Atrazine accumulation,oxidative stress,and defense response in maize seedlings exposed to extraneous atrazine were studied.Accumulation of atrazine in maize increased with increasing exposure concentration.The abscisic acid（ABA） content was positively correlated with the atrazine concentrations in maize roots and shoots（p 0.05）.Hydroxyl radical（.OH） in maize was determined in vivo with electron paramagnetic resonance spectroscopy.Its intensity was positively correlated with atrazine concentration in roots and shoots（p 0.05）,and higher level of.OH generated in roots than in shoots corresponded to the major accumulation of atrazine in roots.Superoxide dismutase,peroxidase and catalase in roots were up-regulated by atrazine exposure at 1 mg/L compared to the control and malondialdehyde content in roots was enhanced when atrazine exposure concentration reached 10 mg/L.These results suggested the exposure and accumulation of atrazine caused oxidative toxicity and antioxidant response in maize.
The toxicity of chlortetracycline （CTC） on maize （Zea mays L.） growth and reactive oxygen species （ROS） generation was studied.The root and shoot lengths and fresh weights of maize seedlings were inhibited by CTC treatment （p 〈 0.05）.Root length was more sensitive than other parameters with the EC 10 value of 0.064 mg/L.The spin trapping technique followed by electron paramagnetic resonance （EPR） analysis was used to quantify the ROS production.The ROS generated in maize roots after exposure to CTC was identified as hydroxyl radical （·OH）.The EPR signal intensity correlated positively with the logarithm of CTC concentrations exposed （p 〈 0.05）.The dynamic changes of malondialdehyde （MDA） contents and the antioxidative enzyme activities in maize roots were also determined.As compared to the control group,CTC was found to significantly increase MDA content.Treatment of maize roots with the ·OH scavenger sodium benzoate （SB） reduced the MDA content and enhanced the antioxidative enzyme activities.The results demonstrated the harmfulness of CTC at high dose to maize in the early developmental stage,and clarified that the inducement of ·OH is one of the mechanisms of CTC toxicity.
Bei WenYu LiuPeng WangTong WUShuzhen ZhangXiaoquan ShanJingfen Lu
The effects of maize root exudates and low-molecular-weight-organic anions （LMWOAs） on the desorption of phenanthrene from eight artificially contaminated soils were evaluated. A significant negative correlation was observed between the amounts of phenanthrene desorbed and the soil organic carbon （SOC） contents （P 〈 0.01）, and the influences of soil pH and clay content on phenanthrene desorption were insignificant （P 〉 0.1）. Neither maize root exudates nor oxalate and citrate anions influenced desorption of phenanthrene with the addition of NaN3. A faster phenanthrene desorption occurred without the addition of NaN3 in the presence of maize root exudates than oxalate or citrate due to the enhanced degradation by root exudates. Without the addition of NAN3, oxalate or citrate at different concentrations could inhibit phenanthrene desorption to different extents and the inhibiting effect by citrate was more significant than by oxalate. This study leads to the conclusion that maize root exudates can not enhance the desorption under abiotic condition with the addition of NaN3 and can promote the desorption of phenanthrene in soils without the addition of NaN3.
ZHU Yanhong, ZHANG Shuzhen, HUANG Honglin, WEN Bei State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Synchrotron-based X-ray techniques have been widely applied to the fields of environmental science due to their element-specific and nondestructive properties and unique spectral and spatial resolution advantages.The techniques are capable of in situ investigating chemical speciation,microstructure and mapping of elements in question at the molecular or nanometer scale,and thus provide direct evidence for reaction mechanisms for various environmental processes.In this contribution,the applications of three types of the techniques commonly used in the fields of environmental research are reviewed,namely X-ray absorption spectroscopy (XAS),X-ray fluorescence (XRF) spectroscopy and scanning transmission X-ray microscopy (STXM).In particular,the recent advances of the techniques in China are elaborated,and a selection of the applied examples are provided in the field of environmental science.Finally,the perspectives of synchrotron-based X-ray techniques are discussed.With their great progress and wide application,the techniques have revolutionized our understanding of significant geo-and bio-chemical processes.It is anticipatable that synchrotron-based X-ray techniques will continue to play a significant role in the fields and significant advances will be obtained in decades ahead.
LUO Lei & ZHANG ShuZhen State Key Laboratory of Environmental Chemistry and Ecotoxicology
Uptake, translocation and debromination of three polybrominated diphenyl ethers （PBDEs）, BDE-28, -47 and -99, in maize were studied in a hydroponic experiment. Roots took up most of the PBDEs in the culture solutions and more highly brominated PBDEs had a stronger uptake capability. PBDEs were detected in the stems and leaves of maize after exposure but rarely detected in the blank control plants. Furthermore, PBDE concentrations decreased from roots to stems and then to leaves, and a very clear decreasing gradient was found in segments upwards along the stem. These altogether provide substantiating evidence for the acropetal translocation of PBDEs in maize. More highly brominated PBDEs were translocated with more difficulty. Radial translocation of PBDEs from nodes to sheath inside maize was also observed. Both acropetal and radial translocations were enhanced at higher transpiration rates, suggesting that PBDE transport was probably driven by the transpiration stream. Debromination of PBDEs occurred in all parts of the maize, and debromination patterns of different parent PBDEs and in different parts of a plant were similar but with some differences. This study for the first time provides direct evidence for the acropetal translocation of PBDEs within plants, elucidates the process of PBDE transport and clarifies the debromination products of PBDEs in maize.
