重金属镉及其与锌组合对黄瓜毛状根生长及其抗氧化酶活性的影响

Influences of heavy metal cadmium alone and in combination with zinc on the growth and activities of antioxidant enzymes of Cucumis sativus hairy roots

为了探讨利用黄瓜毛状根来修复重金属镉(Cd)污染的可能性,研究了重金属Cd单独及其与锌(Zn)组合对黄瓜毛状根生长及其抗氧化酶SOD、POD活性变化的影响。结果表明,Cd≤10mg/L仅在培养5～15d间促进黄瓜毛状根生长,使根增粗;而Cd≥15mg/L则抑制黄瓜毛状根生长,浓度愈高抑制作用愈明显,侧根变得短而细小。在供试的不同浓度Cd培养的黄瓜毛状根中,除10mg/LCd外,其余Cd浓度培养的黄瓜毛状根可溶性蛋白含量随着培养时间的延长而逐渐下降;但其POD和SOD活性则随着培养时间的延长而逐渐升高。与对照(仅添加25mg/LZn)相比,仅1mg/LCd+25mg/LZn组合在培养7～15d期间促进黄瓜毛状根生长;其余浓度Cd和25mg/LZn组合都抑制黄瓜毛状根的生长,且Cd浓度愈高抑制作用越强,侧根数目更少且短小,侧根根尖变得肿胀;同时,除培养5d外,25mg/LZn和不同浓度Cd组合培养的黄瓜毛状根的生物量、POD和SOD活性均比单独添加对应浓度Cd培养的毛状根降低,但其可溶性蛋白含量则较之明显提高。结果表明:黄瓜毛状根具有较强的重金属Cd耐受能力,高浓度Cd则抑制其生长;而镉和锌组合会随着培养时间的延长而加重Cd对黄瓜毛状根生长的抑制作用。

The effects of heavy metal cadmium （Cd）, alone and in combination with zinc （Zn）, on the root growth and activity of antioxidant enzymes superoxide dismutase（SOD） and peroxidase（POD） in Cucumis sativus L. hairy roots were studied. The purpose was to study the possibilities on using C. sativus hairy roots for phytoremediation of cadmium contamination. The results showed that less than 10 mg/L Cd enhanced the growth of C. sativus hairy roots and increased root diameter only in 5-15 days of root culture. At Cd concentrations above 15 mg/L hairy root growth was gradually inhibited with increasing Cd concentration. The roots formed were shorter with smaller lateral roots. Among all the Cd concentrations tested, except with 10 mg/L Cd, the soluble protein contents in the C. sativus hairy roots cultured with the other Cd concentrations decreased, but the POD and SOD activities increased gradually with time during the culture process. Further tests were conducted using a control culture containing 25 mg/L Zn alone. The addition of lmg/L Cd to the 25 mg/L Zn culture stimulated the growth of C. sativus hairy roots after 7-15 days of growth, compared with the control. At all other Cd concentrations the growth of C. sativus hairy roots was inhibited compared to the control. Growth inhibition increased with increasing Cd concentration, and the hairy roots formed fewer, shorter and smaller lateral roots, the tips of which became swollen. After 5 days culture with different concentrations of Cd ＋ 25 mg/L Zn, the root biomass and the activity of POD and SOD were lower than in C. sativus hairy roots cultured without the addition of Zn. However, the soluble protein content was significantly higher when the culture contained 25 mg/L Zn. Our results suggested that C. sativus hairy roots have higher tolerance to heavy metal Cd but higher concentration of Cd inhibited the growth. Cd in combination with Zn would result in more serious Cd-induced growth inhibition.