Loading Effects of Aminoclays in Co-Culture of Two Cyanobacterial Microcystis and Anabaena Species as an Algicidal Role

In recent decades, harmful algal blooms (HABs) have been significantly affecting environments, aquatic ecosystems, and human health, as well as damaging economies, especially near rivers and lakes, and in coastal regions. Microcystis and Anabaena are two genera of harmful cyanobacteria that will often predominate during toxic microalgal blooms. In this study, we employ a method for control and mitigation of HABs by microalgal cell instability using different types of aminoclays (ACs). Allelopathic interactions between the two strains of algae are studied in mono-culture, co-culture, and filtrated cell-free medium in the presence of the ACs. The growth of the Anabaena strain is significantly reduced by the cyanobacterial strains in the co-culture media, and both are significantly affected by the Acs’-enhanced algicidal activity. Anabaena sp. KVSF7 shows higher sensitivity against the ACs than does Microcystis sp. KW. In this way, the algicidal activity of ACs is harnessed, the effects of which are in the order of aluminum aminoclay (AlAC) > magnesium aminoclay (MgAC) > calcium aminoclay (CaAC). The ammonium sites in the ACs carry positive charges to induce instability of HABs along with the electrostatic attraction between algal cells and AC. Therefore, the utilization of the algicidal activity of the ACs can effectively reduce HABs, especially on cyanobacterial blooms.

Allelopathic Interactions between Seeds of Portulaca oleracea L. and Various Crop Species

Allelopathy is described as the interference to plant growth resulting from chemical interactions among plants and other organisms mediated through the release of bioactive secondary metabolites. Since only a few studies have been reported about the role of seed allelopathy, an experiment was designed to evaluate the interactions among seeds of Portulaca oleracea L. and the crop species common bean (Phaseolus vulgaris L.), onion (Allium cepa L.), sugar beet (Beta vulgaris L.), broad bean (Vicia faba L.), and pea (Pisum sativum L.) on seed and seedling growth parameters. The results indicated that P. oleracea seeds had a negative effect on the germination of P. vulgaris and A. cepa. Conversely, germination of P. oleracea in the presence of P. vulgaris, A. cepa, and B. vulgaris seeds was strongly reduced with a higher inhibitory effect found for the seeds of A. cepa. The highest negative effect on root and shoot length was observed in P. vulgaris. Seedling vigor of all crop species decreased in the presence of P. oleracea. Our results suggest that seeds of P. vulgaris, A. cepa, and B. vulgaris exhibited high allelopathic effects against seeds of P. oleracea and can be used as potential bio-herbicides in future screening programs.

Pioneers of Allelopathy: XVI. Udo Blum

Udo Blum had a teaching and research career of 34 years. His primary role was teaching, advising, and mentoring undergraduate and graduate students. He authored or co-authored research publications on plant-plant allelopathic interactions, air pollution biology, and salt marsh biology. He retired in 2002 and has subsequently written a three-volume retrospective analysis of his research on plant-plant allelopathic interactions involving phenolic acids. His primary research goals were to understand: (i) how cinnamic and benzoic acids released from plants into the soil affect sensitive seedlings and soil and rhizosphere microorganisms, (ii) how phenolic acids are distributed and partitioned in seedling-microbe-soil-sand systems and (iii) how their effects on sensitive seedlings are modified by abiotic soil factors (soil pH, soil moisture, soil nutrients, presence of other organic compounds) and soil processes (microbial utilization and soil sorption) in laboratory and field model systems. In 1999 he received the Molisch Award from the International Allelopathic Society for his research contributions to our understanding of Plant-plant allelopathic interactions.

Allelopathic and Competitive Interactions Between Native and Alien Plants

The novel-weapons and homeland-security hypotheses are based on the idea that aliens and natives are not adapted to each other’s allelochemicals as they did not co-evolve. However, as only a few studies have tested this, it remains unclear how important co-evolutionary history is in determining the strength of allelopathic interactions between aliens and natives. Here, we tested for potential pairwise allelopathic effects on each other of five alien and five native herbaceous species in China. We did a germination and a competition experiment. In the germination experiment, we tested whether aqueous extracts of the ten study species had allelopathic effects on each other’s seed germination. In the competition experiment, we tested whether the alien and native species differed in their competitive effects and responses, and whether these were changed by the presence of activated carbon –a presumed allelopathy neutralizer– in the soil. Plant extracts had negative allelopathic effects on seed germination. This was particularly the case for extracts from the native species. Moreover, aqueous extracts had slightly stronger negative effects on germination of the aliens than on germination of the natives. In the competition experiment, on the other hand, the natives suffered more from competition than the alien species did, but we could not relate this to allelopathy. Alien plants had negative competitive and allelopatic effects on native plants, and the reverse was also true. These alien-native interactions, however, were not consistently stronger or weaker than native-native interactions or alien-alien interactions.

Effects of Ozone (O3) on leaf secretory cell characteristics related to allelopathy of woody plants: Modelling allelopathic Interactions

We studied the effects of ozone (O3) on the allelopathic medicinal trees/shrubs that influenced other species growing under their canopy in National Park Sochi, Russia (Caucasus region). Using model reactions, the action of rain leachates from these allelopathic trees/shrubs on the plants growing under their canopy was determined. Depending on the duration and intensity of exposure, the O3 treatment of test woody plants changed their (i) characteristics of leaves and their water extracts, (ii) colour and (iii) autofluorescence of secretory cells. Water extracts from the allelopathic woody donor plants served as model of rain leachates, and their effects were tested on the seeds and pollens germination of acceptor plants (Lavatera trimestris L. var.Rubin and Hippeastrum (Herb.) hybridum ). The effects of water extracts from the ozone treated plants differed from the untreated plants. The allelochemicals in donor plants stimulated, inhibited or had no effects on the recipient plants compared with control. The test-reactions in tropospheric ozone stress should be used in Modelling System of tree/shrub-herbaceous plants interactions, to find the allelopathic interactions in urban conditions.