Salicylic acid alleviates salt-induced phytotoxicity by modulating physiochemical attributes and upregulating the AsA-GSH cycle and glyoxalase system in Capsicum annuum L. seedlings

Abstract

Salt stress is a widespread environmental constraint that impairs crop growth, development, and productivity, reducing seed germination and seedling growth. Plants respond to salinity by modulating physiological and molecular processes, but these responses are inefficient, with salinity issues rapidly escalating worldwide. Salicylic acid (SA) is the most important signal molecules. that protects plants from the damaging effects of salt. This study examined the tolerance potential of 10-day-old Capsicum annuum L. Pusa Sadabahar seedlings against various concentrations of salt stress (0, 25, 50, 75, 100, and 150 mM NaCl) with or without 1 mM salicylic acid (SA) to understand how SA could help Capsicum annuum avoid salt toxicity. The results showed that physiochemical attributes such as seed germination, were higher in the control (0 mM NaCl) and low to medium NaCl (50 and 75 mM) concentrations compared to the high NaCl (150 mM) concentration, which inhibited seed germination, shoot (180.75%) and root (507.20%) lengths, fresh and dry weights, % moisture content, tolerance index, vigor index, chlorophyll content and α-amylase, but increased enzymatic antioxidants like superoxide dismutase (SOD, 37.50%), peroxidase (POX, 62.21%), catalase (CAT), ascorbate peroxidase (APX, 30%), glutathione reductase (GR, 40.46%), glutathione-s-transferase (GST), glutathione peroxidase (GPX), glyoxalase I (Gly I, 44.37%) and glyoxalase II (Gly II, 34.58%) activities, non-enzymatic antioxidants, ascorbate (AsA, 48.51%), carotenoids, phenolics, proline (71.85%), hydrogen peroxide (H2O2), malondialdehyde (MDA, 60.05%), and protein contents. The exogenous SA treatment enhanced all studied parameters except AsA, H2O2, and MDA, protecting the cells from lipid peroxidation and stimulating the ascorbate-glutathione (AsH-GSH) cycle, glyoxalase system, and proline accumulation, which helped to alleviate salt-induced ionic and oxidative damage. Overall, the study highlighted the potential of SA in aiding Capsicum annuum’s resistance to salt stress and reducing its harmful effects.