Salt stress has become a significant issue affecting crop growth, and China has abundant saline soil resources. Sugar beet, as a salt-tolerant crop, efficiently utilizes limited land resources. However, severe salt stress can harm the normal growth of sugar beet. To investigate how to improve its salt tolerance, we conducted a hydroponic experiment using Shuangfeng 8 with five treatments: GABA addition (G + S), 3-MPA addition (T) under salt stress (S) conditions, nutrient solution only (CK), and GABA addition (G) as controls. The results indicate that exogenous GABA pretreatment can mitigate reactive oxygen species damage to membrane lipids and stabilize membrane structure by enhancing antioxidant enzyme activity. It also increased the activity of key enzymes in GABA metabolism and GABA content, providing essential substrates for the tricarboxylic acid cycle. This enhanced the activity of key enzymes in the tricarboxylic acid cycle, ensuring cellular energy supply. GABA can link the tricarboxylic acid cycle with nitrogen metabolism, increasing the activity of nitrogen metabolism enzymes and promoting the synthesis of essential amino acids like glutamate. Ultimately, this improves gas exchange and fluorescence parameters, stabilizing photosynthesis, maintaining normal growth of sugar beet under salt stress, and increasing dry matter accumulation. Reverse validation using GABA inhibitors resulted in significantly higher MAD and ROS levels in sugar beet. Antioxidant enzyme activity, GABA content, photosynthetic fluorescence parameters, and dry matter accumulation were lower than in the treatment with exogenous GABA, further suggesting that exogenous GABA at 1.5 mM L-1 can effectively alleviate salt stress damage in sugar beet.

Licorice is widespread in arid and semi-arid areas, but high soil salinity has always been a limiting factor for vegetation growth in these areas. Gamma-aminobutyric acid (GABA) is a signaling molecule that can regulate tolerance in plant. However, the mechanism by which exogenous GABA regulates the response of licorice to saline-alkali stress is not yet clear. In this study, we investigated the effects of exogenous GABA on growth parameters, oxidative damage, hormone levels and photosynthetic indices of licorice seedlings under different combinations of saline and alkali stress conditions. The experiment involved eight treatments: CK, distilled water (control); CK + GABA, 0.1 mM GABA; salt stress (SS), 150 mM NaCl; SS + GABA, 150 mM NaCl + 0.1 mM GABA; alkali stress (AS), 10 mM Na2CO3; AS + GABA, 10 mM Na2CO3 + 0.1 mM GABA; mixed saline-alkali stress (MAS), 150 mM NaCl + 10 mM Na2CO3; MAS + GABA, 150 mM NaCl + 10 mM Na2CO3 + 0.1 mM GABA. Our results showed that the inhibitory effects of SS and MAS on the seedling height, root length and root-shoot ratio were significantly alleviated by exogenous GABA. Although soluble sugars, chlorophyll a, total chlorophyll, and superoxide dismutase (SOD) activity were lower in the leaves of the seedlings in the SS treatment compared with the control, these physiological parameters increased significantly after GABA application. Exogenous GABA improved glutathione (GSH) activity in both the leaves and roots of the seedlings during the AS treatment. Additionally, take advantage of GABA led to an increase in ABA, GA and IAA contents in leaves under SS, AS and MAS treatments. Furthermore, the photosynthetic parameters, including Pn, gs, Tr, ETR and qP, significantly increased following the utilization of GABA in both the SS and MAS treatments. Therefore, the application of exogenous GABA can reduce the accumulation of harmful substances, preserve cell morphology, and enhance cell function under saline, alkali, and saline-alkali stress. This enhances the resistance of licorice seedlings to stress conditions and reduces physiological damage.