The Synthesis And Release Mechanism Research Of Microcystin Of Microcystin Aeruginosa Exposed To Two Sterilant Herbicides

In recent years, the increasingly frequent algae blooms, and its main secondary metabolites of harmful cyanotoxins, have become a focus of environmental problem. On the other hand, the large use of agricultural pesticides poses a new threat to the aquatic environment. Among them, several kinds of sterilant herbicides are used with genetically modified crops. Their ecological security deserves more attention. However, few studies have focused on the possible link between the use of sterilant herbicides and the outbreak of algae blooms and cyanotoxin production and secretion. This paper choose glufosinate and glyphosate, to research if the two typical sterilant herbicides will have influence on the physiological growth and microcystin-LR(MC-LR) production and secretion of microcystis aeruginosa. The aim is to assess the possible role of glufosinate and glyphosate of environment concentration to the outbreak of cyanobacterial blooms, and the secondary hazard of cyanotoxins. It is necessary to evaluate ecological security risk of glufosinate and glyphosate. Also, it can provide the basis for the prevention for the cyanobacterial harmful algal bloom. The main conclusions in this paper are as follows:The results of exposure experiment of glufosinate:(1) The growth of algae cells, carotenoids, and phycobiliprotein, all have a different stimulus increase at low concentrations of glufosinate (0.5ppm,1ppm). High concentration of glufosinate (5ppm,10ppm) inhibit the growth of algal cells, significantly elevate the malondialdehyde (MDA) content and cell membrane electrolyte leakage (EL) rate. Cell membrane integrity is damaged.(2) Intra-microsystin-LR (intra-MC-LR) and extra-microsystin-LR (extra-MC-LR) content have different amplitude of increase at low concentrations exposure of glufosinate. High concentration of glufosinate inhibits total-microsystin-LR (total-MC-LR) content, but extra-MC-LR content increase.(3) The total-MC-LR content of single cell has no change at low concentrations exposure of glufosinate. The increase of total-MC-LR content is due to the increase of the number of algal cells. But extra-MC-LR of single cell increase, show the toxin-releasing ability of single cell is on the rise.(4) The transcription level of mcyA, mcyD and mcyH have no significant difference at low concentrations exposure of glufosinate. But high concentration of glufosinate raises transcriptional level significantly.The results of exposure experiment of glyphosate:(1) Glyphosate stimulated the growth of algae from the exposure concentration of0.5ppm to10ppm.(2) Total-MC-LR and intra-MC-LR content of exposure group (0.2ppm-2ppm) increase. Extra-MC-LR content has no rise.(3) MC-LR producing ability has no obvious enhancemen. The increase of total MC-LR content is caused by the increase of the number of algal cells.