Effects of hydrogen sulfide-producing bacteria on tobacco growth and stress response

Hydrogen sulfide (H₂S), as a gaseous signaling molecule, plays an important role in plant stress resistance regulation. However, the mechanisms through which H₂S-producing endophytic bacteria influence tobacco growth and stress tolerance remain unclear. This study aims to investigate the regulatory effects of H₂S-producing endophytic bacteria on tobacco growth and abiotic stress responses (specifically salt and drought stress).Using tobacco varieties K326 and Nicotiana benthamiana, H₂S-producing endophytic strains were isolated. The effects of NaHS (an H₂S donor), HA (an H₂S inhibitor), and NaCl treatments on tobacco seedling growth were analyzed. At the four-leaf-one-heart stage, tobacco plants were treated with root-dipping inoculation using the endophytic bacteria. Root system morphology, photosynthetic parameters, antioxidant enzyme activities, and endogenous H₂S content were measured. Drought tolerance was evaluated through drought stress and rewatering experiments. (1) In MS medium, H₂S-producing endophytic bacteria significantly promoted lateral root formation, leaf expansion, and fresh weight accumulation in tobacco seedlings, and alleviated NaCl-induced growth inhibition.(2) After root-dipping treatment, the H₂S-producing endophytes markedly enhanced root vitality and fresh weight, induced endogenous H₂S accumulation in roots, but reduced H₂S content in leaves.(3) Under drought stress, tobacco plants inoculated with H₂S-producing endophytes showed significantly higher biomass, relative leaf water content, and SPAD values compared to the control. SOD activity decreased, while POD and CAT activities increased. After rewatering, plant height recovery was enhanced, with normal growth resumed, leaves fully expanded, and plant height significantly greater than that of the control. H₂S-producing endophytic bacteria synergistically promote tobacco growth and enhance tolerance to salt and drought stress by optimizing root system architecture, regulating endogenous H₂S production and distribution, and strengthening the photosynthetic and antioxidant defense systems.