Growth forms of annual vascular plants in central Europe

The investigation of the vegetative characters of annual species from central Europe showed a hitherto not regarded large spectrum of 20 growth forms within this plant group. These growth forms can be identified by means of a dichotomous key. This is also a new method to present growth form systems. Although several surveys about growth forms have been carried out, the proposed systems are either incomplete or not consequent in the use of their classifying criteria. Moreover, annual species have never been investigated systematically according to their growth forms. Important characters which were used to characterize growth forms are the occurrence of a rosette, the presence or absence of supporting tissue which causes aerostability or aerolability, succulence, growth direction (plagiotropous, orthotropous) and metamorphoses (for scrambling). According to the mode of surviving the resting period, annuals can be grouped into therophytes, hydrophytes, and hemicryptophytes. Whereas therophytic and hydrophytic annuals perennate the winter exclusively as generative diaspores (seeds, spores), hemicryptophytic species survive as seedlings or young plants.     

Mechanical response of periodontal ligament: Effects of specimen geometry, preconditioning cycles and time lapse

This study was conducted as part of research line addressing the mechanical response of periodontal ligament (PDL) to tensile–compressive sinusoidal loading. The aim of the present project was to determine the effect of three potential sources of variability: (1) specimen geometry, (2) tissue preconditioning and (3) tissue structural degradation over time. For the three conditions, selected mechanical parameters were evaluated and compared.(1) Standard flat specimens (obtained by sequentially slicing portions of bone, PDL and dentin using a precision band saw) and new cylindrical specimens (extracted with a diamond-coated trephine drill) were obtained from bovine mandibular first molars and subjected to a sinusoidal load profile. (2) Specimens were loaded with up to 2000 cycles. (3) Specimens were immersed in saline and tested after 0, 30 and 60 min.From the data generated, the following was concluded: (1) specimen geometry and preparation technique do not influence the mechanical response of the PDL; (2) the mechanical response stabilizes after approximately 1000 cycles; and (3) no major structural degradation occurs when PDL is immersed in saline for a time lapse up to 60 min.