Effect of exposure to fluoride,nitrogen compounds and SO2 on the numbers of spruce shoot aphids on Norway spruce seedlings

Summary Development of spruce shoot aphid (Cinara pilicornis Hartig) populations was monitored in natural and artificial infestations of Norway spruce (Picea abies Karst.) seedlings, exposed to air pollutants in an experimental field. The pollutants, applied both singly and in mixtures, were gaseous sulphur dioxide, NaF (30 mg l^-1 F) and Ca(NO₃)₂ or (NH₄)₂SO₄ in aqueous solutions (200 mg l^-1 N). Aphid numbers on 10 seedlings in each treatment and two control plots were counted at 2-week intervals. At the beginning of the experiment aphid numbers did not differ between treatments. Aphid populations peaked in late June and early July. All the pollutants and their combinations significantly increased the numbers of aphids per seedling. Four apterous females were transferred to spruce seedlings which were growing in containers in the same plots. After 4–5 weeks aphid numbers were significantly higher in the fluoride treatment and in the combined treatment of fluoride, nitrogen and SO₂. The pollution treatments did not have a significant effect on shoot growth. Concentrations of F and S in needles were higher in treatments involving these pollutants. There were no significant differences in the concentrations of free amino acids in shoot stems between control and fluoride treatment. However, the relatively low concentration of arginine in the F treatment at the end of the growing season might indicate disturbances in the nitrogen metabolism of spruce seedlings.     

Some effects of long-term ozone fumigation on Norway spruce

Summary Potted cuttings of a 12-year-old Picea abies tree were fumigated with ozone, 100 or 300 g O₃· m^–3 (50 or 150 ppb O₃) being added to charcoal-filtered air during the 1985 growing season for a total of 1215 h. The wax structure of ozone-fumigated needles was no different from that of controls. Because flattened wax structures and fused wax fibrils also occurred in controls, these phenomena could not serve as bioindications for the ozone concentrations applied. A smooth layer was found beneath the soluble wax layer and covered needle surface and stomatal openings of ozone-fumigated needles to a greater extent than in controls. Wax quantity was considerably reduced by fumigation with 300 g O₃ · m^–3. Leaf pigments (as extracted with the wax) were less abundant in needles treated with 300 gO₃; the smooth layer probably contributed to the impeded extraction of pigments.     

Effect of drought stress on chlorophyll a fluorescence and electrical admittance of shoots in Norway spruce seedlings

Effects of mild and severe soil drought on the water status of needles, chlorophyll a fluorescence, shoot electrical admittance, and concentrations of photosynthetic pigments in needles of seedlings of Picea abies (L.) Karst. were examined under controlled greenhouse conditions. Drought stress reduced shoot admittance linearly with a decrease in shoot water potential (_w) and increase in water deficit (WD) and led to a decrease in concentrations of chlorophyll a, b and carotenoids. Severe water stress (shoot _w=–2.4 MPa) had a negative effect on chlorophyll a fluorescence parameters including PSII activity (F_v/F_m), and the vitality index (R_fd). Variations in these parameters suggest an inhibition of the photosynthetic electron transport in spruce needles. Water stress led to a decrease in the mobility of electrolytes in tissues, which was reflected by decreased shoot electrical admittance. After re-watering for 21 days the WD in needles decreased and the shoot water potential increased. In the re-watered plants, the chloroplast function was restored and chlorophyll a fluorescence returned to a similar level as in the control plants. This improved hydraulic adjustment in the seedlings triggered a positive effect on ion flow in the tissues and increased shoot electrical admittance. We conclude that the shoot electrical admittance and photosynthetic electron transport in leaves are closely linked to changes in water status and their decrease is among the initial responses of seedlings to water stress.     

Some effects of long-term ozone fumigations on Norway spruce

Summary Potted cuttings of a 12-year-old, and grafts of an 80-year-old, Norway spruce (Picea abies (L.) Karst.) were subjected to 100 or 300 g O₃·m^–3 for 1215 h (45 h of daylight per week) during the growing season of 1985. At the end of the fumigation the plants did not exhibit any visible signs of injury. Whereas in the fumigation with 100g O₃·m^–3 we did not detect any significant change in gas exchange, 300 g O₃·m^–3 did alter the CO₂ uptake after 27 weeks, and in one clone transpiration was also altered. Stomatal reaction to a change of light suggested sluggishness, but the change was not statistically significant.     

Photosynthetic performance and nutrient status of Norway spruce [Picea abies (L.) Karst.] at forest sites in the Ore Mountains (Erzgebirge)

Summary Photosynthetic performance of several needle age classes of Norway spruce trees [Picea abies (L.) Karst.] in highly SO₂-polluted and heavily damaged forest sites was measured at two different locations in the Ore Mountains (Erzgebirge, Krusne Hory) during early summer. The carboxylation efficiency showed a dramatic drop from current-year's needles to 1-year-old needles with only a slight further decrease with increased needle age. The light use efficiency also revealed these characteristics. For both parameters, no linear decrease with needle age could be found. In contrast, the maximum photosynthetic capacity (A₂₅₀₀) decreased linearly with time and revealed a good correlation with the total sulfur content of the needles. Absolute values measured for A₂₅₀₀ were approximately 50% lower than those of comparable trees in the nearby Fichtelgebirge. Mineral deficiencies or acute nutrient imbalances of the needles were not detected. In contrast to the situation in the forests of the Fichtelgebirge, a direct effect of gaseous SO₂ on the trees in the Ore Mountains seems plausible.This paper is dedicated to our teacher Professor Otto Ludwig Lange on the occasion of his 65th birthday     

Cold acclimation was partially impaired in boron deficient Norway spruce seedlings

Susceptibility of trees to freezing injury has been suggested to increase in boron (B) deficiency but there is no experimental evidence to support this proposition. In this study, Norway spruce (Picea abies L. Karst.) seedlings were cultivated for two growing seasons in deficient, intermediate and ‘optimal’ B levels. Cold hardening of the seedlings was measured after the second growing season. Freezing tolerance in tips of shoots, needles, stems and roots was determined by controlled freezing tests and electrolyte leakage method, and that of buds, in addition, by differential thermal analysis (DTA). Electrical impedance was used to monitor changes in the apoplastic space during cold acclimation. Root dry weight and shoot height growth were lower in B deficiency. Cold acclimation of buds and stems was reduced by B deficiency. When hardened seedlings were subjected to subzero temperatures for 3 weeks, extracellular electrical resistance of stems became the highest at the lowest B supply which was probably due to decreased desiccation tolerance. As a conclusion, susceptibility to freezing damage may be increased by B deficiency in Norway spruce trees.     

Fine-root vitality in a Norway spruce stand subjected to various nutrient supplies

The vitality of fine roots in a Norway spruce stand subjected to application of ammonium sulphate (NS), wood ash (A) and nitrogen-free fertilizer (V) respectively, was investigated using i) vitality classification of fine roots based on morphological characteristics and ii) the triphenyl tetrazolium chloride (TTC) method of estimating dehydrogenase activity.Although the NS-treated areas showed a 30% increase in above-ground production in response to the NS-application, the vitality of the fine-root system in the humus layer appeared to be in a state of deterioration, as indicated by a decrease in fine-root biomass, an increased amount of dead fine (0–1 mm) and small (1–2 mm) roots, a decreased specific root length (SRL = fine root length/fine root dry weight) and an increased dehydrogenase activity. The impact of the the A and V treatments was reflected in a decrease in fine-root biomass and an increase in SRL. The results make it clear that in order to study the vitality of forest trees, both fine-root studies and studies of above-ground tree parts are necessary.     

Peroxisome proliferation in Norway spruce induced by ozone

Summary Catalase (EC 1.11.1.6) activity (both total and specific activity) of particulate fractions of needles of Norway spruce [Picea abies (L.) Karst.] was elevated approximately 2-fold following exposure of trees to 60–70 g/m³ of ozone during the growing season compared to trees receiving charcoal filtered air (about 15 g/m³ ozone). Measurements were from homogenates fractionated into particulate and soluble (supernatent) activities. In contrast, the catalase activity of the supernatant was unchanged in response to ozone treatment. Catalase activity declined as the needles aged comparing current, 1-, and 2-year needles but the ozone-induced increment remained constant. Electron microscope cytochemistry using peroxidatic coupling with 3,3-diaminobenzidine carried out in parallel, revealed catalase-containing peroxisomes both in situ and in the particulate fractions analyzed for catalase activity. The tissue volume occupied by peroxisomes in response to needle age and ozone appeared to vary approximately in proportion to the measured catalase activity. Overall cytochemical reactivity for catalase declined with needle age, but, for all years, was greater in needles of trees receiving air supplemented with ozone compared to those of trees receiving charcoal filtered air.Abbreviations DAB 3,3-diaminobenzidine tetrahydrochloride     

Effects of ozone on starch accumulation in Norway spruce (Picea abies)

Summary Fumigation with 100 g/m³ and 200 g/m³ ozone in closed-top fumigation chambers induced starch accumulation in chloroplasts of Norway spruce. This accumulation was probably due to a partial inhibition of the starch translocation at night. The intensity of the effect was dependent on the season and the age of the needles. The accumulation was reversed in winter. It is therefore unlikely that such an effect has much significance for plant health.     

Effects of varied soil nitrogen supply on Norway spruce (Picea abies [L.] Karst.)

During a seven-month period the effect of different nitrogen (N) availability in soil on growth and nutrient uptake was studied in three-year-old Norway spruce (Picea abies [L.] Karst.) trees. The plants were grown in pots on N-poor forest soil supplied with various amounts and forms (inorganic and organic) of N. Increasing supply of inorganic N (as NH₄NO₃) increased the formation of new shoots and shoot dry weight. The root/shoot dry weight ratio of new growth was drastically decreased from 1.6 in plants without N supply to 0.5 in plants supplied with high levels of NH₄NO₃. This decrease in root/shoot dry weight ratio was associated with distinct changes in root morphology in favour of shorter and thicker roots. The addition of keratin as organic N source did neither affect growth nor root morphology of the trees. The amount of N taken up by plants was closely related to the supply of inorganic N, and trees supplied with highest levels of NH₄NO₃ also had the highest N contents in the dry matter of needles and roots. In contrast, N contents in needles of trees grown without additional N, or with keratin supply, were in the deficiency range. Supply of NH₄NO₃ decreased the contents of phosphate (P) and potassium (K) and therefore markedly increased N/P and N/K ratios in the needles. On the other hand, the contents of calcium (Ca), magnesium (Mg), and manganese (Mn) in the needles were increased in the plants supplied with inorganic N, suggesting high soil availability and promotion of uptake of these divalent cations by high nitrate uptake. The observed effects on root/shoot dry weight ratio, root morphology, and mineral nutrient composition of the needles indicated that high inorganic N supply may increase above-ground productivity but at the same time decrease the tolerance of trees against soil-borne (e.g. deficiency of other mineral nutrients) stress factors. Deceased 21 September 1996 Deceased 21 September 1996     

Karyotype of Norway spruce by multicolor FISH

The chromosomes (2n = 2x = 24) of Norway spruce are very large since their size reflects the huge amount of genomic DNA (2C = 30 × 10⁹ bp). However, the identification of homologous pairs is hampered by their high degree of similarity at the morphological level. Data so far presented in the literature were not sufficient to solve all the ambiguities in chromosome identification. Several genomic Norway spruce DNA clones containing highly repetitive sequences have been identified and characterised in our laboratory. Three of them were selected for fluorescent in situ hybridization (FISH) experiments because of their strong signals and suitability for chromosome identification: PATR140 hybridized at the centromeric site of three chromosome pairs; PAF1 hybridized in six subtelomeric and two centromeric sites; 1PABCD6 co-localized with the subtelomeric sites identified by PAF1. The statistical analysis of microscopic measurements of chromosomes in combination with the FISH signals of these probes allowed the unambigous construction of Norway spruce karyotype. We also compared the karyotype of Norway spruce with that of other spruce species to infer the number and kind of rearrangements that have occurred during the evolution of these species.Communicated by D.B. Neale     

Experimental manipulation of water and nutrient input to a Norway spruce plantation at Klosterhede,Denmark

Water and nutrient supply to forest trees are major factors controlling tree growth and forest vitality. Therefore, changes in the supply of water and nutrients to the trees may be important contributing reasons to the forest damages observed in Europe. Such changes may be caused by several factors, e.g. air pollution, soil acidification and climate change. The present study investigates possible effects on tree growth, growth related parameters and nutrition related to changes in the water and nutrient supply. Water and nutrient supply to the forest soil was manipulated in three roof covered plots. The treatments consisted of 1) summer drought, 2) irrigation and 3) combined irrigation and fertilizer application (fertigation). The results from the roof covered treatment plots were compared to a control plot without roof. Increased supply of water during the spring and early summer increased the diameter growth, whereas application of nutrients in addition to irrigation had no additional effect on tree growth. Addition of nutrients increased the needle content of P, Mn, Ca and Mg. Extended summer drought for 2 months had no effect on the tree growth or other growth parameters, but drought reduced the root development in the upper soil layer. Furthermore, drought induced significant stress symptoms by increasing the cone shredding substantially.     

Effect of nitrogen on drought strain and nutrient uptake in Norway spruce Picea abies (L.) Karst.) trees

A field lysimeter study was established with the aim of investigating the effect of nitrogen availability upon drought strain in Norway spruce trees. Forest soil (Typic Udipsamment) was filled in lysimeters 1 m in diameter and 1 m deep. Small trees of Norway spruce from five different clones were planted in the lysimeters. Roofs under the canopy of the trees ensured full control of water and nutrient input. Three levels of nitrogen were given to the trees during five years; ambient rainwater, and five and fifteen times this N concentration, respectively. Additional N was given as NH₄NO₃ in irrigation water. Mean annual N-addition during the five years corresponded to 5, 27 and 82 kg per ha and year for the three treatments, respectively. During the third and fifth growth season drought was artificially induced. In addition to a watered control, two levels of drought were applied, representing water deprivation for 2 and 3 months, respectively, in 1990 and 3 and 4 months, respectively in 1992. A higher water consumption in the nitrogen fertilized trees during the droughts resulted in a significantly lower pre-dawn shoot water potential compared to the trees receiving ambient rain N. The interaction between drought and nitrogen fertilization was clear also for photosynthesis and transpiration. A decrease in height- and diameter increment caused by drought was most pronounced in the 82 kg N ha^–1 yr^–1 treatment. A water strain integral showed a strong positive correlation to the needle biomass of the trees. Foliar concentrations of several nutrients decreased significantly with increasing drought strain in the trees. Concentration of potassium and boron were especially low and visual symptoms of deficiency occurred.     

Growth and shoot: root ratio of seedlings in relation to nutrient availability

The influence of mineral nutrient availability, light intensity and CO₂ on growth and shoot:root ratio in young plants is reviewed. Special emphasis in this evaluation is given to data from laboratory experiments with small Betula pendula plants, in which the concept of steady-state nutrition has been applied.Three distinctly different dry matter allocation patterns were observed when growth was limited by the availability of mineral nutrients: 1, Root growth was favoured when N, P or S were the major growth constraints. 2, The opposite pattern obtained when K, Mg and Mn restricted growth. 3, Shortage of Ca, Fe and Zn had almost no effect on the shoot:root ratio. The light regime had no effect on dry matter allocation except at very low photon flux densities (< 6.5 mol m^-2 day^-1), in which a small decrease in the root fraction was observed. Shortage of CO₂, on the other hand, strongly decreased root development, while an increase of the atmospheric CO₂ concentration had no influence on dry matter partitioning. An increased allocation of dry matter to below-ground parts was associated with an increased amount of starch in the tissues. Depletion of the carbohydrate stores occurred under all conditions in which root development was inhibited. It is concluded that the internal balance between labile nitrogen and carbon in the root and the shoot system determines how dry matter is being partitioned in the plant. The consistency of this statement with literature data and existing models for shoot:root regulation is examined.     

Isolation of two cytokinin metabolites from the rhizosphere of Norway spruce seedlings (Picea abies L. Karst.)

Roots of young Norway spruce seedlings were incubated under hydroculture conditions in a synthetic nutrient medium containing either ³H-isopentenyladenosine, isopentenyladenosine or zeatin riboside. When feeding with ³H-isopentenyladenosine a new radiaolabelled metabolite was found in the feeding solution as well as in root extracts. Isopentenyladenosine and zeatin riboside were metabolised and for both compounds an unknown metabolite was detected in the feeding solution. The metabolites were purified by solid phase extraction, HPLC and partially characterised. A major characteristic of the metabolites is their reactivity in the presence of NH₄OH, which results in the formation of the cytokinin bases isopentenyladenine or zeatin, respectively. UV-spectra and the chemical characteristics indicate that the new metabolites are closely related. The GC-MS analysis revealed, that the metabolites are true derivatives of isopentenyladenine and zeatin. The biogenesis of the new metabolites is discussed with regard to plant microbial interactions.Abbreviations Ck(s) = cytokinin(s) - GC-MS = gas chromatography-mass spectrometry - iP = isopentenyladenine - [9R]iP = isopentenyladenosine - [9G]iP = isopentenyladenine-9-glucoside - [9R-MP]iP = isopentenyladenosine-5-monophosphate - Z = trans-zeatin - [9R]Z = trans-zeatin riboside     

The influence of ultraviolet-B radiation on the growth, pigment production and chlorophyll fluorescence of Norway spruce seedlings

Norway spruce (Picea abies (L.)Karst.) from seven seed sources was grown in a greenhouse with 8.3 and 14.7 kJ·m⁻²·d⁻¹ m UV-B_BE (biologically effective UV-B: 280–320 nm) irradiation, and with no supplemental irradiation as control. The seedlings total biomass (dry weight) and shoot growth decreased with high UV-B treatment but spruce from low elevation seed sources were more affected. The seedlings grown at the highest UV-B irradiance (14.7 kJ·m⁻²·d⁻¹) showed from 5 to 38% inhibition of total biomass and 15 to 70 % shoot growth inhibition. Norway spruce populations from higher altitude seed sources manifested greater tolerance to UV-B radiation compared to plants from low altitudes. Changes in phospholipids and protective pigments were also determined. The plants grown at the lower UV-B irradiance (8.3 kJ·m⁻²·d⁻¹) showed greater ability to concentrations UV-B-absorbing pigments then control plants. Chlorophyll a fluorescence parameter R_fd, (R_fd=(F_m-F_s)/F_s) showed a significant decrease in needles of UV-B treated plants and this correlated with the altitude of seed source. Exposure to UV-B affect levels of the ratio of variable to maximum fluorescence (F_v/F_m). Results from this study suggest that the response to increased levels of UV-B radiation is depended upon the ecotypic differentiation of Norway spruce and involved changes in metabolites in plant tissues.     

The mycorrhizal fungus Paxillus involutus transports magnesium to Norway spruce seedlings. Evidence from stable isotope labeling

Although it is well established that ectomycorrhizas improve the mineral nutrition of forest trees, there has been little evidence that they mediate uptake of divalent cations such as Mg. We grew nonmycorrhizal seedlings and seedlings mycorrhizal with Paxillus involutus Batsch in a sand culture system with two compartments separated by a 45-μm Nylon mesh. Hyphae, but not roots, can penetrate this net. Labeling the compartment only accessible to hyphae with ²⁵Mg showed that hyphae of the ectomycorrhizal fungus Paxillus involutus transported Mg to their host plant. No label was found in nonmycorrhizal control plants. Our data support the idea that ectomycorrhizas are important for the Mg nutrition of forest trees. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of water and nutrient supply on amount and on nutrient concentration of litterfall and forest floor litter in Eucalyptus globulus plantations

A field experiment was initiated in March 1986 in central Portugal to evaluate the influence of water and nutrient supply on the productivity of E. globulus. The treatments applied were, irrigation plus fertiliser, irrigation and the application of fertilisers in rainfed plots. The control received neither fertilisers nor irrigation. The annual pattern litterfall was measured over a period of 5 years and the litter layer was quantified 6 years after planting. The amount of litterfall varied with the treatments. Simultaneous water and nutrient supply increased significantly litterfall, in respect to control. In rainfed conditions the timing of the maximum of litterfall was anticipated relative to the irrigated plots. However, the time of maximum litterfall did not coincide with the dry season but rather with period of maximum growth in each treatment. The N and P concentration was higher in the litterfall of the two fertilised treatments than in the others. The lowest concentrations of N and P in the leaf litter were coincident with the summer period in all treatments. The withdrawal of N and P ranged between 32 and 65% according to treatment and season. The deliverance of nutrients through litterfall was strongly increased by simultaneous water and nutrient supply. The supply of fertilisers in rainfed conditions promoted higher deliverance of nutrients than in the plots irrigated only. The mass of the litter layer was significantly increased by simultaneous water and nutrient supply. Application of fertilisers induced an increase in N and P concentration and a decrease in C/N ratio of the litter layer. Treatments and C/N values did not influence apparently the proportion of carbon, N and P released through mineralization from the litter layer. The non-fertilized treatments showed a more efficient N cycling than the others.     

Modified expression of the Pa18 gene interferes with somatic embryo development in Norway spruce

The differentiation of a surface layer on the embryonal mass is one ofthe first markers for normal embryo development in Norway spruce. We havepreviously shown that this differentiation is closely interlinked with a switchin the expression pattern of Pa18, a putative lipidtransfer protein (LTP) gene. In transgenic embryos ofNorway spruce under- or overexpressing the Pa18 gene under the maize ubiquitin promoter, there is no switch in the expression pattern ofthe Pa18 gene and the embryos are blocked in theirdevelopment early during maturation. In this work, we describe how under- andoverexpression of Pa18 affect sequential developmentalstages during somatic embryogenesis. The differentiation of somatic embryosfromproembryogenic masses is not affected, but the morphology of early somaticembryos is changed. Both under and overexpressing somatic embryos can gothrougha maturation process, although at a much lower frequency than the controlembryos. Germination is not affected by altered Pa18expression. However, plants regenerated from under and highly overexpressingsomatic embryos cannot survive prolonged culture.     

Studies of crystallinity of Scots pine and Norway spruce cellulose

The variation in the mass fraction of crystalline cellulose (crystallinity of wood), the intrinsic crystallinity of cellulose, and the thickness of cellulose crystallites in early wood of Norway spruce [Picea abies (L.) Karst.], and Scots pine (Pinus sylvestris L.) grown in Finland were studied using wide angle X-ray scattering and nuclear magnetic resonance spectroscopy. The mass fraction of crystalline cellulose in wood increased slightly with the distance from the pith and was about 30±4% in mature wood of both species. The crystallinity of cellulose and the thickness of cellulose crystallites were almost constant for both species. The crystallinity of cellulose was 52±3% for both species and the average thickness of the cellulose crystallites was 32±1 Å and 31±1 Å for Norway spruce and Scots pine, respectively. The mass fraction of cellulose in wood, calculated from the crystallinity values, increased with the distance from the pith for both species.