The investigations described here were carried out in the context of our research project on the physiological, biochemical, and cytomorphological characterization of spruce trees growing in natural habitats and showing damage of varying intensity. Here we report on specific aspects of the photosynthetic apparatus. The aim of the measurements was to analyze whether or not the activity of the photosynthetic electron transport pathway is affected in damaged trees. The investigations were carried out on a 20 to 25-year-old spruce plantation in the Hunsrück mountains and on an 80-year-old spruce plantation in the Westerwald mountains. The photosynthetic electron transport rate was determined by photoreduction of 2,6-dichlorophenolindophenol. A decrease of the electron transport rate was shown in the damaged spruce trees in comparison to the apparently healthy trees. The investigation of the water splitting enzyme system - determined in the Hillreaction by feeding in electrons by means of diphenylcarbazide - indicates that the electron transport on the oxidizing side of photosystem II is impaired. The results imply that the photosynthetic electron transport chains in the thylakoid membranes of the spruce chloroplasts are sites of early injurious effects. This is in agreement with the electron microscopic analyses which show consistently that early damage occurs especially at the cellular membranes. This membrane damage is apparent even in the green needles of damaged spruce trees.

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In order to obtain an insight into the damage of thylakoid membranes of spruce (Picea abies) trees with damage of varying intensity, investigations were performed on the content of Qв-protein, cytochrome f, and P-700 in chloroplasts of spruce needles from apparently healthy and from damaged trees. Needles from the second and third needle year and the seventh whorl were chosen. The investigations were carried out in 1986 on a 20 to 25-year-old spruce plantation in the Hunsriick mountains and on an 80-year-old spruce plantation in the Westerwald mountains. In damaged trees an unequivocal decrease in the content of Qв-protein, cytochrome f, and P-700 was found, even in needle groups that appear visibly green and healthy. The amount of cytochrome f decreased by 25% per dry weight (approximately to the same extent as chlorophyll); the content of Qв-protein and P-700, however, were more drastically reduced compared to the control trees (about 40% and 50%, respectively). These results of measuring the photosynthetic electron transport components imply that the thylakoid membranes are sites of early injurious effects.

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