Abscisic acid signaling reduced transpiration flow, regulated Na[formula omitted] ion homeostasis and antioxidant enzyme activities to induce salinity tolerance in wheat (Triticum aestivum L.) seedlings

Salinity, one of the catastrophic abiotic stresses that uces wheat production around the globe. Abscisic acid (ABA) is a stress phytohormone as a signaling molecule that led us to investigate its potential to improve morpho-physiological characteristics, antioxidant metabolism, and ion homeostasis in wheat (Triticum aestivum L.) seedlings grown under salinity stress (0, 50, and 100 mM NaCl). The findings suggested that salt-induced toxicity significantly (P < 0.05) damaged root morphological characteristics, plant growth, photosynthetic pigments, and water contents, while trigger the oxidative injury, Na+ ion accumulation and uptake in wheat leaf and root tissues with the increasing NaCl concentration in the nutrient media. However, root-zone supply of ABA (0, 5, and 10 μM) prominently alleviated salt induced phytotoxicity. The 10 μM concentration of ABA promoted shoot (81.7%) and root (102.1%) dry weight, root length (38.2%), Chl. a (65.3%), Chl. b (149.0%), carotenoids (95.7%) and membrane damage (36.7%) when NaCl was added at 100 mM, relative to the corresponding treatment without ABA. Moreover, ABA (10 μM) supply decreased Na+ ion uptake (root to leaf) due to reduced transpiration rate (81.1%), and thereby ameliorated oxidative injury by ucing leaf malondialdehyde (MDA) and H2O₂ contents by 36.8% and 29.9%, respectively, at 100 mM NaCl stress, relative to the similar treatment without ABA. In addition, the activities of catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) were upregulated by 143.9%, 20.2%, and 19.5% in leaves and by 144.9%, 23.4% and 41.1% in roots respectively, with 10 μM ABA application under 100 mM salinity stress, compa to the 100 mM NaCl treatment without ABA. Conclusively, this study proposed that root-zone ABA application promoted salinity tolerance in wheat seedlings and could be a practical approach for wheat production in salt-affected regions to ensure food security.