Adjuvant affects cuticular waxes and penetration of glyphosate

The study was conducted to examine the effect of glyphosate (+/- surfactant) applied to Commelina communis and Solanum nigrum plants over 48 h. Uptake and translocation of C-14-glyphosate were significantly higher in S. nigrum than C. communis possibly because of S. nigrum's smooth leaf surface and the presence of large amounts of non-polar waxes on its leaf surface. C-14-glyphosate uptake and control of C. communis were better under shade than under light. The reverse was found in S. nigrum. Shaded and moist conditions favored growth of C. communis. Uptake and translocation of C-14-glyphosate were significantly higher with surfactant than with glyphosate alone in both species. Significantly higher uptake and translocation of C-14-glyphosate was recorded up to 48 h. Uptake and translocation values of C-14-glyphosate were consistent with the percent control of these two weeds by glyphosate (+/- surfactant). Relative comparison of scanning electron micrographs also showed that the application of glyphosate with surfactant either disrupted or dissolved the waxes present on the leaf surface thus allowing for increased penetration of glyphosate a.i. into the plant.