Vegetative response of Arctostaphylos uva-ursi to experimental cutting and burning

Arctostaphylos uva-ursi uses vegetative resprouting to recover rapidly after disturbances. This study aims to widen knowledge of its regeneration response, so it was subjected to experimental cutting and burning. Fifteen pairs of small circular plots (50 cm diameter) were situated at random in an area where this species is abundant and forms homogeneous carpets with close to 100% cover. One plot of each pair was burned and the other one was cut. Initial biomass was estimated as dry weight from the cut plots. A 50 cm diameter circular sampling quadrat, divided into two concentric circles, was used in order to determine cover recovery and the way in which this occurred (predominantly by colonization from outside or uniformly over the whole surface). Initial recovery was very fast after both disturbances, exceeding 30% cover from the fourth month. Recovery of aboveground biomass was also similar on comparing both types of disturbance, but statistically significant differences with respect to initial values were detected.     

Effects of soil pH and calcium on mycorrhizas of Picea abies

The effects of lime, increased soil pH and increased soil Ca concentration on the mycorrhizas of Norway spruce. [Picea abies (L.) Karst.] were studied independently of each other to elucidate the different mechanisms through which lime may influence mycorrhizas in acidic soil. In a field experiment (mature Norway spruce in podzol), lime was applied as CaCO₃; increased Ca concentration without an increase in pH was achieved with CaSO₄; and soil pH was increased without calcium by means of Na₂CO₃ and K₂CO₃ (Na+K treatment). Treatments were done in October, and mycorrhizas were counted from samples collected in the following June and September. All treatments increased the percentage of dead short root tips compared to controls in September, and Na+K already in June. Cenococcum geophilum Fr. increased in proportion in plots treated with Na+K.In a sand culture experiment, Norway spruce seedlings were grown from seed and inoculated with Cenococcum geophilum, or root inoculum, or left uninoculated. When mycorrhizas were beginning to form, CaCO₃ and CaSO₄ treatments were applied. Six weeks later, the percent of dead short root tips in both salt treatments was significantly increased from control, but formation of mycorrhizas was not inhibited by treatments.As all the treatments increased the proportion of dead short root tips, it is concluded that lime directly and adversely affected mycorrhizas of Norway spruce in sand culture and in mor humus. Both increased ionic strength and increased pH may be reasons for this rather than Ca²⁺ specifically.     

Changes in root growth patterns of (Picea abies) spruce roots by inoculation with an ectomycorrhizal fungusPisolithus tinctorius and jasmonic acid treatment

Symbiosis between fungi and plant roots forming a mycorrhiza involves extensive interactions at the molecular level between both partners. The role of plant hormones in the regulation of mycorrhizal infection is not known to involve jasmonates. Their endogenous levels increase during pathogen attack; however, little has been done on their involvement in mycorrhizae. In our recent work, root growth patterns of 2-month-old spruce seedlings after inoculation withPisolithus tinctorius and/or jasmonic acid (JA) treatment were studied using a paper-sandwich technique. Changes in root length, the degree of branching, presence and length of root hairs, and infection parameters were followed using a stereomicroscope. The first mycorrhizal contact of hyphae with roots was significantly accelerated upon treatment with 0.5 M JA. Interactions between root hairs and fungal hyphae were seen by scanning electron microscopy. The multiplication of root hairs of non-mycorrhized seedlings treated with 5.0 M JA and changes of the root surface were observed by the same technique.     

Biochemical symptoms of stress in the mycorrhizal roots of Norway spruce (Picea abies)

Summary The mycorrhizal activity of spruce in a mixed-wood forest was monitored over 1 year by measuring biochemical characters in fine roots of six canopy trees and of a regrowth stand. The concentration of adenosine 5-triphosphate (ATP), a measure of living biomass, showed two peaks per year, one at bud break and one after main shoot growth. The concentration of storage polysaccharides in mycorrhizae showed the same cycles even more pronouncedly. It is proposed that these changes reflect growth and senescence of mycorrhizae and that the timing of the cycles is controlled by translocation of assimilates from the shoot. Differences between mycorrhizae collected from canopy trees and the regrowth stand were small and not significant. Characters known to be related to fungal activity of the mycorrhizal symbiosis (concentration of trehalose, glucose uptake, respiration) also varied little among the six canopy trees. Large differences among fine-root samples from different canopy trees, however, were detected in the concentrations of ATP and storage polysaccharides, measures which seemed to be physiologically integrated within trees. If low concentrations in roots precede losses of foliage from trees, these two symptoms could be used as early indicators of growth decline in individual spruce trees.     

Effects of liming and boron fertilization on boron uptake of Picea abies

The effects of liming on concentrations of boron and other elements in Norway spruce [Picea abies (L) Karst.] needles and in the mor humus layer were studied in long-term field experiments with and without B fertilizer on podzolic soils in Finland. Liming (2000+4000 kg ha^-1 last applied 12 years before sampling) decreased needle B concentrations in the four youngest needle age classes from 6–10 mg kg^-1 to 5 mg kg^-1. In boron fertilized plots the corresponding concentrations were 23–35 mg kg^-1 in control plots and 21–29 mg kg^-1 in limed plots. Both liming and B fertilizer decreased the Mn concentrations of needles. In the humus layer, total B concentration was increased by both lime and B fertilizer, and Ca and Mg concentrations and pH were still considerably higher in the limed plots than controls. Liming decreased the organic matter concentration in humus layer, whilst B fertilizer increased it.The results about B uptake were confirmed in a pot experiment, in which additionally the roles of increased soil pH and increased soil Ca concentration were separated by means of comparing the effects of CaCO₃ and CaSO₄. Two-year-old bare-rooted Norway spruce seedlings were grown in mor humus during the extension growth of the new shoot. The two doses of lime increased the pH of soil from 4.1 to 5.6 to 6.1, and correspondingly decreased the B concentrations in new needles from 22 to 12 to 9 mg kg^-1. However, CaSO₄ did not affect the pH of the soil or needle B concentrations. Hence the liming effect on boron availability in these soils appeared to be caused by the increased pH rather than increased calcium concentration.     

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.     

Nitrate reductase in needles,roots and trunk wood of spruce trees [Picea abies (L.) Karst.]

Summary Nitrate reductase (EC 1.6.6.2) activity (NRA), as measured by an in vivo assay, is present in needle leaves and mycorrhizal fine root tips of adult Norway spruce [Picea abies (L.) Karst.] in at least equal amounts on a fresh weight basis, in both adult and 5-year-old trees. NRA could also be demonstrated in trunk wood of deroted trees after fertilization with 5 mM , exhibiting a longitudinal profile in the trunk. Inducibility in needles can more efficiently be achieved by NO₂ (100 g·m^-3) than by 5 mM nitrate, which is effective only in root-amputated trees. A remarkably high level of needle-NRA in unfertilized trees, which are characterized by a very low level of nitrate in the xylem sap, suggests that NRA in spruce needles may in part be constitutive. Organic-N is a major nitrogen source for the needles even in root-amputated trees, indicating pronounced exchange processes between ray parenchyma and trunk xylem, which in turn are modified by the nitrogen source fed to the trunk stump. Intact trees exhibit a very similar amino acid composition of the xylem sap, regardless of whether or has been fed. The amino acid pattern of the needles is not thrown out of balance by flooding with and , which occurs in fertilized derooted trees. This indicates a distinct potential for homoeostasis of nitrogen entrance-metabolism (i.e. NRA and glutamine synthetase activity) in the needles. In the ectomycorrhiza/fine root-system (EMC), marked differences in NRA were observed depending on root-tip diameter and along the longitudinal profile of the fine roots. EMC-nitrate reductase is strongly enhanced by . Needle-NRA exhibits a circannual rhythm. An early summer maximum is followed by a December minimum. This activity pattern matches well the transitory increase of soluble nitrogen in spring and the total protein maximum in winter. In an indirect way assimilatory NRA may well contribute to nitrogen overfertilization (by consumption of NO_X) as one possible cause of the contemporary decline of spruce populations.     

Ammonium and nitrate uptake rates and rhizosphere pH in non-mycorrhizal roots of Norway spruce [Picea abies (L.) Karst.]

Summary Relationships between root zone temperature, concentrations and uptake rates of NH ₄ ⁺ and NO ₃ ^– were studied in non-mycorrhizal roots of 4-year-old Norway spruce under controlled environmental conditions. Additionally, in a forest stand NH ₄ ⁺ and NO ₃ ^– uptake rates along the root axis and changes in the rhizosphere pH were measured. In the concentration (C_min) range of 100–150 M uptake rates of NH ₄ ⁺ were 3–4 times higher than those of NO ₃ ^– The preference for NH ₄ ⁺ uptake was also reflected in the minimum concentration (C_min) values. Supplying NH₄NO₃, the rate of NO ₃ ^– uptake was very low until the NH ₄ ⁺ concentrations had fallen below about 100 M. The shift from NH ₄ ⁺ to NO ₃ ^– uptake was correlated with a corresponding shift from net H⁺ production to net H⁺ consumption in the external solution. The uptake rates of NH ₄ ⁺ were correlated with equimolar net production of H⁺. With NO ₃ ^– nutrition net consumption of H⁺ was approximately twice as high as uptake rates of NO ₃ ^– In the forest stand the NO ₃ ^– concentration in the soil solution was more than 10 times higher than the NH ₄ ⁺ concentration (<100 M), and the rhizosphere pH of non-mycorrhizal roots considerably higher than the bulk soil pH. The rhizosphere pH increase was particularly evident in apical root zones where the rates of water and NO ₃ ^– uptake and nitrate reductase activity were also higher. The results are summarized in a model of water and nutrient transport to, and uptake by, non-mycorrhizal roots of Norway spruce in a forest stand. Model calculations indicate that delivery to the roots by mass flow may meet most of the plant demand of nitrogen and calcium, and that non-mycorrhizal root tips have the potential to take up most of the delivered nitrate and calcium.     

Effects of liming and boron fertilization on mycorrhizas of Picea abies

Effects of liming and B fertilization on Norway spruce [Picea abies (L.) Karst.] mycorrhizas were studied in factorial field experiments. The lime was applied twice, about 30 years and 12 years before sampling (2000 and 4000 kg ha^-1 dolomite). B was applied at the rate of 1.5 kg B ha^-1 two years before sampling.Boron fertilization doubled the number of root tips in the top 10 mm of the humus layer. The proportion of dead short root tips was increased from 10 % in control plots to 29 % in the limed plots. Numbers of dead root tips were increased when both lime and B were applied. The % of mycorrhizas with external mycelium was slightly increased and the % of Piloderma croceum Erikss. and Hjortst. was decreased by lime. In conclusion, adverse effects of lime on mycorrhizas were found, which were ameliorated by B fertilization, but lime-induced B deficiency alone was not the only reason for the effects of lime on root mortality.     

Distribution of leaf assimilates in the stem of Picea abies L.

Summary Autoradiographic and microautoradiographic studies of 2-year-old Picea abies plants show that in summer leaf assimilates from the second-year shoot are translocated basipetally. Leaf assimilates are first transported to the stem via leaf trace phloem, then to the base of the stem in the sieve cells of the latest increment of secondary phloem. On the way down leaf assimilates move radially from sieve cells into cells of the phloem parenchyma, the vascular cambium, the rays, the inner periderm and certain cells of pith and cortex, including the epithelial cells surrounding the resin ducts. Other cells of pith and cortex remain nearly free of label, despite the long translocation time (20 h). With the exception of the vascular cambial cells, the stem cells that gain leaf assimilates by radial distribution coincide with those that contain chlorophyll and starch.     

ABA consumption in norway spruce (Picea abies) and white spruce (Picea glauca) somatic embryo cultures

Summary We investigated abscisic acid (ABA) metabolism among Norway and white spruce somatic embryo cultures which exhibited differences in maturation response when placed on racemic abscisic acid [(±)-ABA]. Differences in metabolic rate among the spruce genotypes could affect the ABA pool available for the maturation process, and might therefore be responsible for the differences in maturation response. The production of cotyledonary (stage 3) somatic embryos in cultures (genotypes) of Norway spruce (PA86:26A and PA88:25B) and of white spruce (WS1F cryoD and WS46) was compared. In each species pair one of the two genotypes failed to show stage 3 embryo development (respectively, PA88:25B and WS46). The investigation of ABA metabolism of each species pair showed that no substantial differences in ABA consumption or in the production of metabolites occurred. In each case ABA was metabolized to phaseic acid and dihydrophaseic acid over the 42-day culture period, metabolites were recoverable from the agar-solidified medium, and the sum of residual ABA and metabolites were equivalent to the ABA initially supplied. The results indicate that the process of ABA metabolism occurs essentially independently of somatic embryo maturation. NRCC no. 37345.     

Comparative studies on the mycorrhization of Larix decidua and Picea abies by Suillus grevillei

Summary Mycorrhization of Picea abies has been achieved, for the first time, with six strains of Suillus grevillei by a new culture method, using activated charcoal paper and liquid medium as a substrate. Mycorrhization of P. abies and Larix decidua was compared, and the process was found to be significantly different in the two tree species. S. grevillei is not incompatible with P. abies, but it forms mycorrhizae more readily with L. decidua. Hyphal growth was clearly stimulated on the surface of roots of Larix but retarded on Picea. A well organized Hartig net was formed with both tree species, but wall protuberances were frequently observed on the outer cell walls of Picea cortex cells when the Hartig net was not fully developed. No conspicuous cell wall reactions occurred in Larix roots. Cell wall protuberances may be comparable to those in transfer cells and are interpreted as an alternative to Hartig net development. Anatomical differences between roots of Larix and Picea, and physiologically active substances such as recognition factors on the root surfaces, are discussed with respect to their responsibility for the different reactions of S. grevillei.     

Comparative investigations on the differentiation of the endodermis and the development of the Hartig net in mycorrhizae of Picea abies and Larix decidua

Summary The differentiation of the endodermis of mycorrhizal roots of Picea abies and Larix decidua was investigated by means of light and transmission electron microscopy and with fluorescence techniques. The initiation and differentiation of the Hartig net were recorded. Differences between the two tree species were found, as were differences between the two tree species and angiosperms. The Casparian band developed immediately after the origin of endodermal cells from the meristem in mycorrhizae of both tree species. In L. decidua only the primary endodermis was present in most mycorrhizal laterals. The secondary structure of the endodermis was restricted to main roots and proximal parts of larch mycorrhizae. In P. abies mycorrhizae, however, the secondary stage of the endodermis developed soon after the primary endodermis and was characterized by regular alternation of short, active passage cells and elongated, rapidly degenerating cells, the inner surface of which was covered by a thick suberin layer. Hartig net development started in P. abies short roots only after the differentiation of endodermis into the secondary stage, whereas in L. decidua, the Hartig net was already initiated at the primary endodermal stage. Differences were specific for tree species.     

Genetic neighbourhood structure in a population of Picea abies L.

Summary Natural populations are currently the basic material for studying forest tree breeding, but little is known on the genotypic spatial structures in these stands. The use of gene markers, such as isozymes, leads to the determination of part of the allelic constitution of individuals. A method is presented here to estimate the degree of genetic relationship between any pair of genotypes. A French Picea abies population is analyzed by these means and a slight but significant correlation between estimated genetic relationship and topographic distance is found.     

Liming induced stimulation of the amino acid metabolism in mycorrhizal roots of Norway spruce (Picea abies [L.] Karst.)

Localization and activity of three enzymes involved in the amino acid metabolism of ectomycorrhizas were investigated within an interdisciplinary experiment performed in a mature Norway spruce stand in Southern Germany (Höglwald). The enzymes NAD-glutamate dehydrogenase and aspartate aminotransferase were present in root cells, whereas aminopeptidase was found in mycorrhizas of Norway spruce such as Piceirhiza nigra and those with the fungi Cenococcum geophilum, Elaphomyces sp., Russula ochroleuca and Tylospora sp. Mycorrhizas growing in the humus layer contained about double the amount of protein found in those taken from the upper mineral soil (0–5 cm).Acid irrigation of the soil had no effect on the activity of any of the investigated enzymes, soluble protein or total N-contents irrespective of whether roots were taken from the organic layer or from the upper mineral soil. Liming, however, stimulated the activity of the three enzymes in mycorrhizas of the organic layer (O_f+O_h) whereas it had no effect on the activity of the investigated enzymes of mycorrhizas in the upper mineral soil. This effect is attributed to increased contents of soluble organic nitrogen compounds in the soil of the limed plots as compared to the unlimed plots.     

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 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.     

Characterization of embryogenic cell lines of Picea abies in relation to their competence for maturation

Summary Embryogenic cell lines of Picea abies are categorized into three groups (polar, solar, and undeveloped) based on the organization of the somatic embryos within the tissue and the ability of the somatic embryos to proceed through a maturation process when treated with ABA. The polar and the solar types consist of somatic embryos with densely packed embryonic regions subtended by vacuolated suspensors. Both types of tissue regenerate mature somatic embryos when treated with ABA. Almost all mature somatic embryos develop further into shoots or plantlets. The undeveloped type consists of somatic embryos comprised of only a few loosely aggregated cells in their embryonic regions. Mature somatic embryos were not observed with this tissue type.Abbreviations ABA cis-trans abscisic acid - A1 polar type - A2 solar type - B undeveloped type - BA benzyladenine - 2,4-D 2,4 di-chlorophenoxyacetic acid - LP von Arnolds medium (1987)     

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.