Factors influencing the formation of heartwood discolouration in sycamore (<Emphasis Type="Italic">Acer pseudoplatanus</Emphasis> L.)     

Aleš Kadunc 《European Journal of Forest Research》2007,126(3):349-358

Sycamore (Acer pseudoplatanus L.) is a tree species with highly valuable wood. Similar to European beech (Fagus sylvatica L.), the stemwood of sycamore can be devalued due to the discolouration i.e. brown heart (hearwood discolouration, hereafter). This paper aims to establish the influence of tree traits and site characteristics on the formation of heartwood discolouration and the possibility of predicting the occurrence of heartwood discolouration. For this purpose, 351 sycamore trees from 38 sites in Slovenia, most of them on carbonate bedrock and in the mountain vegetation belt, were analysed. Stem analysis was carried out on all the trees and the age, diameter at breast height (dbh), height of crown base, forking and crown size, were established. On the stump and upper fronts of the first and second logs, the maximum heartwood discolouration diameter was measured. Using logistic regression, the positive influence of age, relative crown length and average diameter increment on the formation of heartwood discolouration was ascertained. Conversely, the probability of heartwood discolouration was diminished by diameter increment in the last 20 years. In the less productive sites, the probability of formation of heartwood discolouration was relatively high in small diameter trees, but it increased slowly with diameter. Tree forking also contributed to a large extent of the heartwood discolouration. After the diameter at breast height achieves 45 cm, the formation of heartwood discolouration on the first log is highly probable. As in beech, the heartwood discolouration increases along the stem axis up to a height of 6–8 m, and decreases in the higher parts of the tree.  相似文献   

The Genus <Emphasis Type="Italic">Fragaria </Emphasis>in Croatia     

Dubravka Dujmović Purgar  Boris Duralija  Aleš Vokurka  Marija Todorić  Vesna Židovec 《Erwerbs-Obstbau》2017,59(3):227-233

Only three native species of genus Fragaria (F. moschata, F. vesca and F. viridis) are recorded in three regions of Croatia. These species as well as many of their hybrids, are, or once were, cultivated for their edible fruits. The majority of cultivated strawberries in Europe belong to garden strawberries F. x ananassa (hybrids of F. chiloensis and F. virginiana). The most expanded wild strawberry species in Croatia is a woodland strawberry (F. vesca) whose berries are gathered seasonally as wild edible fruits. They often contain higher amount of nutrients and bioactive compounds in comparison to cultivated varieties. The research on the genus Fragaria species distribution in Croatia has not been carried out, and so is the case with many others wild growing fruit species in Croatia. By summing up a number of individual citations and observations, it is possible to get a perspective regarding the current state of their distribution.  相似文献   

Cultivable microbiota of Lithobates catesbeianus and advances in the selection of lactic acid bacteria as biological control agents in raniculture     

Montel Mendoza G  Pasteris SE  Ale CE  Otero MC  Bühler MI  Nader-Macías ME 《Research in veterinary science》2012,93(3):1160-1167

The cultivable microbiota of skin and cloaca of captive Lithobates catesbeianus includes microorganisms generally accepted as beneficial and potentially pathogenic bacteria. In order to select a group of potentially probiotic bacteria, 136 isolates were evaluated for their surface properties and production of antagonistic metabolites. Then, 11 lactic acid bacteria (LAB) strains were selected and identified as Lactobacillus plantarum, Lb. brevis, Pediococcus pentosaceus, Lactococcus lactis, L. garvieae and Enterococcus gallinarum. Studies of compatibility indicate that all the strains could be included in a multi-strain probiotic, with the exception of Ent. gallinarum CRL 1826 which inhibited LAB species through a bacteriocin-like metabolite. These results contribute to the design of a probiotic product to improve the sanitary status of bullfrogs in intensive culture systems, to avoid the use of antibiotics and thus to reduce production costs. It could also be an alternative to prevent infectious diseases during the ex situ breeding of amphibian species under threat of extinction.  相似文献   

Mobility of mercury in soil as affected by soil physicochemical properties     

Adéla Šípková  Jiřina Száková  Aleš Hanč  Pavel Tlustoš 《Journal of Soils and Sediments》2016,16(9):2234-2241

  相似文献   

In vitro aluminum effects on ectomycorrizal fungi     

Jana Žel  Aleš Blatnik  Nada Gogala 《Water, air, and soil pollution》1992,63(1-2):145-153

This study investigates the effects of soluble Al on different ectomycorrhizal fungi in vitro. Al was added to the medium as A1₂(SO₄)₃ · 18H₂O in the concentration range from 0 to 20 mM Al. The lateral growth, fresh and dry weights of mycelia showed dependance on fungal species and the concentrations of Al. Concentrations from 1 to 20 mM of Al reduced the growth of most species but one strain of Pisolithus tinctorius showed a higher tolerance to all Al concentrations studied. The growth of Suillus variegatus showed the most marked sensitivity to and also changes in the morphology of mycelia grown on 15 mM Al, Lactarius piperatus growth was stimulated at the same Al concentrations and showed no differences from the control with SEM observations.  相似文献   

Influence of nitric oxide and reactive oxygen species on development of lettuce downy mildew in <Emphasis Type="Italic">Lactuca</Emphasis> spp.     

Michaela Sedlářová  Marek Petřivalský  Jana Piterková  Lenka Luhová  Jindra Kočířová  Aleš Lebeda 《European journal of plant pathology / European Foundation for Plant Pathology》2011,129(2):267-280

The role of nitric oxide and reactive oxygen species, molecules indispensable for plant-pathogen signalling, was studied in the Lactuca spp.-Bremia lactucae pathosystem. Using a leaf disc model the translaminar effect of various compounds affecting their metabolism was studied by light microscopy. Time course studies revealed a slowdown in the development of B. lactucae (race BL16) infection structures by rutin (scavenger of reactive nitrogen and oxygen species) and SNP (NO donor) within 48 h post inoculation, followed by a retardation of sporulation. Application of the specific NO scavenger, PTIO, accelerated penetration of B. lactucae but had no further effects on the plant-pathogen interaction. Inhibitors of NO synthase (L-NAME) and nitrate reductase (sodium tungstate) did not influence pathogen development. Our results suggest that drastic change in the NO: hydrogen peroxide ratio seems to determine the pathogen’s fate. NO synthase-like activity significantly increased early after B. lactucae challenge in resistant L. virosa. Confocal laser scanning microscopy revealed the accumulation of nitric oxide in the penetrated cells, pointing to a role in the initiation of the hypersensitive reaction. The tips of germ tubes and appressoria of B. lactucae also accumulated NO, suggesting an essential role for this molecule in penetration of the biotrophic pathogen. Additionally, temporal changes in endogenous levels of rutin and quercetin in extracts from Lactuca spp. leaves will be discussed in connection to their role as part of the antioxidative machinery that influences the plants’ susceptibility/resistance to lettuce downy mildew.  相似文献   

Characterisation of the curing of liquefied wood by rheometry, DEA and DSC     

Aleš Ugovšek  Milan Sernek 《Wood Science and Technology》2013,47(5):1099-1111

Liquefied wood is a naturally based product which has the potential to be used as an adhesive. The bonding of wood with liquefied wood requires a high enough temperature to cure the liquid polymers and achieve bond strength. Dielectric analysis, rheometry and differential scanning calorimetry were used to analyse the curing process of low solvent liquefied wood. For the liquefaction, ethylene glycol was used as a solvent and sulphuric acid was used as a catalyst. The dielectric analysis was used for in situ measurements of the curing of liquefied wood during the bonding of wood. It was found that curing started after a temperature of 100 °C had been reached in the bond. This is correlated with the water evaporation and the diffusion of water and ethylene glycol from the liquefied wood into the wood substrate. Rheological measurements proved the influence of the substrate on the curing of the liquefied wood during bonding. Differential scanning calorimetry showed that the curing of liquefied wood occurs in two parts: first, the initial elimination of water and ethylene glycol from the liquefied wood, and then the chemical reaction of the liquefied wood at higher temperatures.  相似文献   

Structure and variation in the wild-plant pathosystem: <Emphasis Type="Italic">Lactuca serriola–Bremia lactucae</Emphasis>     

Aleš Lebeda  Irena Petrželová  Zbyněk Maryška 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(1):127-146

Over the past decade, extensive research on the wild-plant pathosystem, Lactuca serriola (prickly lettuce)–Bremia lactucae (lettuce downy mildew), has been conducted in the Czech Republic. Studies focused on pathogen occurrence and distribution, host range, variation in symptom expression and disease severity, interactions of B. lactucae with another fungal species (Golovinomyces cichoracearum) on L. serriola, variation in resistance within natural populations of L. serriola, the structure and dynamics of virulence within populations of B. lactucae, sexual reproduction of B. lactucae, and a comparison of virulence structure and changes in B. lactucae populations occurring in wild (L. serriola) and crop (L. sativa) pathosystems. The incidence of B. lactucae on naturally growing L. serriola and other Asteraceae was recorded. Lactuca serriola was the most commonly occurring host species, followed by Sonchus oleraceus. Over the duration of these studies, the incidence of B. lactucae in L. serriola populations varied between 45–87%. Disease incidence and disease prevalence were partly related to the size, density and different habitats of L. serriola populations. In addition to B. lactucae infection, infection by the lettuce powdery mildew fungus (Golovinomyces cichoracearum) was quite common, including co-infection. Variation in resistance to B. lactucae was studied by using ten isolates (NL and BL races with known virulence patterns) at a metapopulation level, i.e. 250 L. serriola samples representing 16 populations from the Czech Republic (CZ). Our comparisons revealed broad variation in host resistance among host populations and also intrapopulation variability. In the CZ populations, 45 resistance phenotypes were recorded, the most frequent were race-specific reaction patterns. Structural and temporal changes in virulence variation of B. lactucae populations on L. serriola were studied during 1998–2005. Altogether, 313 isolates of B. lactucae originating from the Czech Republic were examined for the presence of 32 virulence factors (v-factors), and 93 different virulence phenotypes (v-phenotypes) were recorded. A study of v-factor frequency showed that common v-factors in B. lactucae populations match some of the race-specific resistance genes/factors (Dm genes or R-factors) originating from L. serriola. The highest frequency was recorded by v-factors v7, v11, v15–17, and v24–30. In contrast, v-factors (e.g. v1–4, 6, and 10) matching Dm genes originating from L. sativa were very rare. This demonstrates the close adaptation of B. lactucae virulence to the host (L. serriola) genetic background. Temporal changes in virulence frequencies over the period were recorded. In many v-factors (v11, v14, v16, and v25–28), fluctuations were observed, some (v14 and v17) shifting to higher frequencies, and others (v5/8 and v23) decreasing. The occurrence of mating types was studied (1997–1999) in a set of 59 B. lactucae isolates. Both compatibility types (B1 and B2) were recorded; however the majority of the isolates (96%) were type B2. A comparative study of B. lactucae virulence variation between the wild (L. serriola) and crop (L. sativa) pathosystems showed major differences. Migration and gene flow between both pathosystems and the potential danger of wild B. lactucae populations for cultivated lettuce are discussed. This paper summarizes comprehensive and unique research on an oomycete pathogen (B. lactucae) that is shared between a crop (lettuce, L. sativa) and its close wild relative (prickly lettuce, L. serriola). The data demonstrate clear evidence about race-specific interactions, variation and changes in virulence, and coevolutionary relationships in the wild pathosystem L. serriola–B. lactucae. Conclusions contribute to the broadening and better understanding of gene-for-gene systems in natural host–pathogen populations and their relationships to crop pathosystems.  相似文献   

Virulence variation of cucurbit powdery mildews in the Czech Republic – population approach     

Aleš Lebeda  Eva Křístková  Božena Sedláková  James D. McCreight  Evsey Kosman 《European journal of plant pathology / European Foundation for Plant Pathology》2018,152(2):309-326

Kosman diversity models were applied to analyses of virulence (disease reaction patterns) variation of 115 isolates of two cucurbit powdery mildew (CPM) species, Golovinomyces orontii (Go) and Podosphaera xanthii (Px), collected in the Czech Republic from 2010 through 2012. Diversity within and distances between Go and Px populations and each other in a spatio-temporal context and with regard to original host plant species were analyzed based on virulence patterns of individual isolates on a set of 21 melon (Cucumis melo L.) race differential genotypes. Significant differentiation among the Go and Px pathogen populations was revealed, and the results clearly demonstrate and confirm that the set of differential C. melo genotypes is well composed because of high differentiation capacity. Differentiation of pathogens among years was significant for both species. No significant difference between Go isolates from different host plant species was established due to high variability among Go isolates, but there was significant host-specific differentiation among Px isolates. Differentiation of pathogens among regions was not detected. These results revealed high virulence variation in isolates of Go and Px, and their spatio-temporal fluctuations. High diversity in virulence of Go isolates supports the treatment of Go as a complex of different (sub)species with distinct virulence factors. Similar relationships of selected Go isolates in a UPGMA dendrogram in a previously reported multigene phylogenetic tree support the logic and suitability of the Kosman assignment based approach to population studies of organisms with asexual or mixed modes of reproduction. The approach applied in this study provides a complex view of virulence structures of powdery mildew populations, and when combined with race determination and denomination on melon, it may serve as a base to understandvirulence variation of these CPM species from a spatio-temporal viewpoint.  相似文献   

Automatic assessing and monitoring of weaving density     

Maroš Tunák  Aleš Linka  Petr Volf 《Fibers and Polymers》2009,10(6):830-836

Image restoration using the spectral approach is applied to the problem of automatic assessing of weaving density. A restored image of one set of yarns is obtained with the aid of two dimensional discrete Fourier transform. From the line profile of restored images Fisher’s test of periodicity find out the significant periodical components of specific frequency and defines model of time series. On the basis of frequency of model, the weaving density can be computed automatically. This method is then used for detection of defects associated with the change of weaving density, i.e. the weft direction defects. The detection is based on monitoring of weaving density in direction of length of fabric. Change of weaving density value against expected value indicates failure of regular structure. Control charts were used as a tool for judge the existence of failure or defects of regular structure.  相似文献