Key message Polyethylene glycol elicitor as a drought stress inducer can be effectively improved the content of rosmarinic acid, caffeic acid, and salvianolic acid B in plantlet and callus culture of Salvia leriifolia benth. In this study, different levels of polyethylene glycol (PEG) 6000 (5, 7.5 and 10% w/v) were applied to induce drought stress in the embryo and callus culture of Salvia leriifolia Benth, an Iranian medicinal plant. The results related to the embryo culture showed that the germination percentage, stem length, root and stem diameter and total chlorophyll content of plantlets decreased by increasing the PEG concentration, while the highest root length was obtained at the lower PEG concentration (5%). The short-term callus culturing on the media containing different concentrations of PEG resulted in an insignificant difference in the fresh weight, dry weight, and browning intensity of calli between the PEG-free and 5% PEG medium. The proline, hydrogen peroxide, and malondialdehyde contents as indicators of oxidative stress significantly increased in the plantlets and calli at all PEG concentrations. The activity of antioxidant enzymes including catalase and guaiacol peroxidase also increased while superoxide dismutase activity decreased. The rosmarinic acid, caffeic acid, and salvianolic acid B contents increased significantly in all the plantlets and calli culture media containing the PEG. However, the highest contents of these secondary metabolites in plantlets and callus cultures were observed in the medium with 5% PEG. Totally, the results showed that, the short-term reduction in the osmotic potential of culture medium by low concentration of PEG elicitor can effectively improve the content of rosmarinic acid, caffeic acid, and salvianolic acid B in S. leriifolia, especially in callus cultures.
