Does Exogenously Applied Gallic Acid Regulate the Enzymatic and Non-Enzymatic Antioxidants in Wheat Roots Exposed to Cadmium Stress?

Abstract

The aim of the current study was to determine whether gallic acid (GLA) triggers the growth, osmoregulation and antioxidant system related to defense mechanisms in wheat roots to cadmium (Cd)induced oxidative stress. For this purpose, wheat plants were hydroponically grown for 21 (d) and were treated with GLA (GLA1-2; 25 and 75 M), Cd stress (Cd1-2; 100 and 200 M) and their combination for 7 d. The significant reduction in growth (RGR) and osmotic potential () was observed under stress. After GLA applications in response to stress, RGR,  and proline (Pro) increased, except for 200 M Cd plus 75 M GLA. Under stress, hydrogen peroxide (H2O2) was induced by the activated superoxide dismutase (SOD) activity but, NADPH oxidase (NOX) had no contribution on the accumulation of H2O2. Despite of the increased catalase (CAT) and glutathione reductase (GR), H2O2 did not eliminate and then lipid peroxidation (TBARS content) was induced with the decreased scavenging capacity of hydroxyl radical (OH ) under stress. Besides, to remove of H2O2 content produced by SOD, H2O2 could effectively scavenge through CAT activity in combination form of GLA and Cd. On the other hand, GLA did not induce the enzymes and non-enzymes related to Asada-Halliwell cycle (ascorbate peroxidase (APX), GR, dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), reduced and oxidized contents of glutathione (GSH and GSSG contents). Under high Cd concentration, GLA2 could not eliminate H2O2 content because of increased NOX activity and then in this group (Cd2+GLA2) the scavenging capacity of OH  did not change and TBARS content increased.