Glyphosate-based herbicides (e.g. Roundup Ultra 360 SL) are extensively used in aquatic environment.
Although glyphosate is more environmental favorable than many other herbicides, it may be exceptionally
dangerous for aquatic ecosystems through high water solubility. Thus, the aim of the work was quantification
of influence of Roundup Ultra 360 SL (containing isopropylamine salt of glyphosate as an active
ingredient) on biomass and chlorophyll content within duckweed (Lemna minor L.). Moreover, changes in
polyamine content and activity of such antioxidative enzymes as catalase (CAT) and ascorbate peroxidase
(APX) were assayed in order to determine the biochemical mechanisms of L. minor response to the herbicide
treatment. Obtained results showed that phytotoxicity of the herbicide was connected with
decrease in chlorophyll-a, b and a+b content, and reduction of biomass growth. Roundup, similarly to
some abiotic and biotic stressors, caused over-accumulation of putrescine, spermidine and total polyamines
(PAs) within duckweed tissues. In addition an increase in CAT and APX activities suggested that
stress generated by the herbicide treatment was at least partially connected with oxidative burst. Intensity
of the duckweed responses to the herbicide was dependent on the applied herbicide level and/or
duration of treatment.