Effects of GABA seed priming on alleviating salt stress and physiological and biochemical changes in Capsicum annuum

Abstract

Seed priming is proved to be an efficient way to improve crop salt tolerance, which is a measure of pre-treating seed with various agents while obtaining enhancement to crop performance at growing stage. Gamma amino butyric acid (GABA) is a non-protein amino acid involved in various metabolic processes, and partially protects plants from environmental stress. Enhancing effects of GABA priming on germination characteristics and abiotic stress have been established in several crops. However, the effect and mechanism of GABA seed priming on salt tolerance of pepper (Capsicum annuum) are still unknown. In this study, a hybrid pepper variety of ‘Maoshu 360’ Chaotian pepper was used as material, the effects of seed priming with various concentrations of GABA (0, 1.0, 2.0, 4.0, 6.0, 8.0 μmol·L-1) on plant biomass, leaf osmotic regulating substance, leaf antioxidant capacity, leaf photosynthesis system, potassium and sodium ion uptake and distribution between leaves and shoots of pepper plants under 100 mmol·L-1 NaCl stress applied at 4-6 leaf stage were investigated. The results were as follows: (1) From the point of plant growth under salt stress, the best concentration of GABA for seed priming of pepper was 6.0 μmol·L-1, which greatly boosted the biomass of pepper plants under salt stress. (2) The mechanisms of GABA seed priming promoting salt tolerance of pepper were further analyzed. Seed priming increased the leaf contents of soluble sugar, soluble protein, chlorophyll and proline, decreased the leaf contents of O2- and malondialdehyde (MDA), enhanced the leaf activities of antioxidant enzymes, including super oxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), and raised several chlorophyll fluorescence metrics, including Fv′/Fm′, qP_Lss, QY_Lss, NPQ_Lss and Rfd, reduced the K+ content and K+/Na+ ratio in roots and stems. (3) For a comprehensive understanding of the mechanisms of GABA seed priming promoting salt tolerance of pepper, grey correlation analysis was carried out. Based on results of grey correlation analysis, seed priming with GABA significantly alleviated salt stress to pepper plants by boosting the activities of the antioxidant enzymes POD and CAT as well as increasing the levels of osmotic regulators. In conclusion, seed priming with 6.0 μmol·L-1 GABA significantly increases salt tolerance of pepper seedlings, probably by improving antioxidant and osmotic regulating capacities of pepper plants.

Keywords

• γ-aminobutyric acid (gaba)
• capsicum annuum (pepper)
• seed priming
• salt tolerance
• grey correlation analysis