以陕西汉中地区栽培的柑橘品种大红柑秋梢为试材，采用Hoagland营养液培养方法，研究了外源过氧化氢（H2O2）对低温（4℃）胁迫下大红柑叶片生长状况及生理指标的影响，筛选缓解柑橘低温伤害的最佳H2 O2处理浓度，并探讨外源H2 O2处理对柑橘耐寒能力的影响机制。结果显示，随低温胁迫时间的延长，大红柑叶片卷曲和叶片细胞膜伤害程度逐渐加重。0.1和1.0 mmol· L－1 H2 O2处理均能缓解低温胁迫引起的大红柑叶片卷曲和萎蔫，但1.0 mmol· L－1 H2 O2比0.1 mmol· L－1 H2 O2缓解低温胁迫对大红柑的伤害效果更为显著。1.0 mmol· L－1 H2 O2显著降低叶片中相对电导率（ REC）和丙二醛（ MDA）含量的升高，减轻叶片细胞中超氧阴离子（O．－2）和内源H2O2含量的积累，提高超氧化物歧化酶（SOD）和过氧化氢酶（CAT）的活性，从而降低低温对柑橘叶片细胞膜的伤害。较高浓度的外源H2 O2不仅未起到缓解作用，反而产生了一定的毒害作用。%Fall shoot of citrus (Citrus reticulata Blanco cv.Dahonggan) planted in Hanzhong City, Shaanxi Prov-ince , were cultured in Hoagland hydroponic solution and were used as experimental materials .The effects of different concentrations of H 2 O2 treatments on growth and physiological indexes of Dahonggan leaves under low temperature stress (4℃) were studied, in order to select the optimum concentration of H 2 O2 and to investigate the role of exoge-nous H2 O2 in alleviating chilling injury of citrus to cold .It was shown that the degree of curl and cell membrane dam-age of Dahonggan leaf gradually increased with the extension of low temperature stress time .Both 0.1 and 1.0 mmol· L-1 H2 O2 could ease leaves curling and wilting in Dahonggan caused by low temperature stress ;however , the effect of 1.0 mmol· L-1 H2 O2 was more significant than the concentration of 0.1 mmol· L-1 on alleviating damage of Da-honggan leaves caused by chilling stress .1.0 mmol· L-1 H2 O2 could obviously reduce the damage of cell membrane by lowering the increase of REC and MDA , reducing the accumulation of O .-2 and H2 O2 and improving the activities of SOD and CAT in Dahonggan leaves under low temperature .Relatively high concentrations of exogenous H 2 O2 could not show alleviating effects;on the contrary , it produced some toxic effects .
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