Light availability interferes with absorption and translocation of 14C-glyphosate in Urochloa brizantha cv. Marandu plants

Abstract

This research aimed to evaluate the absorption and translocation of 14C-glyphosate in Urochloa brizantha cv. Marandu subjected to different light availabilities. Six light conditions were studied: application followed by 24, 48 or 72 h of dark, 72 h of light, 24 h of dark + 48 h of light and daytime in different evaluation times: 0, 3, 6, 12, 24, 48, and 72 h after application of 14C-glyphosate (1.67 kBq/plant). The herbicide absorption was higher in plants with less light availability at 72 HAA (48 and 21% for 72 h of darkness and 72 h of light, respectively); however, there was a greater translocation of 14C-glyphosate to roots in the high availability of light (23 and 5% for 72 h of light and 72 h of dark, respectively). Thus, in U. brizantha plants, under conditions of greater light availability, 14C-glyphosate was less absorbed, but the product was more translocated. It is recommended that farmers to apply glyphosate at daytime since the light positively favored translocation, which is essential to the herbicidal activity.