Patterns and mechanisms of transpiration in a large subalpine Norway spruce (Picea abies (L.) Karst.)

In situ water relations of a large subalpine Norway spruce (Picea abies) were analyzed by simultaneous measurements of sap flow at different crown positions. In the diurnal scale, transpiration varied greatly, both spatially and temporally. Over longer periods, however, different parts of the crown transpired in fairly constant proportions. The average estimated transpiration was about 3.5 times greater in the upper than in the lower half and decreased 1.6-fold from south to north. Water intercepted from rain, fog and dew buffered and significantly decreased the transpiration. The effect was strongest in those parts which were least coupled to the free atmosphere. The top of the crown seemed to experience a regular shortage of water shortly after starting transpiration, when it was forced to switch from internal reserves to sources in the soil. Further, lower branches then started transpiring, which may have led them to compete for the water. An enhanced nocturnal sap flow during warm and dry winds (Foehn) indicated that the tree also transpired at night. Shaded twigs had more capacity to intercept water externally than twigs in the sun. The significance of the crown structure for interaction with water in both liquid and vapour phases is discussed.     

Seasonal variation in the monoterpenes in needles of Picea abies (L.) Karst.

Summary This investigation was conducted to obtain information about the fluctuations in composition and amount of needle monoterpenes during the development of spruce needles. Studies conducted with two Norway spruce clones clearly revealed the existence of fluctuations. In juvenile needles, the amounts of the oxygenated terpenes increase constantly with age during the first 2 months of needle growth. The hydrocarbon terpenes dominate within the first weeks, some of them even showing a very distinct first maximum within the first 3 weeks after bud burst. All terpenes, including the oxygenated ones, have a maximum in June/July, which favours the hypothesis of a substitution of the hydrocarbons later on. There are significant changes even in mature needles of Norway spruce. The terpene level of 1-year-old needles of the clonal trees increased from spring to early summer and then dropped again towards winter. In addition, fluctuations in mature needles were shown for a set of ten wild trees. Needles of the same age class, which emerged in 1986, were sampled 4 times from 1986 to 1988. The needle terpene concentrations of the 1 -year-old needles were considerably lower in spring at the time of bud burst than in autumn. The terpene level of older needles thus seems to be influenced by biosynthetic and catabolic activities.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary This is the first in a series of papers on the growth, photosynthetic rate, water and nutrient relations, root distribution and mycorrhizal frequency of two Norway spruce forests at different stages of decline. One of the stands was composed of green trees only while the other included trees ranging in appearance from full green crowns to thin crowns with yellow needles. In this paper we compare the growth and carbohydrate relations of the two stands and examine relationships among growth variables in ten plots. The declining stand produced 65 percent of the wood per ground area compared with the stand in which all trees were green because its foliage produced less wood at any level of leaf area index. The difference in foliage efficiency between the sites could not be explained by differeneces in climate, competition or stand structure. The declining stand appeared to have lower carbon gain as indicated by a smaller increase in reserve carbohydrates before bud break, and weaker sinks for carbohydrates as indicated by less use of the stored carbohydrates than the healthy stand. Thus, growth reduction was probably related to factors which affect both photosynthesis and, even more, the sinks for carbohydrate.     

Phloem transport in Picea abies (L.) Karst. in mid-winter

Summary Translocation of ¹⁴C assimilates was studied on four different transport systems of Picea abies branches after induced activation in January. ¹⁴CO₂ assimilation of terminal shoots for 48 h at 25° C resulted in phloem loading and basipetal transport of ¹⁴C photosynthate into the following, older shoot generations. ¹⁴C import was enhanced, when these older shoot generations were kept in the dark. Microautoradiographs of the labelled terminal shoots showed that ¹⁴C assimilates were exported from needles via sieve elements of the leaf traces and loaded into the latest increment of the axial secondary phloem. No ¹⁴C label appeared in the obliterated sieve cells or in the tracheids. In addition, ¹⁴C photosynthate accumulated densely in the chlorophyllous cells of the cortex and in cells of the resin ducts, indicating certain sink activity. In the darkened 2-year-old shoot, imported ¹⁴C photosynthate was concentrated in the functional secondary phloem, while some ¹⁴C label was unloaded into the latest xylem increment. When 6-year-old shoots were exposed to ¹⁴CO₂ for 48 h in the light, ¹⁴C assimilates accumulated in the phloem of the leaf trace and in the latest increment of the axial secondary phloem. However, a substantial amount of radioactivity was unloaded into ray cells and phloem parenchyma cells. Thus, the presence of functioning phloem in needles and twigs of P. abies during winter allows long-distance translocation and radial distribution of assimilates according to existing source-sink relations.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary The water relations of Picea abies in a healthy stand with green trees only and a declining stand with trees showing different stages of needle yellowing were investigated in northern Bavaria. The present study is based on observations of trees differing in their nutritional status but apparently green on both sites in order to identify changes in the response pattern which might be caused by atmospheric concentrations of air pollutants and could lead to the phenomenon of decline. Transpiration was measured as water flow through the hydroactive xylem using an equilibrium mass-flow measurement system. Total tree transpiration was monitored diurnally, from July 1985 until October 1985 at both sites. The relationship between transpiration and meteorological measurements indicated that transpiration was a linear function of the vapor pressure deficit. No differences in transpiration of green trees were observed between the two sites. Canopy transpiration was 57%–68% of total throughfall and 41%–54% of total rainfall. Due to this positive water balance, soil water potential at 10 and 20 cm depths remained close to-0.02 MPa (max.-0.09 MPa) for most of the summer. Soil water potential was correlated with the difference between the weekly precipitation and transpiration. No differences in the water relations of apparently healthy trees in the two P. abies stands were observed. It is concluded that differences between green trees at the two sites in terms of nutrient relations or growth rate cannot be explained by changes in whole-tree transpiration or soil water status.     

Respiration and photosynthesis in cones of Norway spruce (Picea abies (L.) Karst.)

Summary Dark respiration and photosynthetic carbon dioxide refixation in purple and green Picea abies cones were investigated from budbreak to cone maturity. The rate of dark respiration per unit dry weight and CO₂ refixation capacity decreased during cone maturation. At the beginning of the growing season, photosynthetic CO₂ refixation could reduce the amount of CO₂ released by respiration in green and purple cones by 50% and 40%, respectively. The seasonal performance of the components of the cone carbon balance was calculated using information on the seasonal course of respiration, refixation capacity and the light response curves of cone photosynthesis, as well as the actual light and temperature regime in the field. The daily gain of CO₂ refixation reached 28%–34% of respiration in green and 22%–26% in purple cones during the first month of their growth, but decreased later in the season. Over the entire growth period refixation reduced carbon costs of cone production in both cone colour polymorphs by 16%–17%.     

Naturally occurring monoterpenoids in needles of Picea abies (L.) Karst

Summary An analysis was made of the effects of different sampling and extraction techniques on the amounts and pattern of monoterpenoids isolated from needles of Norway spruce. The following isolation and analysis procedure was finally adopted: liquid nitrogen-cooled needles were pulverized by a microdismembrator, extracted with pentane overnight at 2°–3°C and concentrated to a volume not less than 3 ml/g fresh weight on a Vigreux column. The crude extract was injected splitless (with solvent split) onto a cold programmed temperature vaporized (PTV) precolumn of a gas chromatograph and the vaporizable compounds heated to a capillary column. This method was tested for production of artefacts and quantitative extraction and applied to needles of eleven 80-year-old spruce trees.     

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.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary A declining Picea abies (L.) Karst. stand produced as much foliage and branches as a healthy stand but less stemwood at a similar leaf area index and climate. Nutrient analyses revealed that most biomass components at the declining site had lower concentrations of calcium and magnesium, but similar nitrogen and potassium (except for lower potassium in younger needles) and higher phosphorus, manganese and aluminum than the respective components at the healthy site. Comparison of these data with the results from studies on the nutrition and growth of P. abies seedlings (Ingestad 1959) led to the conclusion that the healthy stand is in a balanced nutritional state, while trees at the declining stand have only 56% of the foliar magnesium concentration required to permit growth at a rate which could be achieved at their nitrogen status. It appears that acidic deposition, which involves an input of nitrogen and a leaching of cations from the soil, causes an imbalance in the availability of nitrogen and magnesium. Growth is eventually reduced as magnesium becomes limiting.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary The development of root tips and apparent ectomycorrhizas was compared in the Fichtelgebirge (FRG) over one growing season in two 30-year-old Picea abies stands, both on soils derived from phyllite but showing varying symptoms of decline. Visual symptoms of tree decline reflected a lower relative and absolute mycorrhizal frequency, a lower number of ectomycorrhizas per m² leaf area and an uneven vertical distribution of root tips and ectomycorrhizas. The number of apparent ectomycorrhizas per ground area was correlated with the amount of magnesium, calcium, and ammonium, and the pH in the free-drainage soil solution, and with the molar calcium to aluminium ratio in mineral soil extracts. The foliage concentrations of magnesium and calcium were correlated with the numbers of apparent ectomycorrhizas per m² leaf or ground area. These observations were used to formulate testable hypotheses concerning the role of the root system and the soil environment in forest decline.     

Resistance to water flow in xylem of Picea abies (L.) Karst. trees grown under contrasting light conditions

Summary The relative hydraulic conductivity (k) of xylem and resistance (R) to water flow through trunk, primary roots and branches in Picea abies trees growing under contrasting light conditions were investigated. The xylem permeability to water was measured by forcing 10 mM water solution of KC1 through excised wood specimens. From the values of k, the sapwood transverse area and the length of conducting segments, R of the whole trunk, branches and roots was calculated. The relative conductivity of xylem in open-grown trees exceeded that of shade-grown trees by 1.4–3.1 times, while k was closely correlated with the hydraulically effective radius (R _e) of the largest tracheids (R ² was 0.85–0.94 for open- and 0.51–0.79 for shade-grown trees). Because of both a low k and a smaller sapwood area in shade-grown trees the resistance to water movement through their trunk, roots and branches was many times higher. The distribution of R between single segments of the water-conducting pathway differed considerably in trees from different sites. At high water status the largest share of the total resistance in open- as well as shade-grown trees resides in the apical part of the trunk. The contribution of the branches to total xylem resistance is supposed to increase with developing water deficit.     

Dendrochronology of Norway spruce (Picea abies (L.) Karst.) from two range centres in lowland Poland

In Europe, spruce grows in two main regions which meet in Poland, one to the north and east, the other to the south and west. The northeastern area ranges from the northern treeline extending from Norway to Siberia, to southern Sweden, north-eastern Poland and the southern Ural mountains. The southwestern spruce region reaches the mountainous areas of the Alps and the Balkans, the mountains and uplands of the Sudety Mountains, the Carpathians and neighbouring lowlands. Opinions about the distribution of Norway spruce have changed over the years, and its scarcity in the centre of Poland has been strongly debated. The favoured current theory is that Norway spruce once had a continuous distribution in Poland. It is assumed that the rare occurrence in the central Polish lowland is due to a combination of unfavourable soil conditions and previous management activity. The main aim of this work was to analyse climate–growth relationships of Norway spruce in eastern Poland and distinguish regions with similar increment patterns with regards to spruce range. Spruce growth in northern Polish sites is positively correlated with rainfall from May to July. Tree-ring widths in southern sites are more correlated with March temperature. Selected homogenous regions are the same as range types. Trees from the so-called “spruceless area” seem to have similar climate–growth relationships to trees from the southern region. This finding does not settle the question of the origin of the trees, but it does indicate that similar environmental conditions exist in these two areas and proves that the climate was not a limiting factor there.

Genetic polymorphism in Norway spruce,Picea abies (L.) Karst,assessed by two-dimensional gel electrophoresis of needle proteins

Summary A comparative analysis of three Norway spruce genotypes by two-dimensional gel electrophoresis is presented. This study has led to the identification of approximately 970 gene products for each genotype. Significant qualitative and quantitative differences have been identified, and qualitative and quantitative divergence indices between genotypes have been computed. Two-dimensional electrophoresis appears to be an efficient tool for studying modifications of gene expression in Norway spruce in response to climatic and pollution stresses.     

Fine-root morphology and uptake of 32P and 35S in a Norway spruce (Picea abies (L.) Karst.) stand subjected to various nutrient and water supplies

An investigation of fine (< 1 mm in diameter) and small (1–2 mm in diameter) roots in the organic soil layer was carried out in a Norway spruce forest stand with different treatments of water and nutrients, including control (C); ammonium sulphate application (NS); nitrogen-free fertilization (V); irrigation with liquid fertilization (a complete nutrient solution) (IF); NS followed by artificial drought (ND); V followed by artificial drought (VD). In order to evaluate the vitality and function of the fine roots, the following approaches were used: i) classification of fine roots, based on morphological characteristics; ii) nutrient uptake bioassay, using ³²P-phosphate and ³⁵S-sulphate; iii) nutrient concentration in fine roots and its relation to nutrient uptake. The NS treatment showed effects on the fine and small roots, with a decrease in amount of living roots, and a decrease in the total amount of fine and small roots. The VD treatment resulted in increased amounts of living small roots, while the ND treatment showed the opposite, as compared with the V and NS treatments, respectively. The uptake of P was negatively related to the P supply, with a higher P uptake for C and NS fine roots than for IF and V fine roots. The specific root length (SRL, m g^-1 DW) decreased for NS fine roots and increased for IF fine roots, indicating a further increase in uptake for NS roots and a decreased uptake for IF roots if calculated on a root length basis. So far, the NS and IF treatments maintain a considerable increase in above-ground biomass with a significantly reduced root biomass and standing crop.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary Photosynthetic rates and nutrient contents of spruce needles were measured in a region with high levels of air pollution in NE Bavaria, Germany (FRG), and compared to spruce grown under clean air conditions at Craigieburn, in the South Island of New Zealand (NZ). The absolute rates of CO₂ uptake, the slope of the CO₂ response curve at 240 l l^–1 internal CO₂ concentration, and the change of photosynthetic rates with needle age at ambient and saturated CO₂ concentrations were virtually identical at both measuring sites. These results confirm an earlier conclusion, that there is no long-term effect of atmospheric pollutants directly on photosynthetic CO₂ uptake rates with persistent exposure at the FRG site to high levels of anthropogenic air pollution. Photosynthetic capacity at saturating CO₂ concentration was three times higher in the NZ spruce. Needles with high photosynthetic capacity in NZ had lower nitrogen and higher calcium concentrations per unit dry weight but higher concentrations of nitrogen, phosphorus, potassium, magnesium and calcium per unit leaf area, and twice the specific leaf weight.     

The seasonal variation of 20 elements in 1st and 2nd year needles of Norway spruce,Picea abies (L.) Karst

Summary The concentration of 20 elements (including eight nutritional elements) in spruce needles was monitored by taking samples at nine different dates in a single year. On each date the youngest and the 1-year-old needles were collected at four different sites. The needles were washed with an organic solvent to remove surface contamination before analysis by instrumental neutron activation. Although the sites showed widely different concentrations for the same element, they could be treated as a uniform population using normalized concentration values. Taking the time dependence of the concentration and the ratio of the concentrations in new and old needles as criteria, the following three groups of elements could be distinguished: 9 group I —Ca, Sr, Ba, and Mn; group II — Al, Br, Co, Fe, Hg, La, Sc, Sb, and Zn; group III — K, Rb, Cs, P, and Cl. Mg and Na did not fit into any of these groups. Within group I and III elements the strongest variations occur during the growing season (late spring and early summer) and the weakest during the dormant season; the variation is greater in the younger needles. Group II elements show an approximately linear increase throughout the year in both the younger and older needles. The concentrations of elements of groups I and II increase with time, while those of group III decrease. Na is unique insofar as its concentration is influenced by foliar uptake of road de-icing salt. The concentration of elements belonging to the same group shows strong inter-element correlations. The grouping of elements deduced here shows similarities with the chemical nature of the elements and with their transportability within the plant.     

Within-population variation in susceptibility to Agrobacterium tumefaciens A281 in Picea abies (L.) Karst

Summary The purpose of this study was to investigate the genetic variation of susceptibility to Agrobacterium within a Picea abies population. Tumor formation was studied in 16 open-pollinated families belonging to a central Swedish population of Picea abies. Strain A281 of Agrobacterium tumefaciens was used to infect 3-monthold seedlings in a five-block greenhouse experiment. The analysis of variance showed strong significance for the between-family variation of tumor-formation percentages, varying from 28% to 73%. The most susceptible material will be suitable for experiments on the production of transgenic plants in vitro using disarmed Agrobacterium strains.     

Fungal injury to seed tissues of Norway spruce,Picea abies (L.) Karst.

Norway spruce bore an abundance of cones in Finland in 2000, but these cones were often fungal-infected. The seeds had structural injuries that were revealed when seed samples were examined using light (LM) and a field emission scanning electron microscope (FESEM). Two main types of spores were found either in the tissues inside the seed coat or on the sarcotesta, the outermost layer of seed coat. The spores of Chrysomyxa pirolata appeared particularly in the nucellar tissue, where the cell walls were disintegrated at the middle lamellae and cytoplasm was disrupted. Degenerated remnants of fungal structures resembling aecial peridium were found close to aeciospores. The tissue of the megagametophyte differed also from that of a normal mature seed. Conidia of Thysanophora penicillioides were often encountered on the sarcotesta where the ordinary wax cover was missing. Fungal injury occurred in the nucellar layers that shelter the embryo and megagametophyte from desiccation and oxidation. Destruction of these structures together with rapid opening of the seed coat advance deterioration of seeds during storage and may cause unexpected economic losses in forest plant production.     

CO2 fixation in stem slices of Picea abies (L.) Karst: microautoradiographic studies

Summary Microautoradiography was used to show that chlorophyllous cells of young Picea abies stem slices are able to fix ¹⁴CO₂, in the dark as well as in the light. The amount of ¹⁴CO₂ fixed in the dark is much lower than that in the light. In the dark the concentration of radioactive label is equally high in all chlorophyllous cells of the stem. In the light, however, a gradient of radioactive assimilates extends from the stem surface to its centre, with the highest concentration being located in the phelloderm and the outer one-third of the cortex. This is in spite of even illumination and CO₂ supply across the whole stem slice. In the dark, stem slices with and without bark show the same amount of radioactive label in the chlorophyllous cells of xylem, perimedullary region and pith. In the light, however, the concentration of radioactive assimilates in these cells is much higher in stem slices with bark than in stem slices without bark. It is assumed therefore that light fixation products of phelloderm and cortex are transported radially into the tissue inside the cambium.     

The ion concentration of dew condensed on Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) needles

Summary Dew droplets collected with pipettes from coniferous needles were analysed for their ionic composition. Almost all samples of dew taken from Scots pine trees (Pinus sylvestris) showed significantly higher ion concentrations than those taken from Norway spruce trees (Picea abies). This can be explained by the micromorphology of the needle surface. The higher microscale roughness of the wax layer of a pine needle causes a more efficient flux of atmospheric aerosol particles compared to the spruce needle surface. Dew on coniferous needles is shown to be capable of maintaining pH values below 3 for several hours.