Assessment of the sensitivity of two freshwater macrophytes to the herbicide Roundup

• Autor(a) principal: Romão, João Pedro Rosado Tirapicos
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/27475
• topic: Freshwater pollution; Bioindicator; Duckweed; Risk assessment

Freshwater ecosystems are home to a multitude of species that live in the aquatic environment and are an integral part of the natural communities. Among these, freshwater macrophytes are particularly important, as their functions extend beyond those commonly provided by other freshwater primary producers, creating a variety of microhabitats for other species and being an important part of the ecosystem’s structure as well. The contamination of freshwater systems by herbicides has been recognized for several decades, and is linked with the increasing trends in the use of these pesticides. Glyphosate is the most widely applied herbicide in the world, with its popularity being attributed to the development of the Roundup formulation by Monsanto, which increases the toxicity of the active ingredient to the plants by promoting its penetration into the tissues. In the present dissertation, we assessed the effects of glyphosate and its commercial formulation Roundup to the two water macrophytes, Lemna minor and Lemna gibba. To better understand the impacts these chemicals have on overall plant health, we evaluated the sensitivity of four growth-endpoints (weight, frond number, frond area, and root length), as well as the assessment of sugar profiles as biochemical endpoints, to address the knowledge gap related to non-target biochemical effects of glyphosate in plants. Results evidenced Roundup to be more toxic to both macrophytes than the active ingredient alone, as well as a higher sensitivity of L. minor compared to L. gibba. The lowest EC10 value (0.75 mg a.i. l-1) was obtained for Yield in weight of L. minor exposed to Roundup. Furthermore, root length experienced an abrupt decrease from the concentration of 1 to 3 mg a.i. l-1 in both macrophytes exposed to Roundup, and is argued to be a good bioindicator of pollution by this compound. The concentrations of the different sugars remained unaltered across the evaluated concentrations for both macrophytes, except for the sugar profiles of L. minor, which displayed a significant increase in their content of xylose, galactose, and glucose at the concentration of 5 mg a.i. l-1 of Roundup, relative to the control