Determination of MDA, H2O2 and OFR content
To determine malonaldehyde (MDA) content in soybean leaves, we referred to the protocol of Hasanuzzaman et al. (2017) with slight modification. The absorbance at 532 and 600 nm were measured on a spectrophotometer. Hydrogen peroxide (H2O2) content was measured according to the method of Hasanuzzaman et al. (2017). The absorbance of the obtained solution was read at 415 nm. The production of an oxygen free radical (OFR) was determined using an OFR reagent kit (Comin Biotechnology, Suzhou, China). OFR scavenging ability was calculated using OD530.