Treatment With Auxin and Paclobutrazol Mediates Ros Regulation, Antioxidant Defence System and Cell Wall Response in Salt Treated Soybean

Abstract

IAA and PBZ play important role in resisting abiotic stress for plants. However, the effects of combination of these regulators in plants under salinity remained obscure. In the current study, the role of 50 ppm IAA and 10 ppm PBZ on mitigating salt stress (200 and 300 mM NaCl) was investigated in soybean (Glycine max L. cv. Planet). We identified that IAA or PBZ and IAA + PBZ improved the physiological parameters that damaged by salinity but PBZ performed best as observed by SEM. However, IAA was more succesfull to induce some antioxidant enzymes (SOD, CAT, APX, POX) although both of them reduced or did not affect GSH- related enzymes (DHAR, MDHAR, GST, GR, GPX). Beside this, combination of IAA and PBZ treatment showed the lowest MDA with inhibited salt stress induced oxidative damage. Additionally, PBZ was more effective against as IAA to reduce the PME and PAL enzyme activities as well as decreased arabinose content, while they were increased with salinity. IAA or PBZ increased lignin content and lead to reduce loosening in roots, while IAA performed best. Overall, this study firstly presents that these regulators ( 50 ppm IAA; 10 ppm PBZ) could be used together to increase salt tolerance in soybean plants via regulating physiological and biochemical metabolism, antioxidant defense system and cell wall modified parameters. Thus, the application of IAA /PBZ to salt treated soybean plants could be utilized as a model to increase plant’s resistance under stress conditions.