Physiological evaluations of translocation of glyphosate in glyphosate resistant crops including interaction with cotton growth regulators

Field studies were conducted in 2004 to evaluate corn tolerance, weed control, grain yield, and net returns in transgenic and non-transgenic corn with various herbicide systems. No significant differences between hybrid systems were observed for weed control. Grain yield was variable between hybrids and locations due to environmental differences. Consequently, net returns for each hybrid system within a location were also variable.; Studies were conducted at three locations in North Carolina in 2004 to evaluate density-dependent effects of glyphosate-resistant (GR) corn on GR cotton growth and lint yield. The examined GR corn densities had a significant effect on cotton yield, but not as significant as many other problematic grass and broadleaf weeds.; Two studies were conducted to investigate the influence of corn growth stage on the absorption and translocation of glyphosate in glyphosate-resistant (GR) corn. Regardless of corn growth stage, the leaves above the treated leaf and roots were the greatest sinks for 14C-glyphosate. These data suggest that reproductive tissues such as the tassel and ear shoots can accumulate 14C-glyphosate at higher concentrations that other tissues, especially when the herbicide treatment is applied postemergence after the V6 stage.; Studies were conducted to evaluate absorption and translocation of 14C-glyphosate in both commercial glyphosate-resistant (GR) cotton events [GR event 1, released 1997 (GRE1) and GR event 2, released 2006 (GRE2)] were evaluated at the 4- leaf (L) and 8-L growth stages. Glyphosate absorption, as a percentage of applied, increased over time. In 8-L cotton, glyphosate absorption was not different between events. Glyphosate translocation patterns were not different between events or harvest timings and exhibited a source-sink relationship. Based on the percentage of 14C exported out of the treated leaf, glyphosate and sucrose translocation patterns were similar, indicating that glyphosate may be used as a photoassimilate model in GRE2 cotton.; Studies examined various morphological characteristics and 14 C-glyphosate translocation in cotton as influenced by 14C-treatment timing and mepiquat chloride (MC). No significant differences in plant height, leaf area, and specific leaf weight were observed for any treatment. Dry weight of first position fruits on nodes 1, 2, and 3 of MC treated plants accumulated greater biomass compared to fruits on non-treated plants. No significant observations were found for 14C-glyphosate translocation.; These data support previous research that showed increased fruit weight and provides insight into the potential for MC treatment to alter source to sink relationship in cotton. Studies examined various morphological characteristics and 14C-glyphosate translocation in cotton as influenced by cotton plant growth regulator regimes and source leaf. MC and MP reduced cotton height and the number of nodes per plant. Total fruit retention and first position fruit retention were not influenced by any treatment. Based on these data, MC and MP do not influence 14C-glyphosate translocation.; Greenhouse studies were conducted to evaluate the rain-free requirement for mepiquat chloride and mepiquat chloride plus cyclanilide with and without surfactant and to evaluate absorption and translocation of cyclanilide. Based on these data, a rain-free period of 8 hours is needed to maximize efficacy, regardless of plant growth regulator or the use of surfactant. Absorption of cyclanilide ranged from 11 to 15% at 3 and 48 HAT, respectively. Averaged over harvest intervals, 18% of the applied cyclanilide remained in the treated leaf while 1.7 and 6.5% of the applied cyclanilide was found in the above and below treated leaf tissue, respectively.