The Role of Gibberellic Acid and Paclobutrazol on Oxidative Stress Responses Induced by In Vitro Salt Stress in Sweet Sorghum

Gibberellic acid (GA(3)) application has been shown to affect salinity tolerance through modulating oxidative stress processes. Moreover, paclobutrazol (PBZ) as a GA(3) biosynthetic inhibitor has been reported to mitigate salt stress in some plant species. In this study, we investigated how GA(3) and its inhibitor, PBZ, reduced the negative effects of salt stress in leaves of sweet sorghum (Sorghum bicolor [L.] Moench cv. Sofra) by changing content of osmoprotectants and activity of ROS-scavenging enzymes. After germination, seedlings of sorghum were cultured in Hoagland solution containing sodium chloride (0, 100 and 200 mM NaCl) supplemented with GA(3) and PBZ for 12 days. The results were analyzed using principal component analysis (PCA) to identify the best target(s) under salinity, GA(3) and PBZ in sweet sorghum. Based on PCA, our findings showed that PBZ and GA(3) treatments acted by different mechanisms under salinity. GA(3) primarily affected the activity of superoxide dismutase (SOD), peroxidase (POD), glutathione reductase (GR), catalase (CAT), and glycine betaine (GB) contents under salinity, whereas PBZ treatment had significant influence on the activity of Delta(1)-pyrroline-5-carboxylate synthetase (P5CS), proline content, activity of CAT, GR, and total antioxidant capacity in leaves of sweet sorghum plants.