When is the structural root system determined in Sitka spruce?

Summary Growth ring analysis was carried out on root systems of Sitka spruce trees which had been planted for 8 and 34 years. Retrospective measurements were made on cross-sectional area increment near the root base. Differentiation of the main laterals into roots of widely different radial growth rates took place mainly during the first eight years, resulting in 3–11 major woody roots and a larger number of small minor ones, with some of intermediate vigour. The major roots established during the first few years constituted the main structural root system at 34 years. Many of the minor roots stopped growing in diameter after a few years, but were still alive and extending at 34 years. The differentiation into major and minor roots is discussed with reference to their origins and the local environment.     

Wood ash treatment affects seasonal N fluctuations in needles of adult<Emphasis Type="Italic"> Picea abies</Emphasis> trees: a <Superscript>15</Superscript>N-tracer study

A ¹⁵N-tracer experiment was carried out in a stand of adult spruce trees [Picea abies (L.) Karst.] located on the Swiss Plateau in order to investigate the effects of wood ash treatment on seasonal nitrogen fluctuations in fine roots and needles. Treatments included irrigation (W), liquid fertilization (LF) and wood ash (A) application. ¹⁵N fluctuation in fine roots and current to 3-year-old needles was studied after one ¹⁵N pulse for 2 consecutive years (1999, 2000). ¹⁵N tracer was rapidly incorporated into the fine roots of adult trees, and ¹⁵N values reached similar levels in all treatments 2 months after the pulse. In the needles, the largest increase in ¹⁵N was observed in those of the current year. Following the initial peak during spring growth, ¹⁵N values in needles of control trees showed an oscillating pattern through the season. This oscillation is attributed to the increased use of internal N sources, as soon as the roots can no longer meet the increased N demand during the sprouting phase. However, W-, LF- and A-treated trees no longer showed the oscillation in ¹⁵N. Additional water (W and LF) as well as fertilizer (A and LF) may have induced shifts in the microbial flora, thus increasing the unlabelled N release from the soil. The strongest dampening was observed for the A treatment, indicating sufficient N availability from the soil, and making intensive use of the internal N sources unnecessary. Treatment with wood ash thus resulted in a similar fertilizer response to liquid fertilization.     

Carbon and nitrogen isotope ratios in different compartments of a healthy and a declining Picea abies forest in the Fichtelgebirge,NE Bavaria

Summary Natural carbon and nitrogen isotope ratios were measured in different compartments (needles and twigs of different ages and crown positions, litter, understorey vegetation, roots and soils of different horizons) on 5 plots of a healthy and on 8 plots of a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), which has recently been described in detail (Oren et al. 1988a; Schulze et al. 1989). The ¹³C values of needles did not differ between sites or change consistently with needle age, but did decrease from the sun-to the shade-crown. This result confirms earlier conclusions from gas exchange measurements that gaseous air pollutants did no long-lasting damage in an area where such damage was expected. Twigs (¹³C between-25.3 and-27.8) were significantly less depleted in ¹³C than needles (¹³C between-27.3 and-29.1), and ¹³C in twigs increased consistently with age. The ¹⁵N values of needles ranged between-2.5 and-4.1 and varied according to stand and age. In young needles ¹⁵N decreased with needle age, but remained constant or increased in needles that were 2 or 3 years old. Needles from the healthy site were more depleted in ¹⁵N than those from the declining site. The difference between sites was greater in old needles than in young ones. This differentiation presumably reflects an earlier onset of nitrogen reallocation in needles of the declining stand. ¹⁵N values in twigs were more negative than in needles (-3.5 to-5.2) and showed age- and stand-dependent trends that were similar to the needles. ¹⁵N values of roots and soil samples increased at both stands with soil depth from-3.5 in the organic layer to +4 in the mineral soil. The ¹⁵N values of roots from the mineral soil were different from those of twigs and needles. Roots from the shallower organic layer had values similar to twigs and needles. Thus, the bulk of the assimilated nitrogen was presumably taken up by the roots from the organic layer. The problem of separation of ammonium or nitrate use by roots from different soil horizons is discussed.     

15N abundance of surface soils,roots and mycorrhizas in profiles of European forest soils

¹⁵N natural abundances of soil total N, roots and mycorrhizas were studied in surface soil profiles in coniferous and broadleaved forests along a transect from central to northern Europe. Under conditions of N limitation in Sweden, there was an increase in ¹⁵N of soil total N of up to 9% from the uppermost horizon of the organic mor layer down to the upper 0–5 cm of the mineral soil. The ¹⁵N of roots was only slightly lower than that of soil total N in the upper organic horizon, but further down roots were up to 5% depleted under such conditions. In experimentally N-enriched forest in Sweden, i.e. in plots which have received an average of c. 100 kg N ha^–1 year^–1 for 20 years and which retain less than 50% of this added N in the stand and the soil down to 20 cm depth, and in some forests in central Europe, the increase in ¹⁵N with depth in soil total N was smaller. An increase in ¹⁵N of the surface soil was even observed on experimentally N-enriched plots, although other data suggest that the N fertilizer added was depleted in¹⁵N. In such cases roots could be enriched in¹⁵N relative to soil total N, suggesting that labelling of the surface soil is via the pathway: — available pools of N-plant N-litter N. Under N-limiting conditions roots of different species sampled from the same soil horizon showed similar ¹⁵N. By contrast, in experimentally N-enriched forest ¹⁵N of roots increased in the sequence: ericaceous dwarf shrubs15N enriched compounds in fungal material, which could contribute to explain the observed ¹⁵N profiles if fungal material is enriched, because it is a precursor of stable organic matter and recalcitrant N. This could act in addition to the previous explanation of the isotopically lighter soil surface in forests: plant uptake of ¹⁵N-depleted N and its redeposition onto the soil surface by litter-fall.     

Altered utilization patterns of young and old soil C by microorganisms caused by temperature shifts and N additions

To determine if changes in microbial community composition and metabolic capacity alter decomposition patterns of young and old soil carbon pools, we incubated soils under conditions of varying temperature, N-availability, and water content. We used a soil from a pineapple plantation (CAM; ¹³C litter = –14.1) that had previously been under tropical forest (C3; ¹³C soil carbon = –26.5). Forest derived carbon represented 'old' carbon and plantation inputs represented 'new' carbon. In order to differentiate utilization of young (< 14 years) and old (> 14 years) soil carbon, we measured the ¹³C of respired CO₂ and microbial phospholipid fatty acids (PLFAs) during a 103 day laboratory incubation. We determined community composition (PLFA and bacterial intergenic transcribed spacer (ITS) analysis) in addition to carbon degrading and nutrient releasing enzyme activities. We observed that greater quantities of older carbon were respired at higher temperatures (20 and 35°C) compared to the lower temperature (5°C). This effect could be explained by changes in microbial community composition and accompanying changes in enzyme activities that affect C degradation. Nitrogen addition stimulated the utilization of older soil carbon, possibly due to greater peroxidase activity, but microbial community composition was unaffected by this treatment. Increasing soil moisture had no effect on the utilization of older SOM, but enzyme activity typically declined. Increased oxidative enzyme activities in response to elevated temperature and nitrogen additions point to a plausible mechanism for alterations in C resource utilization patterns.     

Estimation of symbiotic dinitrogen fixation in alder forest by the method based on natural15N abundance

Annual N₂-fixation in virgin forest ecosystems has been measured using a¹⁵N natural abundance (¹⁵N) procedure. This method was compared to a¹⁵N labelled fertilizer isotopic dilution method. For young alders (5–6 years old), ¹⁵N of leaves gave results in good agreement with the isotopic dilution of fertilizer method. Since ¹⁵N variability was expected according to plant physiology, for alder trees, leaves were collected at various heights after the end of the growing season, and, to take account of isotopic variations coming from derived inputs, ¹⁵N of leaves of a large number of other plants in the same are were measured to give control values. Following this procedure, the ¹⁵N method gave reliable evaluation of the nitrogen supply, by through N₂-fixation, to alders, which were found to maintain high nitrogen fixing capacity in a sequence ranging from first stage of establishment of climactic formation. Moreover, the same method is reported to discriminate various origins ofAlnus glutinosa grown in natural conditions, possibly in relation to the genetic diversity of this species.     

Isotopic fractionation accompanying fertilizer nitrogen transformations in soil and trees of a Scots spine ecosystem

Foliage from a mature stand of Scots pine (Pinus sylvestris L.) receiving increasing doses of ammonium nitrate and urea nitrogen was assayed during the five subsequent growing seasons for total N concentration and ¹⁵N abundance. The aim of the study was to examine the potential of the ¹⁵N technique to provide estimates on fertilizer N recovery and its fate in the ecosystem. The ¹⁵N abundance in the foliage increased in proportion to the dose of fertilizer application. This was generally owing to the fact that the ¹⁵N of the fertilizer N was significantly higher than that in the soil inorganic-N pool, as well as in the needle biomass of the Scots pine trees on the nonfertilized plots. Due to ¹⁵N isotope discrimination occurring during N transformations in soil the relationship was however not very close. Calculations based on the principle of isotope dilution yielded only rough and, in some cases, even misleading estimates of the fraction of the fertilizer-derived nitrogen (N_dff) in the needles. This was especially the case for the urea-N, which undergoes significant isotopic fractionation during the process of ammonia volatilization and possibly microbial NH₄ ⁺ assimilation in soil. Over five growing seasons, foliar total N concentration peaked at the end of the second season while the ¹⁵N abundance continued to increase. Although large methodological errors may be involved when interpreting natural ¹⁵N abundance, the measurement of ¹⁵N seems to provide semi-quantitative information about fertilizer N accumulation and transformation processes in coniferous ecosystems. A better understanding of the tree and soil processes causing isotopic fractionation is a prerequisite for correct interpretation of ¹⁵N data.     

Influence of mycorrhizal associations on foliar δ15N values of legume and non-legume shrubs and trees in the fynbos of South Africa: Implications for estimating N2 fixation using the 15N natural abundance method

In this study, we examined the use of the ¹⁵N natural abundance method to quantify the percentage N derived from fixation of atmospheric N₂ in honeybush (Cyclopia spp.) shrubs and trees in the fynbos, South Africa. Non-fixing shrubs and trees of similar phenology to the Cyclopia species were chosen as reference plants. These reference plants were selected to cover a range of mycorrhizal associations (ericoid mycorrhizal, arbuscular mycorrhizal and non-mycorrhizal). Isotopic analysis revealed a wide range of foliar ¹⁵N values for the reference plants, including many very negative values. The marked differences in ¹⁵N values were defined by the mycorrhizal status of the reference plant species, with the ericoid and arbuscular mycorrhizal plants showing lower foliar ¹⁵N values relative to their non-mycorrhizal counterparts. In contrast, the ¹⁵N values of the N₂-fixing Cyclopia species were uniformly clustered around zero, from –0.11 to –1.43. These findings are consistent with the observation that mycorrhizal fungi discriminate against the heavier ¹⁵N isotope during transfer of N from the fungus to the host plant, leaving the latter depleted in ¹⁵N (i.e. with a more negative ¹⁵N value). However, a major assumption of the ¹⁵N natural abundance method for estimating N₂ fixation is that both legume and reference plant should have the same level of fractionation associated with N uptake. But, because mycorrhizal associations may strongly affect the level of fractionation during N uptake and transfer, the test legume should belong to the same mycorrhizal group as the chosen reference plant species. As shown in this study, if the mycorrhizal status of the legume and the reference plant differs, or cannot be assessed, then the ¹⁵N natural abundance technique cannot be used to quantitatively estimate N₂ fixation.     

Nitrogen uptake and use of two contrasting maize hybrids differing in leaf senescence

In eastern Canada, the use of fertilizer N has been identified as the most energy-consuming component of maize (Zea mays L.) grain production. As the economic and environmental costs of excessive N fertilization rise, there is an increased emphasis on selection of hybrids with greater N use efficiency (NUE; defined as the ratio of the amount of ¹⁵N recovered in grain or stover dry matter to the amount of fertilizer ¹⁵N applied to the soil in this study). Using an ¹⁵N-labelling approach, a field study was conducted on a tile-drained Brandon loam soil (Typic Endoaquoll) on the Central Experimental Farm at Ottawa, Canada (45°22 N, 75°43 W) in 1993 and 1994. Fertilizer N uptake and partitioning within the plant in relation to dry matter changes were monitored during development of a current stay-green maize hybrid and an older early-senescing hybrid grown with three fertilizer N levels (0, 100, 200 kg N ha^-1). Dry matter, N concentration and¹⁵ N atom% enrichment of plant components were determined at five growth stages. The current stay-green hybrid, Pioneer 3902 had greater NUE than the old early-senescing hybrid, Pride 5, which was associated with 24% more dry matter production and 20% more N uptake during grain fill for Pioneer 3902. There was no indication of greater allocation of N to the grain in Pioneer 3902. Our data suggest that prolonged maintenance of green leaf area for photosynthate production during grain fill and the ability to take up available soil N later in grain filling are characteristics of maize hybrids with greater NUE.     

Carbon isotope variations in a plantation of Sitka spruce,and the effect of acid mist

Intra- and inter-tree variations in ¹³C/¹²C ratios were studied within a single clone plantation of 20-year-old Sitka spruce, some of which were treated with mist simulating acidic cloud water. For groups of trees of similar height and the same treatment, sampled at the same whorl height, ¹³C values for current year needles showed variations (1 SD) of between 0.2 and 0.7. The variations reflect the seasonally averaged influences, on intercellular CO₂ concentrations, of slight variations in the microhabitat within a group. For a typical intra-group variation of 0.4 one may be able to distinguish between groups whose mean intercellular CO₂ concentrations differ by only 8 ppm. Acid misting resulted in a lowering of ¹³C values by c. 0.7 (significant at the P0.05 level). This reflects higher intercellular CO₂ concentrations for acid misted trees, which can be interpreted in terms of their having assimilation rates c. 10% lower than those of control trees, and might explain the observed reduction in stem growth for acid-misted trees. Without careful attention to sampling strategy, however, these small inter-tree ¹³C variations can be easily masked by the much larger intra-tree variations with height. Large gradients of increasing needle ¹³C with height, of c. 0.5 m^-1, were observed in two untreated trees of different total height. The gradient was similar for both trees so, though ¹³C values of both trees were identical close to their leaders (–27), the taller tree displayed much lower values close to the ground (–31). The gradients are believed to reflect lower light levels close to the ground, rather than the accumulation of respired CO₂ in the atmosphere. The different height response of stems versus needles, reflected by an increase in ¹³C_stems–¹³C_needles with height (for cellulose), is discussed in terms of stem photosynthetic recapture of internally respired CO₂.     

Measurement of frequency-dependent sexual activity in Drosophila Melanogaster

In experiments on sexual competition in Drosophila melanogaster, the course of mating succes with time is represented by a sigmoid curve. By logarithmic transformation such curves are changed into straight lines that can be compared by covariance analysis. This method allows discrimination of the behaviour of the two types in competition, and allows us to follow it in the course of time. From a sexual competition experiment between the wild type Canton S and the mutant white-ebony we conclude that sexual activity of males and females of both types is generally frequency dependent, with evidence of rare-female advantage as well as rare-male advantage.     

Comparative effects of sorbitol and sucrose as main carbon energy sources in micropropagation of apricot

In vitro proliferation and rooting capacity of San Castrese and Portici apricots (Prunus armeniaca L.) were tested on modified MS medium enriched with varying growth regulator concentrations and sucrose (58.4 mM) or sorbitol (116.8 mM) as main carbon energy sources. The interaction of proliferation and rooting media was also studied.Proliferation of both cultivars was proportional to benzyladenine (BA) concentration and enhanced with sorbitol media. However, 8.8 M BA was often associated with hyperhydricity, particularly when shoots were grown on sucrose media. Newly proliferated shoots elongated better on sorbitol media. The positive influence of sorbitol on proliferation and shoot growth was not due to osmotic effects. Moreover, sorbitol showed a positive carryover effect in hastening rooting of Portici. By contrast, when transferred to sorbitol rooting media, the shoots of both cultivars generally showed low rooting, with short, thick roots.Up to 70% of the plantlets that produced roots in sucrose media enriched with indolebutyric acid were successfully acclimatized when they were dipped in a benomyl (0.075% w/v) suspension before being transplanted with care being taken to prevent over-wetting of soil.Abbreviations BA 6-benzyladenine - IBA indolebutyric acid - GA₃ gibberellic acid - SEM standard error of mean     

Effects of drought on the yellowing status and the dynamics of mineral elements in the xylem sap of declining spruce (Picea abies L.)

In order to test the effects of drought on the occurrence of spruce yellowing, in the Vosges Mountains (northeastern France), the soil of a plot of a 30-year-old spruce stand was protected from throughfall input by a roof for two months during the summer. The degree of yellowing of the trees from the dry and control plots was measured before and after the experiment. Sap flow and sap concentrations were measured in the control plot during the whole of the growing season, and in the dry plot during the drought period. Drought brought about an increase of needle yellowing linked to a reduction in Mg uptake. A decrease in sap concentration of concentration of Ca, Mg and K occurred in the dry plot as compared with the control plot at the end of the drought period. It is concluded that climatic stress could have been the triggering factor of spruce yellowing in the Vosges during the eighties.     

Relationships between EUF-N fractions,N uptake and quality of sugar beet in deep loess soils of Southern Lower Saxony

Summary In field experiments conducted in 1981 on deep loess soils a significant correlation was obtained between EUF-N content in the topsoil and N in sugar beet roots as well as in whole plants. A very close correlation was found to exist between EUF-N values in June 1981 and -amino N in sugar beet roots at harvest. Also other quality criteria such as the contents of sugar, K and Na in roots and yield parameters correlated with EUF-N contents in topsoils.The inorganic and organic EUF-N fractions changed during the vegetation period due to both N uptake by the crop and mineralization. Therefore it appears to be expedient to use both fractions when calculating N fertilizer requirements.The correlation between EUF-N (topsoil samples drawn in the year preceding sugar beet) and sugar yield increases obtained by N fertilization that was found in Austria¹² was confirmed in our experiments with soils from Southern Lower Saxony.     

Effect of organic and inorganic fertigation on yields, δ15N values, and δ13C values of tomato (Lycopersicon esculentum Mill. cv. Saturn)

We examined the effects of fertilizer application, especially the effects of fertigation and types of fertilizer (inorganic and organic) on yields and ¹⁵N and ¹³C values of tomato (Lycopersicon esculentum Mill. cv. Saturn). Fertigation is a method in which an appropriate diluted liquid fertilizer is applied to the plants each time they are drip-irrigated. We developed a method of organic fertigation using corn steep liquor (CSL) as the liquid fertilizer, because it is an industrial byproduct of cornstarch manufacture and can be used very effectively. We compared fruit yield, mineral content, ¹⁵N value, and ¹³C value of tomatoes grown under three different fertilizer treatments, basal dressing: basal dressing with granular chemical fertilizer; inorganic fertigation: fertigation with liquid chemical fertilizer; and organic fertigation: fertigaion with CSL. Mineral contents of tomatoes grown with basal dressing were generally lower than those grown under either fertigation treatment. These results indicated that yields and mineral contents were influenced more by the method of fertilizer application than by whether the fertilizers were inorganic or organic. There were, however, significant differences in the ¹⁵N values of tomato fruits grown under different types of fertilizer applications, especially between inorganic and organic fertilizers. The ¹⁵N value of the chemical fertilizer used for basal dressing was 0.81 ± 0.45{}, that of the chemical fertilizer for fertigation was 0.00 ± 0.04{}, and that of CSL was 8.50 ± 0.71{}. The ¹⁵N values of the soils reflected the ¹⁵N values of the fertilizers. Moreover, the ¹⁵N values of the fruits corresponded to the ¹⁵N values of the applied fertilizers. The ¹⁵N values were 3.18 ± 1.34{} in the fruits grown with a basal dressing of chemical fertilizer, 0.30 ± 0.61 in those grown under inorganic fertigation, and 7.09 ± 0.68 in those grown under organic fertigation. On the other hand, although the ¹³C values in the soil also reflected the ¹³C values of the applied fertilizers, there was no significant difference in the ¹³C values of fruits among the different treatments. In conclusion, because the ¹⁵N values of fertilizers correlated well with those of the fruits, it may be possible to use ¹⁵N values as an indicator of organic products.     

Molecular evolution of the nicotinic acetylcholine receptor: An example of multigene family in excitable cells

An extensive phylogenetic analysis of the nicotinic-acetylcholine-receptor subunit gene family has been performed by cladistic and phenetic methods. The conserved parts of amino acid sequences have been analyzed by CLUSTAL V and PHYLIP software. The structure of the genes was also taken in consideration. The results show that a first gene duplication may have occurred before the appearance of Bilateria. Three subfamilies then appeared: I-the neuronal -bungarotoxin binding-site subunits (7, 8); III-the neuronal nicotinic subunits (2–6, 2–4), which also contain the muscle acetylcholine-binding subunit (1); and IV—the muscle non- subunits (1, , ). The Insecta subunits (subfamily II) could be orthologous to family III and IV. Several tissular switches of expression from neuron to muscle and the converse can be inferred from the extant expression of subunits and the reconstructed trees. The diversification of the neuronal nicotinic subfamily begins in the stem lineage of chordates, the last duplications occurring shortly before the onset of the mammalian lineage. Such evolution parallels the increase in complexity of the cholinergic systems.Abbreviations -Bgt -bungarotoxin - ACh acetylcholine - MP maximum of parsimony - MYA million years ago - NJ neighbor-joining - nAChR nicotinic acetylcholine receptor Correspondence to: N. Le Novère     

The catalysis of nucleotide polymerization by compounds of divalent lead

Summary Soluble lead salts and a number of lead-containing minerals catalyze the formation of oligonucleotides from nucleoside 5-phosphorimidazolides. The effectiveness of lead compounds correlates strongly with their solubility. Under optimal conditions we were able to obtain 18% of pentamer and higher oligomers from ImpA. Reactions involving ImpU gave smaller yields.Abbreviations A adenosine - U uridine - Im imidazole - MeIm 1-methyl-imidazole - EDTA ethylenediaminetetraacetic acid - pA adenosine 5-phosphate - pU uridine 5-phosphate - Ap adenosine cyclic 2:3-phosphate - ATP adenosine 5-triphosphate - AppA P₁,P₂-diadenosine 5-diphosphate - pNp (N = A,U) nucleotide 2(3), 5-diphosphate - ImpA adenosine 5-phosphoreimidazolide - ImpU uridine 5-phosphorimidazolide - A ²pA adenylyl-[25]-adenosine - A ³pA adenylyl-[35]-adenosine - pA ²pA 5-phospho-adenylyl-[25]-adenosine - pA ³pA 5-phospho-adenylyl-[35]-adenosine - pUpU 5-phospho-uridylyl-uridine - pApU 5-phospho-adenylyl-uridine - pUpA 5-phospho-uridylyladenine - (pA)n (n, 2,3,4,) oligoadenylates with 5 terminal phosphate - ImpApA 5-phosphorimidazolide of adenylyl adenosine - (pA) ₅₊ pentamer and higher oligoadenylates with 5 terminal phosphate - (Ap)nA (n = 2,3,4) oligoadenylates without terminal phosphates In the following we do not specify the nature of the internucleotide linkageIn the following we do not specify the nature of the internucleotide linkage     

Production,standing biomass and natural abundance of <Superscript>15</Superscript>N and <Superscript>13</Superscript>C in ectomycorrhizal mycelia collected at different soil depths in two forest types

Nutrient uptake by forest trees is dependent on ectomycorrhizal (EM) mycelia that grow out into the soil from the mycorrhizal root tips. We estimated the production of EM mycelia in root free samples of pure spruce and mixed spruce-oak stands in southern Sweden as mycelia grown into sand-filled mesh bags placed at three different soil depths (0–10, 10–20 and 20–30 cm). The mesh bags were collected after 12 months and we found that 590±70 kg ha^–1 year^–1 of pure mycelia was produced in spruce stands and 420±160 kg ha^–1 year^–1 in mixed stands. The production of EM mycelia in the mesh bags decreased with soil depth in both stand types but tended to be more concentrated in the top soil in the mixed stands compared to the spruce stands. The fungal biomass was also determined in soil samples taken from different depths by using phospholipid fatty acids as markers for fungal biomass. Subsamples were incubated at 20°C for 5 months and the amount of fungal biomass that degraded during the incubation period was used as an estimate of EM fungal biomass. The EM biomass in the soil profile decreased with soil depth and did not differ significantly between the two stand types. The total EM biomass in the pure spruce stands was estimated to be 4.8±0.9×10³ kg ha^–1 and in the mixed stands 5.8±1.1×10³ kg ha^–1 down to 70 cm depth. The biomass and production estimates of EM mycelia suggest a very long turnover time or that necromass has been included in the biomass estimates. The amount of N present in EM mycelia was estimated to be 121 kg N ha^–1 in spruce stands and 187 kg N ha^–1 in mixed stands. The ¹³C value for mycelia in mesh bags was not influenced by soil depth, indicating that the fungi obtained all their carbon from the tree roots. The ¹³C values in mycelia collected from mixed stands were intermediate to values from pure spruce and pure oak stands suggesting that the EM mycelia received carbon from both spruce and oak trees in the mixed stands. The ¹⁵N value for the EM mycelia and the surrounding soil increased with soil depth suggesting that they obtained their entire N from the surrounding soil.     

Comparison of the homologous carboxy-terminal domain and tail of α-crystallin and small heat shock protein

The C-terminal domain and tail, which is the most conserved region of the -crystallin/small heat shock protein (HSP) family, was obtained from rat A-crystallin, bovine B-crystallin and mouse HSP25. All three domains have primarily -sheet conformation and less than 10% of -helix, like the proteins from which they are derived. Whereas the C-terminal part of A-crystallin forms dimers or tetramers, the corresponding regions of B-crystallin and HSP25 form larger aggregates. The heat-protective activity, recently described for the -crystallin/small HSP family, is not retained in the C-terminal domain and tail. In the course of this study some differences with the previously published sequence of HSP25 were observed, and a revision is proposed.Abbreviations A2Dt residues 64–173 of rat -crystallin - B2Dt residues 70–175 of bovine B-crystallin - bp base pair - HSP2Dt residues 92–209 of HSP25 - HSP(s) heat shock protein(s) - HSP25 mouse small HSP - PCR polymerase chain reaction - PMSF phenylmethylsulfonyl chloride - SDS sodium dodecyl sulfate; polyacrylamide - WSF water-soluble fraction     

Occurrence of pppApp-synthesizing activity in actinomycetes and isolation of purine nucleotide pyrophosphotransferase

The occurrence of adenosine 5-triphosphate-3-diphosphate-synthesizing activity was detected in five strains of actinomycetes; Streptomyces morookaensis, Streptomyces aspergilloides, Streptomyces hachijoensis, Actinomyces violascens and Streptoverticillium septatum, out of 825 strains of actinomycetes, bacteria, fungi and imperfecti. Purine nucleotide pyrophosphotransferase were extracellularly excreted associating with the cell growth, and were purified partially or to apparent homogeniety from the culture filtrate. The enzymes are a monomeric protein with a molecular weight of 18000–26000 and synthesize adenosine, guanosine and inosine 5-phosphate (mono, di or tri)-3-diphosphate such as pApp, ppApp, pppApp, pGpp, ppGpp, pppGpp and pppIpp by transferring a pyrophosphoryl group from the 5-position of ATP, dATP and pppApp to the 3-position of purine nucleotides in the presence of a divalent cation and in alkaline state.Abbreviations pppApp adenosine 5-triphosphate 3-diphosphate - ppApp adenosine 5-diphosphate 3-diphosphate - pApp adenosine 5-monophosphate 3-diphosphate - pppGpp guanosine 5-triphosphate 3-diphosphate