On the fracture morphology in wood

Summary Structural changes in spruce and aspen wood samples subjected to axial compression were examined by means of the scanning electron microscope. For comparison, macroscopic model experiments were carried out on tube-shaped samples made of paper so as to represent segments of fibriform xylem cells. The results show that there are fracture patterns characteristic of wood in general and others characteristic of the species of wood. The phenomena characteristic of wood in general are prevalent at the cellular level and in the fracture behaviour of the cell wall layers and perforations. The characteristics of the various species of wood dominate at the level of the growth rings and are decisively influenced by the composition and arrangement of the tissues. The model experiments show that the failure morphology of the individual cells of the xylem may be explained to some extent by their geometry.     

Distribution of Aeolothrips intermedius Bagnall (Thysanoptera: Aeolothripidae) and its potential prey Thysanoptera species on different cultivated host plants

The results of the monitoring of Thysanoptera species on cultivated plants in Slovenia (2000–2001), Croatia (1994–1996), and Serbia and Montenegro (1988–2003) are presented in this study. The aim of the investigation was to study the host plant distribution of the predator Aeolothrips intermedius Bagnall and its potential prey. Banded thrips were found on 30 different host plant species belonging to 16 botanical families, always in mixed populations with phytophagous or facultative phytophagous insects (including 18 Thysanoptera species). On the vegetative parts of the cultivated plants, banded thrips were found less numerous in spite of the massive population of some harmful thrips species. This indicates highly important role of pollen as alternative food for Aeolothrips intermedius.     

Chemical composition of hemicelluloses as a factor participating in the substrate specificity of wood-destroying fungi

Mycelium of twenty species of wood-destroying fungi was cultivated in nutrient solutions with one of the following sugars as the only carbon source: glucose, arabinose, galactose, mannose and xylose. The growth of the species occurring in nature only on the wood of Angiosperms was equal or lower in the solutions with galactose and mannose than in the solution with glucose. The utilization of mannose was practically the same as that of xylose. The species which are specialized in nature in the wood of conifers grow better in the solutions with galactose and mannose, than in the solution with glucose; likewise mannose is beter utilized than xylose. Fungi attacking both kinds of wood do not exhibit any dependence on the utilization of the sugars used in these investigations.     

Stand structure of an uneven-aged fir–beech forest with an irregular diameter structure: modeling the development of the Belevine forest, Croatia

This study focuses on the problem of irregular diameter structure in a silver fir–beech selection (plenter) forest with a “surplus” of large diameter trees and a lack of natural regeneration and small diameter trees. We sampled 274 plots (900 m² each) in the Belevine research site (266.24 ha) in the mountain region Gorski Kotar (Croatia), where diameter (dbh) distribution, diameter increment, and natural regeneration were analyzed in detail. A low density of natural regeneration, weak annual recruitment of small (10 cm dbh) diameter trees (only five trees per hectare), delayed diameter growth of trees, and a low annual rate of trees reaching the next dbh class were attributed to the current irregular dbh structure. The stand development prediction for the next 50 years is based on a simulation model, which considers the current diameter structure, increment, recruitment, and future cutting regime. Intensive cutting in the first of five 10-year cutting cycles (intensity higher of 25%) is needed to initiate natural regeneration and to accelerate growth of young silver fir trees. In the next 50 years, the irregular diameter structure will be gradually improved.     

Technological properties and fire performance of medium density fibreboard (MDF) treated with selected polyphosphate-based fire retardants

ABSTRACT

The objective of the work was to evaluate the efficacy of two new polyphosphate-based fire retardants (FRs) and one commercial product named Siriono^® on the fire performance and physical–mechanical properties of medium density fibreboard (MDF) fabricated in the laboratory from Scots pine (Pinus sylvestris L.) wood. The fibres were treated with aqueous solutions of fire retardants, at 12% loading (dry salt on dry wood), and bonded with a melamine urea formaldehyde (MUF) adhesive. The physical and mechanical properties of panels were assessed using the European standards, whereas their fire performance was evaluated using an in-house method and the Cone calorimeter. In overall, the chemicals added enhanced the fire and smoke properties of the panels to varying degrees. Critical FR parameters such as peak heat release rate (peak HRR), total heat release (THR) and total smoke production (TSP) were significantly improved in the FR-treated panels, as exhibited in cone calorimeter tests. However, the internal bond strength of treated panels largely decreased by the addition of fire retardants, while thickness swell and water absorption negatively affected to a significant extent. In contrast, the formaldehyde release of the panels was considerably decreased at the E1 class level, with the incorporation of the polyphosphate-based additives.     

Parasitoid complex (Hymenoptera, Braconidae, Aphidiinae) of Aphis craccivora Koch (Hemiptera: Aphidoidea) in Iran

The parasitoids (Hymenoptera, Braconidae, Aphidiinae) of the cowpea aphid, Aphis craccivora Koch, were investigated throughout two far distant provinces, Tehran and Sistan-Baluchestan. Colonies of the cowpea aphid were collected from different host plants and reared under laboratory conditions until the parasitoids emerged. The aphids were parasitized by an expected range of parasitoids. The species were Aphidius colemani Viereck, Lysiphlebus fabarum (Marshall), Lysiphlebus confusus Tremblay and Eady, Lysiphlebus testaceipes (Cresson), Binodoxys acalephae (Marshall), Binodoxys angelicae (Haliday), Praon volucre (Haliday) and Ephedrus persicae Froggatt. L. testaceipes is reported here for the first time in Iran. The most common species was L. fabarum followed by B. acalephae and L. confusus. A key is provided for identification and host plant associations are considered.     

Bemerkungen über die Populationsbewegungen der Mittelmeerfruchtfliege (Ceratitis capitata Vied.) an der jugoslawischen Adriaküste

Zusammenfassung Untersuchungen über den Massenwechsel und die Biologie der MittelmeerfruchtfliegeCeratitis capitata Vied. während der letzen 5 Jahre führten zu folgenden Ergebnissen:1. Die Mittelmeerfruchtfliege, die bis 1947 in ganz Jugoslawien unbekannt war, kommt seit mindestens zehn Jahren auch an der Adriaküste vor.2. Erst im Jahre 1958 erwies sich die Fruchtfliege als Schädling verschiedener Obstarten.3. Wie aus Beobachtungen in Obstanlagen an der Adriaküste hervorgeht, befällt die Fliege in erster Linie Pfirsich, ferner auch Birne, Kaki, Feige, Apfel, Pflaume, Orange und grünen Paprika. Im Laboratorium gelang die Zucht außerdem noch an Banane, nicht aber an Tomate und Trauben.4. ObwohlC. capitata ein polyphages Insekt ist, befällt sie an einigen Stellen, wo sie regelmäßig große Häufigkeit aufweist, nur Pfirsich (Split, Debeli Rti) bzw. nur Kaki (Ankaran). In manchen Obstgärten lebt sie aber an verschiedenen Früchten (Podstrana, Stroanac). Es gibt bei der Fruchtfliege also auf Obstarten spezialisierte Populationen und solche, die an verschiedenen Obstarten vorkommen.5. Unter den in unserem Küstenland herrschenden Klimabedingungen kann die Fruchtfliege in einem Jahr 4–5 Generationen entwickeln. Die Herbstgeneration verpuppt sich Ende Oktober/Anfang November in der Erde, die Imagines verlassen bis Januar die Puppen und warten auf das Reifen der ersten, frühen Pfirsichsorten. Die gleiche Überwinterungsweise wurde auch an der Olivenfliege beobachtet.6. Mit Angelica-Öl versehene Fanggläser brachten nur zum Teil befriedigende Ergebnisse, da dieser Lockstoff nur die Männchen anzieht, aber auch nur in der Zeit, in der die Fliegen überhaupt selten sind. Im Spätsommer und Herbst wirkt ein aus Kleie und Biammonphosphat bereiteter Köder auf beide Geschlechter stark anlockend.     

The impact of beaver dam removal on the chemical properties of water in drainage ditches in peatland forests

ABSTRACT

Despite near-extinction in the nineteenth century, after efficient restoration measures the population of Eurasian beaver (Castor fiber L.) in Latvia currently is viable and growing. While the ecological effect of the species on water quality and biodiversity is generally positive, the high number of animals in production forests often creates challenges for management. Drainage ditches are among the most favoured habitats of beavers resulting in flooded stands, reduced tree growth and economical losses. The aim of the study was to evaluate the chemical properties of water in forest drainage ditches, affected by beaver activity, and their changes after the dam removal. Chemical composition of surface water in ditches was analysed in sampling points above dam, below dam and in the ditch itself after removal of the dam; results compared to pristine beaver site nearby on a small stream. Results did not show significant differences between concentrations above and below dams. After removal of the dams, significant increase in DOC, N-NO₃ ^-, N-NH₄ ⁺ and TSS concentrations and significant decrease in TP concentrations were observed in some of the sites. Observed concentrations of all measured parameters were significantly lower in pristine beaver site than in beaver sites on drainage ditches.     

Gill Reaction to Pollutants from the Tamiš River in Three Freshwater Fish Species,Esox lucius L. 1758, Sander lucioperca (L. 1758) and Silurus glanis L. 1758: A Comparative Study

The study evaluated the effects of waterborne pollutants from the Tami? River on gill histology and possible differences in gill reaction patterns between three freshwater fish species, pike Esox lucius L. 1758, pike‐perch Sander lucioperca (L. 1758) and wels catfish Silurus glanis L. 1758 from the Tami? River. Gills from analysed fish species showed moderate to intense histopathological alterations. The most frequent progressive alteration was hyperplasia of epithelium, whereas the most frequent regressive alteration was epithelial lifting. Circulatory disturbances were most often manifested in the form of hyperaemia. During comparative analysis, differences in gill indices, reaction and alteration indices, as well as in gill and filament prevalence between analysed species, were observed. Although all analysed fish species did show both progressive and regressive alterations, there was a significant difference in the level of expression of these reaction patterns. Gill index obtained for pike clearly stands out as the lowest. Wels catfish showed the highest progressive reaction index, significantly higher in comparison with the other two species (P < 0.05), while pike‐perch showed the highest regressive reaction index, also significantly higher in comparison with the other species (P < 0.001). These results may implicate species‐specific gill reactions and thus present a useful tool for better understanding toxic mechanisms of various pollutants.     

Localization of CD9 Molecule on Bull Spermatozoa: Its Involvement in the Sperm–Egg Interaction

Tetraspanin CD9 is one of the egg membrane proteins known to be essential in fertilization process. The presence and localization of CD9 molecule in spermatozoa and its possible function in reproduction are still unclear. In our study, we describe the localization of CD9 on bull spermatozoa. In the immunofluorescence assay, the positive signal has been observed in the high proportion of sperm cells as a fine grains either on the apical part or through the entire anterior region of sperm head. CD9 recognized by monoclonal antibody IVA‐50 was detected on freshly ejaculated (83.4 ± 3.7%) and frozen‐thawed (84.3 ± 2.3%) sperm. The same reaction pattern was observed on sperm capacitated for 1 h, 2 h, 3 h and 4 h (83.6 ± 2.0%; 84.0 ± 1.5%; 85.7 ± 0.8%; 77.5 ± 10.8%). The presence of CD9 exclusively on plasma membrane of the bovine sperm has been detected by Western blot analysis of the protein fractions after the discontinuous sucrose gradient fractionation of the bull sperm. Moreover, probable role of the sperm CD9 molecule in fertilization process of cattle has been suggested as sperm treatment with anti‐CD9 antibody significantly reduced (by 25%, p ≤ 0.001) the number of fertilized oocytes compared to control group in fertilization assay in vitro.