Hydrogen Sulfide Promotes Adventitious Root Development in Cucumber Under Salt Stress by Enhancing Antioxidant Ability

As a gas signal molecule, hydrogen sulfide (HS) can enhance plant stress resistance. Here, cucumber ( 'Xinchun NO. 4') explants were used to investigate the role of HS in adventitious root development under salt stress. The results show that sodium chloride (NaCl) at 10 mM produced moderate salt stress. The 100 µM sodium hydrosulfide (NaHS) treatment, a HS donor, increased root number and root length by 38.37% and 66.75%, respectively, indicating that HS effectively promoted the occurrence of adventitious roots in cucumber explants under salt stress. The results show that under salt stress, NaHS treatment reduced free proline content and increased the soluble sugar and soluble protein content during rooting. Meanwhile, NaHS treatment enhanced the activities of antioxidant enzymes [peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT)], increased the content of ascorbic (ASA) and glutathione (GSH), reduced the content of hydrogen peroxide (HO) and the rate of superoxide radical (O) production, and decreased relative electrical conductivity (REC) and the content of malondialdehyde (MDA). However, the NaHS scavenger hypotaurine (HT) reversed the above effects of NaHS under salt stress. In summary, HS promoted adventitious root development under salt stress through regulating osmotic substance content and enhancing antioxidant ability in explants.