Effect of Gamma-Aminobutyric Acid (GABA) Pretreatment on Antioxidant Responses and Alleviation of Salinity Damage in Prosopis koelziana Seedlings

Prosopis koelziana belongs to the Fabaceae family (formerly Mimosaceae) and grows in arid and semi-arid regions. It is used for the reclamation of dry forests with low fertility and high salt content. This study was conducted to investigate the effect of gamma-aminobutyric acid (GABA) at concentrations of 0.25 and 0.5 mM on enhancing salinity tolerance in Prosopis koelziana seedlings under 400 and 600 mM NaCl. The results showed that salinity stress induced oxidative stress, and malondialdehyde (MDA) content increased in both shoots and roots. Salinity also increased the activities of antioxidant enzymes, including catalase (CAT), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX). However, pretreatment with GABA reduced MDA content and antioxidant enzyme activity. Under 400 and 600 mM salt stress, root sodium (Na⁺) content increased by 55% and 62%, and shoot sodium content increased by 73% and 100%, respectively, compared to controls. GABA (0.25 and 0.5 mM) reduced sodium levels in both organs. Salt stress decreased potassium (K⁺) content in roots and shoot, whereas GABA pretreatment increased potassium levels. The findings indicate that pretreating plants with GABA significantly reduced membrane lipid peroxidation and lowered the activity of antioxidant enzymes. This stress alleviation appears to be primarily due to reduced sodium uptake and transport into plant tissues, along with increased potassium content. Consequently, antioxidant enzyme activity decreased in GABA pretreated plants under stress conditions.