Exogenous IAA differentially affects growth, oxidative stress and antioxidants system in Cd stressed Trigonella foenum-graecum L. seedlings: Toxicity alleviation by up-regulation of ascorbate-glutathione cycle

In the present study, effect of exogenous indole-3-acetic acid at their different levels (i.e. low; IAA(L), 10 mu M and high; IAA(H), 100 mu M) were studied on growth, oxidative stress biomarkers and antioxidant enzymes (SOD, POD, CAT and GST), and metabolites (AsA and GSH) as well as enzymes (APX, GR and DHAR) of ascorbate-glutathione cycle in Trigonella foenum-graecum L. seedlings grown under cadmium (Cd-1, 3 mg Cd kg(-1) soil and Cd-2, 9 mg Cd kg-1 soil) stress. Cadmium (Cd) at both doses caused reduction in growth which was correlated with enhanced lipid peroxidation and damage to membrane as a result of excess accumulation of O-2(center dot-) and H2O2. Cd also enhanced the oxidation of AsA and GSH to DHA and GSSG, respectively which give a clear sign of oxidative stress, despite of accelerated activity of enzymatic antioxidants: SOD, CAT, POD, GST as well as APX, DHAR (except in Cd-2 stress) and GR. Exogenous application of IAA(L) resulted further rise in the activities of these enzymes, and maintained the redox status ( > ratios: AsA/DHA and GSH/GSSG) of cells. The maintained redox status of cells under IAA(L) treatment declined the level of ROS in Cd-1 and Cd-2 treated seedlings thereby alleviated the Cd toxicity and this effect was more pronounced under Cd-1 stress. Contrary to this, exogenous IAA(H) suppressed the activity of DHAR and GR and disturbed the redox status (< ratios: AsA/DHA and GSH/GSSG) of cells, hence excess accumulation of ROS further aggravated the Cd induced damage. Thus, overall results suggest that IAA at low (IAA(L)) and high (IAA(H)) doses affected the Cd toxicity differently by regulating the ascorbate-glutathione cycle as well as activity of other antioxidants in Trigonella seedlings. (C) 2016 Published by Elsevier Inc.