(1/9) Quantitative trends in airborne loads of Celtis sinensis pollen and associations with meteorological variables in a subtropical Australian environment.
Celtis sinensis is an introduced plant species to the southeastern region of Queensland that has had a destructive affect on indigenous plant communities and its pollen has been identified as an allergen source. Pollen belonging to C. sinensis was sampled during a 5-year (June 1994-May 1999) atmospheric pollen-monitoring programme in Brisbane, Australia, using a Burkard 7-day spore trap. The seasonal incidence of airborne C. sinensis pollen (CsP) in Brisbane occurred over a brief period each year during spring (August-September), while peak concentrations were restricted to the beginning of September. Individual CsP seasons were heterogeneous with daily counts within the range 1-10 grains m(-3) on no more than 60 sampling days; however, smaller airborne concentrations of CsP were recorded out of each season. Correlation co-efficients were significant each year for temperature (p < 0.05), but were less consistent for precipitation (p > 0.05) and relative humidity (p > 0.05). A significant relationship (r2 =0.81, p=0.036) was established between the total CsP count and pre-seasonal average maximum temperature; however, periods of precipitation (> 2 mm) were demonstrated to significantly lower the daily concentrations of CsP from the atmosphere. Given the environmental and clinical significance of CsP and its prevalence in the atmosphere of Brisbane, a clinical population-based study is required to further understand the pollen's importance as a seasonal sensitizing source in this region. (+info)
(2/9) Bradyrhizobia isolated from root nodules of Parasponia (Ulmaceae) do not constitute a separate coherent lineage.
Rhizobial bacteria almost exclusively nodulate members of the families Fabaceae, Mimosaceae and Caesalpiniaceae, but are found on a single non-legume taxon, Parasponia (Ulmaceae). Based on their host-range, their nitrogen-fixing ability and strain competition experiments, bacterial strains isolated from Parasponia were thought to constitute a separate lineage that would account for their exceptional host affinity. This hypothesis was investigated by focusing on four isolates that are representative of the morphological and cultural types of Parasponia-nodulating bradyrhizobia. Their evolutionary relationships with other rhizobia were analysed using 16S rRNA gene sequences and their nodulation properties were explored using the nodA gene as a proxy for host-range specificity. Phylogenetic analyses of the 16S rRNA and nodA gene sequences revealed that bacterial isolates from Parasponia species are embedded among other bradyrhizobia. They did not cluster together in topologies based on the 16S rRNA or nodA gene sequences, but were scattered among other bradyrhizobia belonging to either the Bradyrhizobium japonicum or the Bradyrhizobium elkanii lineages. These data suggest that the ability of some bradyrhizobia to nodulate species of the genus Parasponia does not represent a historical relationship that predates the relationship between rhizobia and legumes, but is probably a more recent host switch for some rhizobia. (+info)
(3/9) Integrated analysis of tropical trees growth: a multivariate approach.
BACKGROUND AND AIMS: One of the problems analysing cause-effect relationships of growth and environmental factors is that a single factor could be correlated with other ones directly influencing growth. One attempt to understand tropical trees' growth cause-effect relationships is integrating research about anatomical, physiological and environmental factors that influence growth in order to develop mathematical models. The relevance is to understand the nature of the process of growth and to model this as a function of the environment. METHODS: The relationships of Aphananthe monoica, Pleuranthodendron lindenii and Psychotria costivenia radial growth and phenology with environmental factors (local climate, vertical strata microclimate and physical and chemical soil variables) were evaluated from April 2000 to September 2001. The association among these groups of variables was determined by generalized canonical correlation analysis (GCCA), which considers the probable associations of three or more data groups and the selection of the most important variables for each data group. KEY RESULTS: The GCCA allowed determination of a general model of relationships among tree phenology and radial growth with climate, microclimate and soil factors. A strong influence of climate in phenology and radial growth existed. Leaf initiation and cambial activity periods were associated with maximum temperature and day length, and vascular tissue differentiation with soil moisture and rainfall. The analyses of individual species detected different relationships for the three species. CONCLUSIONS: The analyses of the individual species suggest that each one takes advantage in a different way of the environment in which they are growing, allowing them to coexist. (+info)
(4/9) Two new species of Appendiculella (Meliolaceae) from Panama.
Two new species of Meliolaceae (black mildews) are described based on specimens recently collected in western Panama. Appendiculella lozanellae on leaves of Lozanella enantiophylla is the first species of Appendiculella known on Cannabaceae. Appendiculella chiriquiensis on leaves of Cupania guatemalensis is the first record of a species of Appendiculella on Sapindaceae. These species differ from known species on their respective host relationships by the presence of larviform appendages attached to the perithecia, as well as by characteristics of hyphae, appresoria and ascospores. Sequence data of 18S and 28S rDNA are published for A. lozanellae, which becomes the third species of Meliolales and the first species of the genus Appendiculella for which molecular data are available. (+info)
(5/9) Airborne pollen of Carya, Celtis, Cupressus, Fraxinus and Pinus in the metropolitan area of Monterrey Nuevo Leon, Mexico.
The concentration of pollen grains in the atmosphere over the metropolitan area of Monterrey, Nuevo Leon, Mexico, was analyzed throughout a year from March 2003-February 2004, focused on the genus Carya, Celtis, Cupressus, Fraxinus and Pinus owing to their interest as etiological pollinosis agents in diverse regions of the world. A 7-day Hirst type volumetric spore and pollen trap was located on a building roof of the city at 15 m from ground level for continuous sampling. The total quantity of pollen recorded for the study period was 21,083 grains/m(3), corresponding to 49.75 % of the taxa of interest. February and March were the months with higher pollen amounts in the air with 7,525 and 2,781 grains/m(3), respectively, and amounted to 49 % of total year through pollen. Fraxinus was the genus which contributed to the largest amount of pollen with 28 % of total grains (5,935 grains/m(3)) followed by Cupressus with 13 % (2,742 grains/ m(3)). Celtis, Pinus and Carya contributed with 5.3 % , 2.7 % , and 0.6 % of total pollen, respectively. These results indicate that Fraxinus and Cupressus are present in the area in sufficient quantity to indicate likely involvement in the origin of allergic disorders in the human population. (+info)
(6/9) LysM-type mycorrhizal receptor recruited for rhizobium symbiosis in nonlegume Parasponia.
(7/9) Selective apoptotic effect of Zelkova serrata twig extract on mouth epidermoid carcinoma through p53 activation.
(8/9) Urban tree species show the same hydraulic response to vapor pressure deficit across varying tree size and environmental conditions.