Short-term cold-shock at 1 °C induced chilling tolerance in maize seedlings

1 degrees C is normally considered as an extreme chilling stress temperature and will cause severe chilling injury to chilling-sensitive plants. Chilling acclimation of chilling-sensitive plants was usually achieved by exposure to around or above the threshold chilling temperature (about 10 degrees C or 15 degrees C) for several days. In our present work, a cold-shock pretreatment at 1 degrees C for 4 h, followed by a 6-h recovery at 26.5 degrees C, significantly enhanced survival rate of maize seedlings, mitigated electrolyte leakage of primary roots and alleviated vitality loss of mesocotyls under severe chilling stress at 1 degrees C, indicating that short-term cold-shock could induce chilling tolerance of maize seedlings. The cold-shock pretreatment brought out an endogenous hydrogen peroxide (H2O2) peak, enhanced the activities of five antioxidant enzymes guaiacol peroxidase (GPX), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and superoxide dismutase (SOD) in maize mesocotyls and remained significantly higher activities of these five antioxidant enzymes after chilling stress. These results imply that antioxidant systems play a pivotal role in the cold-shock-induced chilling tolerance of maize seedlings, and H2O2 may be involved in signaling and triggering of this cold-shock-induced chilling tolerance through the mobilization of antioxidant systems.