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A total of 1800 3-year old seedlings of Norway spruce (Picea abies (L.)Karst.) from two Norwegian and one German provenance were treated with two different nitrogen levels during the 1992 growth season. The plants were kept during the following winter at two different temperature levels. In the spring of 1993 the nutrient application was resumed, and the plants were divided between three different treatments, 350 and 650 p.p.m. in open top chambers and a control plot outside the chambers. This treatment was repeated also during the following 1994 season.The growth and primary production was studied by photosynthesis experiments and by non-destructive growth measurements. The results indicate that raised winter temperatures may lead to increased needle loss and reduced growth the following season, particularly in northern provenances. Carbon dioxide significantly influenced growth in addition to nutrient level and winter temperature High CO2 also seemed to cause increased photosynthesis at early season, and earlier budbreak and growth cessation than in control plants.


Roots of Picea abies seedlings were inoculated with pathogenic Pythium dimorphum. The ongoing lignification process, the accumulation of lignin, and the distribution of flavanols and condensed tannins (CT), were related to the concurrent visual disease symptoms, hyphal colonization, and cellular changes. The hyphae ramified in both the cortex and the stele within 24 h. Three days after inoculation the concentration of lignin had increased to a level twice that in noninfected tissues. With histochemical staining, the accumulation of lignin and the ongoing lignification were co-located in the inner cortex layer 4-6 days after infection. Comparison of temporal onset of lignification with the timing of the intruding hyphae shows that this defense response occurs too late to effectively prevent the pathogen from spreading. Flavanols and CT were also detected in both infected and noninfected roots.Increased staining of these compounds in infected roots was often detected in the inner cortex. Electron microscopic studies revealed that at least some of these phenolic compounds were localized either as spherules or as a layer appressed to the tonoplast of the central vacuole.