中文摘要：

研究干旱胁迫对甘草（Glycyrrhiza spp.）幼苗活性氧代谢及保护酶活性的影响.采用聚已二醇（PEG6000）渗透胁迫的方法，测定了不同浓度PEG（5%，10%，15%）模拟干旱胁迫对乌拉尔甘草（Glycyrrhiza uralensisLis ch.）、光果甘草（Glycyrrhiza glabra L.）、胀果甘草（Glycyrrhiza inflata L.）幼苗体内的超氧阴离子自由基（O.2^-）产生速率、过氧化氢（H2O2）、丙二醛（MDA）、可溶性蛋白含量及保护酶（SOD、POD、CAT）活性的影响.随着干旱胁迫程度的加剧，3种甘草幼苗O.2^-产生速率、H2O2含量先上升后下降，MDA和可溶性蛋白则持续上升，SOD和POD活性先升后降，CAT活性则出现持续上升的变化趋势.虽然干旱胁迫会导致甘草体内形成较多自由基，使细胞膜系统受到一定破坏，但甘草体内的保护酶防御系统可以被有效调动以清除和防御自由基的伤害，从而保护细胞免受更大的损伤.

英文摘要：

Effects of drought on active oxygen metabolism and activities of three protective enzymes of licorice seedlings were researched. Nutrient solution hydroponics was adopted to study the effects of mimic drought stress on producing rate of O.2^-, concentration of H2O2, concentration of MDA, content of soluble protein and activities of protective enzymes （SOD, POD and CAT） in the seedlings of Glycyrrhiza uralensis Fisch. , Glycyrrhiza glabra L. and Glycyrrhiza inflata at different concentrations of PEG （5%, 10 % and 15%）. Results showed that with intensification of the degree of drought stress, producing rate of O.2^- , concentration of H2O2 in the seedlings of 3 species of licorices increased at first and then decreased; Concentration of MDA and content of soluble protein continuously increased; Activities of SOD and POD increased at first and then decreased; Activity of CAT continuously increased. Although drought stress could produce more free radicals in licorice to produce some injury to ceil membrane of licorice seedlings, the defense system of protective enzymes could be effectively brought into play to remove and defend the injury of free radicals so as to protect the cell from more injury.