BIOCHEMICAL INDICATORS FOR NOVEL FOREST DECLINE IN SPRUCE

The impact of air pollution on 24 stands of spruce trees in several re gions in Germany was investigated. We looked for evidence of biochemic al and physiological change at the level of the photosynthetic thylako id membranes as well as for changes in the antioxidative system in two year old needles. We observed that, as the chlorophyll content decrea ses in the needles, the amount of D1 protein declines far more rapidly in relation to the redox components P700 and cytochrome f. Consequent ly, the PSII/PSI stoichiometry keeps dropping to progressively lower, meaning unfavorable, values as the chlorophyll content diminishes. Thi s is particularly the case in the higher elevations (>550 m), where th e stronger solar irradiation synergistically accentuates the damaging effect. The alpha-tocopherol concentration characteristically increase s while the D1 protein content falls. The higher alpha-tocopherol valu es, however, are obviously neither able to protect the D1 protein from degradation nor to compensate for the higher oxidative stress. Apart from that the ascorbate/tocopherol ratios remained in the majority of cases in the unfavorable range of far below 10, where an effective pro tection of the membranes from free radicals is not guaranteed. This th en is mirrored in the increased degradation of D1 and the lower PSII/P SI ratio. (C)1998 Elsevier Science Ltd.