H <sub> 2 </ Sub> The O <sub> 2 </ Sub> Dual Role In The Maize Seedling Cold Stress And Adaptation Process With Ca ~ (2 +)-cam

This study included two parts:For the first part, maize seedlings (Zea mays L. DaHuang and Qing No.3) were used as experimental material. Firstly, the survival percentage curve and the dual-peak curve of H2O2 content of two kind of maize seedlings were investigated under chilling stress. Under chilling stress, H2O2 content increased sharply, and showed the first peak at the 4 hour, then decreased sharply. And it also increased following prolong of the time of chilling stress, and showed the second peak at the time of all maize seedlings dead, then decreased. Secondly, the change of MDA content of maize seedlings was measured under chilling stress. According to the inconsistent of time of dead and the second peak of H2O2 and MDA content increase sharply of maize seedlings, we suggested that the increase of H2O2 content had hurt role for maize seedlings at the later stage of chilling stress. The cold-tolerance and the H2O2 content of maize seedlings increased by the H2O2 pre-treated. And we found that the survival percentage of maize seedlings increase by 4 hour cold-shock. So we suggested that the increase quickly of H2O2 content at earlier stage of chilling stress was a stress signal, and induced the increase of cold-tolerance of maize seedlings, the effect of H2O2 pre-treated on the activity of antioxidant enzyme was also measured. It showed that the activity of antioxidant enzyme went up by H2O2 pre-treated, and decrease was slower than the control seedlings. So we suggested that the increase of cold-tolerance of H2O2 induced was often related to the enhance of activity of antioxidant enzyme system in plant.In the first part, we had suggested that H2O2 has dual role, and could induce the increase of cold-tolerance. And in the former results, it indicated that Ca2+-CaM had involved in the signal transduction for cold stress and the formation for cold tolerant of plants. So we might conclude calcium messenger system might involve in the increase of cold-tolerance H2O2-induced. So the effect of modified of Ca2+ and CaM level on the cold-resistance of H2O2 induced of maize seedlings was measured . We found that EGTA, a Ca2+ chelator, andRR, the putative mitochondrial Ca2+ channel blocker, and CaM inhibitor CPZ and TFP all could inhibit the increase of cold-tolerance of H2O2 induced. Our result also showed that the pre-treatment of lower concentration Ca2+ could increase the cold-tolerance of H2O2 induced, but the higher concentration Ca2+ had reverse result. It showed that H2O2 pre-treated could increase H2O2 content and CaM activity .So we demonstrated that Ca2+-CaM might regulate the cold-tolerance of H2O2 induced.