Effects of Plant Growth Promoting Rhizobacteria (PGPR) and Arbuscular Mycorrhizal Fungi Inoculation on Lemon Balm (Melissa officinalis) Under Drought Stress

Subject Areas : Tension

Olia Eshaghi Gorgi ¹ , Hormoz Fallah ² , yousof niknejad ³ , Davood Barari Tari ⁴

1 - Department of Agronomy, Islamic Azad University of Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran
2 - Department of Agronomy, Islamic Azad University of Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran
3 - Department of Agronomy, Ayatollah Amoli Branch Islamic Azad University, Amol, Iran
4 - Effects of different concentrations of lead on some biochemical and physiological parameters of rice

Received: 2022-02-01 Accepted : 2022-04-15 Published : 2024-09-24

Keywords: Chlorophyll, Glomus mosseae, Relative water content, Antioxidant enzymes, Transpiration rate, Azospirillum brasilense,

Abstract :

The use of plant symbiosis with arbuscular mycorrhizal fungi (AMF) and Plant-growth-promoting rhizobacteria (PGPR) is one of the ways to reduce drought stress that has recently been used in agriculture. In the present study, the response of lemon balm (Melissa officinalis L.) plants to microbial inoculation of plant growth-promoting rhizobacteria (PGPR, Azospirillum brasilense) and arbuscular mycorrhizal fungus (AMF, Glomus mosseae) and co-inoculation (AMF+PGPR) under well-irrigated (100% field capacity) or drought stress (50% field capacity) conditions were investigated. This study was conducted in 2020 in the greenhouse of Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran as a factorial experiment based on a completely randomized design with five replications. The results of the present study showed that drought stress by reducing the relative water content (RWC, 17.8%), declined transpiration rate (E, 62.2%), stomatal conductance (gs, 36.8%), intercellular CO2 concentration (Ci, 22.5%), and net photosynthesis (Pn, 48.5%) of the plant compared to control plants. Drought stress also induced oxidative stress by increasing the accumulation of hydrogen peroxide (2.1-fold) and methylglyoxal (2-fold), resulting in damage to bio-membranes and photosynthetic apparatus and reduced growth of lemon balm. However, microbial inoculation, especially co-inoculation of PGPR and AMF, by improving the proline content and RWC, restored Ci, E, gs and Pn under drought stress. Microbial treatments by increasing the activity of antioxidant enzymes and the glyoxalase system reduced the level of hydrogen peroxide and methylglyoxal and alleviated drought stress-induced oxidative stress, which increased the growth of lemon balm under drought stress by protecting bio-membranes and photosynthetic pigments. Therefore, the results showed that the application of G. mosseae and A. brasilense alleviated the negative effects of drought stress on lemon balm.