Abstract
Agrochemical use increases environmental and health risks, making phytotoxicity studies essential. Amidoximes and 1,2,4-oxadiazoles are exogenous sources of NO, which can reduce abiotic stress and the phytotoxicity of agrochemicals; nevertheless, their phytotoxic profile has been poorly studied. Goals and objectives. To assess phytotoxicity of water-soluble compounds: O-para-toluoyl-β-(morpholin-1-yl)propioamidoxime salts (hydrochloride, oxalate, citrate) and three 5-aryl-3-β-(piperidin-1-yl)ethyl-1,2,4-oxadiazoles (aryl: para-MeC₆H₄, para-BrC₆H₄, meta-ClC₆H₄). Methods. Compounds were synthesized via improved multi-step synthesis. Phytotoxicity was tested on Lactuca sativa L. root and stem lengths at 100, 500, 1000 μg/ml. Results. Phytotoxicity depended on concentration and organ; roots were more sensitive. The highest phytotoxic effect was observed for para-bromo-oxadiazole with phytotoxicity from 57-67% at 500-1000 μg/ml 33-72%, followed by meta-chloro-oxadiazole with phytotoxicity from 33-72% at 100-1000 μg/ml. A growth-stimulating effect of amidoxime chloride and oxalate on stem growth is noted. Moderate toxicity was seen for hydrochloride salt and para-methyl oxadiazole. Citrate salt exhibited minimal phytotoxicity, comparable to control. Conclusion. The studied compounds showed different degrees of phytotoxicity depending on concentration and plant organ; roots were more sensitive with increasing concentration. Phytotoxicity is maximum for oxadiazoles with halogen substituents (para-bromo, meta-chloro), moderate/minimal for para-methyl oxadiazole and amidoxime hydrochloride and citrate. Shoot growth was stimulated by amidoxime hydrochloride and oxalate.