ABSTRACT
In declining forests of the Vosges mountains (northeast of France), we previously observed that the yellowing of spruce (Picea abies L. cv. Karsten) needles was associated with impairment of the free radical scavenging capacity of the cells and coincided with chronic exposure to ozone. Chloroplasts of yellow needles were characterized by an abnormal accumulation of photosystem II (PSII) D1-protein in the thylakoids. Further experiments carried out on declining and decline-resistant individual spruce trees characterized in previous studies showed that needle yellowing was associated with impairment of the overall anti-oxidative defense in both the cytosol and the chloroplasts. Both enzymic (peroxidases) and non-enzymic (carotenoids) oxidant scavengers were shown to be affected in the declining spruce. PSII D1-protein accumulation seemed to result from a stabilization of the polypeptide, which led us to hypothesize that oxidative processes might interfere with the specific degradation of this protein in declining spruce, with destructive consequences for the photosystems.
