Bacillus sp. G2 improved the growth of Glycyrrhiza uralensis Fisch. related to antioxidant metabolism and osmotic adjustment

This study was conducted to determine the effects of Bacillus sp. G2 on seed germination, seedling growth, antioxidant metabolism and osmotic adjustment of Glycyrrhiza uralensis (G. uralensis) under different growth conditions. Results showed that Bacillus sp. G2 significantly increased germination rates, germination energy, germination index, and vigor index, radicle length, hypocotyl length, radicle diameter and hypocotyl diameter of early seedlings. Also, Bacillus sp. G2 significantly decreased the contents of superoxide radicals (O-2(-)), hydrogen peroxide (H2O2) and malondialdehyde (MDA) through increasing the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and the contents of glutathione (GSH) and ascorbate (AsA). Bacillus sp. G2 also increased the contents of proline, soluble protein and soluble sugar. Moreover, our results also found that the effects of Bacillus sp. G2 on seed germination, seedling growth, antioxidant metabolism and osmotic adjustment were particularly notable on the 6th-9th day. In addition, Bacillus sp. G2 enhanced antioxidant metabolism of G. uralensis seedling under salt stress condition greater than that under control condition, but the effects of Bacillus sp. G2 on seed germination, seedling growth and osmotic adjustment under control condition were greater than these under salt stress condition. Taken together, our results indicated that Bacillus sp. G2 improved early seedling growth through enhancing antioxidant metabolism including increasing antioxidant enzyme activities and non-enzymatic antioxidant contents, and the modification of osmoregulation substance accumulation; also, the beneficial effects of Bacillus sp. G2 on all parameters were different depending on the growth times and the growth conditions.