DNA cytophotometry of human chromosomes.

The applicability of Feulgen-based parameters to detect variant metaphase chromosomes involved in deletions or translocations, was investigated and algorithms developed to compute such parameters. This report is focused primarily on the magnitude of the errors involved during the prerequisite procedures of photography, measurement and computation. Measurements were performed by stage-scanning of photographic negatives of Feulgen-stained metaphases. In the scanned images the initial chromosome boundaries were obtained by thresholding, while definite chromosomal areas and local background values were obtained by expansion of the initial boundaries. The integrated density profiles and the relative DNA content were computed for the individual chromosomes (straight as well as bent). Total DNA content, DNA arm ratio, as well as length and centromere index can be obtained from the profile. It was shown that under such conditions the experimental errors associated with the measurements are small compared to biologic variations (e.g., differences between homologues) and that the procedures applied allow to detect polymorphisms. In addition to this, mean and standard deviations of both DNA and length parameters are given for metaphases of five subjects. Comparison of the applicability of DNA and length parameters is realized by a classification experiment.     

Characterization of wound responses of stems of paper birch (Betula papyrifera) and European white birch (Betula pendula)

Plants respond to feeding injury by chewing insects by inducing both a general response to mechanical wounding and a specific response to herbivore-associated elicitors. In both cases, plant response involves complex biochemical and physiological changes. We compared chemical and physical responses of paper birch (B. papyrifera) and European white birch (B. pendula) stems to mechanical injury to determine if aspects of their wound response correspond with the much higher resistance of paper birch to bronze birch borer (Agrilus anxius). We also characterized stem responses to mechanical wounding plus bronze birch borer larval homogenate to determine if larval cues elicited a more specific response than mechanical wounding alone. In both species, wounding decreased concentrations of individual phenolics, total phenolics, and condensed tannins, perhaps because they were diverted to lignin biosynthesis, the concentration of which increased. Nitrogen concentration increased in both species while free amino acid concentrations declined, perhaps because they were utilized to synthesize proteins. Application of larval homogenate did not elicit a response different from that induced by mechanical injury. When comparing wound responses of the two birch species, phenolic profiles differed most conspicuously. However, multivariate analyses revealed no differences between constitutive and wound-induced phenolic profiles within each species, and the rate of wound periderm growth was equivalent between species. These results suggest that components of the wound response we measured may not contribute to interspecific variation in bronze birch borer resistance of paper birch and European white birch.     

Decreased anthocyanidin reductase expression strongly decreases silver birch (Betula pendula) growth and alters accumulation of phenolics

Phenolics, formed via a complex phenylpropanoid pathway, are important defensive agents in plants and are strongly affected by nitrogen (N) fertilization. Proanthocyanidins (PAs) are one possible endpoint of the phenylpropanoid pathway, and anthocyanidin reductase (ANR) represents a key enzyme in PA biosynthesis. In this study, the expression of silver birch (Betula pendula) anthocyanidin reductase BpANR was inhibited using the RNA interference (RNAi) method, in three consequent BpANR RNAi (ANRi birches) lines. The growth, the metabolites of the phenylpropanoid pathway, and the number of resin glands of the ANRi birches were studied when grown at two N levels. ANRi birches showed decreased growth and reduction in PA content, while the accumulation of total phenolics in both stems and leaves increased. Moreover, ANRi birches produced more resin glands than did wild‐type (WT) birches. The response of ANRi birches to N depletion varied compared with that of WT birches, and in particular, the concentrations of some phenolics in stems increased in WT birches and decreased in ANRi birches. Because the inhibition of PAs biosynthesis via ANR seriously affected birch growth and resulted in accumulation of the precursors, the native level of PAs in plant tissues is assumed to be the prerequisite for normal plant growth. This draws attention to the real plant developmental importance of PAs in plant tissues.     

In vitro propagation of birch (Betula verrucosa Ehrh)

Shoot t ps, young internodal segments and young developing leaves ofBetula ver rucosa Ehrh. in contact with agar nutrient medium formed tissue with numerous buds if medium contained a low concentration of cytokinin (BAP) and auxin (IBA or NAA). Tissue with induced buds transferred on a fresh nutrient medium continued in a formation of new buds which developed into shoots. Excised shoots were rooted on agar medium with a low concentration of auxin. Regenerated trees showed a genetic uniformity.     

Localisation of the classical DNA satellites on human chromosomes as determined by primed in situ labelling (PRINS)

The chromosomal localisation and relative amounts in humans of the classical DNA satellites I, II and III have been determined by using the primed in situ labelling reaction with a variety of oligonucleotide primers. The centromeres of seven of the human chromosomes, viz. nos 6, 8, 11, 12, 18, 19 and X, are not identifiably marked by any of the primers. A possible phylogenetic explanation of this is suggested and the possible relationship of the classical satellites to the function of the centromere is discussed. Received: 5 November 1996 / Accepted: 25 March 1997     

Nutrition and the ozone sensitivity of birch (Betula pendula)

 Cuttings of a single birch clone (Betula pendula) were grown in field fumigation chambers throughout the growing season in either filtered air (control) or 90/40 nl O₃ l^–1 (day/night). Both regimes were split into plants under high and low nutrient supply (macro- and micronutrients). The stomatal density of leaves was increased by ozone but was lowered at high nutrition, while the inner air space was hardly affected by the treatments. Ozone induced macroscopic leaf injury regardless of nutrition, but leaf shedding was delayed in the low-fertilized plants, despite O₃ uptake being similar to that in high-fertilized plants. The leaf turn-over was enhanced in the O₃-exposed high-fertilized plants, but length growth and leaf formation of stems were not affected by ozone in either nutrient regime. Leaves of high-fertilized plants showed O₃-caused decline in photosynthetic capacity, water-use efficiency, apparent carbon uptake efficiency and quantum yield earlier as compared with low-fertilized plants, whereas chlorophyll fluorescence (F_V/F_M) and leaf nitrogen concentration were rather stable. CO₂ uptake rate and rubisco activity of young leaves compensated for the O₃ injury in the ageing leaves of the low-fertilized plants. In 8-week-old leaves, however, the O₃-induced decline in CO₂ uptake did not differ between the nutrient regimes and was associated with increased dark respiration rather than changed photorespiration. The balance between CO₂ supply and demand was lost, as was stomatal limitation on CO₂ uptake. High nutrition did not help leaves to maintain a high photosynthetic capacity and life span under O₃ stress. Received: 6 July 1996 / Accepted: 4 June 1997     

Manganese toxicity in yellow birch (Betula alleghaniensis Britton) seedlings

Summary Manganese supply in nutrient solution was optimum at 5.0 ppm forBetula alleghaniensis seedlings. Growth was retarded below 0.005 ppm and above 25 ppm supply. Foliar Mn concentrations were deficient below 60 ppm, optimum at 440 ppm, and toxic above 1300 ppm. Chloroses of young leaves were associated with deficient Mn, and marginal necroses plus interveinal necrotic spots on older leaves were characteristic of toxic Mn. The results withB. alleghaniensis correspond well to those reported forB. verrucosa.     

Nuclear DNA content of Pinus sylvestris (L.) as determined by laser flow cytometry

Nuclear DNA content was determined in nuclei isolated from needles, stems and roots of in vitro grown seedlings and from megagametophytes and embryo of mature seeds in three accessions of Pinus sylvestris L. One accession was from Inari, northern Finland at timber line, and two accessions were from the Alpine region in Italy. Nuclei were mechanically isolated by a chopping method, stained with propidium iodide, and DNA content was determined using an EPICS PROFILE laser flow cytometer. Nuclei isolated from leaves of barley (Hordeum vulgare L. cv. Sultan; 2C=11.12 pg) were used as an internal standard for measurement of pine nuclei. Mean 1C nuclear DNA content of P. sylvestris was 27.88 pg as determined from megagametophyte tissue. Mean 2C value was 52.25 pg as determined from stem and root tissue, and 55.58 pg as determined from embryo tissue. The ratio of 2C to 1C value was 1.87 and 1.99, respectively. Extracts of nuclei from needles contained propidium iodide-absorbing debris which may have interfered with measurements and resulted in lower 2C values than those obtained from stem and root.     

Within-stand variation in silver birch (Betula pendula Roth) phenology

Key message

Within a local population genotypes differ in the timing of bud burst, but genotypes with early bud burst unfold their leaves slower, resulting in an equal period of carbon gain.

Abstract

The ability of local populations to cope with disturbances like adverse weather events or a changing climate depends on the genotypic richness of such populations, emphasising the importance of differences between genotypes in traits related to growth and survival at this scale. Due to their longevity, these differences are of special importance in trees, yet for trees, differences between genotypes within local populations remain unexplored. The phenological cycle is important in this respect, since a correct timing of phenological events is critical for growth and survival of trees, especially in environments with strong seasonality and changes in the timing of phenological events has consequences for, among others, net ecosystem productivity and the climate system as a whole. In this light accounting for differences in the timing of phenological events within species is currently identified as a research challenge. This study contributes to the knowledge of differences between genotypes on the small spatial scale of a local population. We examined the timing of phenological events of 15 micropropagated silver birch (Betula pendula Roth) genotypes representing a natural population. Measurements covered bud burst (7 years) and leaf unfolding in spring and chlorophyll degradation in autumn (2 years for both). These data were used to estimate the period of carbon gain. Differences between genotypes in the temperature sum required for bud burst were present, with genotypes showing ‘early’ (i.e. a low temperature sum requirement for bud burst) and ‘late’ bud burst across the 7-year study period. Differences were small in most years (i.e. 3 days), but differences of 16 days were recorded within the 7-year study period as well. Genotypes with ‘early’ bud burst were less sensitive to variations in environmental conditions in spring compared to genotypes with ‘late’ bud burst. Differences in bud burst were not carried over to the estimated period of carbon gain. Due to faster leaf expansion in genotypes with ‘late’ bud burst and the lack of differences between genotypes in autumn senescence the estimated period of carbon gain was similar among genotypes.     

The inhibition of ammonium uptake in excised birch (Betula pendula) roots by batatasin-III

In northern Sweden, plants growing in association with the clonal dwarf shrub Empetrum hermaphroditum usually exhibit limited growth and are N-depleted. Previous studies suggest that this negative effect by E. hermaphroditum may be explained, at least in part, by the release of phenolic compounds, particularly the dihydrostilbene, batatasin-III from foliage to soil. In the present work, we investigated whether batatasin-III has the potential to interfere with NH4+ uptake in birch (Betula pendula) roots. Excised birch roots were exposed to batatasin-III during brief periods in 15NH4+ solutions, and then analyzed for labeled N. Batatasin-III inhibited N-NH4+ uptake by 28, 89 and 95% compared with the control, when roots were treated with 0.1, 1.0 and 2.8 mM of batatasin-III, respectively. The effect of 1.0-mM batatasin-III was greater at pH 4.2 than at pH 6.8. In addition, the inhibition of N-NH4+ uptake by batatasin-III was not reversed after rinsing the roots in water and transferring them to a batatasin-III free solution. Furthermore, birch seedlings immersed in a 1.0-mM batatasin-III solution for 2 h, and then replanted in pots with soil, had decreased growth, such that 10 weeks after treatment, the dry mass of both shoots and roots was reduced by 74 and 73%, respectively, compared with control seedlings. This suggests that a brief exposure to batatasin-III may have a long-term inhibitory effect on whole plant growth. Using plasma membrane vesicles isolated from easily extractable spinach (Spinacia oleracea) leaves, it was found that batatasin-III strongly inhibited proton pumping in isolated plasma membrane vesicles, while it only slightly inhibited ATP hydrolytic activity. The uncoupling of proton pumping from ATP hydrolytic activity suggests that batatasin-III disturbs membrane integrity. This hypothesis was further supported by a greater efflux of ions from birch roots immersed in a batatasin-III solution than from roots in a control solution.     

Autumn colouration and herbivore resistance in mountain birch (Betula pubescens)

We explored Hamilton and Brown's autumn signalling hypothesis in mountain birch (Betula pubescens). As predicted by the hypothesis, early autumn colour change (i.e. high degree of autumn colouration in September) was negatively correlated with insect damage the following season. Furthermore, as expected, indices of physiological stress (i.e. leaf fluctuating asymmetry) and reproductive investment (i.e. catkin production) were positively correlated with insect damage the following season. Indirectly, we also found support for the idea that the proposed handicap signal (i.e. early autumn senescence) might be associated with an honesty ensuring cost in terms of lost primary production. Further work is, however, required to determine whether the link between autumn colours and insect damage observed in this study is causal.     

Element content in leaves of birch (Betula verrucosa Ehrh.) in an air polluted area

 The content of natural (S, N, P, Ca, Mg, K, Mn, Zn, Cu) and extraneous elements (Pb, Cd, Al) in leaves of birch growing in the Krusne hory Mts. (Czech Republic), a territory affected by air pollution (SO₂), was evaluated with regard to the altitude and age of birch stands, and in relation to stand nutrition. The contents of S, Ca, Mg, Zn and Pb culminated at the highest points of the altitudinal transect (elevation 900–1000 m). In contrast, at high altitudes the content of Cd, Al and Mn decreased. The content of elements in leaves was mostly not dependent on tree age. In terms of nutrition and growth of birch, the content of Cu was insufficient, the content of Ca, Mg, N, P and K was optimum, and the content of S, Zn and primarily Mn was higher. The content of Pb and Al was at natural background levels, that of Cd higher. Received: 3 July 1997 / Accepted: 19 May 1998     

Report of Quambalaria cyanescens in association with the birch (Betula pendula)

Long-term microbiological investigation of the pollen of silver birch (Betula pendula) in the Moscow and Moscow oblast areas revealed that almost one-third of the analyzed samples contained the fungus identified by morphological, cultural, and molecular genetic techniques as Quambalaria cyanescens (de Hoog & G.A. de Vries) Z.W. de Beer, Begerow & R. Bauer. This species was previously known mostly as a symbiont of tropical plants of the genera Eucalyptus and Corymbia and have not been isolated in Russia. We revealed a close association between Quambalaria cyanescens and silver birch. The micromycete was regularly detected in pollen samples, as well as on the inside and outside of the aments, and on the surface of leaves and branches. It was never isolated from other plant species in the investigated area. The data on the morphological and cultural characteristics of the fungus, its cell ultrastructure, and occurrence are presented, as well as the phylogenetic analysis of the isolated strains.     

Variation of non-structural carbohydrates in silver birch (Betula pendula Roth) wood

Non-structural carbohydrates in silver birch (Betula pendula Roth) wood were analysed in a 7-year-old clone and in five mature stems. The analysis was conducted to obtain more detailed information on seasonal fluctuation of these components and of the tree-to-tree variation and within stem variation. The sugars were analysed by GLC-MS. The smallest total soluble sugar amounts (consisting of sucrose, fructose, glucose, raffinose and myo-inositol) in young trees were measured during mid-summer (ca. 0.3%) and the largest while in dormancy (ca. 1.6% on wood dry weight basis). Raffinose was detected in autumn as a minor component. The proportion of monosaccharides and the amount of myo-inositol were largest during growth. Compared to other studies silver birch showed more evident seasonal fluctuation in soluble sugars than evergreen tree species. The sugar amount in mature stems was approximately at the same level as in young trees that had the same felling time. Tree-to-tree variation in the non-structural carbohydrates in the mature wood was fairly large. However, the amount of total soluble sugars, sucrose and glucose showed significant variation within the stem. The amount of these sugars was largest in samples that were taken close to the cambium. Starch was also detected close to pith. According to the heartwood definition and starch measurement results in this paper, it could be stated that silver birch does not form heartwood.