Terpenoid and morphological variability of Pinus quadrifolia and the natural hybridization with Pinus monophylla in the San Jacinto Mountains in California

Monoterpenoids from wood of Pinus quadrifolia and Pinus monophylla from south of the San Jacinto Mountains in southern California were analysed by gas-liquid chromatography (GLC). The number of needles per fascicle, the number of resin canals, and the number of abaxial and adaxial stomatal rows in the needles were determined. Percentages of mycrene, α-pinene, and to a minor extent of camphene, β-pinene, limonene, and β-phellandrene, the above mentioned morphological characteristics and previously obtained data were all used for identification and characterisation of species intermediacy in the San Jacinto area. It was concluded that many P. quadrifolia trees in the mixed Buck Ridge stand and some trees in two pure stands of the same area were hybrids and that sympatric and to a lesser extent allopatric introgression of P. monophylla into P. quadrifolia takes place in the San Jacinto region. Introgression of P. quadrifolia into P. monophylla could not be demonstrated.     

Vegetational changes in a wet meadow complex,South Bohemia,Czech Republic

Directional changes of vegetation in a wet meadow complex are described, comparing phytosociological relevés taken in 1956, 1963, 1984 and 1989, and vegetation maps made in 1956 and 1984. The relevés were located at various distances from the pond shore predominantly reflecting differences in water regime and intensity of farming. The data were elaborated using direct and indirect gradient analyses. Alterations of environmental factors (moisture, nitrogen) were expressed using Ellenberg's indicator values. Over most of the area, the former distinct vegetation mosaic has been replaced by uniform meadows due to intensive farming. The area was eutrophicated and partly drained, clearly shown in Ellenberg's indicator values, in species composition and vegetation pattern. Rapid processes of ruderalization took place. A scheme of successional pathways which finally emerged can be applied to analogous wet meadows in comparable geographical regions and used as a tool for prognoses of successional processes in meadows under human impact. The paper demonstrates ways to exploit earlier phytosociological records.     

Thermal melting and circular dichroism of DNA complexes with (Lys-Ala-Ala)10 and (Lys-Ala-Ala)n: effect of polypeptide chain length

DNA complexes with polypeptides (Lys-Ala-Ala)₁)] and (Lys-Ala-Ala)₃₄ have been studied using the methods of thermal melting and circular dichroism. Derivative melting curves of (Lys-Ala-Ala)₁₀ DNA differed substantially from those of (Lys-Ala-Ala)₃₄ prepared either by salt gradient dialysis or by direct mixing. Melting curves of the former complex were unimodal or bimodal with T_m increasing continuously withn input lysin-to-DNA phosphate ratio (r); those of the latter complex consisted of three separate transitions with T_m values almost independent of r. Complete reversibility of binding in the (Lys-Ala-Ala)₁₀-DNA system but a slow redistribution of (Lys-Ala-Ala)₃₄ on DNA at low temperature were found in the redistribution experiments Much faster redistribution from denatured to native DNA occurs at the temperature of melting, contributing to the unusual trimodal melting pattern. Circular dichroism curves are very similar for both complexes and indicate little change of DNA conformation upon polypeptide binding.     

New species of the genusEchinodorus from South Brazil

In recent years 4 species of the genusEchinodorus have been imported in large quantities to Europe from Southern Brazil, being cultivated as decorative plants in aquaria. In spite of the fact that up to now not all organs from these plants are known, they differ so greatly from the known species by character of the submersed leaves that there is no doubt that the species, in question, viz.E. osiris, E. opacus, E. horemani andE. portoalegrensis, are new.     

A Comparative study on the reactions for protein sulphydryl,carboxyl and tyrosine in plant nuclei

V této práci byly aplikovány na rostlinných objektech reakce s β-oxynaftyl-merkurichloridem a p-nitrobromacetofenonem, popsané k pr?kazu bílkovinných SH na materiálu ?ivo?i?ném. V rostlinných meristematických buňkách obě tyto techniky stejně jako DDD¹ a RSR¹ jeví vět?inou intensivněj?í zbarvení jader ne? cytoplasmy. Rovně? po aplikaci reakcí na bílkovinné karboxyly a tyrosin je jádro intensivněji zbarveno ne? cytoplasma. Z toho lze soudit, ?e rozdíly v intensitě zbarvení jádra a cytoplasmy v meristematických buňkách rostlinných technikami k pr?kazu bílkovinných SH jsou zp?sobeny spí? rozdílem v celkové koncentraci bílkovin ne? zv??ením podílu cysteinu v jaderných bílkovinách.     

Biomass partitioning in twoCalamagrostis villosa stands on deforested sites

Calamagrostis villosa stands occurring in areas deforested by air-pollution impact in the Moravian-Silesian Beskydy Mountains were characterized by a high dry mass of total underground biomass (3 300 g. m^?2—the slope site, 2 850 g. m^?2—the flat site). The percentage of living roots and rhizomes in total underground biomass was very high (about 70%). The total aboveground biomass was respectively, 321 g.m^?2 (the slope site) and 726 g. m^?2 (the flat site). In unstabilized habitats on steep slope, the higher plant biomass produced was allocated to a more developed root system.     

The atokous-epitokous border is determined before the onset of heteronereid development in Platynereis dumerilii (Annelida,Polychaeta)

Summary In most nereids sexual maturation is accompanied by a dramatic reorganization of the body that enables swarming of the formerly benthic worms. However, a border exists between unchanged anterior (atokous) and metamorphosed posterior (epitokous) segments. The site of this atokous-epitokous border (a/e border) is different in sexually mature males and females of Platynereis dumerilii. There is no correlation between the total number of setigerous segments of a specimen and the location of the a/e border. The location of the a/e border and sexual development are affected neither by cutting off caudal segments of juveniles (including the prospective a/e border) nor by transecting the ventral nerve cord. When parapodia are transplanted from prospective epitokous regions to prospective atokous regions and vice versa, they maintain their original character during metamorphosis. The results presented here suggest that prospective atokous as well as epitokous characters are determined at or only very shortly after formation of the respective segments. Thus the a/e border is established well in advance of the onset of epitokous metamorphosis.