The effect of atmospheric NH3 deposition on freezing tolerance of needles of Scots pine was investigated. Needles from 3 month old seedlings and from 20-30 year old field-grown Scots pine (Pinus sylvestris L.) trees were studied. Seedlings were exposed to NH3 during the first stage of hardening in the laboratory. Field-grown trees were growing in a "clean" or an NH3 polluted area. In the 3 month old seedlings, exposure to 1000 ml 1** (-1) NH3 for 4 weeks resulted in a 40 increase of total nitrogen content. Freezing tolerance of the needles was significantly enhanced in the NH3 exposed seedlings. In the field-grown trees, current and one year old needles were studied. Freezing tolerance of the current year needles did not differ significantly between the two forest stands. However, one year old needles from the NH3 polluted stand were significantly less frost hardened from October until February. Total nitrogen content was higher in both current and one year old needles from the NH3 polluted stand. At the same time, potassium content of these needles was lower compared to the needles from the clean stand. The content of calcium, magnesium and phosphorus did not differ significantly. It was concluded that a decrease of freezing tolerance upon atmospheric NH3 was not directly related to an increased nitrogen content, but might probably be due to the nutrient imbalance of the needles.

Distribution patterns of ectomycorrhizal types and length density of finest roots were investigated in three comparable Scots pine ecosystems located along a deposition gradient of air pollutants in the new states of Germany. The plots Rosa, located near Bitterfeld and Halle, had received high depositions loads of SO2, NOX and alkaline fly ashes due to chemical industries and brown coal fired power plants in the former German Democratic Republic. Taura, located near Leipzig, was moderately affected by air pollutants. The background site Neuglobsow is located in a remonte area north of Berlin. All the three plots were dominated by only a few mycorrhizal types. Mycorrhizal projection area of these types was highest in Neuglobsow and strongly reduced at the polluted plots. The distribution patterns of mycorrhizal types differed also qualitatively. Length density of finest roots was lower in the humus layer of Neuglobsow than in the humus layer of Rosa and Taura. The results are correlated to high nutrient inputs and high rates of N-mineralization at the impacted plots.

The paper summarizes the main results of reach on heavy metal detoxification in ectomycorrhizas of Rhizopogon roseolus, Paxillus involutus, Cenococcum geophilum and Pisolithus arrhizus formed on Pinus sylvestris roots collected from heavily polluted areas in Poland. The data were obtained by methods including electron microscopy (TEM, SEM) accompanied by EELS and EDAX, cytochemical stainings and capillary electrophoresis. All of the species described in the paper are fungi highly resistant to toxic elements. As detoxification in mycorrhizas is dependent on both partners, the phenomenon was studied in fungi and in Pinus sylvestris roots. The strongest element-filtering effect was observed in R. roseolus / P. sylvestris symbiosis. This mycorrhiza type was characterized by the accumulation of heavy metals in the fungal mantle, and a gradual decrease of these elements was observed along the Hartig net towards the inside of the root. Potentially toxic elements were localized intercellularly in crystals deposited on the mantle and hyphal surface and in pigmented layer of the cell wall of the extramatrical hyphae, and the hyphae of the outer mantle layer. They were also detected intracellularly within electron-opaque depositions in the vacuoles. Much lower levels of toxic elements were detected in plant cells. The most common place for heavy metal accumulation was the phenolic material of the cortical cells.