Toxicity Assessment of Volatile Organic Compounds in Poplar Trees

A method is described to assess the toxicity of selected volatile organic compounds (VOCs) in poplar trees. The method is illustrated for a specific aqueous mixture of VOCs that contaminates the groundwater at a site for which phytoremediation was being considered. The VOC mixture contained a variety of aromatic compounds, chlorinated aliphatics, and alcohols. Poplar tree cuttings planted in 50-gallon barrels in the greenhouse were watered via subirrigation. The subirrigant contained either a low (42 mg/L), medium (85 mg/L), or high (169 mg/L) dose of the VOC mixture, or water only (experimental control). Phytotoxicity was evaluated by measuring the physiological parameters of stomatal conductance, shoot elongation, and biomass production. Two experiments are briefly described: (1) The poplar tree cuttings were allowed to become established in the barrels and then treated to gradually increasing concentrations of the VOC mixture until the final dose was reached. The objective was to establish a detailed dose-response relationship. (2) The poplar tree cuttings were given the low, medium, or high dose of the VOC mixture immediately after planting. The aim of this experiment was to determine if the VOC mixture would be inhibitory to root development. Phytotoxic effects were not observed in either experiment.     

Relating Hybrid Poplar Fine Root Production,Soil Nutrients,and Hydrocarbon Contamination

Quantifying the effects of hydrocarbon contamination on hybrid poplar fine root dynamics provides information about how well these trees tolerate the adverse conditions imposed by the presence of petroleum in the soil. The objective of this research was to investigate the relationship between the varying concentrations of total petroleum hydrocarbons (TPH) and nutrients across a hydrocarbon-contaminated site, and quantify the effects of these properties on the spatial and temporal patterns of fine root production of hybrid poplar (P. deltoides × P. petrowskyana C. V. Griffin) Twelve minirhizotron tubes were distributed across a TPH-contaminated site at Hendon, SK, Canada, and facilitated quantification of fine root production in areas of varying contamination levels. Residual hydrocarbon contamination was positively correlated with soil total C and N, which may suggest that the hydrocarbons remaining in the soil are associated with organic forms of these nutrients. Fine root production was stimulated by small amounts of hydrocarbon contamination at the field site. Nonlinear regression described fine root production as increasing linearly up to approximately 500 mg kg^{? 1} TPH, then remaining constant as contamination increased. Stimulation of hybrid poplar fine root production in hydrocarbon-contaminated soil could to lead to enhanced contaminant degradation as a result of stimulated microbial activity via a greater rhizosphere effect.     

Monitoring the Effect of Poplar Trees on Petroleum-Hydrocarbon and Chlorinated-Solvent Contaminated Ground Water

At contaminated groundwater sites, poplar trees can be used to affect ground-water levels, flow directions, and ultimately total groundwater and contaminant flux to areas downgradient of the trees. The magnitude of the hydrologic changes can be monitored using fundamental concepts of groundwater hydrology, in addition to plant physiology-based approaches, and can be viewed as being almost independent of the contaminant released. The affect of poplar trees on the fate of groundwater contaminants, however, is contaminant dependent. Some petroleum hydrocarbons or chlorinated solvents may be mineralized or transformed to innocuous compounds by rhizospheric bacteria associated with the tree roots, mineralized or transformed by plant tissues in the transpiration stream or leaves after uptake, or passively volatilized and rapidly dispersed or oxidized in the atmosphere. These processes also can be monitored using a combination of physiological- or geochemical-based field or laboratory approaches. When combined, such hydrologic and contaminant monitoring approaches can result in a more accurate assessment of the use of poplar trees to meet regulatory goals at contaminated groundwater sites, verify that these goals continue to be met in the future, and ultimately lead to a consensus on how the performance of plant-based remedial strategies (phytoremediation) is to be assessed.     

Phytoextraction of Risk Elements by Willow and Poplar Trees

To characterize the phytoextraction efficiency of two clones of willow trees (Salix x smithiana Willd., Salix rubens) and two clones of poplar trees (Populus nigra x maximowiczii, Populus nigra Wolterson) were planted in contaminated soil (0.4–2.0 mg Cd.kg^?1, 78–313 mg Zn.kg^?1, 21.3–118 mg Cu.kg^?1). Field experiment was carried out in Czech Republic. The study investigated their ability to accumulate heavy metals (Cd, Zn, and Cu) in harvestable plant parts. The poplars produced higher amount of biomass than willows. Both Salix clones accumulated higher amount of Cd, Zn and Cu in their biomass (maximum 6.8 mg Cd.kg^?1, 909 mg Zn.kg^?1, and 17.7 mg Cu.kg^?1) compared to Populus clones (maximum 2.06 mg Cd.kg^?1, 463 mg Zn.kg^?1, and 11.8 mg Cu.kg^?1). There were no significant differences between clones of individual species. BCs for Cd and Zn were greater than 1 (the highest in willow leaves). BCs values of Cu were very low. These results indicate that Salix is more suitable plant for phytoextraction of Cd and Zn than Populus. The Cu phytoextraction potential of Salix and Populus trees was not confirmed in this experiment due to low soil availability of this element.     

Phytoextraction and Accumulation of Boron and Selenium by Poplar (Populus) Hybrid Clones

There has been much interest recently in central California for reusing drainage water to grow trees. A sand-culture study was conducted to investigate the accumulation of boron (B) and selenium (Se) in eight hybrid poplar (Populus) clones irrigated with synthetic agricultural effluent containing increasing levels of chloride salt, B, and Se. Electrical conductivity (EC) ranged from 1.5 to 15 dS m^-1, B levels from 1 to 5 mg L^-1, and Se levels from 100 to 500 μg L^-1. Compared with all tree organs, the leaves accumulated the greatest concentrations of B and Se at the time of harvest. The results show that pooled leaf B concentrations were positively correlated with EC levels (r = 0.78, P < 0.001) and negatively correlated (r = -0.53, P < 0.001) with leaf dry matter for all clones at all tested B levels. Combined leaf and stem Se data show, respectively, a significant decrease (P < 0.05 level) in tissue accumulation of Se with increased salinity. Toxicity symptoms (e.g., burning leaf margins, shoot die back) occurred in most clones grown at 12 and 15 dS m^-1 treatments leading to leaf abscission. Based on the data, clone 49177 (Populus trichocarpa × P. deltoidus) best tolerated the tested parameters among the clones and accumulated the greatest amount of B and Se. The moderate ability of the Populus species to remove and accumulate B and Se from saline effluent is most effective at salinity levels less than 7 dS m^-1.     

Tolerance of Hybrid Poplar (Populus) Trees Irrigated with Varied Levels of Salt,Selenium, and Boron

Agricultural drainage waters and industrial effluents often consist of waste waters laden with salts, boron (B), selenium (Se), molybdenum (Mo), and other contaminants. However, increasing shortages of high-quality water in arid and semiarid regions and increasing demands to maintain the water quality in rivers, lakes, streams, and groundwater have made water reuse an imperative. Trees have been viewed as potential candidates for wastewater reuse because of their capacities for high evapotranspiration, high growth rates, and abilities to accumulate salts and specific ions in a marketable product that is not biologically hazardous. Clones of eight hybrid poplar (Populus spp.) crosses were tested for salt tolerance and ion uptake characteristics in a sand culture study in Riverside, CA. After hardwood cuttings were planted and established under nonsaline conditions, young saplings were treated with artificial waste waters containing different levels of salts, Se, and B. High salt concentrations reduced growth and led to leaf damage and shedding; however, Se and B had no detrimental effect on growth. Salinity affected Se and B accumulation patterns in leaves. A significant degree of genetic variation in salt tolerance was noted among the clones. The salinity at which dry weight was reduced ranged from about 3.3 to about 7.6 dS m^-1 depending on clone, and the relative decrease in dry weight yield with increasing salinity varied among clones and ranged from about 10 to 15% per dS m^-1. This would indicate that poplars, whereas certainly more salt tolerant than avocado trees, are significantly less salt tolerant than eucalyptus. Leaf C1 concentrations increased in relation to the C1 concentrations in the irrigation waters, but also were subject to clonal variation. Salt tolerance in poplar was generally related to C1 in the leaves and stems but was also influenced by growth and vigor characteristics, as well as the allometric relationships between leaves and stems that influenced the sinks in which ions could accumulate before reaching toxic levels.     

Disposition of Atrazine Metabolites Following Uptake and Degradation of Atrazine in Switchgrass

Extensive use of the agricultural herbicide atrazine has led to contamination of numerous ground and surface water bodies. Research has shown that it can have a variety of negative impacts on numerous non-target organisms in the environment. Phytoremediation is one strategy that has been studied to remove atrazine contamination. This paper investigates the hypothesis that switchgrass (Panicum virgatum) can exude metabolites of atrazine after uptake and degradation, which has been suggested by prior research. Pots planted with switchgrass were treated with a 4 ppm solution of atrazine spiked with [¹⁴C]atrazine. After 4 days, switchgrass plants were transplanted to new pots with fresh sand. Four days later, the pots were sacrificed, and sand and plant samples were extracted. Plant and sand samples were analyzed for the presence of atrazine and its major metabolites. The percentage of radiotracer remaining as the parent atrazine was observed to decrease over the course of the study while the percentages of the metabolites were observed to increase. The presence of the metabolite cyanuric acid in a switchgrass phytoremediation system is reported for the first time.     

转双抗虫基因杂种741毛白杨的研究

用部分改造后的苏云金芽孢杆菌 (Bt)杀虫蛋白基因和慈菇蛋白酶抑制剂 (API)基因A构建了植物表达载体。然后通过根癌土壤杆菌 (Agrobacteriumtumefaciens (SmithetTownsend)Conn .)介导将此表达载体上的双抗虫基因转入杂种 741毛白杨 [PopulusalbaL .× (P .davidianaDode P .simoniiCarr.)×P .tomentosaCarr.]获得了一批抗卡那霉素的转化再生植株。用杨扇舟蛾 (Closteraanachoreta (Fabricius) )进行虫试的结果表明有 3株抗虫杨树 ,其中有1株杨树的叶片可使试虫在 6天内的死亡率达 90 %以上 ,而且存活幼虫的生长发育受到了明显的抑制。PCR检测及基因组DNASouthern杂交分析的结果都表明Bt杀虫蛋白基因和API基因已整合到以上 3株抗虫杨树的基因组中 ,而且表现为单拷贝整合。用Bt毒蛋白抗血清进行滤膜免疫反应及ELISA检测结果表明 3株转基因杨树都有Bt杀虫蛋白的表达 ,表达量约占叶总可溶性蛋白的 0 .0 15 %。这是国内外首次报道用双抗虫基因获得的抗虫 741毛白杨植株。     

The Potential of the Ni-Resistant TCE-Degrading Pseudomonas putida W619-TCE to Reduce Phytotoxicity and Improve Phytoremediation Efficiency of Poplar Cuttings on A Ni-TCE Co-Contamination

To examine the potential of Pseudomonas putida W619-TCE to improve phytoremediation of Ni-TCE co-contamination, the effects of inoculation of a Ni-resistant, TCE-degrading root endophyte on Ni-TCE phytotoxicity, Ni uptake and trichloroethylene (TCE) degradation of Ni-TCE-exposed poplar cuttings are evaluated.

After inoculation with P. putida W619-TCE, root weight of non-exposed poplar cuttings significantly increased. Further, inoculation induced a mitigation of the Ni-TCE phytotoxicity, which was illustrated by a diminished exposure-induced increase in activity of antioxidative enzymes. Considering phytoremediation efficiency, inoculation with P. putida W619-TCE resulted in a 45% increased Ni uptake in roots as well as a slightly significant reduction in TCE concentration in leaves and TCE evapotranspiration to the atmosphere.

These results indicate that endophytes equipped with the appropriate characteristics can assist their host plant to deal with co-contamination of toxic metals and organic contaminants during phytoremediation. Furthermore, as poplar is an excellent plant for biomass production as well as for phytoremediation, the obtained results can be exploited to produce biomass for energy and industrial feedstock applications in a highly productive manner on contaminated land that is not suited for normal agriculture. Exploiting this land for biomass production could contribute to diminish the conflict between food and bioenergy production.     

转基因植物对有机污染物的吸收、转化和降解

有机污染物是土壤、水体和大气环境的重要污染物.利用和加强植物修复作用是控制环境污染的有效途径.近年来,一些具有修复功能的外源基因被陆续引入到植物中,使转基因植物的生物修复能力大大增强.文章介绍了植物对污染环境中有机污染物,尤其是持久性有机污染物(POPs)的吸收、转化和降解作用,阐述了转基因植物用于被污染环境修复方面的研究进展和应用前景.     

杂种白杨离体再生体系的建立

以杂种白杨'717杨'(Populus tremula×Populus alba)和'353杨'(Populus tremula×Populus tremuloides)的叶片为材料,研究不同基因型、激素组合对叶片分化和不定芽生根的影响.结果表明:'717杨'叶片最适分化培养基是MS+0.5 mg/L 6-BA+0.2 mg/L NAA,'353杨'叶片最适分化培养基是MS+0.5 mg/L 6-BA+0.2 mg/L NAA+0.01 mg/L TDZ;最佳生根培养基为1/2 MS+0.2 mg/L IBA+0.2 mg/L NAA,生根率达100%;叶片培养的最佳位置是自茎尖展叶的1～3片叶;20 mg/L卡那霉素可以抑制'717杨'和'353杨'叶片的诱导分化,40 mg/L卡那霉素可以抑制'717杨'和'353杨'不定芽的生根.     

三倍体白杨杂种无性系指纹图谱的构建

目的:构建三倍体白杨杂种无性系指纹图谱,鉴定三倍体白杨杂种无性系。方法:分离纯化三倍体白杨杂种DNA模板,采用扩增片段长度多态性(AFLP)分子标记技术构建三倍体白杨杂种无性系指纹图谱。结果:从64对引物组合中筛选出M-CTA/E-CAG、M-CAC/E-CCA、M-ACT/E-CTC和M-CTT/E-CTG等4对多态性较高的引物组合,并应用该引物组合对21个三倍体白杨杂种无性系进行了AFLP分析,构建了21个三倍体白杨杂种无性系指纹图谱。结论:构建无性系指纹图谱是鉴别三倍体白杨杂种无性系的有效方法,能够有效鉴别21个三倍体白杨杂种无性系。本研究为品种鉴定及新品种权保护奠定了基础。     

Performance of Deep-Rooted Phreatophytic Trees at a Site Containing Total Petroleum Hydrocarbons

Poplar and willow tree stands were installed in 2003 at a site in Raleigh, North Carolina containing total petroleum hydrocarbon – contaminated groundwater. The objective was groundwater uptake and plume control. The water table was 5 to 6 m below ground surface (bgs) and therefore methods were used to encourage deep root development. Growth rates, rooting depth and sap flow were measured for trees in Plot A located in the center of the plume and in Plot B peripheral to the plume. The trees were initially sub-irrigated with vertically installed drip-lines and by 2005 had roots 4 to 5 m bgs. Water balance calculations suggested groundwater uptake. In 2007, the average sap flow was higher for Plot B (～59 L per day per tree) than for Plot A (～23 L per day per tree), probably as a result of TPH-induced stress in Plot A. Nevertheless, the estimated rate of groundwater uptake for Plot A was sufficient, relative to the calculated rate of groundwater flux beneath the stand, that a high level of plume control was achieved based on MODFLOW modeling results. Down-gradient groundwater monitoring wells installed in late 2011 should provide quantitative data for plume control.     

植物源挥发性有机物的生态意义(综述)

植物释放的挥发性有机气体(volatile organic compounds, VOCs)在对流层大气中通过一系列氧化还原反应,改变大气的化学组成,对臭氧合成、一氧化碳生成、甲烷氧化等有重要作用,其氧化物质对区域乃至全球的环境和气候都产生一定的影响。本文综述植物释放的VOCs对大气化学、温室效应、光化学烟雾的影响;介绍VOCs释放机制、合成途径及排放速率;对今后研究方向和大面积种植林木、城市绿化提出建议。     

Leaching of contaminated leaves following uptake and phytoremediation of RDX, HMX, and TNT by poplar

The uptake and fate of 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by hybrid poplars in hydroponic systems were compared and exposed leaves were leached with water to simulate potential exposure pathways from groundwater in the field. TNT was removed from solution more quickly than nitramine explosives. Most of radioactivity remained in root tissues for 14C-TNT, but in leaves for 14C-RDX and 14C-HMX. Radiolabel recovery for TNT and HMX was over 94%, but that of RDX decreased over time, suggesting a loss of volatile products. A considerable fraction (45.5%) of radioactivity taken up by whole plants exposed to 14C-HMX was released into deionized water, mostly as parent compound after 5 d of leaching. About a quarter (24.0%) and 1.2% were leached for RDX and TNT, respectively, mostly as transformed products. Leached radioactivity from roots was insignificant in all cases (< 2%). This is the first report in which small amounts of transformation products of RDX leach from dried leaves following uptake by poplars. Such behavior for HMX was reported earlier and is reconfirmed here. All three compounds differ substantially in their fate and transport during the leaching process.     

Uptake of Amino Acids and Other Organic Compounds by Lemna paucicostata Hegelm. 6746

A survey of the capacity of Lemna paucicostata to take up organic compounds such as might be present in the natural environment of this plant has identified eight discrete transport systems. Reciprocal inhibition studies defined the preferred substrates for these systems as follows: (a) neutral l-α-amino acids, (b) basic amino acids, (c) purine bases, (d) choline, (e) ethanolamine, (f) tyramine, (g) urea, and (h) aldohexoses. Each of these systems takes up its preferred substrates at high rates. At low concentrations, each Lemna frond during each minute takes up amounts which would be found in volumes ranging from 0.4 (tyramine) to 3.9 (urea) times its own volume. The two systems for amino acid transport both showed kinetics of the biphasic type, so that uptake by each can be described as the composite result of two Michaelis-Menten processes. The neutral amino acid system neither transports basic amino acids nor is inhibited by these compounds. The basic amino acid system does not transport neutral amino acids but is strongly inhibited by some, but not all, of these compounds. It is argued that the maintenance of these active, specific, and discrete systems in Lemna suggests they play important roles permitting this plant to utilize organic compounds occurring naturally in its environment.     

The Distribution of Mineral Elements Following Leaf and Root Uptake

The initial and subsequent distribution of ²²Na, ⁴³K, ⁸⁶Rb, ¹³⁴Cs, ³²P, ³⁵S, ⁴⁵Ca, ⁶⁵Zn and ⁸⁵Sr in bean plants, following leaf and root uptake was studied under controlled environmental conditions. Autoradiographic and counting methods reveal vascular connections between leaves and roots and two patterns of distribution in the leaves following root uptake are reported. Distribution following treatment of specific parts of the leaves or roots points to a morphological unity in the bean plant. A possible circulation pattern for some ions is discussed.     

Effects of Light Stress on Oxygen Evolution and Photochemical Energy Storage of Hybrid Poplar Clones Determined by Photoacoustic Technique

The oxygen evolution, thermal dissipation, and photochemical energy storage of three hybrid poplar clones, namely the triploid clone B342, the diploid clone B11［( Populus alba×P. glandulosa)×(P.tomentosa×P.bolleana)］ , and the triploid clone B346 ［ (P.tomentosa×P. bolleana)×(P. alba×P.glandulosa )］, under light stress were studied using photoacoustics. The oxygen evolution signal and photochemical energy storage varied negatively with the pretreatment-PFD (photon flux density), whereas the thermal signal varied positively with the pretreatment-PFD. Photochemical energy storage was reallocated to PSⅡ more than to PSⅠ, while the photochemical energy storage in PSⅠ was more stable than that in PSⅡ when subjected to light stress. The inhibitors streptomycin (SM), dithiothreitol (DTT) and sodium fluoride (NaF) could all affect the oxygen evolution signal. Clones B11 and B342 were more resistant to light stress than clone B346.     

鞭角华扁叶蜂对自然生境柏木挥发物释放的影响

植物挥发物（Volatile organic compounds;VOCs）在植物抵御害虫侵袭的过程中具有重要作用。本研究以重庆市云阳县长江林场人工林中健康和受害柏木为研究对象,通过VOCs测定分析发现鞭角华扁叶蜂虫害发生之前,两种柏木共计有37种VOCs成分,主要为萜类化合物,其次为醇、酯、醛、烷烃等类化合物;其中健康柏木特有驱赶作用的2-莰醇（龙脑）,受害柏木特有吸引作用的顺式-2-癸烯醛,其余35种为共有成分;各成分浓度在两种柏木中存在较大差异。虫害发生之后,两种柏木共计有32种VOCs成分,而2-莰醇、顺式-2-癸烯醛、薄荷醇、臭樟脑和α-石竹烯等5种成分消失;许多成分的浓度变化趋势与虫害发生前的相反。结果表明健康与受害柏木VOCs释放的差异可能是柏木能否抵御鞭角华扁叶蜂侵害的主要防御机制之一,这将为优良抗虫柏木选育提供理论依据和参考指标。     

杉木挥发性有机物释放特征研究

为了明确杉木(Cunninghamialanceolata)挥发性有机物(VOCs)的成分组成和含量的变化规律,采用动态顶空采集法和热脱附-气质联用(TDS-GC-MS)技术,对杉木释放的VOCs成分组成和相对含量的季节性变化进行分析。结果表明,杉木释放的VOCs中共鉴定出60种化合物,一年中释放的化合物种数随季节变化呈先升后降的趋势,夏季释放种类最多,达42种。检测到的烷烃类、醛类、酯类和醇类化合物种类最多,占检测到的化合物总种类数的73.33%。春季杉木释放的VOCs以醇类化合物为主,总相对含量为27.19%;夏季以萜烯类化合物为主,总相对含量为17.29%;秋季以醛类化合物为主,总相对含量为23.55%。综上,杉木具有一定的康养功效,夏季是在杉木林中进行康养活动的最佳时期。