…Fell Upas Sits, the Hydra-Tree of Death †, or the Phytotoxicity of Trees

Assessing Impacts of Transgenic Plants on Soil Using Functional Indicators: Twenty Years of Research and Perspectives

Assessment of the effects of transgenic plants on microbiota and soil fertility is an important part of the overall assessment of their biosafety. However, the environmental risk assessment of genetically modified plants has long been focused on the aboveground effects. In this review, we discuss the results of two decades of research on the impact of transgenic plants on the physicochemical properties of soil, its enzyme activities and microbial biomass. These indicators allow us to assess both the short-term effects and long-term effects of cultivating transgenic plants. Most studies have shown that the effect of transgenic plants on the soil is temporary and inconsistent. Moreover, many other factors, such as the site location, weather conditions, varietal differences and management system, have a greater impact on soil quality than the transgenic status of the plants. In addition to the effects of transgenic crop cultivation, the review also considers the effects of transgenic plant residues on soil processes, and discusses the future prospects for studying the impact of genetically modified plants on soil ecosystems.

Influence of Pholiota spp. (Strophariaceae, Basidiomycote) mycelial biomass on seed germination and seedlings growth of Lepidum sativum L. and Cucumis sativus L

Basidiomycetes represent a very diverse group of eukaryotic organisms in terms physiological parameters. Some organisms such as plants or fungi release certain secondary metabolites, which can affect the organisms around them. Some of the substances released by mushrooms could have effects on the growth and further development of nearby plants. Studies of fungi and their biologically active components have grown significantly, with the aim of potential introduction to various biotechnological processes.The allelopathic effect of Pholiota species has been investigated in this study. Mycelial biomass of seven screened Pholiota species were tested to study cucumber (Cucumis sativus L.) and lettuce (Lepidium sativum L.) seed germination and the sprouting growth. The results of our experiment showed that the biomass of the species of the genus Pholiota did not affect the germination of seeds of both plant species. 100% seed germination was recorded in both control and experimental samples. The addition of mycelial biomass of the Pholiota species led to a suppressive allelopathic effect, which affects seed germination, the length of the studied plant (both shoots and roots), as well as changes the morphology of the roots (pubescence, changes in lateral roots). The inhibitory effect on sprouting length was 8,6%-87,1% in the case of C. sativus and 42,2%-91,8% if specify for L. sativum in depence on Pholiota species. Allelopathic properties of Pholiota subochracea, where sprouting growth ratio did not exceed 12.9%, compared to the control group, should be noted. This result suggests that Pholiota mushrooms have a significant regulatory effect on lettuce and cucumber sprouting growth. The given results suggest that the studied species may play a significant role in relationships within ecosystems.

Physiological and Biochemical Mechanisms Mediated by Allelochemical Isoliquiritigenin on the Growth of Lettuce Seedlings

Isoliquiritigenin, a natural chalcone-type flavonoid, has been recognized as an allelochemical with phytotoxicity to lettuce; however, not enough attention has been paid to the mechanisms of this secondary metabolite. In this work, we investigated the physiological and biochemical mechanisms of isoliquiritigenin on lettuce seedlings. The results show that isoliquiritigenin has a concentration-dependent inhibitory effect on radicle elongation of lettuce seedlings, but no significant impact on lettuce germination. Microscopy analyses suggest that the surface morphology of lettuce radicle tips was atrophied and the intracellular tissue structure deformed at high concentrations. Isoliquiritigenin induced the overproduction of reactive oxygen species (ROS), which led to loss of cell viability in the radicle cells. In addition, malondialdehyde (a product of lipid peroxidation) and free proline levels were found to have increased, while chlorophyll content in lettuce seedlings decreased. All these changes suggest that the primary allelopathic mechanism of isoliquiritigenin by which it inhibits radicle elongation in lettuce seedlings might be due to the overproduction of ROS, which causes oxidative damage to membrane lipids and cell death.