鬼针草(Bidens pilosa L.)对镉污染农田的修复潜力

为探究富集植物鬼针草对镉(Cd)污染农田土壤的修复潜力,通过野外调查,原土盆栽试验和田间试验,测定鬼针草及其根系土壤Cd含量,计算鬼针草的富集系数和去除率。结果表明,野外调查中不同铅锌矿区生长的鬼针草叶片中Cd含量最大值为53.3 mg/kg。盆栽试验中,低浓度Cd土壤处理(T1),鬼针草地上部Cd的富集系数为4.70,转运系数1.59,大于1。高浓度Cd土壤处理(T2 13.4 mg/kg),其地上部Cd积累量达到43.1 mg/kg,其地上部Cd富集系数为3.51。鬼针草对Cd表现出稳定的积累特性。田间试验小区中,土壤Cd含量均值为2.66 mg/kg,鬼针草中地上部Cd含量均值为10.9 mg/kg,富集系数为4.16,使用鬼针草修复Cd污染土壤每公顷地种植一茬鬼针草的去除率为4.3%—6.2%。使用富集植物鬼针草修复农田Cd污染具有较好的工程应用前景。     

珊瑚树（Viburnum odoratissinum）对污染土壤中镉的耐受和富集特征

通过温室盆栽试验,研究珊瑚树对土壤中镉(Cd)的耐受和富集特征。研究结果表明,珊瑚树对污染土壤中Cd具有较强的耐受能力。培养56 d内,土壤中Cd含量对珊瑚树生物量影响不明显;随着培养时间的延长(105—203 d),珊瑚树的生长明显受到土壤中Cd的抑制作用。与对照处理(土壤中Cd含量为3.6 mg/kg)相比,培养154 d后,土壤中Cd含量为24.6 mg/kg处理下珊瑚树叶片中叶绿素a、叶绿素b、类胡萝卜素和丙二醛(MDA)含量没有明显变化;培养203 d后,土壤中Cd含量为24.6mg/kg处理下珊瑚树叶片中类胡萝卜素和MDA含量无明显变化,但叶片中叶绿素a和叶绿素b含量明显受到抑制,从而导致珊瑚树叶片的生长明显受到抑制(P0.05)。培养203 d后,珊瑚树对土壤中Cd的富集系数和转运系数均大于1,表明珊瑚树对土壤中Cd具有一定的富集和转运能力。上述结果表明,珊瑚树对Cd污染土壤具有一定的生态修复潜力。     

水生植物有翅星蕨(Microsorum pteropus)对镉的超富集能力及抗性生理研究

超富集植物能耐受高浓度的重金属并将其储存于植物各组织中,对于重金属污染环境的修复具有重要意义.本文以沉水植物有翅星蕨(Microsorum pteropus)为研究对象,设置了低浓度镉暴露组(0,0.1,1,5,10,20 mg/L)和高浓度镉暴露组(0.20,40,60,80,100 mg/L),暴露7天,发现有翅星蕨各组织镉富集浓度的大小顺序为:不定根羽片叶柄根状茎,在0.1mg/L镉暴露情况下,不定根的最大生物富集系数达920.21.各暴露组有翅星蕨对培养液中Cd的去除效率为39.12%~53.99%.当镉暴露浓度为60mg/L时,不定根和羽片中镉的富集浓度分别达到了(3738.39±348.03)及(10652.53±2477.74)mg/kg,具有极强的镉富集能力.同时,各暴露组有翅星蕨的叶绿素、丙二醛、过氧化物酶与超氧化物歧化酶活性、以及叶绿素荧光参数等生理生化和光合作用指标相较对照组并未出现显著的变化.研究表明,有翅星蕨对水体中的Cd具有超强的富集能力,可用于镉污染水体的修复.     

镉胁迫对小报春幼苗生长及生理特性的影响

该研究采用盆栽控制试验,测定不同浓度(0、5、50、100、150、200 mg/kg)土壤Cd胁迫下小报春幼苗生长及生理生化指标,以探究小报春(Primula forbesii Franch.)对重金属镉(Cd)污染的抗性和敏感性,为新型香花地被植物应用于Cd污染土壤提供理论依据。结果表明:(1)低浓度(5 mg/kg)Cd胁迫能促进小报春株高和根长的伸长,高浓度(≥150 mg/kg)Cd胁迫下株高、根长和生物量明显降低。(2)随Cd胁迫浓度增加,小报春幼苗叶片光合作用、叶绿素含量、SOD和CAT活性先上升后下降,而其超氧阴离子产生速率、过氧化氢、丙二醛含量、叶相对电导率和POD活性持续升高。(3)在Cd胁迫条件下,小报春体内K、Zn含量降低,叶和根中Ca、Mg含量显著增加,体内Cd含量明显升高,且根系Cd含量远远高于叶和叶柄。研究发现,小报春幼苗对Cd胁迫具有一定的耐性,低浓度(5 mg/kg)Cd胁迫对小报春生长影响较小,但高浓度(≥150 mg/kg)Cd胁迫对小报春产生明显的毒害作用,影响其正常生长;小报春可能通过增强体内抗氧化酶系统活性、增加叶和根中Ca、Mg含量和根系截留镉来减轻镉胁迫的伤害,提高自身耐受镉胁迫能力。     

铅镉抗性菌株JB11强化植物对污染土壤中铅镉的吸收

研究了铅、镉抗性菌株(JB11)和生物降解螯合剂乙二胺二琥珀酸(S,S)-EDDS)提高高羊茅和红三叶草吸收土壤中铅、镉的能力。从土壤样品中筛选出1株对Cd、Pb具有较强抗性的菌株JB11,经鉴定为成团泛菌属(Pantoea agglomerans)。JB11对Pb2+、Cd2+、Cr6+、Cu2+、Zn2+、Ni2+等多种重金属和卡那霉素、氨苄青霉素、链霉素、四环素等抗生素具有抗性,在温度15—35℃和pH为5.0—9.0范围内生长良好,最适生长温度为30℃,最适pH值为7.0左右,在低于3%的NaCl浓度下生长良好。盆栽试验研究了菌株JB11、EDDS及1/2EDDS+JB11 3种处理下对生长在Cd 100 mg/kg、Cd 200 mg/kg、Pb 500 mg/kg和Pb 1000mg/kg的土壤中的高羊茅和红三叶生长及从土壤富集Cd、Pb能力的影响。结果表明,外加JB11能使高羊茅和红三叶的干重分别比对照都有增加。除外加JB11后在经Pb 1000 mg/kg处理的土壤中高羊茅地上部的Pb浓度、经Cd 200 mg/kg处理的土壤中红三叶地上部的Cd浓度以及经Cd 100 mg/kg处理的土壤中高羊茅和红三叶根部的Cd浓度以外,外加JB11后对其他重金属处理植物中Pb和Cd的含量都显著增加。外加EDDS后除在经Pb 500 mg/kg的土壤中高羊茅根部的Pb浓度增加差异不显著,对其余重金属处理都可产生显著的影响(P0.05)。1/2EDDS+JB11的复合处理下植物重金属吸收量多数高于JB11和EDDS单独处理,JB11用于植物修复土壤Pb和Cd污染具有很大的潜力。     

一种新发现的镉超积累植物--钻叶紫菀(Aster subulatus Michx.)

通过野外调查和温室营养液砂培试验,发现并鉴定出钻叶紫菀（Aster subulatus Michx.）是一种新的镉（Cd）超积累植物。调查结果发现,钻叶紫菀对土壤中高含量的Cd有很强的忍耐、吸收和积累能力,其地上部茎、叶Cd含量分别为90.0-150.7mg/kg和119.8-172.6mg/kg,平均值分别为132.8mg/kg和139.2mg/kg。砂基营养液培养试验证明,钻叶紫菀对生长介质中的Cd有很强的忍耐能力,当生长介质中Cd浓度高达150mg/L时,植株仍生长正常,其株高与对照相比无显著差异;地上部Cd含量及其积累量均随生长介质中Cd浓度的增加而增加,当生长介质中Cd浓度为120mg/L时,地上部茎Cd含量和积累量达到最高值,分别为5672.50mg/kg、4.93mg/株。结果表明,钻叶紫菀是一种新的Cd超积累植物,为今后探明植物超积累Cd的机理和Cd污染土壤的植物修复提供一种新的种质资源。     

施肥对两种苋菜吸收积累镉的影响

通过盆栽试验,研究了生长在5 mg/kg镉(Cd)污染土壤中的两种苋菜(红苋(Amaranthus Paniculatus L.)和绿苋(Amaranthus Paniculatus L.))在3种施肥处理下(N、NP和NPK)的生长状况和对Cd的吸收积累情况。结果表明,两种苋菜能够在污染土壤中正常生长,各器官中叶Cd含量最高,范围为124.1—225.9 mg/kg;根中次之,范围为57.1—100.6 mg/kg;茎中最低,范围为56.2—87.6 mg/kg;富集系数高达22.4—40.2。施加N,NP,NPK肥对两种苋菜器官中的Cd含量和生物量有显著影响。其中,施加NPK肥使红苋和绿苋的生物量分别达到不施肥(对照)处理的3.5和3.2倍,单株提取Cd的总量是对照3.2和5.0倍。综上表明,两种苋菜(红苋和绿苋)具有生物量大、易栽培、施加NPK肥能够大幅增加生物量的同时不减少器官对Cd的吸收等优点,作为Cd污染土壤的修复植物有巨大应用前景。     

镉在土壤-香根草系统中的迁移及转化特征

以无植物组处理为对照,采用盆栽试验方式探讨不同Cd浓度胁迫条件下香根草根际土壤中重金属Cd的积累、迁移及转化特征。土壤Cd处理设4个浓度梯度,分别为0、2、20、80 mg/kg土壤干重。结果表明:(1)香根草可以显著降低土壤中生物有效态Cd和总Cd含量。(2)香根草各部分Cd积累量随处理浓度的增加和处理时间的延长而增加,90 d时80 mg/kg处理组地上部分和根的Cd积累量分别高达180.42 mg/kg和241.54 mg/kg。(3)各浓度Cd处理下,富集系数随着Cd处理浓度的增加而显著降低,随处理时间的延长而升高。(4)香根草地上部分Cd含量小于根部,各处理转移系数均小于1。随着处理时间的延长,中低浓度处理组的转移系数稍有降低,高浓度处理组的转移系数则显著上升。(5)种植香根草使其根际土中残渣态的Cd转化为生物有效态Cd,提高Cd清除效率。研究结果表明,香根草能够有效地吸收土壤中的Cd,降低土壤中总Cd含量,提高土壤安全性,可作为Cd污染地区植物修复的备选物种。     

镉在土壤-金丝垂柳系统中的迁移特征

以金丝垂柳为试验对象,采用盆栽试验方式,设置无植物和金丝垂柳两组试验,分别对两组试验的土壤做梯度浓度Cd处理:0(无镉处理)、2(低浓度处理)、20(中浓度处理)、80(高浓度处理) mg/kg 土壤干重,无植物组各处理分别定义为CK(无镉处理)、L(低浓度处理)、M(中浓度处理)、H(高浓度处理),金丝垂柳组各处理分别定义为CKP(无镉处理)、LP(低浓度处理)、MP(中浓度处理)、HP(高浓度处理)。通过对土壤中各形态Cd含量及金丝垂柳叶、韧皮部、木质部、根部的Cd含量测定,分析了金丝垂柳及不同浓度Cd处理对土壤中中性交换态、螯合态和残渣态Cd含量的影响,并评价了富集指数(BCF)、转移系数(TF)和生物有效性(BF),明确了Cd在土壤-金丝垂柳系统中的转移特征及金丝垂柳对土壤中Cd的清除效果。结果表明:(1)金丝垂柳对土壤中中性交换态、有效态Cd含量及总Cd量的降低具有极显著影响,HP组与无植物H组相比,中性交换态及有效态Cd含量分别降低了52.73%、25.34%,MP、HP组与对应的无植物处理组的总Cd量相比分别降低了11.33%、13.89%;(2)金丝垂柳各处理组的Cd积累量随Cd处理浓度的增加和处理时间的延长而增加,处理90 d后,HP处理中木质部和根部的Cd含量可达170.64 mg/kg、212.49 mg/kg;(3)各浓度Cd处理下,金丝垂柳各部位生物富集系数呈根>木质部>韧皮部、叶,且随着Cd处理浓度的增加而显著降低,随处理时间的延长而升高;与40 d相比,90 d时LP组叶的生物富集系数增加了6.90倍,增幅最大。(4)各部分转移系数均随处理时间的延长而降低,90 d时LP、MP的转移系数分别比40 d时的结果低47.94%、41.34%。(5)金丝垂柳LP、HP组土壤Cd的生物有效性显著低于相应的无植物处理L、H组,分别低70.73%、88.46%,MP组与M组无显著差异。研究结果表明,金丝垂柳能有效地吸收土壤中的有效态Cd,降低土壤中Cd的生物有效性及总Cd量,提高土壤的安全性,并能将吸收的Cd有效地转移至地上部分,尤其是木质部储存。随着植株不断生长,生物量的增加,金丝垂柳可有效地清除土壤中的Cd,适用于对Cd污染地区进行长期植物修复。     

超富集植物短毛蓼对锰的富集特征

通过野外调查和营养液培养试验,研究了锰在短毛蓼体内的富集特征和对其生长的影响.在锰含量高达2.5×105mg/kg的锰矿废弃地上短毛蓼生长良好,叶锰含量高达1.66×104mg/kg.营养液培养条件下,随着生长介质中Mn浓度的升高,短毛蓼根、茎、叶中的Mn含量逐渐增加,当锰供应水平为1.000mmol/L时,叶锰含量超过10000mg/kg;当锰供应水平为20 000mmol/L时,短毛蓼仍能生长,根、茎和叶3部分的锰含量均达到最大值,分别为9923,18112mg/kg和55750mg/kg.在所有锰供应水平下,短毛蓼茎和叶中的锰含量都比根部的高.结果表明,短毛蓼是一种锰超富集植物,这一发现为锰污染土壤的植物修复和探讨锰在植物体内的超富集机理提供了一种新的种质资源.     

印度芥菜-苜蓿间作对镉胁迫的生态响应

采用温室盆栽试验,研究了重金属镉（Cd）胁迫对印度芥菜和苜蓿间作下的土壤-植物系统的影响,同时对苜蓿的Cd饲用安全进行了评估.结果表明：在土壤Cd含量为0.37～20.37 mg·kg^-1范围内,与单作印度芥菜和苜蓿相比,间作使印度芥菜生物量降低了0.4%～11.8%,而使苜蓿生物量提高了55.3%~70.0%.土壤有效Cd主要受土壤全量Cd和种植植物种类的影响,种植方式对其影响不大.在土壤Cd含量为5.37 mg·kg^-1时,间作印度芥菜地上部Cd含量较单作提高了14.5%,而间作苜蓿地上部Cd含量较单作降低了57.1%;此时,单作和间作苜蓿地上部Cd含量分别为0.21和0.09 mg·kg^-1,均未超过饲料卫生限定标准(0.5 mg·kg^-1).在土壤Cd含量为10.37～20.37 mg·kg^-1范围内,虽然单作和间作苜蓿Cd含量均超过饲料卫生限定标准,但间作种植方式仍然使苜蓿地上部Cd含量较单作降低了2.8%～48.3%,印度芥菜地上部Cd含量也较单作降低了1.1%～48.6%.不论单作还是间作印度芥菜的Cd转运系数都远高于苜蓿.     

Assessing the potential for cadmium phytoremediation with Calamagrostis epigejos: a pot experiment

A pot experiment was conducted for three vegetation periods on a sandy soil (pH 7.5) to study the uptake and distribution of Cd in plant tissues of Calamagrostis epigejos (L.) Roth. Cadmium was applied as CdCl2 (a total of 11 solution of 0, 20. 100, and 200 mg Cd l(-1)). HNO3- and water-extractable concentrations of Cd in 2- and 20-cm soil depths were correlated with the applied Cd showing that Cd was very mobile in the soil. The uptake of Cd from soil by Calamagrostis epigejos was directly related to the total soil Cd content and to the water-soluble pool of Cd. The concentrations of Cd in plant tissues (roots, rhizomes, leaves) and litter increased with increased applied Cd. Most of the Cd that was taken up was accumulated in roots (range from 1.88+/-0.42 to 40.96+/-16.71 mg kg(-1) dry mass), followed by rhizomes (0.52+/-0.13 to 25.70+/-6.35 mg kg(-1)) and leaves (0.30+/-0.06 to 9.20+/-1.93 mg kg(-1)). Cd concentrations of the litter were about twofold greater than the concentrations in the leaves (0.67+/-0.07 to 18.98+/-7.00 mg kg(-1)). The bioaccumulation factor (leaf/soil concentration ratio) increased significantly from 0.70+/-0.10 (control) to 1.1+/-0.17 (100 mg Cd l(-1)), but decreased again at the highest Cd level (200 mg Cd l(-1)) toward 0.74+/-0.34, which was not significantly different from the control. The low transfer of Cd from soil to above-ground organs at higher soil Cd concentrations indicates an exclusion mechanism. The leaf/root Cd concentration ratio (translocation factor) shows no significant relationship to increasing soil contamination. Only 4-7% of the total plant Cd was accumulated in the above-ground tissues. The phytoextraction potential (total Cd removed from soil) within three growing seasons ranged from 0.11 to 0.25% of the total soil Cd. Total output in above-ground living and dead plant material of C. epigejos would be approximately 20 g ha(-1) a(-1) for the lowest contamination level (+20 mg Cd per pot) and approximately 275 g ha(-1) a(-1) for the highest contamination level (+200 mg Cd per pot). This is within the range where an application for phytoextraction of Cd has been suggested by other authors. However, we conclude that the practical use of C. epigejos for phytoremediation is not mainly in the field of phytoextraction, but phytostabilization. C. epigejos has the capability to structurally stabilize the soil and reduce Cd contamination spread due to erosion. The uptake of the available Cd pool and accumulation in below-ground biomass may further prevent leaching into ground water.     

Effects of cadmium and arsenic on growth and metal accumulation of Cd-hyperaccumulator Solanum nigrum L

Remediation of heavy metal contaminated sites using hyperaccumulators presents a promising alternative to current environmental methodologies. In the pot-culture experiment, the effects of Cd, and Cd-As on the growth and its accumulation in the Cd-hyperaccumulator (Solanum nigrum L.) were determined. No reduction in plant height and shoot dry biomass was noted when the plants were grown at Cd concentration of 1.0. The plant can be classified as a Cd-hyperaccumulator. Growing in the presence of 10 mg/kg Cd and 50 mg/kg As, the plant height and shoot dry matter yields did not decrease significantly (p>0.05) compared to that at 10 mg/kg Cd, however the stem Cd content increased by 28%. It was also observed that S. nigrum used exclusion strategy to reduce As uptake in the roots and restricted translocation into the shoots, resulting in As contents of the plant being root>leaf>stem>seed. The Cd accumulation capacity coupled with its relatively high As tolerance ability could make it useful for phytoremediation of sites co-contaminated by Cd and As.     

Leaching of microelement contaminants: a long-term field study

A field experiment with microelement loads was set up on loamy textured, calcareous chernozem soil formed on loess. The ploughed layer contained ca. 5% CaCO3 and 3% humus. The soil was well supplied with Ca, Mg, Mn and Cu, moderately supplied with N and K, and weakly supplied with P and Zn. The water table is at the depth of 15 m, the water balance of the area is negative, and the site is drought sensitive. Salts of the 13 examined microelements were applied at 4 doses in the spring of 1991. Treatments were arranged in a split-plot design, in a total of 104 plots with two replications. Loading rates were 0, 90, 270 and 810 kg/ha per element in the form of AlCl3, NaAsO2, BaCl2, CdSO4, K2CrO4, CuSO4, HgCl2, (NH4)6Mo7O24, NiSO4, Pb(NO3)2, Na2SeO3, SrSO4, ZnSO4. Soil profiles of the control and the 810 kg/ha treated plots were sampled in the 3rd, 6th and 10th year of the trial. The mixed samples, consisting of 5 cores/plot were taken in 30 cm steps to 60 cm (year 1993), 90 cm (year 1996), and 290 cm (year 2000). Ammonium acetate + EDTA-soluble element content was determined. The main conclusions of the study are: (1) In soils contaminated with 810 kg/ha load rates As, Hg, Ni, Cu, Pb, Ba and Sr displayed no significant vertical movement. There is little uptake and translocation in plants of these elements: their concentration in the above-ground plant parts usually remains below 5-10 mg/kg dry mass with the exception of Ba and Sr showing a somewhat higher accumulation. Under our conditions the above elements did not behave as dangerous contaminants to the soil, groundwater, or plants. (2) Moderate leaching of Zn and Cd was detected when applied at higher doses. Their accumulation was also moderate in the above-ground plants parts. Zn is not a dangerous pollutant for soil, plants or groundwater at our site. Cd, however, is a very dangerous element because of its high toxicity to mammals, soil life and crops. (3) Cr, Se, and Mo (in the form of chromate, selenate and molybdenate anions) exhibited great mobility in the soil and partly in the soil-plant system. Cr was hardly detectable in the above-ground parts of plants. Still, its rapid leaching can jeopardize groundwater quality. Se was strongly accumulated in all plant organs and was highly toxic for all crops. Mo, too, showed 2-3 orders of magnitude greater accumulation in plant parts, resulting in products unfit for animal or human consumption. Under our experimental conditions Cr(VI), Se, Mo can be classified as dangerous contaminants, since the anion forms remained stabile for a long time in this well-aerated calcareous environment.     

改良剂对酸性土壤上伴矿景天铝毒缓解作用及镉锌吸收性的影响

为探究不同改良剂对酸性土壤铝(Al)胁迫条件下镉(Cd)锌(Zn)超积累植物伴矿景天Sedum plumbizincicola生长以及镉和锌吸取修复效率的影响,分别添加不同种类改良剂(钙镁磷肥(CMP)、MgCO3、KH2PO4)和不同浓度CMP进行温室盆栽试验。结果表明,CMP能够一定程度上提高土壤pH值并降低土壤交换性Al的浓度,MgCO3能够显著提高土壤pH值和降低土壤交换性Al的浓度,KH2PO4能够降低土壤中交换性Al浓度但未改变土壤pH值。施用适量的CMP(9.39 mg/kg)能够提高伴矿景天生物量和Cd、Zn吸取修复效率,用量过高会抑制伴矿景天生长和Cd、Zn修复效率;施用MgCO3可增大伴矿景天生物量和Cd、Zn修复效率,施用KH2PO4反而抑制了伴矿景天生长。酸性土壤上施用适量的CMP和MgCO3能够缓解伴矿景天的铝毒作用,维持较高的重金属吸收效率。     

Evaluation of the role of submerged plant beds in the metal budget of a fluvial lake

In a study of a large fluvial lake (Lake St. Pierre, St. Lawrence River system, Québec), we have determined the biomass of the submerged vegetation (dominated by Vallisneria americana and Potamogeton spp) during the peak seasonal biomass (August) and senescence (October), and have estimated the content of Cd, Cr, Cu, Ni, Pb and Zn in the above-ground portions of these plants. Multispectral remote sensing data (MEIS-II) were used to extrapolate from point measures of biomass (g m⁻²) to the entire area of the lake (Lavoie et al., 1991). By combining field information (biomass values and metal concentrations) with the more extensive remote sensing data base of biomass values, and by using geostatistical estimation techniques (kriging), we have estimated the seasonal storage of metals in Lake St. Pierre plants to be: 30 kg Cd, 89 kg Cr, 450 kg Cu, 280 kg Ni, 71 kg Pb and 2200 kg Zn. During the seasonal biomass peak, the quantities of Cd, Pb and Zn stored in the plants were higher than those dissolved in the water column, but much lower than those present in the surficial, recent sediments. Mass balance calculations for the summer months indicated that the ‘macrophyte’ compartment represented only a small proportion of the metals entering the lake: Cu and Ni, <1%; Cd and Zn, 2%; Pb, 4%. Senescence and the downstream drifting of plant material noted in October suggested that most of the metals associated with the above-ground parts of the submerged vegetation were not recycled within the lake, but instead were exported at the end of the summer.     

青葙对土壤锰的耐性和富集特征

通过盆栽试验,研究了青葙(Celosia argentea Linn.)对不同浓度(0、50、100、200、300、500 mg/kg)锰(Mn)污染土壤的吸收和积累特性。结果表明,青葙的锰含量、生物富集系数和生物量均随着土壤锰浓度的增加而增加。当土壤锰含量为300 mg/kg时,青葙生长良好。在锰浓度500 mg/kg时,青葙叶片边缘出现轻微褪绿现象,但是植株的生长未受到抑制,并且叶片生物量显著增加(P0.05)。此时,叶片中锰含量达到最大值42927 mg/kg,生物富集系数为69.20。青葙吸收的锰有95%—97%被转移到地上部分,表明该植物对锰具有很强转运能力。本研究的结果为利用青葙修复锰污染土壤提供了有力证据。     

西洋参根残体对自身生长的双重作用

无论在自然生态环境还是在人工农田环境下,植株残体进入土壤后都会对土壤的物理化学性质以及后茬植物的生长产生重要影响。西洋参（Panax quinquefolium L.）为人参属多年生名贵药材,在栽培生产中存在严重的连作障碍问题。为了探明秋后残留在土壤中的须根降解产物对来年植株生长的影响,以及收获后残留在田间的根茬对连作西洋参生长的作用,本实验以3年生西洋参苗为研究对象,采用室内水培试验以及田间盆栽试验,通过添加西洋参根的粉碎物模拟根残体,测定其对西洋参生长的影响。水培试验中全营养液中分别添加0.02 mg/mL、0.1 mg/mL、0.5 mg/mL西洋参根粉碎物,处理后每隔5天测定植株叶片展开情况、株高、冠幅等生长指标。盆栽试验在土壤中添加0.1 mg/g根粉碎物,于栽种后1-2个月测定西洋参叶片展开情况、株高、冠幅等生长指标;水培及盆栽试验均于展叶期、现蕾期、结果期测定地上部及地下部生物量。采用高效液相色谱法（HPLC）测定根围土壤中8种酚酸类化合物的含量。试验结果表明,水培溶液中添加0.02-0.5 mg/mL根残体,可显著抑制西洋参自身地上部分生长,推迟展叶期,结果期生物量降低14.9%-45.0%;对地下部分的影响主要表现为在展叶期显著促进须根生长(p<0.05)。与水培试验相比,盆栽土壤中添加0.1 mg/g根残体同样导致西洋参展叶期推迟;不同的是处理组的地上、地下部及须根的平均生物量均高于对照。另外,添加根残体后盆栽西洋参根围土壤中丁香酸、香草醛、p-香豆酸、阿魏酸等酚酸类化感物质含量下降49.1%-81.4%,但作为逆境信号物质的水杨酸含量升高59.9%。以上结果可以初步确认根残体对西洋参早期生长具有自毒和促进的双重作用,表现为抑制地上部分生长,导致生物量显著下降;同时在生长早期促进须根生长;但在田间环境下,自毒作用可能受根残体降解速度以及土壤对降解产物吸附的影响有所减弱,使促进作用更为明显。