Germinação sob efeito do glifosato afeta morfologia, anatomia e ciclo celular de plântulas de soja

Abstract

Soybean is a crop of great economic interest in the world´s agribusiness, and the most cultivated is transgenic, tolerant to the non-selective herbicide glyphosate. Glyphosate is characterized by intervening in the biosynthesis pathway of aromatic amino acids phenylalanine, tryptophan and tyrosine, inhibiting protein synthesis, leading plants sensitive to senescence and death. In-depth study at the anatomical and cytological levels is important, as research shows glyphosate generating a phytotoxic effect, affecting water use efficiency, photosynthesis, biomass accumulation, amino acid synthesis and secondary compounds in soybean. This work investigates the behavior of transgenic and conventional soybean germinated in different glyphosate concentrations. Three soybean cultivars were evaluated: one first-generation transgenic P98Y11; Second generation transgenic NS6906IPRO; and a conventional UFV-16. Germination, seedling length and dry mass distribution tests were used to evaluate the physiological quality of soybean, correlating with the possible effects of glyphosate for these parameters. At the cytological level, the cell cycle was studied by evaluating the mitotic index (MI) and checking for the presence of abnormalities in each phase of the cycle. In the field of botany, the study turned to the internal anatomy of the seedlings, evaluating changes in the diametrical measurements of the stem-root tissues evaluated. The results confirm the most pronounced reduction of the UFV-16 mitotic index is related to greater impairment of germination, seedling length, dry mass mobilization, anatomical adaptations, and cell cycle. The cultivars P98Y11 and NS6906IPRO, even with the EPSPS enzyme isoform that gives resistance to the herbicide, were tolerant but not resistant, being affected to the effects of glyphosate to a lesser extent, compromising the physiological quality, anatomy and cell cycle.