Amino Acid Content and Biomass Productivity of Selected Weed Species as an Indicator of Their Response to Herbicide Stress

Biomass reduction and amino acid content in plants of Papaver rhoeas L. and Stellaria media L. were investigated to evaluate response of these species to herbicide stress under various temperature (25/16 and 8/2 C) and relative humidity (50 and 75%) regimes. Weeds were treated with tribenuron methyl (15 g × ha), a mixture of 2.4-D with florasulam (180 + 3.75 g × ha), and a mixture of 2.4-D with dicamba (1252.5 + 97.5 g × ha). The fresh weight of weeds and the content of free branched-chain amino acids (valine, leucine and isoleucine) in plant tissue were recorded. Tribenuron methyl was the herbicide that most limited biomass productivity, regardless of weed species and climate conditions. S. media was more sensitive to herbicides than P. rhoeas. Weed response to herbicides was dependent on temperature, but not on relative humidity. Tribenuron methyl applied to both weed species under various temperature regimes caused significant amino acid deficiency. The reduction in amino acid content in plants of P. rhoeas was greater at warm temperature compared to the cold regime due to stronger reaction to tribenuron methyl applied under these conditions. In most of cases, the mixture of 2.4-D + dicamba induced overproduction of amino acids.