Plant growth-promoting rhizobacteria improved growth and physio-biochemical properties of geranium (Pelargonium graveolens L.) under salinity stress

Subject Areas : Phytochemistry

Qolamreza Mirzakhani ¹ , Marzieh Ghanbari Jahromi ² , Vahid Abdossi ³

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Received: 2024-02-15 Accepted : 2024-09-25 Published : 2025-02-01

Keywords: Azotobacter, Pseudomonas, Growth regulation, Salt stress, Secondary metabolites ,

Abstract :

The use of plant growth-promoting bacteria (PGPRs) to modulate salinity is of utmost importance for enhancing plant growth and adaptation in saline environments. This study aimed to investigate the effects of Azotobacter chroococcum and Pseudomonas putida on the growth and biochemical characteristics of rose-scented geranium under salinity stress. The experiment was conducted using a factorial design with four levels of PGPR treatment (control, Azotobacter, Pseudomonas, and Azotobacter + Pseudomonas) and three levels of salt at 0, 60, and 120 mM NaCl. The results indicate that salinity stress resulted in a decrease in plant yield, with the high est reduction observed at 120 mM salinity. This led to reductions in plant weight (31%), root weight (37%), total chlorophyll (33%), relative water content (RWC, 19%), essential oil yield (25%), as well as increases in malondialdehyde (MDA, 45%), catalase activity (179%), and superoxide dismutase activity (100%). However, the inoculation of geranium plants with PGPRs, particularly the simultaneous application of Azotobacter and Pseudomonas, resulted in stress mitigation. This was evident through an increase in biomass, photosynthetic rate, RWC, as well as a reduction in the activity of antioxidant enzymes and MDA in the leaves. Among the different treatments, the combined application of Azotobacter and Pseudomonas, along with a salinity stress level of 60 mM, resulted in the highest production of secondary metabolites, including total phenols, flavonoids, and essential oil content. In conclusion, the combined treatment of Azotobacter and Pseudomonas is recommended as an effective approach to mitigate salinity stress and increase plant yield in rose-scented geranium.

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