# Application of γ-aminobutyric acid alleviates salinity-mediated growth decline and oxidative damage by increasing proline and antioxidant functioning in olive (Olea europaea L.)

## TL;DR

Applying GABA helps olive plants resist salt stress by improving water balance, reducing damage, and boosting antioxidants.

## Contribution

Demonstrates GABA's effectiveness in mitigating salinity stress through multiple physiological mechanisms in olive plants.

## Key findings

- GABA application reduced oxidative stress and improved growth under salinity.
- GABA enhanced antioxidant enzyme activity and osmolyte accumulation in olive plants.
- GABA improved nutrient uptake and reduced sodium accumulation in salt-stressed plants.

## Abstract

Salinity stress is a major environmental constraint limiting crop productivity by inducing osmotic imbalance, ion toxicity, and oxidative damage. This study investigated the potential of exogenous γ-aminobutyric acid (GABA) to enhance plant tolerance under saline conditions. Plants were subjected to three salinity levels (0, 100, 150 mM NaCl) with or without foliar application of GABA (0, 1, 2 mM). Salinity significantly reduced growth parameters, including plant height, leaf area, and biomass accumulation, while increasing oxidative stress markers such as malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anions (O2•−). However, GABA application, particularly at 1 mM, substantially mitigated these negative effects. GABA-treated plants exhibited higher relative water content (RWC), membrane stability index (MSI), and accumulation of osmolytes (proline, soluble sugars), reflecting improved water status and metabolic adjustment. Antioxidant defense was enhanced, with increased activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR), alongside elevated levels of ascorbate (AsA), glutathione (GSH), and favorable redox ratios (AsA/DHA, GSH/GSSG). GABA also improved nutrient uptake by increasing macronutrient (N, P, K, Ca) and micronutrient (Fe, Mn, Zn, Cu) levels while reducing Na+ accumulation and Na+/K+ ratios. Multivariate analyses (heatmap, PCA) revealed that GABA-treated plants under moderate salinity closely clustered with non-stressed controls, highlighting its protective role. Overall, GABA enhances salinity tolerance by modulating osmotic balance, ion homeostasis, and antioxidant defense mechanisms, supporting its use as a promising agrochemical for improving plant resilience under salt stress.