PHOTOSYNTHETIC PERFORMANCE AND MYCORRHIZATION IN ROUNDUP READY SOYBEAN PLANTS TREATED WITH DIFFERENT FORMULATIONS OF GLYPHOSATE

The expansion of soybean resistant to glyphosate has caused considerable increase in the use of this herbicide as well as the number of formulations based on this active ingredient. The aim is evaluate the effect of six formulations of glyphosate (Roundup Original (R), Trop (R), Roundup Ultra (R), Roundup WG (R), Roundup Transorb R (R) e Zapp Qi (R)) in photosynthetic parameters, mycorrhizal colonization and soybean yield (TMG 125 Roundup Ready), in the Alto Paranaiba. It was used a randomized block design with four replications. A single application of herbicides (780 g a.e ha(-1)) was performed between stages V-2-V-3. At 3 and 7 days after application of the treatments were evaluated instantaneous gas exchange between 08:00 and 9:00 am, in fully expanded leaflets. Then, the photosynthetic performance was evaluated by means of light curves (CO2 assimilation rate vs. irradiance). The mycorrhizal colonization, plant height and shoot dry matter were assessed when the soybean plants reached the stage R-2. In addition, we evaluated the weight of seeds and soybean yield. The different formulations of glyphosate did not affect gas exchange of soybean plants and the efficiency of these plants in the use of irradiance, therefore also no observed significant differences in shoot dry weight, mycorrhizal colonization and soybean yield.