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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.

zeitschrift für naturforschung c

Investigation on the Photosynthetic Membranes of Spruce Needles in Relation to the Occurrence of Novel Forest Decline I. The Photosynthetic Electron Transport