Exogenous salicylic acid application alleviates chromium toxicity in seedlings of Pea ( <i>Pisum sativum</i> L.) by reducing chromium uptake and enhancing antioxidative capacity

Pea (<i>Pisum sativum</i> L.) productivity is influenced by various biotic and abiotic stresses, particularly heavy metal toxicity. Although many phytohormones, such as salicylic acid, jasmonic acid, and gibberellic acid, have been widely documented to ameliorate specific abiotic stressors in plants, their comparative and interacting effects under heavy metal stress, particularly chromium toxicity, are not well recognized. Our work addresses this gap by investigating the impact of foliar spray of SA (0.5 and 1 mM) to decrease the harmful impact of various chromium (Cr) concentrations (150, 300 µM of Cr⁺⁶ and 1, 2, and 3 mM of Cr⁺³) in pea plants. The findings showed that Cr treatments reduced the overall growth rate and generated oxidative injury in a dose-specific way. The Cr stress decreased photosynthetic pigments (total chlorophyll, 55.8%), chlorophyll stability index (48.78%), and relative water content (43%). Moreover, lipid peroxidation (59%), proline (69%), total soluble sugar (61%), and antioxidant enzymes, including catalase (CAT, 20%), superoxide dismutase (SOD, 56%), and peroxidase (POX, 35.6%) were enhanced during Cr stress. However, foliar spraying with SA considerably decreased the Cr-induced impacts on plant performance, including growth (shoot length and root length, 56.25% and 27.54% respectively) and photosynthetic characteristics (total chlorophyll and carotenoids, 38.4% and 27.5% respectively). It alleviates the detrimental effect by boosting the enzymatic antioxidant systems (CAT, 9.41%; SOD, 17%; POX, 15.3%), and soluble sugars (7%). SA (1 mM) was more effective and considerably alleviated plant growth during stress. These results support that foliar spray with SA (1 mM) comprehensively mitigates Cr stress and can be a model for promising Cr-tolerant cultivation. Our experimental results will pave the way for further investigation into applied SA to discover the consequences of new genes in Cr resistance enhancement.