Temperature Effects on Glyphosate Absorption, Translocation, and Distribution in Quackgrass (Agropyron repens)

Absorption, translocation, and distribution of14C-glyphosate [N-(phosphonomethyl)glycine] were examined in quackgrass [Agropyron repens(L.) Beauv.] plants growing at 10/8, 15/12, and 21/18 C day/night temperatures at 300 μE·m-2·s-1. Absorption of14C-glyphosate followed similar trends in all environments, apart from an initial delay at the highest temperature. Approximately 67% of the applied14C-glyphosate was absorbed after 120 h. Glyphosate translocation to the rhizomes was initially slower in plants growing at 10/8 C than at the higher temperatures, but after 24 h continued at a rate similar to that observed at the higher temperatures. CO2exchange rates (CER) were only slightly influenced by temperature between 5 and 25 C, which may explain the lack of temperature effect on the rate of glyphosate translocation. Approximately 47% of the applied14C-glyphosate was recovered in the rhizomes and associated roots 120 h after application in all environments. Glyphosate accumulated predominantly in new rhizomes under all growing conditions.