Abstract
Cobalt is heavy metal that possesses significant abiotic stress to plants adversely affecting growth and development by interfering with key physiological, biochemical and metabolic processes. Excess cobalt in soil can lead to reduced nutrients uptake, impaired photosynthesis and accumulation of reactive oxygen species ultimately compromising plant productivity. To investigate the impact of cobalt stress and evaluate strategies for its mitigation, a pot experiment was conducted at the Department of Botany, University of Balochistan, Quetta. The lentil variety Black Panjgur was grown under cobalt stress at a concentration of 30 µM, and seeds were primed with different plant growth regulators (PGRs), including salicylic acid (SA, 250 µM), moringa leaf extract (MLE, 10%), and thiourea (TU, 10 µM). The experiment was arranged in a completely randomized design (CRD) with three replicates. The result showed that cobalt stress inhibited seedling growth, reducing root and shoot length and decreasing chlorophyll and carotenoid contents. Metabolites such as soluble sugars, soluble phenolics and anthocyanins were also adversely affected indicating oxidative and metabolic stress. Application of PGRs alleviated these negative affects by enhancing morphophysiological attributes and boosting biochemical defense mechanisms. Among the treatments, MLE 10% exhibited the strongest positive impact, improving seedling growth, photosynthetic pigments, and stress-related biochemical compounds more effectively than SA or TU. These findings demonstrate that priming of PGRs particularly MLE can effectively mitigate cobalt induced toxicity in lentils. This strategy offers a practical approach to enhance plant tolerance against heavy metal stress and supports sustainable crop production in contaminated soils. The study provides valuable insights into the role of natural plant extracts and chemical regulators in improving plant resilience and productivity under metal-induced stress conditions.
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