Evaluation of morphological and metabolic responses to glyphosate exposure in two neotropical plant species

The use of aerial spraying herbicide in large areas is common in Brazil, especially glyphosate, which is the most extensively used herbicide worldwide. A portion of the herbicide can reach non-target species, resulting in damage in these species and causing severe implications for the local biodiversity. Thus, this study aimed to evaluate the responses of the leaves of Handroanthus chrysotricus (Mart. Ex DC) Mattos (Bignoniaceae) and Garcinia gardneriana (Planch. & Triana) Zappi (Clusiaceae) to glyphosate and its potential for biomonitoring purposes, seeking to establish biomarkers that could indicate the effects of the herbicide in its foliar tissues. Eight months old plants were exposed to the aerial application of herbicide in the concentrations of 0, 360, 720, 1080 and 1440 g. a.i. ha(-1). An accumulation of shikimic acid in the leaves of both species was observed. H. chrysotrichus displayed a drastic decrease in A, gs, E, Fv/Fm, Qp, NPQ and ETR and an increase in MDA, POX glucose, fructose, sucrose and chlorophyll a values whereas G. gardneriana displayed greater activity on CAT, APX, SOD, GR and an increase in starch, amino acids and fumarate values. Visible damages were found only in H. chrysotrichus, whereas anatomical and ultrastructural damages were observed in both species. H. chrysotrichus was considered the most sensitive species of this work because it presented more pronounced alterations. The presence of visible damages suggests that H. chrysotricus has remarkable potential as a bioindicator of glyphosate presence in the environment. Shikimic acid accumulation and photosynthesis disruption can be used as biomarkers for glyphosate presence in its leaf's tissues. The anatomical damages and the increase of enzymatic antioxidative system activity can indicate the glyphosate presence in G. gardneriana leaves.