冬季农田杂草繁缕对镉的积累特性研究

为进一步筛选出更多的镉超富集植物作为植物修复的材料,本文以冬季农田杂草作为研究对象,采用土壤种子库-金属筛选法进行筛选,以期从冬季农田杂草中筛选出镉超富集植物,为镉污染农田土壤的冬季植物修复提供材料。通过土壤种子库-金属筛选法初步研究发现,冬季农田杂草繁缕(Stellaria media)地上部分镉含量接近超富集植物的临界值(100 mg·kg-1),但转运系数(TF)小于1,可能是镉富集植物。为此,采用盆栽试验进行了进一步的浓度梯度鉴定。结果表明,随土壤镉含量的增加,繁缕根系生物量、地上部分生物量、主枝长度、根系长度、抗性系数及耐性系数均随土壤镉含量的增加而下降,但繁缕根系及地上部分镉含量呈显著增加的趋势。与对照相比,在土壤镉质量分数为25、50、75、100和125 mg·kg-1时,繁缕总生物量分别下降了17.31%、34.87%、44.79%、52.12%和59.32%,但各个处理均没有表现出明显毒害症状。土壤镉含量为75~125 mg·kg-1时,繁缕地上部分镉含量均大于100 mg·kg-1,最大值为135.79 mg·kg-1,地上部分富集系数(BCF)大于1,但转运系数(TF)小于1。在土壤镉含量为100 mg·kg-1时,繁缕地上部分镉提取量达到最大值,为87.42μg·plant-1。这些结果表明繁缕是一种镉富集植物。虽然繁缕的单株镉提取率较低,但繁缕具有分蘖力强、繁殖力强、生长密度大、耐荫性强等特点,因此适用于冬季农田镉污染的修复。     

锰超积累植物——水蓼

超积累植物筛选是重金属污染土壤植物修复的基础和核心问题,同时也是重金属污染环境植物修复的难点及前沿。本文通过野外调查与营养液模拟试验相结合的方法,初次发现并证实水蓼(Polygonum hydropiper L)是一种锰超积累植物。野外调查结果表明,生长在土壤锰含量为2000mg·kg-1的水蓼,叶部锰的富集量可达3675.89mg·kg-1,且转移系数为1.37。营养液模拟培养试验证实,当营养液中锰的浓度为5000μmol·L-1时,水蓼植株生长正常,但叶中锰含量超过了10000mg·kg-1,达到了锰超积累植物应达到的临界含量标准,水蓼地上部富集系数高达19.41(大于1),转移系数为1.05(也大于1)。当营养液中锰的浓度为15000μmol·L-1时,水蓼叶、根和茎三部分的锰含量均达到最大值,分别为24447.17mg·kg-1、11574.47mg·kg-1和10343.52mg·kg-1。这一发现为锰污染土壤和水体的植物修复提供了一种新的可能的种质资源。     

细叶美女樱(Verbena Tenera Spreng)对镉的耐性和富集特征研究

为探讨观赏花卉应用于植物修复技术的可行性,以细叶美女樱(Verbena Tenera Spreng)为材料,采用盆栽试验,研究了细叶美女樱对镉的耐性、吸收和富集能力,以期为今后观赏植物应用于重金属污染土壤修复提供理论依据。结果表明,随着镉处理浓度的增加,细叶美女樱干重呈先升高后降低的趋势,20~80 mg·kg~(-1)镉处理能促进植株的生长,100~120 mg·kg~(-1)镉处理对生长无影响,表明细叶美女樱对镉有较强的耐性。镉处理下,根系中丙二醛(MDA)含量和电解质渗透率分别于20和60 mg·kg~(-1)镉处理时开始显著高于对照,叶片中MDA含量和电解质渗透率分别于120和80 mg·kg~(-1)镉处理时开始显著高于对照,说明细叶美女樱受到了氧化伤害,且根系受伤害程度较大;氧化伤害更大程度地刺激了抗氧化防御系统,根系中POD、CAT活性的升高幅度大于叶片中CAT、APX活性的升高幅度,但抗氧化酶不能完全消除膜质过氧化引起的伤害。细叶美女樱各器官中镉含量表现为根茎叶的分布格局,植株对镉的转运系数小于1;但是地上部镉富集量高于根系,地上部最大富集量为778.31μg·pot~(-1)。这些结果表明细叶美女樱对镉有很强的耐性和富集能力,是一种良好的修复镉污染土壤的观赏绿化植物。     

喷施烯效唑(S3307)对2种生态型鬼针草镉积累的影响

随着土壤重金属污染的加剧,探究提高超富集植物对土壤修复效率的方法具有十分重要的现实意义。为揭示烯效唑(S3307)对超富集植物鬼针草(Bidens pilosa)生长和重金属积累的影响,通过盆栽试验,研究喷施不同浓度S3307溶液(0、25、50、75、100和125 mg·L~(-1))对2种生态型(农田生态型和矿山生态型)鬼针草生长和镉积累的影响。结果表明,与对照相比,S3307对2种生态型鬼针草的生长均表现出抑制作用,显著降低其生物量及株高。与对照相比,S3307显著提高2种生态型鬼针草叶绿素a、叶绿素b和类胡萝卜素等光合色素以及镉含量。当ρ(S3307)为125 mg·L~(-1)时,农田生态型和矿山生态型鬼针草地上部分镉含量均达到最大值,分别比对照提高91.44%和77.79%。对鬼针草镉积累量而言,当ρ(S3307)为25 mg·L~(-1)时2种生态型鬼针草地上部分和整株镉积累量均达到最大值。适当浓度的S3307可以有效提高农田生态型和矿山生态型鬼针草对镉污染土壤的修复能力,当ρ(S3307)为25 mg·L~(-1)时效果最好。     

不同浓度胺鲜酯对籽粒苋富集重金属镉锌的影响

植物生长调节剂具有提高植物富集土壤重金属的能力,从而提高植物修复污染农田土壤的效率。采用盆栽方式,比较叶面喷施不同质量浓度(0、5、10、15 mg·L~(-1))胺鲜酯(DA-6)对籽粒苋(Amaranthus hypochondriacus L.)生长、富集镉(Cd)和锌(Zn)及土壤有效态Cd和Zn的影响。结果表明,10 mg·L~(-1)处理显著提高籽粒苋植株的生物量;DA-6对籽粒苋根系分布层土壤和根际土pH无显著影响,但能显著提高籽粒苋根际土有效态Cd和Zn含量;DA-6处理的籽粒苋叶、茎和根中Cd含量均呈增加趋势,但仅15 mg·L~(-1)处理能显著提高籽粒苋叶、茎中Cd含量,DA-6处理对籽粒苋根中Cd含量无显著影响;DA-6对籽粒苋叶、茎、根中Zn含量均无显著影响;10 mg·L~(-1)处理能显著强化籽粒苋叶、茎对Cd和Zn的累积量,DA-6处理对籽粒苋根中Cd和Zn的累积量无显著影响;DA-6处理籽粒苋后,除籽粒苋叶中5 mg·L~(-1)处理和10 mg·L~(-1)处理的Zn富集系数显著低于对照外,其它处理的籽粒苋叶、茎、根中Cd和Zn富集系数及运转系数均无显著差异。因此,叶面喷施10 mg·L~(-1)DA-6能显著强化籽粒苋地上部对Cd、Zn的累积量,但DA-6处理对Cd和Zn的富集和运转并无显著促进作用。     

3种土壤类型下镉胁迫对红椿生物量分配及其镉富集特性的影响

红椿(Toona ciliata Roem.)为中国国家级(Ⅱ)重点保护植物,同时也是(亚)热带珍贵速生用材树种。为了解镉(Cd)胁迫对红椿生长及镉富集特性的影响,采用盆栽控制试验研究了长江上游3种典型土壤(黄壤、酸性紫色土和冲积土)条件下,不同浓度Cd处理[0(对照)、20、40、80和160 mg·kg-1]对其幼树生长发育、生物量分配、镉积累与分配及镉富集特性的影响,为深入认识镉污染土壤的有效修复提供理论依据。结果显示,(1)低浓度镉胁迫(40 mg·kg~(-1))可促进红椿幼树生长,而高浓度镉胁迫(≥40 mg·kg~(-1))则表现为严重抑制;各器官生物量随镉浓度增加而先升后降,除酸性紫色土壤上茎生物量外。(2)3种土壤条件下,红椿幼树各器官镉含量均随镉处理浓度增大而增大。相同镉浓度处理下主根镉含量表现为:黄壤酸性紫色土≥冲积土,而冲积土条件下侧根镉含量均低于黄壤或酸性紫色土。同时,3种土壤下各器官镉含量随土壤镉浓度增大而增加,且地下部显著大于地上部。(3)随着镉处理浓度增大,除地上部富集系数(BC)在冲积土条件下无显著差异外,其他土壤条件下地上和地下部均显著增大;而3种土壤条件下转移系数(TF)均逐渐降低。高浓度镉胁迫下,幼树BC和TF虽均大于1,但地上部镉含量低于100 mg·kg~(-1)。随着镉浓度升高,3种土壤条件下红椿耐性指数(TI)均先增后降,高镉处理下冲积土TI显著大于黄壤和酸性紫色土壤。红椿虽不是典型的镉超富集植物,但其能在较严重镉污染土壤中较好生存,可作为镉污染区域(特别是镉污染冲击土)潜在的土壤修复树种。     

不同品种蓖麻对镉的响应及修复能力评价

蓖麻(Ricinus communis L.)是一种有价值的能源作物,可用于修复镉污染农田同时生产生物能源。本研究在温室条件下(5~32℃)采用盆栽试验,设定2个镉质量分数梯度(2和5 mg·kg~(-1)),对比研究镉胁迫下30个蓖麻品种的生长状况,评估蓖麻对镉的耐性及蓖麻茎、叶和果实中镉的富集特征,以及不同蓖麻品种对镉的修复能力。研究发现,随着土壤中镉质量分数增加,10个蓖麻品种的生物量增加,20个蓖麻品种的生物量减少;表明不同品种蓖麻对镉的耐受程度不同。2 mg·kg~(-1)镉胁迫下,茎、叶和果实中镉质量分数变化范围分别为0.600~1.670、0.310~1.970和0.130~0.909 mg·kg~(-1),平均值分别为1.030、0.831和0.362 mg·kg~(-1)。5 mg·kg~(-1)镉胁迫下,茎、叶和果实中镉质量分数变化范围分别为1.012~4.032、0.698~3.514和0.227~1.525mg·kg~(-1),平均值分别为1.964、1.583和0.694 mg·kg~(-1)。蓖麻地上部分对镉的富集能力大小依次为茎、叶、果实。基于蓖麻品种茎、叶和果实中镉的质量分数,采用聚类分析的方法分析发现,30个蓖麻品种对镉的富集能力存在差异:4个蓖麻品种为高镉富集型,25个蓖麻品种为低镉富集型。根据蓖麻地上部分中镉质量分数及富集系数(小于1),判断蓖麻不是镉的超富集植物。2 mg·kg~(-1)镉胁迫下,蓖麻地上部分吸收的镉含量变化范围为26.3~65.7μg·pot~(-1),平均值为42.4μg·pot~(-1)。5 mg·kg~(-1)镉胁迫下,蓖麻地上部分吸收的镉含量变化范围为37.0~121.6μg·pot~(-1),平均值为76.0μg·pot~(-1)。蓖麻地上部分对镉的富集能力及提取能力主要由品种决定,受土壤中镉浓度的影响相对较小。因此,蓖麻作为一种潜在的镉的植物修复作物,不适用于植物提取的用途,可用于植物固定的用途;选用对镉具有较高耐性蓖麻品种种植可以在健康合理地利用镉污染农田的同时生产生物能源。     

镉污染环境下中华蚊母树的镉积累与生长及叶绿素荧光动力学响应

以三峡库区优势物种中华蚊母树(Distylium chinense)为试验对象,在其生长土壤中添加不同w(Cd~(2+))(0、2、5、15、30 mg·kg~(-1)),研究植物镉积累、生长高度及叶绿素荧光参数对不同含量镉胁迫的响应。结果表明,中、高含量镉胁迫对植物的生长高度及叶绿素总量具有显著抑制作用;叶绿素荧光参数对植物的耐受性可以进行生理学解释,镉胁迫下植物光反应中心PSⅡ受到可逆性损伤,叶绿素荧光参数Fv/Fm与RET值随胁迫时间先降低后逐渐恢复;添加w(Cd~(2+))为2 mg·kg~(-1)时,根、茎、叶的镉富集系数最大,分别为7.4、8.1和8.2;茎、叶的转移系数最大,分别为1.01和0.94;中华蚊母树具有很强的富集性和转移能力,可以作为镉污染土壤植物修复技术的潜能物种。     

土霉素、镉复合污染土壤的植物-微生物联合修复实验研究

选用紫茉莉(Mirabilis jalapa L.)与孔雀草(Tagetes patula L.)两种植物与对土霉素有良好降解效果的细菌紫金牛叶杆菌(Phyllobacterium-myrsinacearum)和真菌胶红酵母(Rhodotorula mucilaginosa)的混合菌液,对土霉素、镉复合污染土壤进行联合修复。模拟受不同浓度镉、土霉素污染的土壤,在温室进行90 d盆栽实验,通过其修复效果,探讨植物-微生物联合修复土霉素、镉复合污染土壤的可行性。实验结果表明,紫茉莉和孔雀草对镉均表现出良好耐性,孔雀草、紫茉莉生物量都随土壤中土霉素含量增加而下降,土霉素抑制植物对镉的富集;土霉素降解菌有利于提高植物生物量,促进孔雀草、紫茉莉对镉吸收并提高紫茉莉对镉的富集系数。当土霉素质量分数为5 mg·kg-1时,土霉素降解率最差为30.8%(9号处理),降解效果最好为70.6%(22号处理)。当土霉素质量分数为30 mg·kg-1时,土霉素降解率最差为17.2%(11号处理);土霉素降解率最高为59.3%(24号处理)。综合比较,孔雀草无论在镉富集能力还是土霉素降解效果上均优于紫茉莉。     

吲哚乙酸和激动素配合施用提高蜈蚣草和龙葵对砷、镉富集的田间试验

植物激素可打破重金属超富集植物的种子休眠、促进发芽和快速生长,从而提高其富集重金属的效率。虽然人工合成的植物生长调节剂在促进超富集植物生长和提高重金属富集方面已取得很多成果,但大多是盆栽试验,大田试验甚少。文章在课题组前期室内盆栽试验筛选出的吲哚乙酸(IAA)和激动素(KT)提高砷(As)超富集植物蜈蚣草(Pteris vittata L.)砷提取效率的最佳配比(IAA:KT=25 mg·L~(-1):20 mg·L~(-1))基础上,在云南省个旧市大屯镇重金属污染农田分45个小区、喷施2次激素开展IAA和KT配合施用对As超富集植物蜈蚣草和镉(Cd)超富集植物龙葵(Solanum nigrum L.)超富集As和Cd的影响和机理研究。结果表明,大田条件下IAA和KT配合施用能够促进2种超富集植物快速生长,在含Cd为3.12 mg·kg~(-1)、含砷As 98.7 mg·kg~(-1)的农田土壤上,与未施用植物激素的对照相比,25 mg·L~(-1) IAA和20 mg·L~(-1) KT配合施用后,龙葵和蜈蚣草的株高、鲜物质量、地上部和地下部Cd/As含量、Cd/As转运系数和富集系数均显著增加,且龙葵对Cd、蜈蚣草对As的提取效率最高可分别达7.52%和6.06%。第2次喷施激素后,单加KT和激素配合施用条件下,龙葵和蜈蚣草间作时两种植物叶片过氧化物酶(POD)活性均显著增加。逐步回归分析结果表明,龙葵对As、蜈蚣草对Cd的提取效率均与叶片POD活性成显著正相关。因此,叶片保持较高的POD活性对两种超富集植物对Cd和As的提取具有重要意义。     

DDTs对水生哺乳动物的组织残留基准初步研究

作为一种曾经广泛使用的氯化烃杀虫剂,DDT及其主要代谢产物DDE和DDD(合称为DDTs)是一类典型的具有持久性和生物累积性的有毒污染物。亲脂性和持久性使得DDTs可以通过食物链进行生物放大,从而对处于高营养级的水生哺乳动物造成严重的毒害作用。在综述DDTs对哺乳动物的毒性研究基础上,采用物种敏感度分布(species sensitivity distribution,SSD)和毒性百分数排序法(toxicity percentile rank method,TPRM)推导DDTs保护水生哺乳动物的组织残留基准(Tissue Residue Guideline,TRG)。使用SSD和TPRM得到的TRG分别为23.9和22.7 ng·g-1食物(湿重)。相应的,DDTs保护水生哺乳动物的水质基准分别为188.2和178.7 pg·L-1。依据研究得到的DDTs的组织残留基准及其在鱼类体内的含量评估对水生哺乳动物的风险。研究结果可用于评估DDTs对水生哺乳动物的生态风险,并为DDTs的风险管理提供理论依据。     

Pattern of distribution of selected trace elements in the marine brown alga,Sargassum filipendula Ag. from Sri Lanka

Baseline concentrations together with biological variations of 29 trace elements (Ag, As, Au, Ba, Br, Cd, Ce, Co, Cr, Cs, Eu, Fe, Hf, I, Mn, Mo, Ni, Pb, Rb, Sb, Sc, Se, Sm, Sr, Tb, Th, Yb, Zn and Zr) were investigated in the brown alga, Sargassum filipendula collected from the western coast of Sri Lanka. Several elements (Co, Cr, Fe, Hf, Ni, Sc, Se, Th, Zr and the rare earth elements) were found to be enriched in S. filipendula compared to NIES No. 9 Sargasso reference material. Concentration of strontium in S. filipendula was highest at all sites. Chemical abundance of the rare earth elements decreased approximately linearly with increasing atomic numbers. The pattern of elemental distribution appears to be due to the fact that S. filipendula seems capable of concentrating high levels of trace elements under conditions of their very low availability in sea water. Concentration factors for elements in S. filipendula lie in a higher range compared with those reported in the literaure for brown algae.     

Antennal responses of four species of tree-killing bark beetles (Coleoptera: Scolytidae) to volatiles collected from beetles,and their host and nonhost conifers

Summary. Host selection in tree-killing bark beetles (Coleoptera: Scolytidae) is mediated by a complex of semiochemical cues. Using gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric analyses, we conducted a comparative study of the electrophysiological responses of four species of tree-killing bark beetles, the Douglas-fir beetle, Dendroctonus pseudotsugae, Hopkins, the mountain pine beetle, D. ponderosae Hopkins, the spruce beetle, D. rufipennis Kirby, and the western balsam bark beetle, Dryocoetes confusus Swaine, to volatiles captured by aeration of 1) bole and foliage of four sympatric species of conifers, Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, lodgepole pine, Pinus contorta var. latifolia Engelm., interior spruce, Picea engelmannii x glauca, and interior fir, Abies lasiocarpa x bifolia, and 2) con- and heterospecific beetles at three stages of attack. We identified 13 monoterpenes in the conifers and nine compounds in the volatiles of beetles that elicited antennal responses. There was no qualitative difference in the terpene constitution of the four species of conifers and very little difference across beetle species in their antennal response to compounds from conifers or beetles. The lack of species-specific major or minor components in conifers suggests that beetles would need to detect differences in the ratios of different compounds in conifers to discriminate among them. Attraction to hosts and avoidance of nonhost conifers may be accentuated by perception of compounds emitted by con- and heterospecific beetles, respectively. The 22 compounds identified are candidate semiochemicals with potential behavioural roles in host location and discrimination.     

Diet-induced chemical phytomimesis by twig-like caterpillars of Biston robustum Butler (Lepidoptera: Geometridae)

Summary. Polyphagous caterpillars of the giant geometer Biston robustum resemble the twigs of their respective food sources in color and shape. Common predatory ants, including Lasius and Formica, were often observed to freely prowl directly on caterpillars bodies, even after antennal contact. This suggests that the cuticular chemicals of the caterpillars resemble those of the twigs of the foodplants, so we analyzed both by GC and GC-MS. The chemical compositions differed among caterpillars fed on a cherry, Prunus yedoensis, a chinquapin Castanopsis cuspidata, and a camellia Camellia japonica. The cuticular chemicals of the caterpillars resembled those of their corresponding food sources. When the caterpillar diets were switched from the cherry to camellia or chinquapin at the 4^th instars, the caterpillars cuticular chemicals changed after molting to resemble those of their respective foods. Caterpillars also changed their cuticular chemicals when they perched on cherry twigs and fed on camellia or chinquapin leaves, but not when they perched on camellia or chinquapin twigs and fed on cherry leaves. The chemical similarities between the caterpillars and the twigs were due to the digestion of host leaves, which indicates that this is a diet-induced adaptation.     

Some polyphagous Homoptera gain protection from their natural enemies by feeding on the toxic plantsSpartium junceum andErythrina corallodendrum (Leguminosae)

Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range.     

Comparison of the insecticidal effects of water extracted and intact aromatic plants onAcanthoscelides obtectus,a bruchid beetle pest of kidney beans

Summary Acanthoscelides obtectus (Say) is one of the most damaging pests of kidney beans,Phaseolus vulgaris L. worldwide. However, aromatic plants from the families Lamiaceae, Lauraceae, Myrtaceae and Poaceae can protect kidney beans by direct or delayed insecticidal effect, through increased adult mortality and inhibition of beetle reproduction (both oviposition and adult emergence). The efficiency of hydrodistillated and intact plants fromThymus vulgaris andT. serpyllum, Mentha piperata, Rosmarinus officinalis, Satureia hortensis, Eucalyptus globulus, Laurus nobilis, Origanum vulgare, andCymbopogon nardus was compared. For both extracts,Origanum vulgare had the best effect. The insecticidal effect was induced by more than the essential oils because no significant difference was noticed between distilled and intact plants extract. Inhibition of reproduction was particularly important. These results suggest that lipidic as well as non lipidic, allelochemicals, such as phenolics, or non-protein amino-acids, or flavonoids may be involved in the toxicity of aromatic plants to this beetle.     

Benthic macrophyte communities in the Ghar El Melh lagoon (North Tunisia)

This work deals with the biodiversity and distribution of benthic macrophytes in the Ghar El Melh lagoon, a Mediterranean coastal lagoon located in the North of Tunisia. An inventory was made of the benthic flora and submerged macrophyte communities were mapped during two successive campaigns (the summer of 1999 and the winter of 2000). The following 24 macrophyte species were identified: seven red algae, two brown algae, 11 green algae, and four marine angiosperms. The results were compared with available data from the literature. Ruppia cirrhosa is the most dominant species. It is found in all lagoon parts, except in the west sector.Ruppia beds are usually associated withCladophora forming heterogeneous communities. During summerRuppia cirrhosa shows a large distribution, covering an area of ca. 21.4 km², with dense, extensive beds covering 80–100%. In winter, severalCladophora species have a very large distribution as well, covering nearly an area of 28.5 km² with an average cover of 46%. The green algaeCaulerpa prolifera is confined to the eastern part of the lagoon which is mainly affected by seawater. In comparison with previous situations, many transformations were observed in biodiversity and spatial distribution of the dominant communities. Thus,Cymodocea nodosa andZostera beds, which dominated in the 1970s, were replaced byZostera andCaulerpa prolifera in the 1980s and are currently succeeded byRuppia cirrhosa andCladophora. Restoration of the Ghar El Melh lagoon will enable an increase in the exchange with the open sea and the circulation of water, in particular in the confined zones. This should considerably improve the water quality and would positively influence the phytobenthic communities.     

Absolute configuration of the major sex pheromone component of the satin moth, Leucoma salicis, verified by field trapping test in Hungary

Summary. Male satin moths, Leucoma (Stilpnotia) salicis L. (Lepidoptera, Lymantriidae) were attracted only to (3Z,6R,7S,9R,10S)-isomer out of the four (3Z)-cis-6,7-cis-9,10-diepoxy-3-henicosenes (leucomalure). This was demonstrated by field trapping test with a bivoltine population in a mixed poplar-willow forest along the flood area of the river Danube at Adony, Hungary.     

Increase of multi-metal tolerance of three leguminous plants by arbuscular mycorrhizal fungi colonization

A greenhouse pot experiment was conducted to investigate the effects of the colonization of arbuscular mycorrhizal fungus (AMF) Glomus mosseae on the growth and metal uptake of three leguminous plants (Sesbania rostrata, Sesbania cannabina, Medicago sativa) grown in multi-metal contaminated soil. AMF colonization increased the growth of the legumes, indicating that AMF colonization increased the plant’s resistance to heavy metals. It also significantly stimulated the formation of root nodules and increased the N and P uptake of all of the tested leguminous plants, which might be one of the tolerance mechanisms conferred by AMF. Compared with the control, colonization by G. mosseae decreased the concentration of metals, such as Cu, in the shoots of the three legumes, indicating that the decreased heavy metals uptake and growth dilution were induced by AMF treatment, thereby reducing the heavy metal toxicity to the plants. The root/shoot ratios of Cu in the three legumes and Zn in M. sativa were significantly increased (P < 0.05) with AMF colonization, indicating that heavy metals were immobilized by the mycorrhiza and the heavy metal translocations to the shoot were decreased.     

Net energetic advantage drives honey bees (Apis mellifera L) to nectar larceny in Vaccinium ashei Reade

Carpenter bees (Xylocopa spp.) act as primary nectar thieves in rabbiteye blueberry (Vaccinium ashei Reade), piercing corollas laterally to imbibe nectar at basal nectaries. Honey bees (Apis mellifera L) learn to visit these perforations and thus become secondary nectar thieves. We tested the hypothesis that honey bees make this behavioral switch in response to an energetic advantage realized by nectar-robbing flower visits. Nectar volume and sugar quantity were higher in intact than perforated flowers, but bees (robbers) visiting perforated flowers were able to extract a higher percentage of available nectar and sugar so that absolute amount of sugar (mg) removed by one bee visit is the same for each flower type. However, because perforated flowers facilitate higher rates of bee flower visitation and the same or higher rates of nectar ingestion, they are rendered more profitable than intact flowers in temporal terms. Accordingly, net energy (J) gain per second flower handling time was higher for robbers on most days sampled. We conclude that the majority evidence indicates an energetic advantage for honey bees that engage in secondary nectar thievery in V. ashei.Communicated by R. Page