Physiological responses of Dracocephalum kotschyi Boiss. to drought stress and Bio-fertilizers

This study aimed to investigate the possible impact of the drought stress at three levels (80, 60 and 40% field capacity) and bio-fertilizers at four levels (Nitroxin, Super Nitro Plus, Biophosphorus, and non-biofertilizer) on Dracocephalum kotschyi. The experiments were conducted as factorial based on a completely randomized design, with 3 repetitions. The results showed that drought stress significantly enhanced electrolyte leakage (EL), reactive oxygen species (H2O2), and malondialdehyde content in the leaves. The proline content of the leaves increased corresponding to the drought stress progress. The application of bio-fertilizers intensified the proline accumulation in response to drought. The use of bio-fertilizers in 60 and 40% of FC treatments significantly increased the relative water content (RWC), while it reduced EL in D.kotschyi plants, as compared to non-inoculated plants. The highest levels of anthocyanins (82.37 mg g(-1) FW) and flavonoid compounds (62.16 mg g(-1) FW) were recorded in the plants grown under severe drought stress conditions (40% FC) and biophosphorus application. Furthermore, the results indicated that the activity of guaiacol peroxidase (GPX), superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) were all increased under drought stress conditions. The use of bio-fertilizers alleviated the negative impacts of drought stress by modifying the antioxidant enzyme activity. Overall, the results revealed that the use of these bio-fertilizers, especially super nitroplus, improved most physiological parameters of D. kotschyi plants under drought stress conditions. (C) 2022 SAAB. Published by Elsevier B.V. All rights reserved.