Ten seedlings were randomly selected from each treatment group and washed with deionized water in order to remove surface adhered electrolytes, and cut and divided into shoots and roots.
Samples (2 g fresh weight) of the shoots and roots were submerged in 15 ml of deionized water in 50 ml conical tubes and kept at 20 °C for 1 h, and the electrical conduction of effusion was measured (R1). The tissues of the samples were killed by heating tubes in a boiling bath for 40 min, cooled down to 20 °C, and electrical conduction of the effusion was measured once again (R2). The MI was evaluated with the formula MI -R1 R2 x 100%.