to be the most sensitive, S. cerevsisiae and S. bayanus were more tolerant, while Z. bailii showed the highest tolerance. Then, increasing medium chain fatty acid levels up to 40 mg l-1 combined with 100 mg l-1 sulphur dioxide was introduced into a Tokaj Essence under refermentation. After 56 days, the highest dosage had pronounced effect on the yeast population, but the refermentation was not inhibited completely. Medium chain fatty acids have varying inhibitory effect on botrytised wine-related yeasts, moreover, it could be used effectively in media with high ethanol content, unlike Tokaj Essence.

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Experiments were carried out on sperm cryopreservation of two European percid fish species, the pikeperch (Sander lucioperca) and the Volga pikeperch (S. volgensis) . Two experiments were conducted on pikeperch sperm. In the first, the effects of three extenders (Glucose, KCl, Sucrose) and two cryoprotectants (dimethyl-sulfoxide: DMSO, methanol: MeOH) were tested on motility and fertilization. In the second, the effects of two dilution ratios (1: 1, 1: 9) and two cryoprotectants (DMSO, MeOH) on hatching were investigated. In the experiment on Volga pikeperch the suitability of using cryopreservation for fertilization was investigated. In the first experiment on pikeperch the highest post-thaw motility (28 ± 21%) and fertilization rate (43 ± 12%) was found with DMSO as cryoprotectant in combination with Glucose extender. In the second, the highest hatch rate (41 ± 22%) was observed with MeOH as cryoprotectant and 1: 1 sperm dilution ratio, however no significant difference was found among the results. In the experiment on Volga pikeperch hatch rates with cryopreserved sperm (60 ± 2%) did not significantly differ from the control (60 ± 6%). Contamination of sperm with urine seems to be a key problem in the success of sperm cryopreservation of these species.

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During the ageing in barrels, the contact with the fine lees triggers several processes in wine. Lees has a reductive effect by absorbing dissolved oxygen and reducing the amount, which will remain in the wine. At present, minimizing the addition of sulphur dioxide is the trend in all viticultural areas. In this study, the effect of various sulphur dioxide levels was monitored in presence of the lees to determine which dose is appropriate to provide the protection of susceptible white wine against oxidation.

Without SO2 protection, the rH and redox potential changed slightly, so the level of dissolved oxygen seemed to be controlled during the ageing period by the lees, though the antioxidant effect of lees in itself was not appropriate to protect the polyphenol content from chemical oxidation, which led to considerable browning. With the addition of a lower amount of SO2 — 40 mg l2, the lees is already able to protect the white wine samples in all aspects.

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Certain classes of bioactive compounds can be separated using planar chromatography. Some biological effects (e.g. antibacterial) of these compounds can be investigated directly by examining the growth of a test organism on a specially treated sorbent of thin layer chromatography (TLC). A special method of detection, direct bioautography, is suitable for studying the antimicrobial activity of plant extracts of natural origin by using TLC. Zones of inhibition are visualised by use of a dehydrogenase-activity-detecting, tetrazol-type reagent. Zones of inhibition appeared as pale spots separating well from the dark background. The antibacterial effect of the main essential oil components of some Thymus taxa, as well as that of two antibiotics (streptomycin sulphate and gentamycin) known and applied in practice was investigated against plant pathogenic bacteria. Results showed that thyme essential oil and its components inhibited the growth of test bacteria, but not so considerably as the antibiotics applied. Compositions of the essential oils were analysed by gas chromatography (GC). It could be verified that among the essential oil components, thymol and carvacrol had the strongest inhibitory effect.

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Regional habitat pattern of the Danube-Tisza Interfluve in Hungary II

The sand, the steppe and the riverine vegetation, degraded and regenerating habitats, regional habitat destruction

Acta Botanica Hungarica
Authors:
M. Biró
,
A. Révész
,
Zs. Molnár
,
F. Horváth
, and
B. Czúcz

The increased endangerment and rapid devastation of the vegetation on the Danube-Tisza Interfluve are quite complex processes that can be approached from a manifold ways. One of the most important factors having influenced the vegetation in the recent past is the decline of the groundwater-level, the extent of which is well known and the reasons for that have been investigated for a long time. However, only few have studied its dramatic effect on the vegetation outside the local scale. In the first part of our bipartite article we discuss the regional habitat-pattern of the landscape, the background factors determining it, and the basic features of fen and alkali vegetation (Biró et al. 2007). In this second part, this will be completed by the sand, riverine and steppe vegetation and the data on habitat devastation on the regional scale. The analysis of the present habitat-pattern of the region was based on data of the actual (1996–2000) habitat map of Danube-Tisza Interfluve (Molnár et al. 2000, Biró et al. 2003) and on our experiences during the field survey. The quantitative analysis of the vegetation pattern was carried out considering the vegetation subregions. Our aim is to expose the actual state of the landscape, the vegetation and the rapid devastation of the natural habitats, by quantifying the current processes.Our results demonstrate that the extension of those habitats on the Danube-Tisza Interfluve that were not under cultivation in the 1980s has decreased drastically, by 40,074 ha (approx. 15%). The main reasons for grassland devastations are ploughing, afforestation, the invasion of shrubs and trees, the building in activity and the establishment of open water surfaces. The most serious decline in the recent past was observed in the case of fen vegetation: the decrease of its extension was estimated to be 10–11%. More than half of the habitats disappeared as a result of ploughing and grassland-devastation due to urbanisation (building in, development of infrastructure, etc.) was covered by fen vegetation, while about a quarter of them consisted of alkali habitats. Sand areas mostly decline because of the spontaneous invasion of alien species and afforestation, which led to the devastation of approx. 4% of the natural and disturbed sand vegetation. Astonishing is the fact that the total extension of the more-or-less disturbed or devastated habitats altogether comprise roughly half (49%) of the actually mapped vegetation patches of the Interfluve (137,908 ha). By summing up the areas of the most frequent habitat types of the vegetation subregions, it became evident that the grasslands, ploughed in the past 15 years, are among the first five most spacious habitat types in all subregions.

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Experiments were carried out on the sperm cryopreservation of artificially induced eels. The effects of several extenders and two cryoprotectants on the motility of spermatozoa were investigated. The highest post-thaw motility was observed with the combination of Tanaka's extender and DMSO as cryoprotectant. Further dilution after thawing resulted in complete loss of motility in samples frozen in presence of DMSO while sperm frozen with methanol as cryoprotectant retained its motility after further dilution.

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Community Ecology
Authors:
B. Tajthi
,
R. Horváth
,
Sz. Mizser
,
D. D. Nagy
, and
B. Tóthmérész

Urban areas have been growing radically worldwide, causing considerable changes in biodiversity of natural habitats. In floodplain forests, we studied the effects of urbanization on ground-dwelling spider assemblages along a rural–suburban–urban gradient in Hungary. We tested three traditional hypotheses (intermediate disturbance hypothesis, habitat specialist hypothesis and hygrophilous species hypothesis) and two novel expectations (shade-preferring species hypothesis, and disturbance sensitive species hypothesis) on spiders. We found that the total number of species was higher in the suburban habitat than in rural and urban ones, supporting the intermediate disturbance hypothesis. We found a decrease in the species richness of forest specialist and shade-preferring species along the urbanization gradient. We found that the number of hygrophilous and disturbance sensitive species was the lowest in the urban habitat. The spider assemblages of the rural and suburban habitats were clearly separated from the assemblages of urban habitats. Based on our findings we emphasize that low and moderate intensity of forest management contributes to the preservation of the local species richness in floodplain forests.

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