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%.