Abstract: This research aimed to clarify the physiological role of γ-aminobutyric acid (GABA) in the protection of the photosynthetic system of maize seedlings under drought stress. The maize variety studied was Zheng Dan 958, and the exogenous application of GABA at a concentration of 1 mmol·L^-1 was used tested in a hydroponic culture experiment where drought stress was simulated by adding PEG-6000. The experiment comprised four treatments: Blank control (CK), 1 mmol·L^-1 GABA treatment (G), 20% PEG (PEG-6000) simulated drought stress (D), 20% PEG (PEG-6000) simulated drought stress and 1 mmol·L^-1 GABA treatment (DG). It was found that: Application of 1 mmol·L^-1 exogenous GABA significantly improved the activities of superoxide dismutase, peroxidase and catalase and decreased the malondialdehyde, superoxide anion and hydrogen peroxide concentrations of leaf tissue. Leaf relative conductivity was also reduced. Furthermore, exogenous GABA significantly increased the content of soluble protein, soluble sugar and proline in leaves under drought stress, thereby improving the water retention capacity of cells. Exogenous application of GABA significantly reduced the chlorophyll fluorescence F₀ value; and improved the F_v, F_m and F_v/F_m values, thereby reducing photochemical damage in leaves. Compared with the D treatment, SPAD, P_n, T_r and G_s of the DG treatment were increased by 8.25%, 7.69%, 9.13% and 7.38%, respectively in 5th day after stress. In addition, C_i was decreased by 2.93%. In summary, exogenous GABA improved the drought resistance in leaves by reducing oxidative damage and increasing the capacity for cell water retention, thereby protecting the photosynthetic system in maize seedlings.

Key words: γ-aminobutyric acid (GABA);, maize, drought stress, photosynthesis