Physiological conditioning is a technique that consists in controlling the speed of water uptake by seeds, with osmotic solutions, aiming to improve their quality, reducing time and increasing germination rate. Eremanthus erythropappus (D.C.) MacLeish seeds were subjected to priming with polyethylene glycol 6000 (PEG), potassium nitrate (KNO3) and the combination of the two at the concentrations of 0.4; -0.8; -1.0; -1.2 and -1.4 MPa for four, six and eight days. Germination, germination speed index (GSI), emergence, emergence speed index (ESI) and expression of superoxide dismutase (SOD), catalase (CAT) and peroxidase (PO) enzymes were assessed. E. erythropappus seed priming in polyethylene glycol solution with potentials between -0.8 MPa and -1.4 MPa is not satisfactory because it adversely affects germination and reduces the activity of peroxidase and catalase enzymes. The other substances were not significant so there is a need for further research with other substances and / or concentrations