<italic>γ</italic>-Aminobutyricacidonoxidativedamageandendogenoushormonesinmaizeseedlingrootsundersaltstress

In this study, effects of γ-aminobutyric acid (GABA) on the oxidative damage and endogenous hormones of maize seedling roots and the physiological pathway that results in the GABA induced salt resistance improvement in roots under salt stress were investigated. Zhengdan 958 was used as tested material in this study. Four hydroponic experiments including control (CK), 0.5 mmol/L GABA (G)treatment, 150 mmol/L NaCl (N) treatment and 0.5 mmol/L GABA treatment under 150 mmol/L NaCl (NG) were conducted. Root morphology, dry matter accumulation, root vitality, endogenous GABA content, osmotic adjustment substance, antioxidant enzyme activity, malondialdehyde (MDA) content, superoxide anion (\cdot \rm O_2^- ) and endogenous hormones content were investigated in maize seedling roots. The results show that root length, root surface area, root volume, root tip number and root dry matter were increased by exogenous GABA treatment under salt stress. The mean diameter of root was decreased 9.32%. Endogenous GABA content, root activity and soluble protein content were increased and relative conductivity in roots was also declined significantly. Exogenous GABA significantly increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in roots. Thus, the accumulation of MDA and \cdot \rm O_2^- contents were reduced. Endogenous hormones could be affected by GABA. Specifically, auxin (IAA), gibberellin (GA₃) and zeatin-riboside (ZR) contents were increased while abscisic acid (ABA) content was reduced. Furthermore, the ratio of promote hormones to inhibitory hormone was improved. Exogenous GABA could induce the increase of endogenous GABA content. Higher GABA concentration would further increase the antioxidant enzyme activity and change the balance of endogenous hormone, which would result in the improvement of root growth status, including the reduction of the oxidative damage to the root system, the integrity of cell membrane, the improvement of root activity, and the promotion of root absorption and nutrients transportation.