The cause of the prevalent directions of the spiral grain patterns in conifers

 A new theory is presented on the cause of the prevalent directions of the spiral grain patterns found in conifers. The hypothesis is based upon the assumption that spiral grain has a function, i.e. that it represents a growth strategy to ensure survival of the trees. The mechanical function of the tree trunk is placed in focus, that is the ability of the trees to withstand external mechanical loads, mainly from wind. Spiral grain is an optimized growth feature when the trees are exposed to combined bending and torsion. Torsion occurs when the crown is asymmetric in the plane perpendicular to the wind direction. Systematic crown asymmetry, with heavier crowns on the south side, was confirmed by measuring the crown projections on 253 sparsely grown pines; 76.7% of the trees had longer branches on the south than on the north side, and the average length difference was 40.8 cm. By studying wind maps it was seen that most of the coniferous forests have prevailing westerly winds, which, when combined with the crown asymmetry, leads to a prevailing torque. Right-handed spiral grain in the outermost layers of mature trees is proposed to be a strategy to withstand this torque, i.e. to avoid stem breakage. Received: 30 June 1997 / Accepted: 17 November 1997     

Epilobio dodonaei-Melilotetum albi,eine neue Pflanzenassoziation

In der vorliegenden Arbeit wird eine neue PflanzenassoziationEpilobio dodonaei-Melilotetum albi Slavík 1978 beschrieben. Diese Assoziation ist an Kiesanschwemmungen in der niederen Lagen der warmen Region am Fuss der Karpaten gebunden und kann auch anderswo in Mitteleuropa vorausgesetzt werden. Sie stellt eine Parallele zum verwandtenMelilotetum albo-officinalis Sissingh 1950.     

Microbial transformations of cardioglycosides

Summary Penicillium vermiculatum deglycosylated lanatosid C to acetyldigoxin and Arthrobacter citreus deacetylated the latter to digoxin. Both reactions were carried out in a short time with high yields. Lanatosid A was transformed by P. vermiculatum simultaneously to acetyldigitoxin and digitoxin. A. citreus transformed lanatosid A directly to digitoxin and lanatosid C to digoxin, but the reactions took a long time and the yields were low.     

Über Zytolyse durch fettlösende Mittel und die Bedeutung des Lezithins und Kalziums für das physikalisch-chemische Verhalten des Protoplasmas

Zusammenfassung Die fettlösenden Mittel werden gewöhnlich ohne Unterschied als hämolytisch und überhaupt cytolytisch wirkende Agenzien angeführt; in der vorliegenden Arbeit wird gezeigt, daß einzelne dieser Lösungsmittel in kleinen Konzentrationen nicht nur keine destruktive Wirkung haben, sondern daß sie die Cytolyse, welche durch andere fettlösende Mittel hervorgerufen wird, in ausgedehntem Maße zu hemmen imstande sind. Wenn also die Äthercytolyse durch Azeton gehemmt wird, so kann bei dieser Cytolyse nur ein solcher Stoff als Angriffspunkt betrachtet werden, welcher zu den beiden Lösungsmitteln ein antagonistisches Verhalten zeigt. So kann vermutet werden, daß die Äther- und Alkoholcytolyse durch Auflösung des Lezithins in der Zelle, die Azetonhemmung dieser Cytolyse aber durch Verhinderung dieser Auflösung bewirkt wird.Die Äther- und Alkoholcytolyse wird aber auch durch kalziumbindende Salze sehr stark gehemmt: es scheint also, daß in der Struktur des Protoplasmas ein gewisses Kalzium-Lezithingleichgewicht herrscht, welches durch Einwirkung auf die eine oder andere Komponente beeinflußt werden kann.     

A plant-geographical study of the genusDorycnium MILL. (Fabaceae) in the Czech Republic

Two species of the genusDorycnium with the most northern distribution reach the absolute northern limit of their distribution areas in the Czech Republic.Dorycnium germanicum, a less ecologically plastic and more xerothermic species, covers a compact area in south Moravia, connected with its occurrence in Lower Austria.Dorycnium herbaceum, and ecologically more tolerant species, has its primary distribution area in south-east Moravia; this is connected with the Slovak part of the area of this species; secondary occurrences are scattered throughout other parts of Moravia and Bohemia. The distribution of both species was evaluated, using 23 herbarium collections. Climatic characteristics are provided for 54 climatic and ombrometric stations from the distribution area of both species. In the Czech RepublicD. germanicum represents the Illyrian-Noric migration element whileD. herbaceum represents the Carpathian one. There is a clear climatic differentiation between the localities of both species:D. germanicum occurs in dryer and warmer regions thanD. herbaceum. An introgression, zone was identified in the vicinity of the twon of Uherské Hardi?tě and the area south-east of this town. This zone coincides with the area where most of the identification problems with these species occurred.