ULTRASTRUCTURE OF MESOPHYLL CELL CHLOROPLASTS OF SPRUCE NEEDLES EXPOSED TO O-3, SO-2 AND NO-2 ALONE AND IN COMBINATION

Four-year-old spruce trees (Picea abies (L.) Karst) were fumigated in a phytotron either with O3, SO2 or NO2 (1000 ppb each) for 3 weeks, and for 2 weeks with O3 + NO2 (600 + 360 ppb) or with 03 + NO2 + SO2 (600 + 360 + 240 ppb). At the end of the experiments, samples from 1-year-old needles were subjected to light and electron microscopic investigations. O3 treatment resulted in starch accumulation in the plastids; other effects were. not detected. Fumigation with SO2 or NO2 led to swollen thylakoids and a reduction in the number of grana stacks, when compared with the control. Starch contents were reduced by SO2, but enhanced by NO2. After treatment with gas mixtures, starch contents increased together with a partial swelling of thylakoids. Despite the high amounts of gases applied in the mixtures, a clear degradation of membranes could not be observed. For every treatment the cytological response of the cells was slightly different. Though clear stress symptoms appeared in the samples, there was no typical cytological reaction for a defined treatment, either for single gases or for their mixtures under the applied conditions.