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The article discusses gaseous air pollutants that have the greatest impact on forest ecosystems. This group of pollutants ncludes sulfur dioxide (SO2), nitric oxides (NO and NO2) and ozone (O3). In the 20th century, the major contributor to forest degradation was sulfur dioxide, a gaseous substance with direct and powerful phytotoxic and acidifying effects. Since then, sulfur dioxide emissions have been significantly reduced in Europe and North America, but they continue to grow in East Asia along with China’s economic boom. Nitric oxides affect woody plants directly by entering through the stomata and indirectly through soil acidification and environmental eutrophication. Ozone, in turn, is found in photochemical smog and is produced by conversion of its precursors (nitric oxides, organic compounds and carbon monoxide). It is a strong oxidizing agent which disrupts various physiological processes, mostly photosynthesis and water use in plants, but is also the air pollutant that exerts the most toxic effect on forest ecosystems.

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Abstract.Lomefloxacin is an antibiotic used in human and animal medicine that is excreted to the environment, where it is taken up by plants. In the present study, we identified a new, universal parameter of lomefloxacin's toxicity to pea. We showed that activity of arginine decarboxylase and putrescine, which is synthetised in this pathway is a very good toxicity parameter, as confirmed by the calculated EC indices. The lomefloxacin toxicity resulted in a complete inactivation of ornithine decarboxylase and increase of activities of arginine decarboxylase, and S-adenosylmethionine decarboxylase. We propose that putrescine is not synthesised directly from ornithine. Instead, we suggest that the biosynthesis pathway proceeds from arginine to agmatine and is catalysed by arginine decarboxylase, which is followed by the formation of N-carbamoylputrescine with the participation of agmatine imniohydrolase. N-carbamoylputrescine amidohydrolase is involved in the synthesis of putrescine with Ncarbamoylputrescine. The activity of S-adenosylmethionine decarboxylase in the roots and stems increased almost 5-fold, arginine decarboxylase in the roots increased up to 18-fold, while in the stems it increased 6-fold, and ornithine decarboxylase in the roots and stems increased 3.5-fold. The highest biogenic amines content was found in seedlings growing in soil contaminated with 50 mg×kg -1 of soil lomefloxacin. We also recommend quantifying the activity of decarboxylases by measuring the secreted CO 2 volume with a multi-gas analyser equipped with an infrared detector. It is a simple, reliable, and cheap technique. Keywords: morphological parameters of plants, decarboxylases activity, toxicity, infrared detectorAbbreviations: Lomefloxacin -LOM; Effect concentration for the inhibition of growth rate at the level of x % (x = 10,