X-ray spectroscopy fostering the understanding of foliar uptake and transport of Mn by soybean (Glycine max L. Merril): Kinetics, chemical speciation and effects of glyphosate.

Increasing soybean yield is a humankind challenge dependent on several management practices, such as fertilizing and weed control. While glyphosate contributes to controlling weeds, it can interfere with spray mixtures stability and, supposedly, complexing with micronutrients within the plant tissue. This study investigated the effects of glyphosate on soybean foliar uptake and transport of Mn supplied as MnSO4, MnHPO3, Mn-EDTA, and MnCO3. Those fertilizers induced ultrastructural changes on the leaf cuticle, regardless of glyphosate mixture. Except for MnCO3, all tested sources increased Mn content in the petiole. The mixture of glyphosate impaired Mn transport from MnSO4 and MnHPO3, but no evidence of Mn-glyphosate complexation within the plant was found. Manganese is rather transported in a similar chemical environment regardless of the source, except for Mn-EDTA, which was absorbed and transported in its pristine form. Interferences of glyphosate seem related to complexations in the tank mixture rather than affecting nutrients' metabolism.