Repetition of hydrogen peroxide treatment induces a chilling tolerance comparable to cold acclimation in mung bean

Mung bean seedlings (Vigna radiata L.) of the cultivar Tainan No. 5 (a chilling-sensitive cultivar) pretreated N ith multiple sprays of 200 mM H2O2 showed a tolerance to chilling at 4 degrees C for 36 h, measured by electrolyte leakage, that was greater than that induced by a single treatment and similar to that induced by cold-acclimation at 10 degrees C for 48 h. Two H2O2 treatments at an interval of 3 h gave the optimum chilling tolerance. Tolerance induced by H2O2 could be distinguished from that induced by acclimation at 10 degrees C according to length at 4 degrees C and corresponding electrolyte leakage. Chilling tolerance induced by H2O2 depended on accumulation of glutathione (GSH), which could be significantly reversed by pretreatment with buthionine sulfoximine (BSO). In contrast, tolerance induced by incubation at 10 degrees C for 48 h in light was neither accompanied by accumulation of GSH nor reversed by BSO, suggesting that there are at least two independent mechanisms of developing chilling tolerance. Chilling tolerance of both cold-acclimated and H2O2-treated seedlings was decreased by ethyleneglycol-bis(aminoethylether)-N,N'-tetraacetic acid (EGTA) but not by ruthenium red, indicating that the influx of Ca2+ from extracellular, but not intracellular, pools is an important signal in the induction of tolerance. In confirmation, sprays of Ca2+ could be substituted for H2O2.