Allelopathic growth inhibition and colony formation of the green alga Scenedesmus obliquus by the aquatic macrophytes Stratiotes aloides

Laboratory experiments were conducted to elucidate the allelopathic effects of exudates from the aquatic macrophyte Stratiotes aloides on the growth and morphology of the green alga Scenedesmus obliquus. Both water originating from a S. aloides culture and water that had not been in contact with S. aloides was simultaneously inoculated with S. obliquus cells. In all experiments we observed a highly significant inhibitory effect of Stratiotes water on the green alga. The duration of the lag phase as well as the initial biovolume doubling time of S. obliquus were extended. The growth rate of S. obliquus was only significantly inhibited by the younger Stratiotes plants. Furthermore, the mean particle volume (MPV) of Scenedesmus increased significantly in the presence of Stratiotes water in all three experiments. Microscopic analyses confirmed that S. obliquus forms more colonies in the presence of water from a S. aloides culture. Colonies of phytoplankton have higher sinking rates than single phytoplankton cells of the same species and disappear faster from the upper water layers, reducing the competition for light between algae and macrophytes. [KEYWORDS: Colony formation ; Growth inhibition ; Infochemical ; Macrophytes ; Sedimentation]

Pension funds and corporate social performance : an empirical analysis

This study examines the relationship between pension fund ownership of companies and corporate social performance using a unique database of more than 500 publicly listed U.K. companies. The empirical analysis emphasizes the heterogeneous character of pension fund holdings and the multidimensional nature of corporate social performance. The results highlight that the characteristics of pension fund management are significant drivers of preferences for social performance and that employee-related aspects of social performance are preferred by pension funds