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The impact of a crude extract of Microcystis aeruginosa (PCC7820) containing 14 microcystin variants was investigated on seeds germination and radicles development of four agricultural plants: two tomato varieties Solanum lycopersicum (MicroTom and Saint-Pierre), the wheat Triticum aestivum and the lettuce Lactuca sativa. In addition, the effect of 14 d-exposure to irrigation water containing realistic concentrations of microcystins (0-0.1 mg eq. microcystin-LRL(-1)) on the tomato MicroTom seedling growth was further evaluated on roots and aerial part biomasses. Impacts on soil bacterial parameters, as such extracellular enzymatic activities, nitrification activity and abundances of ammonia-oxidizing microorganisms were also investigated. In germination-test, the cyanobacterial extract inhibited only the germination of the wheat seeds, with an EC50 of 11 mg eq. microcystin-LRL(-1); which is 13 times lower than that of the cadmium chloride (EC50 of 145 mg L(-1)). Moreover, the cyanobacterial extract containing low concentrations of microcystins increased the growth of primary roots; however, high concentrations decreased it for all plants except for the wheat. In the soil-plant approach, only aerial part biomass of the tomato MicroTom was enhanced significantly. In addition, only soil nitrification potential and ammonia-oxidizing bacterial abundances were consistently impacted. A significant positive correlation (r=0.56) was found between the increase of nitrification potential and abundances of ammonia-oxidizing bacteria. This work suggested, that exposure to a cyanobacterial extract containing realistic environmental microcystins concentrations could affect seed germination, depending plant species. It was also highlighted, for the first time, disturbances in soil bacteria functioning, evidences on soil nitrification process., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The occurrence of harmful cyanobacterial blooms in surface waters is often accompanied by the production of a variety of cyanotoxins. These toxins are designed to target in humans and animals specific organs on which they act: hepatotoxins (liver), neurotoxins (nervous system), cytotoxic alkaloids, and dermatotoxins (skin), but they often have important side effects too. When introduced into the soil ecosystem by spray irrigation of crops they may affect the same molecular pathways in plants having identical or similar target organs, tissues, cells or biomolecules. There are also several indications that terrestrial plants, including food crop plants, can bioaccumulate cyanotoxins and present, therefore, potential health hazards for human and animals. The number of publications concerned with phytotoxic effects of cyanotoxins on agricultural plants has increased recently. In this review, we first examine different cyanotoxins and their modes of actions in humans and mammals and occurrence of target biomolecules in vegetable organisms. Then we present environmental concentrations of cyanotoxins in freshwaters and their fate in aquatic and soil ecosystems. Finally, we highlight bioaccumulation of cyanotoxins in plants used for feed and food and its consequences on animals and human health. Overall, our review shows that the information on the effects of cyanotoxins on non-target organisms in the terrestrial environment is particularly scarce, and that there are still serious gaps in the knowledge about the fate in the soil ecosystems and phytotoxicity of these toxins., (Copyright © 2013 Elsevier Ltd. All rights reserved.)