Yang H, Wong J W, Yang Z M, Zhou L X
College of Science, Nanjing Agricultural University, Nanjing 210095, China.
J Environ Sci (China). 2001 Jul;13(3):368-75.
Agrogyron elongatum were grown in nutrient solution containing moderate to high amounts of separate heavy metal of Cd, Cu, Ni and Pb in a greenhouse for a 9-day. Cd, Cu, Ni and Pb generally led to decrease in the elongation of roots although the length of seedlings exposed to Cd and Pb at 0.05 and 0.5 mg/L showed to be slightly greater than that of controls. Of the four metals in the experiment, Pb was absorbed and accumulated to the highest level, with the concentrations of 92,754 mg/kg dry weight (DW) in roots and 11,683 mg/kg DW in shoots. Cd was moderately accumulated in Agrogyron elongatum, but the maximum bioaccumulation coefficients (BCs) for roots and shoots were observed. The patterns for Cu and Ni uptake and distribution in plants differed from those of Pb and Cd, as it was showed that the shoot accumulation of Cu and Ni was significantly higher than in roots. A. elongatum had the highest Ni concentration in shoots (30,261 mg/kg DW) at the external concentration of 250 mg/L. Cu ranked second, with a shoot concentration of 12,230 mg/kg DW when 50 mg/L Cu in solution was applied. For the four trace elements tested, the highest concentrations in shoots decreased by the order of Ni > Cu > Pb > Cd (mg/kg DW), and those in roots were Pb > Cd > Ni > Cu (mg/kg DW). Malic, oxalic and citric acids exuded by roots exposed to 1 and 50 mg/L of the metals were detected. Release of organic acids from plants significantly differed among the metal treatments. Cu was most effectively in inducing root exudation of the three types of organic acids. Cd, and Ni were also the inducers of secretion of malic and oxalic acids. With reference of Pb, a small amounts of malic and oxalic acids were detected in the root exudates, but few quantities of citric acid were found. However, no correlation between alternations in root exudation of organic acids and metal accumulation could be established.
长穗偃麦草在温室中于含有适量至高量镉、铜、镍和铅等单一重金属的营养液中培养9天。镉、铜、镍和铅通常会导致根伸长减少，不过暴露于0.05和0.5 mg/L镉和铅中的幼苗长度略长于对照。在该实验的四种金属中，铅的吸收和积累水平最高，根中干重浓度为92,754 mg/kg，地上部为11,683 mg/kg干重。镉在长穗偃麦草中有一定积累，但根和地上部的最大生物积累系数被观测到。铜和镍在植物中的吸收和分布模式与铅和镉不同，因为显示出铜和镍在地上部的积累显著高于根。在外部浓度为250 mg/L时，长穗偃麦草地上部镍浓度最高（30,261 mg/kg干重）。铜排第二，当溶液中铜浓度为50 mg/L时，地上部浓度为12,230 mg/kg干重。对于所测试的四种微量元素，地上部最高浓度按镍>铜>铅>镉（mg/kg干重）的顺序降低，根中则为铅>镉>镍>铜（mg/kg干重）。检测到暴露于1和50 mg/L这些金属的根分泌的苹果酸、草酸和柠檬酸。植物释放有机酸在不同金属处理间有显著差异。铜最有效地诱导了三种有机酸从根中渗出。镉和镍也是苹果酸和草酸分泌的诱导剂。对于铅，在根分泌物中检测到少量苹果酸和草酸，但柠檬酸含量很少。然而，无法建立有机酸根渗出变化与金属积累之间的相关性。
