Absorção e translocação do herbicida 14C-glyphosate em Borreria latifolia e Richardia brasiliensis

Abstract

Several mechanisms are developed by the weeds to tolerate the herbicide molecules for this reason it is extremely important to investigate which of these mechanisms is effectively reducing the herbicidal effect. The objective of this study was to evaluate the absorption and translocation of the herbicide glyphosate-14c in biotypes Borreria latifolia and Richardia brasiliensis. Seeds were collected from transgenic soybean crops or in places without by glyphosate selection pressure for municipalities in Paraná and Northern Santa Catarina. Two experiments were conducted on the premises of the Center for Nuclear Energy in Agriculture - CENA, Campus Luiz de Queiroz, Piracicaba, University of São Paulo, one for each Rubiaceae species (B. latifolia and R. brasiliensis). Plants were grown in a greenhouse on the premises of the Federal Technological University of Paraná to reach the application stage 4-6 fully expanded leaves, at which time their transfer to the Laboratory of Ecotoxicology-CENA / USP was held, where it is effected laboratory analysis. The studies were carried out in a completely randomized design with three replications, arranged in a factorial (x periods biotypes), where each plant represented an experimental plot. The evaluation periods were 2, 8, 24, 48 and 72 hours after application (HAA) herbicide, totaling 15 plants per biotype, a total of 30 plants for the two biotypes of each weed species studied. In each experiment were analyzed one biotype considered tolerant and another considered sensitive to glyphosate. As were germinating, they were transplanted into pots with 500 ml capacity, consisting of soil sifted and left in a greenhouse with controlled conditions. When the plants reached application stage, proceeded application of glyphosate 14C in phosphonomethyl radical. The herbicide solution was composed of a mixture of14 Cglyphosate and an analytical standard, at a concentration of 360 g of glyphosate (acid equivalent) in 200 L ha-1. This solution was applied in the adaxial side of the last pair of fully expanded leaves as ten drops of 1.0 ul per a total of 20 drops per plant. After the end of each reading period, the treated leaves were washed and the radioactivity determined by liquid scintillation spectrometry (LSS). The absorption of herbicide was determined by the percentage of radioactivity present within the plant (leaves treated above leaves, leaves below the treated stem and root) compared to the total radioactivity recovered (rinsing liquid + radioactivity within the plant). Subsequently, each plant underwent combustion in organic oxidizer and quantitation of radioactivity using LSS. For sensitive biotype A. brasiliensis absorbed over the radiolabeled glyphosate tolerant, 75 and 70%, respectively. Similar behavior occurred with the species B. latifolia, however, did not show a difference between the sensitive and tolerant biotypes. For the two species showed that much of the applied herbicide not translocated, leaving only the sheet applied, except for the tests conducted 48 (R. brasiliensis) and 72 (R. brasiliensis and B. latifolia) HAA, the differential translocation of the herbicide could be verified in both species tolerant biotype considered.