Strawberry cultivar Elsanta was grown in peat based substrate in a green house. Full dose and 50% reduced nitrogen and potassium fertilization were applied during fruit bearing period in spring, along with biostimulators Viva®, Megafol® and their combination. The specific activities of guaiacol peroxidase (GPXs; EC 1.11.1.7), catalase (CATs; EC 1.11.1.6), ascorbate peroxidase (APXs; EC 1.11.1.11) and glutathione reductase (GRs; EC 1.6.4.2) in strawberry leaf were stimulated by biostimulators and reduced fertilization. The strongest link seen here was between the enzymes of ascorbate-glutathione cycle (APXs and GRs), which were positively related to trifoliate leaf fresh mass (TLFM). The highest TLFM was observed in Megafol® treated plants.