Effects of watering and simulated acid rain on quantity of phyllosphere fungi of birch leaves.

The effects of simulated acid rain on the population of birch phyllosphere fungi and species/genera/group composition of fungi on birch leaves were investigated in a field study in the subarctic region of northern Finland. The acid rain treatments consisted of a mixture of H2SO4 and HNO3 with a mass ratio of 2.86∶1 (S∶N) with acidities of pH 4 (A4) and pH 3 (A3). Dry control (DC) plots received only natural precipitation; irrigated control (IC) plots received spring water (pH 6) in a volume equal to the acid treatment plots. Treatments began in 1985. Culturing of the fungi inhabiting the birch leaves was performed five times during the summer of 1988. The number of fungal colonies was significantly decreased on one of five sampling dates in the pH 4 treatment and on three of five sampling dates in the pH 3 treatment. Irrigation with spring water did not have a significant effect. The acid rain treatments affected the microflora of the upper branches (at a height of 2 m) and of the lower branches (at a height of 0.5 m) equally. The lower branches had significantly more fungi than the upper ones on three of five sampling dates. The number of phyllosphere fungi isolated from birch leaves was greater in late summer than in early summer. The most abundant taxon (∼80%) wasAureobasidium pullulons, followed byHormonema sp. and zygomycetes.

Simulated acid rain affects birch leaf endophyte populations.

Endophytes were frequently isolated from mountain birch (Betula pubescens var. tortuosa (Ledeb.) Nyman) leaves at a subarctic site where natural air pollution is low. We tested whether simulated acid rain had any influence on the occurrence of endophytes. Dry controls with only ambient rain and irrigated controls treated with spring water of pH 6 were compared with acid treatments at pH 3 and pH 4, prepared by adding both sulphuric and nitric acids. Treatments began in 1985 and leaf samples were taken twice during the summer of 1992. Leaves were surface sterilized, five leaf disks from each leaf placed on malt extract agar, and growing colonies were counted and identified. The most frequently isolated endophyte from birch leaves was a Fusicladium anamorph of Venturia sp. (88% of all the isolates in July and 75% of all the isolates in August), followed by a sterile mycelium and Melanconium sp. The number of endophytes isolated and the species number increased from July to August. Endophytes were most frequently isolated from the basal part of the midrib. The percentage of colonization by endophytes was similar in short and long shoots. More endophytes were isolated from leaves of branches taken at 1 m height than at 2 m height. The stronger acid rain treatment (pH 3) reduced by approximately 25% the number of isolated endophytes in August. Treatments did not have any effect on species composition of endophyte assemblages in birch leaves.

Does cutting of mugwort stands affect airborne pollen concentrations?

Pollen of mugwort (Artemisia vulgaris L.) is the most important allergenic pollen in urban areas of south and central Finland in late summer. The purpose of this study was to investigate, experimentally, whether the cutting of mugwort stands affects its airborne pollen concentrations. Experimental plots were either cut (4 plots) or uncut (4 plots) in 2 previous seasons: 4 of them were small (less than 0.5 hectare) and 4 large (greater than 5 hectares). Finally, the plots were divided randomly into 2 groups according to a third variable, cutting in the study season, 1989. Samples were taken on 2 rainless mornings at the peak mugwort flowering time. Two rotorod type samplers were used at heights of 1 and 2 m from ground level, simulating the inhalation heights of children and adults, respectively. The results indicate that cutting mugwort stands significantly reduces airborne pollen concentrations, but the treated areas have to be large, since in the town area there are plenty of mugwort pollen sources. The pollen concentrations at the 2 heights tested did not differ significantly.

Effects of air pollution and other environmental factors on birch pollen allergens.

To determine the effects of anthropogenic pollution on water-soluble proteins and specifically allergens in birch (Betula pendula and B. pubescens) pollen, we analyzed extracts of pollen from the pollution gradient around a factory complex (emitting sulfur oxides and heavy metals) by sodium dodecyl sulfate (SDS)--polyacrylamide gel electrophoresis (PAGE) and IgE immunoblotting. In addition, tree density-associated shading of the tree habitat, and quantity and quality of proteins and allergens in pollen of the two birch species were studied. The two studied birch species gave identical allergen profiles even though their protein profiles differed. Distance from the factory did not affect the amount of birch pollen major allergen, Bet v 1 (17 kDa), or of two other strong allergens (23 and 36 kDa). Trees growing in shaded places had significantly stronger responses to Bet v 1 and to the 23-kDa allergen than trees growing in open or half-open environments. Thus, we propose that combined heavy metal and sulfur dioxide pollution does not have an important effect on birch pollen allergens. Instead, other factors, e.g., shading and soil properties of the tree habitat, as well as the genetic background of the tree, may have a stronger influence on the quantity and relative composition of allergens.

Genetic and environmental factors affecting the allergenicity of birch (Betula pubescens ssp. czerepanovii [Orl.] Hämet-ahti) pollen.

BACKGROUND: Environmental variation, such as an increase of mean temperature due to the greenhouse effect, as well as the genetic factors may affect the allergenicity of pollen and thus, the prevalence of allergies. The connection between these factors and the allergen content of pollen is poorly understood. OBJECTIVES: To evaluate the role of environmental and genetic factors on the allergenicity of birch pollen. METHODS: Mountain birch (Betula pubescens ssp. czerepanovii (Orl.) Hämet-Ahti) pollen was studied using SDS-PAGE and IgE-immunoblotting. Pollen samples were collected from the trees of 10 half-sib families. The study trees from each family were reared in two tree line gardens where the daily mean temperatures were different during the growing season. RESULTS: The quantitative analysis of band intensities suggested that the responses of the major birch pollen allergen, Bet v 1, were stronger in the samples collected from the garden with higher daily mean temperature. Half-sib families and individual trees differed in their Bet v 1 content. CONCLUSIONS: Our results show that both genetic and environmental factors have an effect on the amount of Bet v 1. This suggests that breeding for trees low in allergen content may be possible.