Are there seasonal variations of trace element concentrations (Cd,Pb, Zn) in wood of Fagus trees in Germany?

Concentrations of Cd, Pb and Zn were determined in stem wood of beech trees (Fagus sylvatica L.) from 3 sites in northern Germany. Distinct radial distribution patterns of the elements were observed in the xylem. Concentrations of Cd and Pb increased from the youngest, outermost annual rings towards the center of the stem. With Zn intermediate concentrations were observed in the sapwood and higher levels at the center of the stem.Temporal and spatial stability of such distribution patterns in the trunks was investigated. Wood samples taken from the same individual tree in different months of the year were analysed. Marked seasonal variations of mineral concentrations were observed. Also the shape of the distribution patterns of the elements varied with the season. Such variations were larger than those observed with samples taken simultaneously from different sides of the trunk. Furthermore, Pb concentrations in the stem showed variations with height above ground.The results indicate, that radial distribution patterns of Cd, Pb and Zn in xylem rings of beech are not stable. Biomonitoring trace element pollution levels by analysis of beech wood is, thus, questionable. To obtain a reliable historical record of pollution from tree rings, the distribution patterns should be stable over a long period of time. This basic requirement of the dendroanalytical method does not hold for the examined beech. Still, with other tree species and under more favourable conditions the dendroanalytical biomonitoring method may prove valuable.Presented as symposium paper at the V International Congress of Ecology, Yokohama, August 23–30, 1990.     

Formation of the Dermal Chromatophore Unit (DCU) in the Tree Frog Hyla Arborea

In the tadpole of the tree frog Hyla arborea, the color of the dorsal skin was dark brown. Dermal melanophores, xanthophores, and iridophores were scattered randomly under the subepidermal collagen layer (SCL). After metamorphosis, the dorsal color of the animal changed to green and the animal acquired the ability of dramatic color change, demonstrating that the dermal chromatophore unit (DCU) was formed at metamorphosis. Fibroblasts invaded the SCL and divided it into two parts: the stratum spongiosum (SS) and the stratum compactum (SC). The activity of collagenase increased at metamorphosis. The fibroblasts appeared to dissolve the collagen matrix as they invaded the SCL. Then, three types of chromatophores migrated through the SCL and the DCU was formed in the SS. The mechanism how the three types of chromatophores were organized into a DCU is uncertain, but different migration rates of the three chromatophore types may be a factor that determines the position of the chromatophores in the DCU. Almost an equal number of each chromatophore type is necessary to form the DCUs. However, the number of dermal melanophores in the tadpoles was less than the number of xanthophores and iridophores. It was suggested that epidermal melanophores migrated to the dermis at metamorphosis and developed into dermal melanophores. This change may account for smaller number of dermal melanophores available to form the DCU_s.     

模糊图论在山西植被区划中的应用

本文用模糊图论的最大树方法对山西植被区划进行了数量分类研究,将山西植被分为2个植被地带,6个植被地区,17个植被小区。与在植物群落学中应用的模糊聚类分析和其它方法相比,模糊图论的最大树方法直接依模糊相似系数矩阵得到树状图,从而避免了相似系数矩阵复杂的合成运算,而分类结果不仅更具直观性,而且也是令人满意的。我们认为模糊图论应用于植被区划是合适的。     

Immunocytochemical studies on translocation of phosphorylated aquaporin-h2 protein in granular cells of the frog urinary bladder before and after stimulation with vasotocin

We have generated a specific antibody against phosphorylated aquaporin-h2 (pAQP-h2) protein to investigate the role of phosphorylation in the translocation of AQP-h2 protein within the granule cells of the urinary bladder of the frog (Hyla japonica). The antibody was generated against a synthetic peptide (ST-160) corresponding to amino acids 255–268, with a phosphorylated Ser-262, a residue that is putatively phosphorylated by protein A kinase. Using this antibody, we found, by Western blot analysis, that phosphorylation of the AQP-h2 protein rapidly increased within 2 min after vasotocin (AVT) stimulation and remained at a higher than normal level for 15 min. Moreover, quantitative immunoelectron microscopy indicated that the location of the AQP-h2 protein dramatically changed after AVT stimulation. Before stimulation, pAQP-h2 protein was localized in only a small number of intracellular vesicles near the nucleus of the granular cells, whereas the labeling density of the intracellular vesicles and the apical membrane rapidly increased after stimulation. This finding was also confirmed by the results of an immunofluorescence study. Thus, phosphorylation of AQP-h2 protein seems to be essential for translocation of the protein from the cytoplasmic pool to the apical plasma membrane of the granular cells in frog urinary bladder. This work was supported in part by a grant-in-aid for scientific research from the Ministry of Education, Science, Sports, and Culture of Japan to S.T.     

Direct Calculation of a Tree Length Using a Distance Matrix

Comparative studies of tree-building methods have shown minimum evolution to be in general an accurate criterion for selecting a true tree. To improve the use of this criterion, this paper proposes a method for rapidly and directly calculating a length of a dichotomous tree without having to resort to branch length calculations. This direct calculation (DC) method applies to the complete final topology, giving equal importance to each branch after a dichotomy. According to this method, the tree length S _DC is S _DC =∑ _i ∑ _j (D _ij /2 ^Bij ) = (∑ _i<j ∑D _ij 2 ^Bmax−Bij )/2 ^{Bmax −1} where D _ij is the observed distance between taxa i and j, B _ij is the number of branches connecting i and j, Bmax is the greatest B _ij in the tree, and the powers of two are due to the dichotomy of the tree. This tree length expression may be used as a rapid method for selecting the shortest tree from a set of hypothetical or subobtimal trees. Received: 2 March 2000 / Accepted: 24 March 2000     

Characterization of the complete chloroplast genome of Hevea brasiliensis reveals genome rearrangement, RNA editing sites and phylogenetic relationships

Rubber tree (Hevea brasiliensis) is an economical plant and widely grown for natural rubber production. However, genomic research of rubber tree has lagged behind other species in the Euphorbiaceae family. We report the complete chloroplast genome sequence of rubber tree as being 161,191 bp in length including a pair of inverted repeats of 26,810 bp separated by a small single copy region of 18,362 bp and a large single copy region of 89,209 bp. The chloroplast genome contains 112 unique genes, 16 of which are duplicated in the inverted repeat. Of the 112 unique genes, 78 are predicted protein-coding genes, 4 are ribosomal RNA genes and 30 are tRNA genes. Relative to other plant chloroplast genomes, we observed a unique rearrangement in the rubber tree chloroplast genome: a 30-kb inversion between the trnE(UUC)-trnS(GCU) and the trnT(GGU)-trnR(UCU). A comparison between the rubber tree chloroplast genes and cDNA sequences revealed 51 RNA editing sites in which most (48 sites) were located in 26 protein coding genes and the other 3 sites were in introns. Phylogenetic analysis based on chloroplast genes demonstrated a close relationship between Hevea and Manihot in Euphorbiaceae and provided a strong support for a monophyletic group of the eurosid I.     

Genetic differentiation of the Iberian tree frogs Hyla arborea molleri and Hyla meridionalis (Amphibia: Anura)

Genetic differentiation of Hyla arborea molleri and H. meridionalis was studied through allozyme electrophoresis and through essays of artificial hybridization. Samples were taken at several localities in Portugal, where these species occur either in sympatry or allopatry, and at one locality in France. Of the 21 presumptive loci analyzed, 6 were monoallelic, while 9 loci were discriminative between both species. A relatively high level of genetic differentiation was found between the two species (NEI's D = 0.725), contrasting with their morphological similarity. Remarkably low levels of genetic variability were found within species, with greater differentiation found among samples of H. meridionalis than of H. a. molleri. Although the capacity for interspecific hybridization was low, hybrid embryos resulted from both reciprocal crosses, but with much greater success in the cross ♂H. a. molleri x δH. meridionalis. Hybrids showed greater similarity with the male parent, and showed heterozygote allozymic phenotypes for discriminative loci. Results are compared with those of similar studies on the same and different species of Hyla, and differentiation of H. a. molleri and H. meridionalis is discussed in relation to their taxonomic status and origin.     

Tree structure,regeneration and survival of seedlings and sprouts in highmontane forests of the Garhwal Himalayas,India

The tree structure of some timberline and sub-alpine forests of the Garhwal Himalayas was studied with reference to the regeneration status and survival of tree seedlings and sprouts. Nine tree and shrub species were chosen. The dominating tree species wereAbies pindrow andQuercus semicarpifolia. Sprouts were found to have a higher survival rate than seedlings, but both suffered from winter conditions. Girth class measurements showed that trees between 1.6 and 2.5 m were best represented.