In temperate European forests invaded by Prunus serotina Ehrh. (black cherry), a reduction in the spontaneous regeneration capacity of Pinus sylvestris L. (Scots pine) is observed. It could be caused by various factors, including allelopathic properties of this invasive plant. In this study the phytotoxic effect of P. serotina volatile compounds on P. sylvestris and the seasonal variation in this effect were assessed. Simple assays showed that volatiles emitted from P. serotina leaves significantly inhibited root growth of P. sylvestris seedlings. Their negative effect on stem growth was much weaker. The strongest phytotoxic effect on Scots pine seedlings was caused by the volatiles emitted from the youngest black cherry leaves. In fresh foliage of P. serotina, nineteen volatile organic compounds were identified by gas chromatography–mass spectrometry (GC–MS). The dominant compound was benzaldehyde. On the basis of tests of linalool alone, it was found that this monoterpene present in the volatile fraction has a strong allelopathic potential and inhibits germination, root elongation and shoot elongation of pine seedlings. The results of our research suggest that volatile compounds from P. serotina leaves could limited survival of P. sylvestris individuals in the seedling phase.

No abstract

Abandoned agricultural land present in most European countries constitutes a resource of land that can be restored to agricultural production. Fallow colonization by invasive plant species contributes to changes in the course of natural secondary succession. This may modify the possibilities of returning fallow lands to agriculture, which constitutes an issue that needs to be investigated. In this study, the phytotoxic effect of invasive black cherry (Prunus serotina Ehrh.) on two crop plants commonly used for fallow land utilization, white mustard (Sinapis alba L.) and common buckwheat (Fagopyrum esculentum Moench), was assessed. The influence of water extracts from P. serotina litter and the soil collected under the individuals of this species was investigated. Sinapis alba was found to be more sensitive to allelochemicals released by P. serotina than F. esculentum. Litter extracts and soil with residues of P. serotina significantly inhibited both germination and growth of S. alba seedlings, estimated with length and mass of the above-ground and underground parts. In the case of F. esculentum, a negative effect of the tested extracts and soil on root mass reduction was observed. Preliminary results of our laboratory tests suggest that cultivation of white mustard should be avoided in the reclamation of fallows with black cherry.

Abstract:The subject of this study is to analyse changes in the taxonomic structure and development intensity of phytoplankton and, thus, to determine the diversity of cyanobacteria and algae along with the trophy state of two oxbow lakes in the Wrocław area (south-western Poland). The analysis of samples and data from previous years showed a total of 244 cyanobacteria and algae species within these two lakes. The species composition changed significantly in both of them -there were found 90 species new to the studied flora (37% of current flora) and 74 species which were previously recorded. The diversity of cyanobacteria and algae reflects the conditions in these water bodies and each change in ecological conditions (e.g., anthropological dangers) is reflected by a change in the phytoplankton assemblage structure. Consequently, knowledge of taxonomic diversity is useful in monitoring water bodies to preserve them in good conditions. Both studied oxbow lakes belong to eutrophic ecosystems as evidenced by their phycoflora, which is rich in species characteristic of high-trophy water, and recorded water blooms. The analysis of changes in cyanobacterial and algal assemblages in these lakes was also a basis for determining their trophy and finding it to be progressively eutrophic. Regular phycological studies of Wrocław numerous water bodies are essential and, in the future, will allow us to protect them and to react quickly in case of danger to these ecosystems. It will also allow us to study eutrophication processes in the water bodies that are crucial to the city.

No abstract