Does Exogenously Applied Gallic Acid Regulate the Enzymatic and NonEnzymatic 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 weretreated with GLA (GLA1-2; 25 and 75 M), Cd stress (Cd1-2; 100 and 200 M) and their combination for7 d. The significant reduction in growth (RGR) and osmotic potential () was observed under stress. AfterGLA applications in response to stress, RGR,  and proline (Pro) increased, except for 200 M Cd plus75 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 ofthe increased catalase (CAT) and glutathione reductase (GR), H2O2 did not eliminate and then lipidperoxidation (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 scavengethrough CAT activity in combination form of GLA and Cd. On the other hand, GLA did not induce theenzymes and non-enzymes related to Asada-Halliwell cycle (ascorbate peroxidase (APX), GR,dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), reduced and oxidizedcontents of glutathione (GSH and GSSG contents). Under high Cd concentration, GLA2 could not eliminateH2O2 content because of increased NOX activity and then in this group (Cd2+GLA2) the scavengingcapacity of OH did not change and TBARS content increased.