Effects of nitrogen availability on secondary compounds, mycorrhizal infection, and aphid growth of 1-year-old Scots pine (Pinus sylvestris L.) seedlings were studied during one growing season. Seedlings were fertilized with nutrient solutions containing low, optimum, and two elevated (2 × and 4 × optimum) levels of NH4NO3. At the end of growing season foliar nitrogen concentration, needle biomass, needle length, water contents of needles, root collar diameter, and number of buds increased with enhanced nitrogen availability. Addition of nitrogen did not have effect on concentrations of monoterpenes in growing needles, but in mature needles significantly decreased concentrations of some individual and total monoterpenes were detected. In growing needles the concentrations of some individual resin acids decreased, and in mature needles concentrations of some individual and total resin acids increased with increased nitrogen fertilization. Higher numbers of resin ducts were found in mature needles with nitrogen fertilization. Nitrogen fertilization decreased total phenolic concentrations in growing and mature needles of the current year, but in needles of the previous year no significant differences occurred. Mycorrhizal infection was highest at medium (optimum and 2 × optimum) nitrogen fertilization levels. The relative growth rate (RGR) of grey pine aphid [Schizolachnus pineti (F.)] responded positively to the increase in foliar nitrogen content. However, the increase in aphid performance between optimum and the highest fertilization level was slight. This may indicate a deterring effect of resin acids on aphids. The results indicate that carbon/nutrient balance hypothesis fails to predict directly the effects of nitrogen availability on concentrations of carbon-based defensive compounds in mature foliage. Altered nitrogen supply affects allocation to secondary metabolites differently, depending on the developmental state of the plant and the biosynthesis pathway, cost of synthesis, and storage of compounds.

Monoterpenes were analysed in needles of clonal Picea abies (L.) Karst. exposed to drought and waterlogging. In drought-stressed trees the amounts of tricyclene, α-pinene, and camphene were significantly (p < 0.05) higher than in the control trees. In the drought treatment the total terpene concentration was also significantly (p < 0.05) higher. Waterlogging did not have significant effects on individual terpenes and total terpene concentration. However, multivariate redundancy analysis indicated that the effect of treatments on all the compounds simultaneously was not significant (p = 0.12). These results are discussed in terms of their potential impact on preferential selection of host plant by insects. Key words: drought, needles, Picea abies, terpenes, waterlogging.

No abstract

The ultrastructure of current and previous year needles of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L.) Karst. was studied after exposures to several different ozone concentrations (100 to 600 nL∙L−1) and doses in a chamber system. The ultrastructural changes observed in different experiments in both of these species were qualitatively very similar. Changes were observed in the mesophyll tissue, in which increased density of chloroplast stroma and an increase of ribosome-like granules were the early symptoms, followed by a decrease of the size of chloroplasts and starch grains. Simultaneously a decline of needle starch content could be measured. After fumigation with the lower concentrations, hypertrophy of microbodies were also apparent. When the seedlings were fumigated with the highest concentration (600 nL∙L−1) a subsequent disintegration of cytoplasm and other cell organelles and finally a collapse of the contents of the mesophyll cells, leading to visible injuries, was found. Scots pine nursery stock seedlings appeared to be about equal in sensitivity to ozone as Norway spruce clonal stock. The spruce clones showed differences in sensitivity to the ozone fumigations. Since the observed symptoms are consistent in two species through a concentration gradient of ozone, and also agree with the information dealing with ozone injuries in literature, it is possible to use ultrastructural observations for diagnosing the presence of ozone injuries. Keywords: ozone, Picea abies, Pinus sylvestris, needle ultrastructure, starch.

SUMMARYThe responses of Norway spruce and Scots pine to the effects of increased O^ and Ca or Mg deficiency stress, singly and in combination, for two growing seasons, were investigated in this study. The combination of openair exposure to O. conctntrations of 1-3-1-6 times higher than ambient, and an inadequate supply of Ca or Mg, did nol affect root uptake and leachinf> of minerals from the needles of 3-yr-old seediings, indicating that they had not dexeloptd se\t'rf nutrient detiLifncy, Howevt-r, concentration of X decreased in the 1-yr-old needles of seedlings exposed to O.,. The height of the new shoots was promoted w ithout an increase in shttot dry weight, which together with stimulated mywirrhiza development and decreased shoot-to-root radio indicated allocation of carbon from shoots to roots as an early effect of low-le\'el O^ exposure. Although the ultrastructural study did not reveal clear O3 related injuries in cells, starch accumulated in chloroplasts ofthe fumigated seedlings grown with adequate, but not with deficient nutrients. The outcome of this study suggests that in medium-term exposure of conifer seedlings to low concentrations of ()., iind nutrient deficienc\, stress can be tolerated by activated defence metabolism and compensation reactions, but adverse effects may be apparent in long-term continuous exposure.