DANOS FISIOLÓGICOS EM PLANTAS DE Eichhornia crassipes EXPOSTAS A ATRAZINA SÃO REDUZIDOS NA PRESENÇA DE NANOPARTÍCULAS DE ZINCO: UMA ABORDAGEM VISANDO A OTIMIZAÇÃO DA FITORREMEDIAÇÃO

Abstract

Pesticides are widely used to increase agricultural productivity, with Brazil standing out as one of the world's largest consumers of these pesticides. Among the widely used pesticides is atrazine, a herbicide used to control weeds that affect agricultural crops. Exposure to these products, however, has triggered problems for humans and the environment due to the intense application in agricultural areas, causing water resources contamination and affecting various organisms. Given these factors, there is a great need to assess and monitor water quality, especially in freshwater ecosystems adjacent to areas of agricultural cultivation. Alternatives to clean up contaminated areas, such as phytoremediation, which consists of using plants to decontaminate and remove pollutants, are promising. A macrophyte species that has the property of accumulating and removing pollutants from aquatic environments is Eichhornia crassipes. Zinc oxide nanopoparticles (NP ZnO) can be used as nutritious substances and promote benefits to plants exposed to toxic compounds. Therefore, the objective of this study was to evaluate the potential of zinc oxide nanoparticles to attenuate the damage triggered by the herbicide atrazine in E. crassipes. E. crassipes plants were kept in a greenhouse and submitted to four treatments with six replications each, namely: T1 – control (nutrient solution only); T2 – control and zinc oxide nanoparticles – ZnO NP (10 mg L-1); T3 - Atrazine (Atz) (0.025 mg L-1); T4 - Atz + ZnO NP (10 mg L-1). The plants remained under these conditions for a period of 15 days and, soon after, the assessment of photosynthetic pigments, gas exchange and chlorophyll a fluorescence were carried out. The atrazine herbicide application, without the nanoparticles, decreased the parameters of gas exchange and fluorescence of chlorophyll a, which is an expected result due to the herbicide action mode. In addition to these analyses, chlorophyll autofluorescence was evaluated, which pointed to extensive degradation of the photosynthetic pigment, however, the NP ZnO addition was able to partially restore chlorophyll autofluorescence. By determining the MDA content it was verified that the plant did not suffer oxidative stress, a result that was also confirmed through the electrolyte leakage analysis, indicating that there was no excessive ROS production in the plants exposed to ATZ. The CAT enzyme showed greater activity in plants in the ATZ+NP treatment compared to plants exposed only to the herbicide, which may be related to other physiological processes, such as photorespiration. Furthermore, to verify the phytoremediation capacity of E. crassipes, an ecotoxicological assay with the planarian G. tigrina was carried out and it was verified that the plant was able to reduce the toxicity of the solution contaminated by ATZ in non-target organisms, giving E. crassipes a high phytoremediation potential.

Keywords: Water hyacinth; Bioassays; Herbicide; Macrophyte; Environmental decontamination.