The dynamics of a non-forested stand in the Krušné Mts.: the effect of a short-lived medieval village on the local environment

Vegetation History and Archaeobotany - Medieval vegetation–human–climate interactions were studied from a sediment profile situated in the centre of a short-lived medieval village...     

Estimation of tree biomass of Norway spruce forest in the Plešné Lake catchment,the Bohemian Forest

This paper evaluates the total biomass and pools of major nutrients and ecologically important metals of the tree layer in the catchment of Ple?né jezero (PL) in the Bohemian Forest (?umava, Czech Republic), and compares them to analogous data on understory vegetation and soils. The results are based on field measurements and semi-automatic image analyses of aerial orthophotographs. The tree layer was relatively sparse with open canopy in some parts of the catchment. Stand density varied between 44 and 328 individuals per hectare. The catchment weighted mean total biomass of trees was 134 t ha^?1 dry weight, of which needles, branches, roots, and stems represented 5%, 10%, 14%, and 71%, respectively. The stem wood and bark represented 67% and 4%, respectively, of the total tree biomass. The catchment weighted mean element pools were 568 and 3.0 mol m^?2 (i.e., 68 and 0.42 t ha^?1) for C and N, respectively. The other pools were 76 mmol P m^?2, 602 mmol Ca m^?2, 133 mmol Mg m^?2, 39 mmol Na m^?2, 347 mmol K m^?2, 19 mmol Al m^?2, 6.2 mmol Fe m^?2, and 35 mmol Mn m^?2. The element pools accumulated in the tree biomass represented from < 1% (Al, Fe) to 37% (C) of their total pools (soil + tree layer + understory vegetation) in the catchment. Pools of Ca and Mg in the tree biomass were similar to their exchangeable pools in the catchment soils, while those of K were 3 times higher. Nutrient (N, P, Ca, Mg, and K) and C pools in the tree biomass were 2–11 times higher than those in the understory vegetation, with the minimum for P and maximum for C.     

1. Fláje–Kiefern (Krušné Hory Mountains): Late Glacial and Holocene vegetation development

This work characterises monofloral honeys of the Yucatán Peninsula based on their pollen content. The sampling was carried out from January to July 2000. We examined 78 different honey samples from various parts of the Yucatán Peninsula including the states of Yucatán, Campeche and Quintana Roo. Pollen separated from honey was acetolysed, identified and counted. Through pollen analysis, 250 pollen taxa were identified, 180 of which had not been reported previously in Mexican honeys. Thirteen different types of monofloral honeys were found (with a percentage of ≥ 45%) within the honey produced in the Yucatán, Peninsula. These were: Viguiera dentata, Bursera simaruba, Piscidia piscipula, Eugenia sp. 2, Pimenta dioica, Melothria pendula, Gymnanthes lucida, Phoradendron quadrangulare, Gymnopodium floribundum, Rubiaceae 1, Thouinia paucidentata, Thouinia sp. 1, and Pouteria mammosa. This is the first study of monofloral honeys in Mexico and Central America. The characterisation of the honey may give an added market value as it permits us to separate the honeys of monofloral or multifloral origin. The results of this study indicate that it is possible to produce several monofloral honeys in a region with great plant diversity as the Yucatán Peninsula. We recommend installing apiaries in disturbed vegetation zones of the Yucatán Peninsula where an advanced succession of a tree layer exists. This supplies the nectar and pollen during the critical period in March and April which is the driest season.     

The long-term succession of cladoceran fauna and palaeoclimate forcing: A 14,600-year record from Plešné Lake,the Bohemian Forest

A sediment record of cladoceran remains was analysed in a 543 cm long core from Ple?né jezero (Ple?né Lake), the Bohemian Forest, Czech Republic. The core covered the time period from the Oldest Dryas to the present. Littoral and benthic Cladocera included 11 species of the family Chydoridae while three species (Bosmina longispina, Daphnia cf. pulicaria and D. cf. longispina) lived in the open water. Remains of Alona quadrangularis and Chydrous sphaericus occurred in the oldest sediment layers from the beginning of the Bølling chronozone. Bosmina longispina and Daphnia cf. pulicaria appeared about 400 years later. Inorganic sediment accumulated at a relatively high rate of ～ 90 mg cm^?2 yr^?1 at that time, diluting cladoceran remains and organic matter. Remains of Cladocera accumulated at 0.1 to 0.01 of the Holocene rate, making it difficult to observe effects of climate variation on the species structure of Cladocera in the Late-Glacial. Production of remains increased after warming during the Younger Dryas-Preboreal transition at ～11.6 kyr BP, and the proportion of littoral species increased. The most important change in cladoceran fauna occurred at ～10.5 kyr BP and culminated with afforestation of the catchment around 10.3 kyr BP. The domaination of Bosmina longispina lasted for ～250 years. The afforestation occurred concurrently with a decrease in lake water pH. Bosmina longispina and Daphnia cf. pulicaria disappeared, production of cladoceran remains decreased, but biodiversity increased. Planktonic Cladocera were represented by Daphnia cf. longispina during most of the rest of the Holocene. The production of Cladocera never reached the Preboreal level. Since ～ 5 cal. kyr BP, the inferred pH continuously decreased. The final decline was likely caused by cooling during the Little Ice Age and by sulphur emissions from ore smelting. The recent acidification of lake water and impoverishment of aquatic fauna was brought about by emissions of sulphur and nitrogen compounds in the 20^th century.     

Adventitious bud regeneration from leaf expiants of the shrubby ornamental honeysuckle,Lonicera nitida Wils. cv. ‘Maigrün’: effects of thidiazuron and 2,3,5-triiodobenzoic acid

Different combinations of auxins and cytokinins were employed to assess the regeneration capacity from in vitro leaf explants of Lonicera nitida Wils. cv Maïgrün. A high frequency of rhizogenesis was noticed, with 2.3 M thidiazuron plus 2.9 M indole-3-acetic acid as the only hormonal combination to support caulogenic responses. Increasing thidiazuron concentration and/or suppressing auxin did not improve caulogenesis. Combining thidiazuron with 2,3,5-triiodobenzoic acid produced a dramatic increase in the percentage of caulogenic explants. A maximum of 74% of adventitious bud forming explants was obtained with 2.3 M thidiazuron plus 20 M 2,3,5-triiodobenzoic acid. Buds were often in a rosette form and were vitreous, so that shoot elongation was difficult to obtain. The effect of the duration of the 2,3,5-triiodobenzoic acid treatment on shoot elongation was investigated.Abbreviations BAP benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - GA3 gibberellic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - 2 IP 2-isopentenyladenine - MS Murashige and Skoog - NAA -naphthylacetic acid - TDZ N-phenyl-N-1,2,3-thidiazol-5-ylurea (thidiazuron) - TIBA 2,3,5-triiodobenzoic acid - Z zeatin     

Trypanosoma cruzi: molecular identification and characterization of new members of the Tc13 family. Description of the interaction between the Tc13 antigen from Tulahuén strain and the second extracellular loop of the beta(1)-adrenergic receptor

Trypanosoma cruzi Tc13 antigens belong to the trans-sialidase superfamily. Their sequences have been described only partially and, up to now, their physiological activity has not been elucidated. Here we present two new members of this family from the Tulahuén strain (Tc13 Tul) and the CL Brener clone (Tc13 CL), being the latter the first Tc13 sequence fully described. Alignment of all Tc13 sequences allowed us to define two sub-families that differ in the number of repeats and the presence or absence of the GPI addition site. Chromoblots demonstrate that Tc13 antigens are mainly located in chromosome III and its homologous. Pull down assays suggest that recombinant MBP-Tc13 Tul interacts with the second extracellular loop of the beta(1)-adrenergic receptor. This is the first evidence that a Tc13 antigen acts as a ligand interacting with a neurotransmitter receptor. These observations might add some light to the development of chagasic pathology.     

Amino acid residues involved in the action of endo-(1→3)-β- d-glucanase II from Flavobacterium dormitator var. glucanolyticae FA-5

The pH-dependence of the kinetic parameters for the hydrolysis of yeast glucan with endo-(1→3)-β- d-glucanase II from Flav. dormitator var. glucanolyticae FA-5 suggests that two residues (histidyl and carboxyl) are involved in the enzyme action. Chemical modification of the enzyme has been studied in order to identify the kinds and the number of amino acid residues involved in enzyme action. Photo-oxidation and carbethoxylation of the enzyme indicated that the decomposition of a histidine residue is responsible for the loss of activity. Modification of the enzyme with Woodward's reagent K indicated that ～ 12 carboxyl residues in the enzyme are involved in the catalytic and/or substrate binding-site.