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Effect of Salicylic Acid on Proline Accumulation in Soybean Grown under Lead Stress
Siddhi Gupta
Abstract:
Salicylic Acid (SA) is a vital signalling molecule among naturally occurring plant hormones, recognized for its role in regulating various physiological processes. This study aimed to explore whether the exogenous application of SA could effectively enhance plant resilience in metal-contaminated environments. Various concentrations of lead acetate (200, 400, 600, 800, and 1000 mg/kg of soil) were administered to soybean seedlings alongside a 0.5 mM SA treatment and compared with control groups. Observations were conducted at three stages: pre-flowering (30 days), peak-flowering (45 days), and post-flowering (60 days), with the experiment replicated three times. Compared to the control group, there was a consistent increase in proline content corresponding to the rising metal concentrations in the soil. The highest proline levels were recorded at the 1000 mg/kg lead treatment, measuring 31.226, 32.594, and 35.604 µ moles at the pre-, peak-, and post-flowering stages, respectively. Proline accumulation is crucial for plants coping with heavy metal stress, as it functions as an osmolyte, reactive oxygen species (ROS) detoxifier, and protein stabilizer. Furthermore, the exogenous application of SA significantly enhanced proline accumulation under lead stress across all concentrations. For example, at the 1000 mg/kg lead treatment, proline levels reached 48.646±0.47 µ moles with SA, a significant increase compared to the untreated group (p = 0.01). These findings suggest that salicylic acid may act as a protective agent against heavy metal toxicity, potentially bolstering the internal immunity of soybean plants and increasing their resilience to environmental stressors, thereby providing valuable insights for agricultural practices.
Keywords: Heavy metal, Lead, Proline, Salicylic acid, Pre-flowering, Peak-flowering, Post-flowering
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