The objective of this work was to evaluate the effects of the application of the glyphosate herbicide on seed reserve mobilization and seedling morphology of genetically modified soybean. Two herbicide-tolerant (TMG 1264RR and P98Y11) and two herbicide-sensitive (Emgopa 315 and UFUS 7415) cultivars were selected for the study and subjected to germination, seedling length, and reserve mobilization tests after treatments with glyphosate solutions at the concentrations of 0.00, 0.06, and 0.12%. The hypocotyl/radicle ratio and the efficiency of conversion of reserves to seedlings were also determined. The higher the concentration of glyphosate, the lower the percentage of normal seedlings and the shorter seedling length, mainly in the herbicide-sensitive cultivars. The 'TMG 1264RR' glyphosate-tolerant genotype mobilized more reserves and was more efficient in converting biomass into seedlings. Herbicide application reduced the average length of the seedlings and caused the roots to become shorter than the hypocotyls. During germination, the herbicide changes seedling morphology since the seedling hypocotyl becomes proportionally larger than the radicle. Although, when applied, glyphosate altered the length, weight, and reserve mobilization of the four evaluated genotypes, the most affected were 'Emgopa 315' and 'UFUS 7415', the glyphosate-sensitive ones.

Germination and initial seedling development are physiological processes that determine the establishment of crops. During heterotrophic growth, each seedling develops from the biomass of its seeds. Thus, verifying the potential of genotypes to mobilize reserves under stress has been important. The aim of this study was to investigate how glyphosate affects the mobilization of reserves and seedling morphology. Two tolerant and two herbicide-sensitive cultivars were submitted to germination, seedling length and reserve mobilization tests, including treatments with glyphosate solutions (0, 0.06 and 0.12 %). The hypocotyl / radicle ratio and the efficiency of conversion of reserves to seedlings were also verified. The data were submitted to analysis of variance and test of means. It was observed that the percentage of normal seedlings and length seedlings were affected due to the concentration of the herbicide in the treatments, being the consequences more pronounced for sensitive cultivars; the glyphosate-tolerant genotype and with the best physiological quality mobilized more reserves and was more efficient in converting biomass to seedlings; in morphology, the average length of the seedlings was reduced due to the herbicide, being the roots affected in such a way that they became smaller than the hypocotyls. The herbicide affects the morphology of the seedlings mainly the radicle, and the mobilization of the reserves discriminates the genotypes regarding tolerance to glyphosate.