Abstract
γ-Aminobutyric acid (GABA) has high physiological activity in plant stress physiology. This study showed that the application of exogenous GABA by root drenching to moderately (MS, 150 mM salt concentration) and severely salt-stressed (SS, 300 mM salt concentration) plants significantly increased endogenous GABA concentration and improved maize seedling growth but decreased glutamate decarboxylase (GAD) activity compared with non-treated ones. Exogenous GABA alleviated damage to membranes, increased in proline and soluble sugar content in leaves, and reduced water loss. After the application of GABA, maize seedling leaves suffered less oxidative damage in terms of superoxide anion (O2·−) and malondialdehyde (MDA) content. GABA-treated MS and SS maize seedlings showed increased enzymatic antioxidant activity compared with that of untreated controls, and GABA-treated MS maize seedlings had a greater increase in enzymatic antioxidant activity than SS maize seedlings. Salt stress severely damaged cell function and inhibited photosynthesis, especially in SS maize seedlings. Exogenous GABA application could reduce the accumulation of harmful substances, help maintain cell morphology, and improve the function of cells during salt stress. These effects could reduce the damage to the photosynthetic system from salt stress and improve photosynthesis and chlorophyll fluorescence parameters. GABA enhanced the salt tolerance of maize seedlings.
Highlights
Maize (Zea mays L.) is one of the most important cereal crops and is grown under a wide spectrum of soil and climatic conditions
To further elucidate the protective effects of GABA and its regulatory role in maize seedlings under salt stress, we investigated GABA concentration in the leaf, the growth of maize seedlings, membrane damage and leaf relative water content, the activities of antioxidant enzymes, proline and soluble sugar contents and photosynthesis in GABA-treated and untreated maize seedlings
Our examination of glutamate decarboxylase (GAD) activity revealed that GAD activity significantly increased in moderately salt-stressed (MS) plants but significantly decreased in SS plants compared with that in controls, and this trend was similar to endogenous GABA concentration
Summary
Maize (Zea mays L.) is one of the most important cereal crops and is grown under a wide spectrum of soil and climatic conditions. Salt stress may lead to membrane damage[6], a reduction in leaf relative water content[7,8], the denaturation of proteins, the accumulation of oxidizing substances[9], the inactivation of enzymes and the decline of photosynthesis in maize. Some reports have shown that the GABA shunt may be associated with various physiological responses, including signalling, osmoregulation, response to a fungal elicitor, nitrogen metabolism, carbon fluxes in the tricarboxylic acid cycle, the regulation of cytosolic pH19, and protection against oxidative stress. To further elucidate the protective effects of GABA and its regulatory role in maize seedlings under salt stress, we investigated GABA concentration in the leaf, the growth of maize seedlings, membrane damage and leaf relative water content, the activities of antioxidant enzymes, proline and soluble sugar contents and photosynthesis in GABA-treated and untreated maize seedlings. The aim of this study was to provide a theoretical basis for the application of GABA in maize under salt stress
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