Abstract: Drought and salinity are two major stressors that severely limit seed germination and plant growth. γ-aminobutyric acid (GABA) plays a crucial role in regulating osmotic balance and alleviating oxidative stress, while chlorinated hemin can enhance salt tolerance and promote plant growth. Psathyrostachys juncea is a species commonly used in ecological restoration. We conducted germination tests for this species under drought condition (15% PEG-6000) after soaking seeds in various concentrations of GABA (0, 1, 1.5, 2, and 2.5 mmol·L^-1) and under salt stress (150 mmol·L^-1 NaCl) with different concentrations of chlorinated hemin (0, 100, 150, 200, and 250 μmol·L^-1) to determine the optimal soaking levels. We further conducted a pot experiment under combined drought stress and salt stress (45% soil moisture+100 mmol·L^-1 NaCl), using a seed coating technique that integrated soaking and pelleting. The results showed that soaking seeds in 2 mmol·L^-1 GABA performed best under drought stress, while 150 μmol·L^-1 chlorinated hemin was the most effective under salt stress. When both compounds were combined, they significantly outperformed individual treatments under combined drought and salt stress, increasing germination rate by 28.7%, germination potential by 70.5%, and enhancing catalase and superoxide dismutase activities by 38.3% and 44.8%, respectively. The pot experiment further demonstrated that seed coating with the combined treatment increased aboveground and belowground biomass by 28.1% and 21.1%, respectively, and improved leaf net photosynthetic rate by 45.6% compared to the naked seeds. These findings suggested that seed coating with a combination of GABA and chlorinated hemin could effectively alleviate drought stress and salt stress, which would provide technological support for grassland restoration.

Key words: drought stress, salt stress, γ-aminobutyric acid, chlorinated hemin, seed coating