CONDITION OF SCOTS PINE FINE ROOTS AND MYCORRHIZA AFTER FUNGICIDE APPLICATION AND LOW-LEVEL OZONE EXPOSURE IN A 2-YEAR FIELD EXPERIMENT

In a 2-year experiment at an open-air ozone fumigation field, the effe cts of fungicide application and low-level ozone exposure, single and combined, on fine root and mycorrhiza condition of Scots pine (Pinus s ylvestris) seedlings were studied. Two different fungicides, copper ox ychloride and propiconazole, with different modes of actions, were use d. Propiconazole treatment reduced mycorrhizal infection in both years while copper oxychloride treatment and ozone exposure slightly stimul ated mycorrhizal infection after the first year. Different mycorrhizal morphotypes showed different kinds of responses to the two fungicides . Light brown morphotype appeared to be the most sensitive one to prop iconazole treatment. After the second year, ectendomycorrhizas disappe ared in propiconazole treatment while in control treatment ectendomyco rrhizas formed the majority of the light brown morphotype. The root bi omass was not affected by fungicide treatments, but ozone exposure inc reased the total amount of short roots and the fresh weight of propico nazole treated roots. No significant differences in the concentrations of ergosterol, starch and total phenolics in pine roots between treat ments were found. However, ergosterol concentration correlated positiv ely with the mycorrhizal infection level. Both fungicides reduced the soil respiration compared to controls. At the ultrastructural level, b oth fungicides caused increased transparency and gradual granulation a nd degeneration of cytoplasm in the fungal symbiont of mycorrhizal sho rt roots. Slightly elevated ozone did not have harmful effects on root ultrastructure. These results suggest that fungicides have deleteriou s effects on the quantity and quality of mycorrhizas in Scots pine roo ts and also side-effects on non-target soil fungi. Some of these delet erious effects were noticeable only at the ultrastructural level.