2-硝基芴DNA加合物的研究

2-硝基芴直接与小牛胸腺DNA反应(in vitro),用~(32)P后标记方法能够测定出有多种DNA加合物生成.将定量的2-硝基芴一次注射入大鼠(SD)和经过Aroclor诱导的大鼠腹腔内,24h后取其肝、肾、肺、脾、血等诸器官,用P_1加强灵敏度的~(32)P后标记方法测定各组织中的DNA加合物.其结果是:在诱导和非诱导的大鼠体内各器官中均发现有DNA加合物的存在,Aroclor诱导对DNA加合物的生成有明显的促进作用.在非诱导的大鼠体内肝脏和血中,分别测出与体外反应相对应的多个DNA加合物,证明2-硝基芴有直接损伤生物体内DNA,形成DNA加合物的能力.     

^32P后标记法测DNA加合物

＾３２Ｐ后标记方法测ＤＮＡ－致癌物的加合物过程是用小球菌核酸酶和脾核酸酶将ＤＮＡ及加合物酶解成２′－脱氧核苷３′－单磷酸（３′－ｄＮｍＰ＋３′－ｄｘｍＰ）,以它为底物,用Ｔ４多核苷酸激酶催化,使γ＾３２ＰＡＴＰ的放射＾３２Ｐ转移反应到底物上,形成２′－脱氧核苷３′５′．ｄＮＤＰ＋３′５′＊ｄｘＤＰ）,用ＯＤＳ－ＴＬＣ和ＰＥＩ－ＴＬＣ结合将标记过的二磷酸分离分辨,用自显影制成加合物的指纹图,液闪计数     

用^32P后标记方法测定典型有毒污染物的DNA加合物

＾３２Ｐ后标记方法测定生物样品里的有毒污染物－ＤＮＡ加合物的过程是用小球菌核酸酶和脾核酸酶将ＤＮＡ及加合物酶解成为２‘－脱氧核苷３’－单磷酸，以它为底物，在Ｔ４多核到激酶的催化下，与γ＾３２ＰＡＴＰ进行文笔磷的转移反应，形成带放射磷的２‘－脱氧核苷３’，５‘－二磷酸酯ＯＤＳ－ＴＬＣ吸附薄层板和ＰＥＩ－ＴＬＣ阴离子交换薄层板将标记过的带放射磷的＾＊３’，５‘－二磷酸酯分离分辨，然后用自显影技术制成加     

用~(32)P后标记方法测定职业接触苯乙烯工人静脉血中DNA-环氧苯乙烯加合物

用~(32)P后标记方法,对一组22例接触苯乙烯的工人和8例未接触苯乙烯(空白)的工人进行测试,其静脉血中的淋巴细胞有4例(高浓度,大于40ppm)发现DNA-环氧苯乙烯加合物;而另外接触高浓度苯乙烯、低浓度苯乙烯和空白试样中,均未发现。在已测出的4例中,加合物形成水平为0.07—3.38加合物/10~7正常核酸,DNA的总损伤水平为5—9加合物/10~7正常核酸。 用小牛胸腺DNA、四种脱氧核苷3′-单磷酸分别与环氧苯乙烯进行体外反应,然后用~(32)P后标记法测定产物中的DNA加合物,初步确证有六种加合物及其衍生物存在,修饰位置是鸟苷碱基。并确证了其中三种加合物的化学结构,另外几种加合物的结构有待进一步鉴定。 ~(32)P后标记法测DNA加合物,灵敏度高达1加合物/10~(10)正常核酸,近于人体二倍体细胞基因水平(1.2×10~(10)碱基)。     

The “Tsesis” oil spill: Acute and long-term impact on the benthos

The “Tsesis” oil spill in October 1977 resulted in the release of over 1 000 tons of medium grade fuel oil in an archipelago in the brackish Baltic Sea. Considerable oil quantities reached the benthos by sedimentation. Within 16 d benthic amphipods of the genus Pontoporeia, as well as the polychaete Harmothoe sarsi Kinberg, showed reduction to less than 5% of pre-spill biomasses at the most impacted station. The clam Macoma balthica (L.) was more resistant, and showed little or no mortality, but was heavily contaminated by oil (about 2 000 μg g^-1 dry wt total hydrocarbons). The meiofauna was strongly affected, with ostracods, harpacticoids, Turbellaria and kinorhynchs showing clear reductions in abundance, while nematodes, as a group, were more resistant. In the winter following the spill gravid Pontoporeia affinis Lindström females showed a statistically significant increase in the frequency of abnormal or undifferentiated eggs. Food-chain transfer of oil to flounder [Platichthys flesus (L.)] was indicated. Not until the second summer after the spill were the first signs of recovery noted at the most heavily impacted station: Amphipods, H. sarsi and harpacticoids increased and the oil concentrations in M. balthica decreased (to about 1 000 μg g^-1). In the area where amphipods had been virtually eliminated, there was an unusually heavy recruitment of M. balthica, reaching 4 000 juveniles, of 1.5–2 mm length, per square metre, probably from settling in summer 1978. Three years after the spill Pontoporeia spp. biomass was still depressed in the most affected area, while H. sarsi showed normal biomass, and M. balthica abundance was inflated. Oil concentrations in M. balthica (about 250 μg g^-1) and flounder were only slightly elevated and the oil could no longer be confidently ascribed to “Tsesis” origin, even using GC/MS-analysis. Recovery was thus underway, but the long lifespan of M. balthica implies that the disturbed community composition may persist for many years at this station. Full recovery is likely to require more than 5 yr and may take a decade or more. An effort to evaluate the accumulated monetary loss to fishery from the accident indicates that direct costs of shoreline cleanup and vessel damage were considerably greater.     

Short-term effects of an oil spill on the West coast of the Cape Peninsula, South Africa

In 1994, the sinking of the ‘Apollo Sea’ off the West coast of South Africa led to the deposition of ca. 2 500 tons of heavy fuel oil over 150 km of coastline. The impact of the spill on rocky shore invertebrates, rock-pool fish fauna and rock lobsters was assessed by conducting surveys shortly after the spill, and again two months later. Where possible, results of these surveys were compared with existing data from before the sinking of the Apollo Sea. Among the fish fauna of rock-pools, changes in total density of fishes were largely due to changes in the abundance ofClinus superciliosus and were within the range of natural variation for the species and the community as a whole. Community structure of the rock-pool fish fauna also remained unaffected. At three of four impacted rocky shore sites no changes could be detected in overall benthic community structure, although the winkleNodilittorina africana was affected. At the fourth site, a boulder beach, statistical analysis showed distinct differences in community structure between heavily and lightly contaminated areas, as well as between all areas compared with previously existing data. There were also significant changes in the lightly oiled areas between the first and second surveys after the spill. Oil-fouled lobster were found at one of three sites investigated. Ca. 7 % of the seabed in this particular area was polluted. Antennae and forelegs of almost all lobsters in the vicinity of the oil were fouled. Examination of the gut-contents confirmed that oil inhibits the ability of lobster to feed. Although there was no evidence that mortalities of lobster were caused by the spill, growth rates may be reduced by the decreased feeding rate. Overall, the impact of the spill was strikingly less than might have been predicted from the effects of other oil spills. Nomenclature: Names of fish species follow Smith & Heemstra (1986).     

Maritime oil spills— Environmental lessons and experiences with special reference to low-risk coastlines

Oil spill contingency plans are available for most coastlines but the amount of useful environmental data is variable. The information should be held on a GIS base. High risk areas should be identified and the pre-existing store of environmental knowledge should be commensurately extensive and should be available in considerable spatial detail. Contingency plans still depend on basic lists of coastal types as defined by static, sediment based shoreline characteristics. There is a lack of dynamic, process information. TheBraer oil spill of 1993 provides a case study of the application of sound coastal geomorphological and ecological data to impact assessment. Monitoring of the ecological effects of this massive oil spill reinforces other research which indicates that most coastlines can recover naturally from oil spills, and that oil spill clean up techniques may not necessarily benefit rapid shoreline recovery. Although pre-existing environmental informations is important, the key decisions must be taken quickly and are frequently judgmental and, therefore, place a premium on gathering appropriate scientific expertise to the site of the spill as soon as possible and with sufficient powers to affect both the oil spill response, to initiate early surveys of damage and to facilitate the initial monitoring programme.     

Gene flow at three spatial scales in a coral reef fish, the three-spot dascyllus, Dascyllus trimaculatus

Dispersal in coral reef fishes occurs predominantly during the larval planktonic stage of their life cycle. With relatively brief larval stages, damselfishes (Pomacentridae) are likely to exhibit limited dispersal. This study evaluates gene flow at three spatial scales in one species of coral reef damselfish, Dascyllus trimaculatus. Samples were collected at seven locations at Moorea, Society Islands, French Polynesia. Phylogenetic relationships and gene flow based on mitochondrial control region DNA sequences between these locations were evaluated (first spatial scale). Although spatial structure was not found, molecular markers showed clear temporal structure, which may be because pulses of settling larvae have distinct genetic composition. Moorea samples were then compared with individuals from a distant island (750 km), Rangiroa, Tuamotu Archipelago, French Polynesia (second spatial scale). Post-recruitment events (selection) and gene flow were probably responsible for the lack of structure observed between populations from Moorea and Rangiroa. Finally, samples from six Indo-West Pacific locations, Zanzibar, Indonesia, Japan, Christmas Island, Hawaii, and French Polynesia were compared (third spatial scale). Strong population structure was observed between Indo-West Pacific populations. Received: 26 May 2000 / Accepted: 10 October 2000     

消油剂与120#燃料油对马粪海胆(Hemicentrotus pul-cherrimus)抗氧化酶活性的影响

在溢油事故应急处置中,消油剂的使用备受争议。为探究消油剂和溢油对海洋底栖模式生物海胆(Hemicentrotus pulcherrimus)复合毒性效应,通过WAFs(Water-accommodated fractions)和CEWAFs(Chemically enhanced water-accommodated fractions)的96 h暴露实验,测定海胆肠和性腺中过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、谷胱甘肽硫转移酶(GST)、谷胱甘肽过氧化物酶(GPx)活性的变化。实验结果表明:随油水配比浓度的增加,4种酶活性呈现先升高后降低趋势,且酶活性峰值均极显著高于海水对照组水平(P0.01)。肠中4种酶活性最大诱导倍数均高于性腺。相同暴露浓度下,CEWAFs组4种酶活性诱导程度均高于WAFs组。消油剂对照组和海水对照组间4种酶活性则无显著性差异(P0.05)。     

Cytochrome P450 1A activity in liver and fixed wavelength fluorescence detection of polycyclic aromatic hydrocarbons in the bile of tongue-fish (Cynoglossus acrolepidotus, Bleeker) in relation to petroleum hydrocarbons in the eastern Gulf of Thailand.

This investigation was conducted in an area of oil spill along the east coast of Thailand to examine the relations among cytochrome P450 1A activity in liver and PAHs in the bile of the tonguefish and petroleum hydrocarbons in the sediments. PAH sediment concentrations in the reference and oil spill areas were 5.03 +/- 0.42 and 0.21 +/- 0.043 microg(-1) dry weight respectively Cytochrome activity in fish liver from oil spill area was 45.40 +/- 3.50 pmoles/ min/mg protein, almost threefold higher than that from the reference sites. Flourescense detection in bile metabolites at the oil spill area, 69.8 +/- 9.9 flourescense unit was significantly higher than that at the reference sites, 22.9 +/- 5.5 and 22.2 +/- 3.5 fluorescence unit. A strong correlation was found among cytochrome P450 1A activity in liver, PAH of bile metabolites and petroleum hydrocarbons. Both cytochrome and bile metabolites activity decreased seaward varying to the distance from the oil polluted area. We concluded that both detections in tonguefish can be regarded as a complementary biomarkers for the exposure of PAHs in tropical marine environments.     

Recovery of benthic communities at Macquarie Island (sub-Antarctic) following a small oil spill

Intertidal communities at Macquarie Island (sub-Antarctic) were re-evaluated seven years after a small oil spill resulting from the grounding of the “Nella Dan”, and six years after the first assessment of biological impact. Sampling was conducted to evaluate community structure in three zones of the exposed rocky shore (upper red, kelp, and lower red) and in samples of Durvillaea antarctica holdfasts. There were no significant differences between the community structure in oiled and control locations in any of the three shore zones, but holdfast macrofaunal communities at oiled sites still showed evidence of impact. Holdfast community-structure in samples from heavily oiled sites showed moderate levels of recovery, with increased abundances of species which were considered sensitive to the oiling in the first post-impact studies and decreased abundances of opportunistic polychaete and oligochaete worms. In contrast, samples collected from the moderately oiled location at Secluded Bay showed little evidence of recovery. Holdfasts at this site were filled with sediment containing traces of diesel oil, and the macrofaunal community was dominated by opportunistic worms. This study clearly indicates that even small incidents of anthropogenic perturbation can have long-lasting consequences for marine communities at Macquarie Island. Received: 23 July 1997 / Accepted: 5 February 1998     

6种苯系物对球等鞭金藻和新月菱形藻的生长抑制

海洋环境中苯系物污染主要来源于海洋溢油事故以及沿海石油化工企业的废水排放。为探究苯系物对海洋微藻的毒性作用,选择球等鞭金藻和新月菱形藻作为受试生物,分别考察了苯、甲苯、乙基苯、邻-二甲苯、间-二甲苯和对-二甲苯6种苯系物对2种海洋微藻生长的影响。结果表明,在0.25~64.0 mg·L-1暴露浓度下,6种苯系物对2种微藻生长具有显著的抑制作用,随着暴露浓度的升高,抑制作用明显增强。苯、甲苯、乙基苯、邻-二甲苯、间-二甲苯、对-二甲苯对球等鞭金藻的24 h的半数效应浓度(24 h-EC50)分别为:17.07、12.88、7.58、0.55、0.36、0.27 mg·L-1;对新月菱形藻的24 h-EC50值分别为:1.03、0.68、0.46、0.40、0.42、0.38 mg·L-1。上述研究结果为确定苯系物海洋环境质量标准、保护海洋生态环境提供了基础数据。     

基于物种敏感性分布的保护海水水生生物的石油烃急性毒性基准研究

溢油污染对水生生物的危害以及分散剂使用对原油毒性的影响一直是溢油应急响应及危害评估时关注的焦点。本研究收集筛选了基于标准测试方法的90组急性毒性数据(LC50/EC50),其中37组毒性数据来自15种油品的水容纳组分(water accommodated fraction,WAF),53组来自11种化学分散剂与15种油品的分散液(chemically dispersed water accommodated fraction,CEWAF),应用物种敏感性分布(species sensitivity distribution,SSD)方法推导了基于水生生物保护的石油烃总量(total petroleum hydrocarbon,TPH)的急性毒性基准值,同时还分析了分散剂和不同暴露方式对原油毒性的影响。结果显示,以名义浓度(nominal concentrations)所表示的毒性结果可能高估分散剂对原油毒性的影响,基于CEWAF和WAF的LC50/EC50所推导的有害浓度(HC5s)差异较小,计算出的保护水生生物TPH急性毒性基准值为0.38 mg·L-1(TPH);鱼类对原油污染的响应明显敏感于甲壳类;同时证明了SSD方法在溢油毒性评估及风险阈值推导中具有可行性和合理性。     

Relationship between growth and biochemical indices in laboratory-reared juvenile Japanese flounder (Paralichthys olivaceus), and its application to wild fish

In order to estimate growth rates based on biochemical indices of the liver of wild Japanese flounder (Paralichthys olivaceus), juveniles were reared at six ration levels (0, 0.5, 2, 4, 6 and 8% body weight day⁻¹) in the laboratory for 14 days, and the relationship between their growth rates and biochemical indices (RNA/DNA, protein/DNA, triglyceride/DNA, phospholipid/DNA and cathepsin D activities) were determined. Positive and approximately linear relationships were seen between growth rates and the indices of RNA/DNA, protein/DNA and phospholipid/DNA. The triglyceride/DNA ratio decreased with increasing growth rates up to approximately 1% body weight day⁻¹, then increased linearly with increasing growth rates. There was no significant correlation between growth rates and cathepsin D activity, and the highest values were obtained in the starved fish. Compared with laboratory-reared specimens, wild specimens of similar sizes were found to have significantly larger livers. The RNA/DNA, protein/DNA and phospholipid/DNA ratios of wild specimens fell in a broad range between ration groups of reared juveniles. The protein/DNA ratios of wild specimens were low and outside the range of the reared juveniles at six ration levels. In contrast, the levels of cathepsin D activity of wild fish were highest compared to the reared fish. Estimated growth rates of wild fish from the RNA/DNA, protein/DNA and phospholipid/DNA regressions obtained from the rearing experiment were 1.66, −1.74 and 0.10% day⁻¹, respectively. Based on our results, the RNA/DNA index may be regarded as the most valid and reliable growth estimator. It is noted that the larger liver size, the lower liver protein/DNA ratio and the unexpectedly high level of cathepsin D activities of wild specimens found in this study may reflect the different metabolic conditions of fish reared in the laboratory compared to those collected in the field. Received: 29 February 2000 / Accepted: 26 August 2000     

A graphical assessment and spatial clustering of the Deepwater Horizon oil spill impact on Laughing Gulls

The Deepwater Horizon oil spill occurred in the Gulf of Mexico on April 20, 2010. Considered the largest accidental marine oil spill in history, oil flowed for three months and approximately five million barrels of oil spilled through by mid-July 2010. In this article, we analyze bird data to assess the impact of the oil spill on the Gulf wildlife. Particularly, we want to determine in which regions Laughing Gulls were mostly affected by the oil spill, and whether those regions spatially shifted throughout the year 2010. Though our data sets have some limitations to apply statistical analysis methods, we obtained very interesting results. Our analyses showed the general consistency of the results based on two population data sets (from the 2011 Data Expo and from the eBird community) and justified the use of both publicly available data sets. We showed that the closer the surface oil spill area approached to the Laughing Gulls habitats, the more significant clusters of bird cases were observed.     

Lack of genotoxic potential of permethrin in mice evaluated by the comet assay and micronucleus test

Permethrin is a common insecticide that does not show genotoxic potential in standard in vitro and in vivo assays. To investigate the genotoxic potential of permethrin in more detail, two in vivo studies were conducted on female mice to assess DNA damage in tumor target organs by the comet assay and micronucleus test. For this, mice were administered permethrin at doses of 150, 300, or 600 mg/kg/day by gavage for 2 days, and their lung, liver, glandular stomach, peripheral blood, and bone marrow cells were examined for DNA damage. There were no significant increases in % tail DNA in the organs examined and no increase in micronuclei in peripheral blood by flow cytometry. Taken together, the present findings provide evidence that permethrin has no genotoxic, aneugenic, or clastogenic potential.     

Microsatellite analysis of albacore tuna (<Emphasis Type="Italic">Thunnus alalunga</Emphasis>): population genetic structure in the North-East Atlantic Ocean and Mediterranean Sea

Stock heterogeneity was investigated in albacore tuna (Thunnus alalunga, Bonnaterre 1788), a commercially important species in the North Atlantic Ocean and Mediterranean Sea. Twelve polymorphic microsatellite loci were examined in 581 albacore tuna from nine locations, four in the north-east Atlantic Ocean (NEA), three in the Mediterranean Sea (MED) and two in the south-western Pacific Ocean (SWP). Maximum numbers of alleles per locus ranged from 9 to 38 (sample mean, 5.2–22.6 per locus; overall mean, 14.2 ± 0.47 SE), and observed heterozygosities per locus ranged from 0.44 to 1.00 (overall mean: 0.79 ± 0.19 SE). Significant deficits of heterozygotes were observed in 20% of tests. Multilocus F _ST values were observed ranging from 0.00 to Θ = 0.036 and Θ′ = 0.253, with a mean of Θ = 0.013 and Θ′ = 0.079. Pairwise F _ST values showed that the SWP, NEA and MED stocks were significantly distinct from one another, thus corroborating findings in previous studies based on mitochondrial DNA, nuclear DNA (other than microsatellites) and allozyme analyses. Heterogeneity was observed for the first time between samples within the Mediterranean Sea. GENELAND indicated the potential presence of three populations across the NEA and two separate populations in the Mediterranean Sea. Observed genetic structure may be related to migration patterns and timing of movements of subpopulations to the feeding grounds in either summer or autumn. We suggest that a more intensive survey be conducted throughout the entire fishing season to ratify or refute the currently accepted genetic homogeneity within the NEA albacore stock.     

Relationship between filtration activity and food availability in the Mediterranean mussel <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis>

The filtration activity of the Mediterranean mussel, Mytilus galloprovincialis, was assessed under different concentrations and compositions of seston by using a new automated image acquisition and analysis system. This approach allowed for frequent and simultaneous measurements of valve gape and exhalant siphon area. Filtration rates were measured through clearance measurements whereas pumping rates were measured using hot-film probes. The average filtration rate (17.5 l g h⁻¹ DW⁻¹ for a 0.36 g DW mussel) recorded during the present study was higher than those available for Mytilus edulis when standardized to flesh dry weight but almost equivalent (17.5 l h⁻¹ g DW⁻¹ for a 53 mm shell length mussel) to those rates when standardized to shell length. Immediately after the addition of algal cells (Isochrysis galbana; 4.5 μm in size), valve gape, exhalant siphon area and filtration rate increased quickly as mussels reached their maximum filtration activity. These three parameters then gradually decreased until complete closure of the shell. The algal cell concentration inducing this transition was close to 800 cells ml⁻¹ and 0.5 μg Chl a l⁻¹. When algal concentration was maintained above this threshold by successive algal additions, both valve gape and exhalant siphon area remained maximal. Temporal changes in the exhalant siphon area were continuous as opposed to those of valve gape. Therefore, despite the significant correlation between these two parameters, valves and siphon were sometimes dissociated due to a reduction of the area or even a closure of the exhalant siphon while the valves remained open. The velocity of exhaled water tended to be constant irrespective of exhalant siphon area and thus pumping rates were a linear function of exhalant siphon area. Consequently, reductions in exhalant siphon area and pumping rate were almost similar in M. galloprovincialis. Our results thus clearly support the hypothesis that exhalant siphon area constitutes a better proxy of pumping rate than valve gape as already suggested for Mytilus edulis. Finally, the high filtration rates measured during the present study together with the high concentrations of inorganic matter (> 40 mg DW l⁻¹) requested to alter those rates suggest that the studied mussels were well adapted to oligotrophic waters featuring strong hydrodynamism and frequent sediment resuspension events.     

S -phenylcysteine adduct concentration in serum albumin of countryside residents and factory workers in Estonia

In this communication we present data on S-phenylcysteine (SPC) in human serum albumin in an Estonian cohort. A total of 112 human samples were collected from workers of a benzene processing plant in Kohtla-Järve, Estonia and another 56 samples from nearby countryside residents. Albumin was isolated using a sequential precipitation method designed for low volume plasma samples. The adducted cysteine derivatives were cleaved off from the albumin and subsequently derivatized to phenyl trifluorothioacetate (PTTA) derivatives. Derivatized adducts were subjected to GC/MS analysis utilizing negative chemical ionization and a selected ion monitoring (SIM) technique. The detection limit for the PTTA adduct was 0.2?pmol?g^?1 albumin and the limit of quantification was 2?pmol?g^?1 albumin. The method utilized deuterated SPC as an internal standard. The analysis revealed that adduct levels were also high in the population that was not occupationally exposed to benzene. The reason for this is unknown, but may cause problems if not of environmental origin, when one is attempting to monitor low level occupational or environmental benzene exposure.     

Sequestration of As by iron plaque on the roots of three rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) cultivars in a low-P soil with or without P fertilizer

A pot experiment was carried out in a greenhouse to investigate the sequestration of As in iron plaques on root surface of three rice (Oryza sativa L.) cultivars. Phosphate (P) fertilization increased both plant biomass and tissue P concentrations significantly, indicating that the soils used in this study was highly P-deficient. Results from this study confirmed that low P supply improved the formation of iron plaque on rice roots. As a consequence, arsenic (As) concentrations in DCB-extracts with no P addition were significantly higher than those with P fertilization. Arsenic was highly sequestrated in iron plaque; arsenic concentration in iron was up to nearly 120 mg kg⁻¹, while arsenic concentrations in roots were just several mg kg⁻¹. Both arsenic and phosphate concentrations in iron plaque were highly positively correlated with the amounts of iron plaque (DCB-extractable Fe). Contrary to normal understanding that increasing P supply could reduced As accumulation in plants, results from the present study showed that P fertilization did not inhibit the As uptake by plants (As accumulation in aboveground), which was probably due to the fact that iron plaque formation was improved under low P conditions, thus leading to more As sequestration in the iron plaque. Thus results obtained in this study indicated that the iron plaque may inhibit the transfer of As from roots to shoots, and thus alter the P–As interaction in plant As uptake processes.