Alleviation of the effects of on drought stress Verbascum nudicuale by methyl jasmonate and titanium dioxide nanoparticles

Drought stress causes severe metabolic dysfunctions by formation of oxidative stress that may lead to damage in DNA, inactivation of enzymes, and lipid peroxidation. Plants have developed different morphological, physiological, and biochemical mechanisms to withstand the drought stress. Plant growth regulators (PGRs) are one of the most important endogenous substances involved in the amelioration of tolerance in various plant species. In this study, the possible recovery ability of Verbascum nudicuale plants from drought stress conditions was assessed using methyl jasmonate (MJA), titanium dioxide nanoparticles (TiO2NPs), and their interactions as the PGRs in liquid culture media. Results showed that the growth parameters and photosynthetic pigment content markedly decreased due to polyethylene glycol (PEG)- induced drought stress. The treatment of V. nudicuale plants with TiO2NPs showed a considerably improving effect on pigments synthesis and biomass production during the treatment. However, cultures containing MJA negatively affected the growth parameters and increased the content of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Treatment of plants with PGRs showed a considerable improvement in increasing the synthesis of the phenolic compounds and proline accumulation. Alteration in the activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and polyphenol oxidase (PPO) significantly varied in different treatments. These findings suggest that the recovery treatment with PGRs proved to be very effective in alleviating the adverse effects of drought stress.