Glycine betaine affects the antioxidant system and ion accumulation and reduces salinity-induced damage in safflower seedlings

Safflower (Carthamus tinctorius L.) is an important oilseed crop, usually grown on a small scale and in salt-affected soils. Salinity stress can cause oxidative damage to plants. Upregulation of the antioxidant defense system induced by glycine betaine (GlyBet) alleviates the damaging effects of oxidative stress in plants. In the present investigation, seeds were treated with 0, 10, 30 and 60 mM of GlyBet solutions. Germination and the primary growth of the seedling were examined using sodium chloride salt (NaCl) at 0 (non-stress), 50, 100 and 150 mM concentrations. The obtained results indicate that at 50 and 100 mM NaCl, priming with 30 and 60 mM GlyBet increased root and shoot lengths compared to the control (0 mM). In addition, at all stress levels, priming with 60 mM GlyBet led to lower malondialdehyde, total soluble sugars and proline contents than in control seedlings. Priming with GlyBet increased catalase (CAT), superoxide dismutase (SOD) enzyme activities and protein content, while it reduced the activity of peroxidase (POD) under salinity stress. In addition, priming with GlyBet reduced the Na+/K(+)ratio of seedlings and increased K+ under all salinity stress levels. Priming with 60 mM GlyBet also reduced the Na+ content under 150 mM NaCl. Together, these results show that 60 mM GlyBet had the most pronounced effect on tolerance to salinity stress in safflower seedling. The GlyBet-increased tolerance to salt in safflower was mainly related to increased CAT and SOD activities, and the prevention of cell membrane damage as a result of reduced lipid peroxidation and improved ion homeostasis under salinity stress condition.