Pouteria torta is a remarkable native plant for biomonitoring the glyphosate effects on Cerrado vegetation

Abstract

Cerrado is a Brazilian savannah ecosystem that has a high diversity of flora and fauna and originally covered 2 million km2, but in recent years more than 50% of its area has been converted to grain crops and pastures. The intensive grain production in Cerrado has been accompanied by an increase in pesticide and herbicide use, glyphosate is the most common. This may have implications for biodiversity loss that are still unknown. Seeking this understanding, we assessed biochemical changes in two native Cerrado plants species subjected to glyphosate. The aim of this study was to identify biomarkers in Pouteria torta and Alibertia edulis treated with glyphosate and evaluate their use as phytoindicators of the herbicide on the Cerrado vegetation. The plants were challenged with glyphosate [Roundup Transorb®, containing 480 g L−1 acid equivalent (a. e.)] in two independent experiments. In both, glyphosate was used at 0, 200, 400, and 800 g a. e. ha−1. The activities of the enzymes phenylalanine ammonia lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO), and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), as well as the concentrations of shikimic acid, phenolic compounds, amino acids, proteins, and malondialdehyde (MDA) were evaluated at 1 and 13 and at 1 and 72 days post-application in P. torta and A. edulis leaves, respectively. Glyphosate had reduced EPSPS activity and blocks the shikimate pathway in P. torta and A. edulis. Thus, this biochemical changes can be biomarkers of glyphosate in both native Cerrado plants. The activity of the PAL and PPO enzymes also showed this potential. Glyphosate caused leaf chlorosis and necrosis in P. torta, in addition, the concentrations of phenolic compounds, proteins, and amino acids were altered only in this species. Thus, concentrations of these cell compounds can be biomarkers of glyphosate stress in susceptible plants. The herbicide did not have the same effects on A. edulis. The changes in P. torta leaves occurred more quickly than in A. edulis. Thus, A. edulis plants may be used as a glyphosate biosensor. P. torta were susceptible and can be a phytoindicator of the herbicide. Its high sensitivity is useful for monitoring the initial effects of glyphosate on native Cerrado vegetation.