Zinc oxide nanoparticles mitigate drought stress and enhance secondary metabolite production in Hypericum perforatum

Drought stress represents a major abiotic factor responsible for reducing the growth, yield and quality of important plants. This research was investigated the potential of ZnO Nano particles (ZnO NPs) to alleviate drought stress in Hypericum perforatum (common St. John’s Wort). A factorial experiment using randomized complete block design (RCBD) was performed with 3 replications and 4 different irrigation treatments (100%, 70%, 40%, and 25% of field capacity) combined with 4 different concentra