结缕草对重金属镉的生理响应

Physiological response of Zoysia japonica to Cd^(2+)

采用水培的方法研究了不同浓度的Cd2+对结缕草叶片枯黄程度的影响,结果表明5mg/L、10mg/L和30mg/L Cd2+处理对结缕草叶片的枯黄比例无显著影响;以10mg/L的Cd2+处理结缕草植株,研究了结缕草对镉的生理响应。与对照相比,Cd2+处理30d时结缕草叶片的超氧阴离子自由基(O2-.)含量、丙二醛(MDA)含量和相对电导率(RC)显著升高,升高幅度分别为58.69%、38.52%和68.69%,表明Cd2+对结缕草叶片产生了氧化胁迫。与对照相比,Cd2+处理30d时最大量子产量(Fv/Fm)和实际量子产量(Fv'/Fm')分别显著下降3.90%和11.36%;处理20d时实际光化学效率(ΦPSⅡ)和相对电子传递速率(rETR)分别显著下降22.22%、22.66%,处理30d时分别显著上升12.5%、18.12%;处理20d时光化学猝灭系数(qp)显著下降14.29%,非光化学猝灭系数(NPQ)则显著上升38.54%,表明结缕草叶片的光反应机构受到了伤害,而光保护能力得到了提高。与对照相比,Cd2+处理下超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性先升高后降低,而过氧化物酶(POD)活性先降低后升高;脯氨酸、可溶性糖含量升高,处理30d时可溶性糖含量显著上升63.35%;处理前20d时可溶性蛋白的含量高于对照,处理30d时却低于对照。随着Cd2+处理时间的增加,结缕草地下部Cd含量逐渐升高;地上部Cd含量先升高后降低,差异显著;处理20d时地上部镉含量最高,转运系数最高,达到45.84%;处理10d时镉在结缕草地上部的分布比例小于地下部,而处理20d、30d时地上部镉的分布比例占优势,表明结缕草具备修复植物的潜质。镉在结缕草地下部水溶态所占比例最大,其次是氯化钠和醋酸提取态;与地下部不同,结缕草地上部醋酸提取态镉的含量要高于氯化钠提取态。综上,结缕草对Cd2+具有一定的耐受性。

Zoysia japonica is an important native grass species in China.The objective of this study was to study the physiological responses of Zoysia japonica to Cd2＋.The plants were treated with six level of Cd2＋ from 0 to 100mg/L for two weeks.The results demonstrated that the proportion of litter was not significantly affected when treated under 5,10and 30mg/L Cd2＋.And the physiological responses of Zoysia japonica to 10mg/L Cd2＋ were studied.Compared with the control,superoxide anion radical（O-2·）,malondialdehyde（MDA） and Relative Conductivity（RC） of Zoysia japonica leaves significantly increased by 58.69%、38.52% and 68.69% after treatment for 30 days respectively,indicating that leaves were exposed to oxidative stress.Compared with the control,the maximum photochemical efficiency of PSⅡ（Fv/Fm） and photochemical efficiency in the light（Fv′/Fm′） significantly decreased by 3.90% and 11.36% after treatment for 30 days,respectively.The effective PSⅡquantum yield（ΦPSⅡ） and the relative electron transport rate（rETR） significantly decreased by 22.22% and 22.66% after treatment for 20 days respectively,however,they significantly decreased by 12.5% and 18.12% after treatment for 30 days.After treatment for 20 days,the photochemical quenching coefficient（qp） significantly decreased by 14.29%,whereas the non-photochemical quenching coefficient（NPQ） significantly increased by 38.54%.The results demonstrated that the photoreaction agency was injured,whereas the capacity of photo-protective was increased.The activities of superoxide dismutase（SOD） and catalase（CAT） firstly increased and then decreased,whereas the activity of peroxidase（POD） presented inverse trend.The contents of proline and soluble sugar both increased.The soluble sugar content significant increased by 63.35% compared with the control after treatment for 30 days.Compared with the control,the content of soluble protein increased after treatment for 20 days,whereas decreased after treatment for 30 days.With the treatment time increasing,Cd concentration in under-ground part gradually increased,and Cd concentration in above-ground part firstly increased and then decreased with significance.After treatment for 20 days,the Cd content in above-ground part reached the peak with the highest transport coefficient of 45.84%.After treatment for 10 days,the Cd distribution proportion in above-ground part was lower than that in the under-ground part,whereas higher after treatment for 20 and 30 days,indicating that Zoysia japonica owned potential for phytoremediation of Cd pollution.The proportion of different forms of Cd in the under-ground part was highest for water extractable,followed by sodium chloride and acetic acid extractable.However,the proportion of acetate acid extractable was higher than the sodium chloride extractable in above-ground part.In conclusion,Zoysia japonica showed some resistance and tolerance to Cd2＋ up to 10mg/L.