Ozone tolerance in Phaseolus vulgaris depends on more than one mechanism

Two bean cultivars with different sensitivity to ozone, i.e. the O₃-sensitive Cannellino and the O₃-tolerant Top Crop, were exposed to acute O₃-stress (165 nL L⁻¹) with the aim of evaluating physiological and biochemical traits that may confer O₃-tolerance. Stomatal conductance was smaller and the ability to dissipate excess energy, via regulated and unregulated nonphotochemical quenching mechanisms was greater in Top Crop than in Cannellino. These morphological and physiological-traits allowed the O₃-tolerant cultivar to compensate for the light-induced declines in Φ_PSII, to preserve photosystem II from excitation-energy, and likely to prevent the generation of ROS to a superior degree than the O₃-sensitive cultivar. Furthermore, the potential capacities to reducing the superoxide anion and H₂O₂ were significantly greater in Top Crop than in Cannellino. These findings are consistent with the early accumulation of H₂O₂, the almost complete disruption of cell structure, and irreversible damages to the photosynthetic apparatus observed in the O₃-sensitive cultivar.     

Oxidative stress in duckweed (Lemna minor L.) caused by short-term cadmium exposure

The mechanisms of plant defence against cadmium toxicity have been studied by short-term exposure of Lemna minor L. (common duckweed) to concentrations of CdCl2 ranging from 0 to 500microM. High accumulation of cadmium was observed (12,320+/-2155microgg(-1) at 500microM CdCl2), which caused a gradual decrease of plant growth, increased lipid peroxidation, and weakened the entire antioxidative defence. Total glutathione concentration decreased significantly; however, the concentration of oxidized glutathione remained stable. The responses of four antioxidant enzymes showed that catalase was the most inhibited after CdCl2 exposure, ascorbate peroxidase and guaiacol peroxidase moderately, and glutathione reductase least. The total antioxidative potential revealed an induced antioxidative network at 0.1microM CdCl2 (137+/-13.2% of the control) and its reduction to only 47.4+/-4.0% of the control at higher cadmium concentrations. The possible application of the examined biomarkers in ecotoxicological research is discussed.     

Evaluation of various tests for the diagnosis of soil contamination by 2,4,5-trichlorophenol (2,4,5-TCP)

Soil response to contamination with 2,4,5-triclorophenol was studied to test the validity of the concept of Generic Reference Levels (GRL), the main criterion used to define soil contamination. Soil samples were artificially contaminated with doses between 0 and 5000 mg kg⁻¹ of 2,4,5-triclorophenol, and analysed by various tests. Where possible, the response of soils to the contaminant was modelled by a sigmoidal dose-response curve in order to estimate the ED₅₀ values. The tests provided different responses, but only microbial biomass-C and dehydrogenase and urease activities demonstrated soil deterioration in response to contamination. The results suggest that the diagnosis of soil contamination has been greatly simplified in the legislation by the provision of a single figure for each compound, and that the GRL concept could perhaps be substituted by measurement of ED₅₀ values, which better reflect the alteration of a soil due to the presence of a xenobiotic substance.     

黑藻对十二烷基苯磺酸钠和多聚磷酸钠胁迫的响应

研究了在十二烷基苯磺酸钠(SDBS)和多聚磷酸钠(STPP)及其复合胁迫下,黑藻过氧化物酶(POD)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)活性变化及其耐受浓度.结果表明,POD活性随着处理浓度的增加而逐渐增大;CAT在低浓度胁迫时活性逐渐增加,在较高浓度胁迫时活性降低;实验初期(6h时),SOD活性逐渐升高,随着SDBS处理浓度的提高及时间延长,SOD活性下降,并且在8mg/L浓度处理72h,SOD失活.SDBS对黑藻SOD的抑制作用大于STPP.黑藻对SDBS的耐受浓度(8mg/L)明显小于STPP的耐受浓度(256mg/L).黑藻对SDBS和STPP复合胁迫的耐受浓度值为(32+64)mg/L.     

Evaluation of antioxidant enzymes activities and identification of intermediate products during phytoremediation of an anionic dye (C. I. Acid Blue 92) by pennywort (Hydrocotyle vulgaris)

The potential of pennywort(Hydrocotyle vulgaris)for phytoremediation of C.I.Acid Blue 92(AB92)was evaluated.The efects of various experimental parameters including pH,temperature,dye concentration and plant weight on dye removal efciency were investigated.The results showed that the optimal condition for dye removal were pH 3.5 and temperature 25°C.Moreover,the absolute dye removal enhanced with increase in the initial dye concentration and plant weight.Pennywort showed the same removal efciency in repeated experiments(four runs)as that obtained from the first run(a 6-day period).Therefore,the ability of the plant in consecutive removal of AB92 confirmed the biodegradation process.Accordingly,a number of produced intermediate compounds were identified.The efect of treatment on photosynthesis and antioxidant defense system including superoxide dismutase,peroxidase and catalase in plant roots and leaves were evaluated.The results revealed a reduction in photosynthetic pigments content under dye treatments.Antioxidant enzyme responses showed marked variations with respect to the plant organ and dye concentration in the liquid medium.Overall,the increase in antioxidant enzyme activity under AB92 stress in the roots was much higher than that in the leaves.Nevertheless,no significant increase in malondialdehyde content was detected in roots or leaves,implying that the high efciency of antioxidant system in the elimination of reactive oxygen species.Based on these results,pennywort was founded to be a capable species for phytoremediation of AB92-contaminated water,may be efective for phytoremediation dye-contaminated polluted aquatic ecosystems.     

全氟辛烷磺酸对蚯蚓体内4种酶活性的影响

采用人工土壤法,研究了不同暴露浓度的全氟辛烷磺酸(PFOS)对赤子爱胜蚓(Eisenia fetida)体内过氧化氢酶(CAT)、超氧化物歧化酶(SOD)及谷胱甘肽过氧化物酶(GSH-PX)活性及蚯蚓细胞色素P450(CYP450)含量的影响。研究结果表明,各指标敏感性总体为CYP450>CAT>GSH-PX>SOD。人工土壤试验中PFOS诱导CYP450含量增加,同时又抑制CAT活性。试验第4天时,50mg/kg处理组CAT活性是对照组的2.83倍,SOD活性达到190.769 U/mg,是对照组的2.19倍;12.5 mg/kg处理组GSH-PX活性最高,CYP450含量是对照组的3.85倍。PFOS暴露浓度与蚯蚓CAT、SOD和CYP450活性存在剂量-效应关系,在PFOS环境污染诊断时,可将第4天时的CAT、GSH-PX活性和CYP450含量作为生物标志物。为赤子爱胜蚓体内抗氧化酶和CYP450作为PFOS污染的早期诊断和生态风险监测生物标志物的可行性提供科学依据。     

不同污染区巨菌草生物炭内源污染物分布及其生物毒性

由于生物质原料来源广泛,缺乏生物炭内源污染物及其用量限制标准,极有可能将含有高内源污染物的生物炭用于环境修复,产生潜在的环境风险.采用清洁区、中度和重度污染区的巨菌草为原料制备生物炭,考察其内源铜（Cu）和镉（Cd）全量及其酸溶态含量和持久性自由基（PFRs）分布,并研究生物炭浸出液对小麦根伸长抑制率和抗氧化酶活性的影响.结果表明,重度污染区九牛生物炭Cu和中度污染区水泉生物炭中Cd含量分别是清洁区红壤生物炭Cu和Cd的3.73倍和4.43倍,九牛生物炭中酸溶态Cu含量分别是水泉和红壤生物炭的3.32倍和2.84倍,水泉和九牛生物炭中酸溶态Cd含量分别是红壤生物炭的7.95倍和5.11倍.3种生物炭中均含有相邻氧原子以碳为中心的PFRs,表现为：红壤>九牛>水泉.3种生物炭浸出液对小麦根伸长均表现为抑制作用,但均不同程度地提高了小麦幼苗超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性,其中九牛生物炭浸出液对小麦根伸长抑制率最高,达到27.7%.本研究表明,生物炭中内源重金属及PFRs等污染物的共同作用对小麦幼苗产生了显著的生物毒性,后期的研究需关注生物炭内源污染物的潜在环境风险,避免产生二次污染等环境问题.     

H2S信号在拟南芥响应SO2胁迫过程中的作用

以拟南芥为实验材料,研究植物对H₂S和SO₂处理的转录响应及其关系,并利用外源喷施H₂S及其清除剂的方法,检测SO₂熏气后植株体内H₂S的产生及其生理效应,探讨气体信号分子H₂S在植物响应SO₂胁迫过程中的作用.高通量测序结果发现,H₂S和SO₂处理诱导拟南芥植株多个基因转录水平改变,并有1220个基因在两种处理条件下均差异表达,其中包括多个硫代谢和谷胱甘肽代谢相关基因,表明H₂S和SO₂在调控硫代谢途径中具有交互作用.SO₂熏气诱导拟南芥植株体内H₂S合成酶基因LCD和DES1转录水平提高,胞内H₂S含量增多.同时,超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性升高,含硫抗氧化物谷胱甘肽(GSH)含量及其相关酶谷胱甘肽硫转移酶(GST)和谷胱甘肽过氧化物酶(GPX)活性提高,活性氧H₂O₂含量增加,膜脂过氧化产物丙二醛(MDA)含量与对照相比无显著差异.外源喷施H₂S可进一步提高SO₂熏气下拟南芥植株GSH含量及其相关防御酶的活性,H₂O₂含量降低.但喷施亚牛磺酸(HT)清除H₂S后,SO₂熏气拟南芥植株GSH含量、抗氧化酶SOD、CAT和GST活性降低,MDA含量大幅增加.结果表明,SO₂熏气诱导产生的H₂S可作为信号分子,提高机体抗氧化防御能力,增强植物对SO₂胁迫的抗性.     

Long-term impacts of graphene oxide and Ag nanoparticles on anammox process: Performance, microbial community and toxic mechanism

The increasing application of engineered nanoparticles (NPs) has posed an emerging challenge to constructed wetland wastewater treatment. The performance, microbial community and toxic mechanism of anammox-based unplanted subsurface-flow constructed wetlands (USFCWs) were investigated under the long-term exposure of different graphene oxides (GOs) and Ag NP concentrations. Results showed that the addition of GO could promote TN removal, manifesting as function anammox bacteria C. Anammoxoglobus having a relative high abundance, for GO did not cause significant damage to the cell integrity though there was an increase in ROS concentrations. TN removal would not be obviously affected under exposure of 1?mg/L Ag NPs, for the function gene related to cell biogenesis and repair was up-regulated; while the addition of 10?mg/L Ag NPs would have an inhibiting effect on TN removal in the USFCWs, for the disappearance of some species having anammox ability. Key enzymes of anammox process (NIR and HDH) decreased to some extent under GO and Ag NP exposure, and function gene of defense mechanisms had an increase trend in samples.     

Nitrogen-cycling microbial community functional potential and enzyme activities in cultured biofilms with response to inorganic nitrogen availability

Biofilms mediate crucial biochemical processes in aquatic ecosystems. It was hypothesized that eutrophication may promote the growth of biofilms, resulting in larger numbers of functional genes. However, the metabolic activity and the roles of biofilms in N cycling will be affected by ambient inorganic nitrogen availability, not by the abundance of functional genes. Biofilms were cultured either with replete inorganic nitrogen(N-rep) or without exogenous inorganic nitrogen supply(N-def) in a flow incubator, and the N-cycling gene abundances(nifH, N_2 fixation; amoA, ammonia oxidation, archaea and bacteria; nirS and nirK, denitrification) and enzyme activities(nitrogenase and nitrate reductase) were analyzed. The results showed that, comparing the N-def and N-rep biofilms, the former contained lower nifH gene abundance, but higher nitrogenase activity(NA), while the latter contained higher nifH gene abundance, but lower NA. Different patterns of NA diel variations corresponded to the dynamic microbial community composition and different stages of biofilm colonization. Ammonia oxidizing bacteria(AOB), detected only in N-def biofilms, were responsible for nitrification in biofilms. N-rep biofilms contained high nirS and nirK gene abundance and high denitrification enzyme activity, but N-def biofilms contained significantly lower denitrification gene abundance and activity. In general,the strong N_2 fixation in N-def biofilms and strong denitrification in N-rep biofilms assured the balance of aquatic ecosystems. The results suggested that evaluation of the functional processes of N cycling should not only focus on genetic potential, but also on the physiological activity of biofilms.