干旱胁迫下γ-氨基丁酸保护玉米幼苗光合系统的生理响应

为明确干旱胁迫下γ-氨基丁酸(GABA)保护玉米幼苗光合系统的生理响应,以郑单958为试验材料,依据玉米幼苗生长数据,选择1 mmol·L^-1为γ-氨基丁酸(GABA)供试浓度,设置空白对照(CK)、1 mmol·L^-1 GABA(G)、20%聚乙二醇(PEG-6000)模拟干旱胁迫(D)、20%聚乙二醇(PEG-6000)模拟干旱胁迫和1 mmol·L^-1 GABA(DG)4个处理开展玉米水培试验。结果表明:不同浓度GABA能缓解干旱胁迫的抑制作用,使玉米幼苗恢复生长,其中1 mmol·L^-1 GABA效果最好。干旱胁迫下,外源施用1 mmol·L^-1 GABA能显著提高叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性,减少丙二醛(MDA)、超氧阴离子($O_{2}^{-}$)和过氧化氢(H₂O₂)积累,降低叶片相对电导率。此外,外源GABA能显著提高干旱胁迫下叶片内可溶性蛋白、可溶性糖和脯氨酸含量,从而提高细胞保水能力。外源施用GABA能显著降低叶片干旱胁迫下初始荧光(F₀),提高暗适应下最大可变荧光(F_v)、最大荧光(F_m)和最大光量子效率(F_v/F_m),从而降低叶片光化学损伤。在干旱胁迫第5天,与D处理相比,DG处理SPAD数值、净光合速率(P_n)、蒸腾速率(T_r)和气孔导度(G_s)分别提高8.25%、7.69%、9.13%和7.38%,胞间CO₂浓度(C_i)降低2.93%。因此,外源GABA能通过降低叶片的氧化损伤和提高细胞保水能力来改善叶片对干旱胁迫的适应能力,从而保护玉米幼苗光合系统。

Physiological role of γ-aminobutyric acid in protecting the photosynthetic system of maize seedlings under drought stress

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.