Some physiological effects of biocide treatment on the lichen Pseudeverniafurfuracea (L.) Zopf.

Detrimental effects of biocides on epiphytic lichens are known from mapping studies but their effects at the physiological level are not well studied. Pseudevernia furfuracea (L.) Zopf. thalli were transplanted from a natural forest habitat (Abieti-Fagetum dinaricum, Tregubov, 1957) to experimental plots of the Agronomy Department of the University of Ljubljana to study th e effects of biocide treatment on lichens in intensive apple cultivation. T he response of this lichen to the fungicide Score 250EC was also studied un der laboratory conditions and by spraying in the field. Net photosynthesis, chlorophyll fluorescence and pigment content (chlorophyll a and b, beta -c arotene, lutein and zeaxanthine) were analysed. Immersion of lichen into th e fungicide solution had little or no damaging effect on the optimal quantu m yield of photosystem II and on the concentrations of total chlorophyll, l utein, beta -carotene and zeaxanthine, but showed a significant depression of net photosynthesis together with a decrease of effective quantum yield o f photosystem II. Spraying with the same fungicide during the vegetation pe riod significantly decreased net photosynthesis in July and August but had avery slight effect on optimal and effective quantum yield of photosystem I I and an the content of pigments except zeaxanthine, the concentration of w hich increased after sprayings. The response of Pseudevernia furfuracea to a mixture of biocides during the regular spraying programme in an intensive apple cultivation showed a decline in net photosynthesis from June to Augu st and a small effect on the optimal and effective quantum yield of photosy stem II. This treatment also resulted in a decrease of total chlorophyll fr om May till beginning of July but had a diverse effect on the content of lu tein, beta -carotene and zeaxanthine. The response of the lichen to the tre atments in the field and laboratory conditions was partly different in type and extent of measured parameters due to the state of the lichen thalli un der experiment, dose of biocide applied and interference of heterogeneity o f lichen thalli and environmental conditions.