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Abstract

Lead (Pb) is a toxic heavy metal that can have detrimental effects on plant growth and development. Sunflowers are effective in bioremediation, utilizing their extensive root systems to absorb and remove heavy metals and other contaminants from soil and water. PGPR can enhance plant growth and reduce heavy metal accumulation by sequestering metals in the rhizosphere, thus minimizing their uptake by plants. This study investigates the efficacy of plant growth promoting rhizobacteria (PGPR) in mitigating lead (Pb) stress in sunflowers through a pot experiment. Lead stress significantly elevated the enzymatic antioxidants activity, including CAT, POD and SOD which play critical roles in eliminating reactive oxygen species. Seed treatment with PGPR significantly enhanced dry weight of shoot and root, total achene weight per plant and 100 achene weight. Additionally, it increased catalase, SOD, peroxidase activities, total soluble proteins, total phenolic content, ascorbic acid levels. This enhancement suggests that PGPR-treated sunflowers were better equipped to handle oxidative stress induced by Pb compared to non-treated plants. Additionally, PGPR application significantly reduced lipid peroxidation levels, as showed by lower malondialdehyde content in PGPR treated plants under Pb contaminated soil. Among the sunflower varieties tested, T-40318 exhibited robust performance overall and showed increased tolerance to Pb stress. In contrast, variety Agsun-5270 showed improved characteristics with PGPR application under stress conditions but did not perform well in the control group. Conversely, variety Fh-721 did not demonstrate significant benefits from PGPR application across treatments.

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