Ecotoxicological Assessment of a Glyphosate-Based Herbicide in Cover Plants: Medicago sativa L. as a Model Species

Beatriz Fernandes,Rafael Ferreira,Cláudia Braga,Anabela Cachada,Fernanda Fidalgo,Ruth Pereira,Joana Ferreira,Ana Rebotim,Cristiano Soares

doi:10.3390/app10155098

Abstract

Despite the several innovations that have been incorporated in agriculture, the use of herbicides, especially glyphosate (GLY), is still the major tool for weed control. Although this herbicide has a notable worldwide representation, concerns about its environmental safety were recently raised, with a lot of divergence between studies on its non-target toxicity. Therefore, it is of utmost importance to understand the risks of this herbicide to non-target plants, including cover crop species, which have a crucial role in maintaining agroecosystems functions and in preventing soil erosion. Thus, this work aims to evaluate the growth and physiological responses of a cover plant species (Medicago sativa L.) exposed to increasing concentrations of a GLY-based herbicide (GBH), particularly focusing on the oxidative metabolism. The growth of roots and shoots was affected, being this effect accompanied by a rise of lipid peroxidation, suggesting the occurrence of oxidative stress, and by an activation of the antioxidant (AOX) system. Indeed, the results showed that adverse effects are visible at active ingredient concentrations of 8.0 mg kg−1, with the lowest EC50 being 12 mg kg−1, showing that GBH-contaminated soils may pose a risk to the survival of non-target plants in the most contaminated areas. Overall, these findings proved that GBH greatly impairs the growth of a non-target plant, strengthening the need of additional studies to unravel the real risks associated with the over usage of this pesticide, since there is an evident lack of studies performed with contaminated soils.

Highlights

Plant protection products, referred to as pesticides, are widely used in agriculture in order to improve productivity, prevent crop loss or yield reduction, and control disease vectors or agents.Appl
Aiming to assess the nutritional status of M. sativa under GLY exposure, the present study evaluated the activity of glutamine synthetase (GS), an enzyme that is involved in the first step of ammonium (NH4+ ) assimilation, that which is absorbed by roots, and the one generated from photorespiration, proteolysis and processes that are increased by several stresses [84,85]
The results revealed that GS was dysregulated for almost all tested concentrations, indicating that, at least under the experimental conditions of the present work, GLY-based herbicide (GBH) interfered with nitrogen (N) metabolism

Summary

Introduction

Referred to as pesticides, are widely used in agriculture in order to improve productivity, prevent crop loss or yield reduction, and control disease vectors or agents.Appl. Depending on the persistence of each substance, soil contamination can occur, thereby affecting soil quality, compromising its ability to perform its functions and leading to an irreversible degradation of this non-renewable resource [3,4,5,6,7]. For this reason, concerns about the use of pesticides are increasing, and the most controversial at the moment is probably glyphosate (GLY), a post-emergence and systemic herbicide of broad spectrum (non-selective). Right after its discovery in the 1970s, GLY quickly became the most applied herbicide worldwide and, in 2014, the volume applied was sufficient to treat between 22%

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