Glyphosate Absorption and Translocation in Bermudagrass (Cynodon dactylon) and Activity in Horsenettle (Solanum carolinense)

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Abstract
The effects of temperature, relative humidity (RH) and light on absorption and translocation of 14C-glyphosate [N-(phosphonomethyl)glycine] in common bermudagrass [Cynodon dactylon (L.) Pers. ‘Common’] and the effect of temperature and stage of growth on glyphosate activity in horsenettle (Solanum carolinense L.) were determined. 14C-glyphosate was used to evaluate the absorption and translocation of foliar-applied herbicide in bermudagrass plants grown at 22 or 31 C and 35 or 80% RH and absorption in excised leaf tips and stem sections. Autoradiography of bermudagrass indicated that downward translocation of 14C was extensive with large accumulations in new roots and rapidly growing stolons. RH of 35% decreased 14C-glyphosate translocation to the untreated foliage of plants grown at 31 C as compared to 80% RH. RH of 35% also decreased the translocation of 14C to the rhizomes and roots of plants grown at 22 C. The absorption of 14C was greater in excised leaf tips than stem sections and was greater in the light than in the dark. Horsenettle plants grown at 32 C had shoots which were more rapidly killed by glyphosate but had more regrowth than plants treated at 13 C. Shoots of plants treated while blooming were also more rapidly killed than those treated in the prebloom stage of growth, but the regrowth was not significantly different.